Table of Contents
WELCOME LETTER...... 2
TUC FLOOR PLAN...... 3
5th ICLPRP TECHNICAL PROGRAM May 10-15, 2015...... 4
LIST OF POSTERS...... 11
COMMITTEE ...... 12
GENERAL INFO AND SOCIAL EVENTS...... 14
ORAL ABSTRACTS (LISTED IN PRESENTATION ORDER)...... 16
POSTER ABSTRACTS...... 84
ABSTRACT INDEX...... 96
http://ceas.uc.edu/lspcenter/lspconference.html
1 Welcome Message
May 10, 2015
Dear 5th ICLPRP attendee,
On behalf of the organizing committee, it is with great pleasure that we welcome you to the vibrant and scenic Ohio river valley city of Cincinnati and the 5th International Conference on Laser Peening and Related Phenomena (5th ICLPRP). We are pleased that the University of Cincinnati, with its beautiful campus, has been chosen as your conference site. The “Ohio Center for Laser Shock Processing for Advanced Materials and Devices” (LSP Center); in the UC College of Engineering and Applied Science (CEAS), Department of Mechanical and Materials Engineering is pleased to host this conference. The CEAS was established in 1900 and was the founder of Cooperative Education in the USA. It is organized into six departments covering a wide range of engineering disciplines.
The LSP Center has been established at University of Cincinnati (UC), Cincinnati, Ohio, in collaboration with industry, universities and a $3 million award from the State of Ohio, Department of Development Third Frontier Program. The Center’s far-reaching mission is to: 1. Develop a balanced research and education infrastructure to serve both academia and industry 2. Advance research in critical areas and help develop and commercialize new products for the orthopedic/ spinal implant industry in the short term 3. Foster proliferation of this technology to many products through R&D, entrepreneurial and commercialization activities 4. Nurture and develop the best-trained scientific and technical workforce of the 21st century
The LSP Center has state-of-the-art equipment for advanced surface treatment research and researchers with expertise in a wide variety of fields including surface enhancement processes, physical metallurgy, mechanical behavior of materials, corrosion, materials characterization and modeling and simulations. The Center is open for an industry consortium for process and product development and prototyping activities.
Your contribution has made it possible for us to put together an exciting technical program, featuring plenary, invited and contributed presentations in 15 thematic sessions on fundamental and applied topics and industrial applications, as well as a dedicated session on modeling and poster sessions. There will also be a program of events around the conference, including a visit to the National Museum of the United States Air Force and dinner at the Engineers Club in Dayton, OH and the conference dinner riverboat cruise on the Ohio river.
We are looking forward to your contribution and active participation and hope you enjoy your visit to Cincinnati and have a successful conference. We also hope that your professional plans will bring you to this region, which will play a big role in the future of Laser Peening research, development, and manufacturing.
Please let us know If we can do anything to make your stay more pleasant and productive. Thank you for joining the 5th ICLPRP conference.
Sincerely, Professor S. R. (Manny) Mannava; co-chair Professor Vijay K. Vasudevan; co-chair University of Cincinnati, College of Engineering & Applied Science, Department of Mechanical and Materials Engineering 2 TUC Floor plan
TANGEMAN UNIVERSITY CENTER
SESSIONS
MONDAY/WEDNESDAY LUNCH
MONDAY MODELING WORKSHOP
3 5th ICLPRP Technical Program
Sunday, May 10
5:00 – 7:00 pm 5th ICLPRP Conference Opening Reception...... Grand Ballroom, 2nd Level, Kingsgate Marriott Monday, May 11
8:00 am – 5:00 pm Conference Registration...... 4th Floor, TUC
8:00 – 8:30 am Light Breakfast...... Great Hall, TUC
8:30 – 9:00 am Welcome and Opening Remarks...... Great Hall, TUC Professor Seetha Ramaiah Mannava, Director Ohio LSP Center, CEAS Mechanical and Materials Engineering, University of Cincinnati, United States Dr. Teik C. Lim, Dean, College of Engineering and Applied Science, University of Cincinnati, United States Dr. Jay Kim, Head, Department of Mechanical and Materials Engineering, University of Cincinnati, United States Professor Vijay K. Vasudevan, Professor, CEAS Mechanical and Materials Engineering, University of Cincinnati, United States Professor Michael E. Fitzpatrick, Coventry University, Coventry, United Kingdom
9:00 – 9:15 am David Linger, CEO, University of Cincinnati Research Institute...... Great Hall, TUC UCRI: Plug, Play, Innovate: “One of UCRI’s many focus areas is advanced manufacturing. By both leveraging surface engineering techniques to solve industry needs, and by helping promote awareness of various surface engineering techniques, this also drives industry innovation.”
9:15 – 9:30 am Group Photo...... Front Steps, TUC
SESSION 1: APPLICATIONS DEVELOPMENT AND LIFE EXTENSION Chair: Michael E. Fitzpatrick, Coventry University, Coventry, United Kingdom 9:30 – 10:00 am Keynote Presentation...... Great Hall, TUC Dr. Domenico Furfari, Airbus Operations, GmgH, Germany #1015: Laser Shock Peening as Surface Technology to extend Fatigue Life in Metallic Airframe Structures
10:00 – 10:40 am Oral Presentations Dean van Aswegen, University of the Witwatersrand, South Africa #852: Laser Shock Peening for Fatigue Crack Retardation in Airframe StructuresSungho Seetha Ramaiah Mannava, University of Cincinnati, United States #1012: Smart Surface Technology Development for Aerospace, Industrial and Biomedical Systems
10:40 – 11:00 am Poster Introductions (#843, #847, #856)
11:00 – 11:15 am Break...... Great Hall, TUC
SESSION 2: LIFE EXTENSION - FATIGUE, WEAR AND EROSION Chair: Dong Qian, University of Texas at Dallas, United States
4 11:15 am – 12:40 pm Oral Presentations INVITED Yuji Kobayashi, SINTOKOGIO, LTD, Japan #907: Fatigue Strength of High Strength Al Alloy in High Humidity Condition Elke Hombergsmeier, Airbus, Germany #1009: Fatigue Crack Retardation in Laser Shock Peened High Strength Steel Lloyd Hackel, Curtiss Wright, CA, United States #853: Reduction of Cavitation Erosion by Laser Peening Sungho Jeong, Gwangju Institute of Science and Technology, Republic of Korea #827: Effects of Laser Peening on Friction Characteristics of Aluminum Alloy
12:40 – 1:40 pm Lunch...... 400 ABC, TUC
SESSION 3: NOVEL LASER PROCESSES AND TECHNOLOGIES Chair: José L. Ocaña, Polytechnical University of Madrid and UPM Laser Center, Madrid, Spain 1:45 – 2:15 pm Keynote Presentation...... Great Hall, TUC Dr. Ric Allott, STFC Rutherford Appleton Laboratory, United Kingdom #933: The DiPOLE Laser –Efficiently Delivering Very High Energy Pulses with High Average Power
2:15 – 4:10 pm Oral Presentations INVITED Yuji Sano, ImPACT, Japan #864: ImPACT: A Newly-funded Japanese National Program to Realize Ultra-compact Power Lasers Jan Brajer, Academy of Sciences of the Czech Republic #831: New Possibilities of Efficient Peening by Using Diode-Pumped kW-class Lasers Jeff Dulaney,LSP Technologies, Inc., United States #866: New High Power Laser 0Peening System Claudia Polese, University of the Witwatersrand, South Africa Laser Peening Facilities and Activities at the National Laser Center Derek Roland, RPMC Lasers Inc., United States High Energy Lasers for Laser Shock Peening
4:10 – 4:15 pm Break...... Great Hall, TUC
4:15 – 5:00 pm Tour CEAS LSP Center ...... Meet at 4th Floor Lobby, TUC 5:00 – 5:45 pm Tour CEAS LSP Center ...... Meet at 4th Floor Lobby, TUC 4:15 – 6:15 pm Modeling Workshop...... 400ABC, TUC
6:15 pm Dinner on Own Tuesday, May 12
7:30 am – 12:00 pm Conference Registration...... 4th Floor, TUC
7:30 – 8:00 am Light Breakfast...... Great Hall, TUC
SESSION 4: FUNDAMENTAL MECHANISMS AND LIFE PREDICTION Chair: Yuji Sano, ImPACT, Japan 8:00 – 8:30 am Keynote Presentation...... Great Hall, TUC Dr. Tommaso Ghidini, European Space Agency (ESA) #1014: Assessing Laser Shock Peening for Stress-Corrosion Cracking and Fatigue Resistance Enhancement of Launchers External Structures 5 8:30 – 10:00 am Oral Presentations INVITED Itaru Chida, Toshiba Corporation, Yokohama, Japan #859: Residual Stress Improvement of Nickel Base Superalloy Alloy 706 by Laser Peening Michael Fitzpatrick, Coventry University, Coventry, United Kingdom #846: Residual Stresses in Laser and Shot Peened Marine Butt welds Sergey Chupakhin, Helmholtz-Zentrum Geesthacht, Germany #821: Effect of Elasto-plastic Material Behaviour on Determination of Laser Shock Peening induced Residual Stress Profiles using the Hole Drilling Method Hongchao Qiao, Shenyang Institute of Automation Chinese Academy of Sciences #858: Effects of Laser Peening on Deformation Microstructure Evolution and Residual Stress in TiAl Alloy
10:00 – 10:15 am Break...... Great Hall, TUC
SESSION 5: FUNDAMENTAL MECHANISMS AND LIFE PREDICTION Chair: Claudia Polese, University of Witwatersrand, South Africa 10:15 am – 12:00 pm Oral Presentations INVITED Damien Courapied, PIMM Laboratory, France #844: Physical Understanding of the Water Confined Plasma Regime for Laser Shock Processing José L. Ocaña, Universidad Politécnica de Madrid and UPM Laser Center, Madrid, Spain #823: Alpha-Line Characterization of Electronic Density in Plasmas Generated by Laser Shock Processing David Busse, Cranfield University, United Kingdom #850: Predicting Stress Intensity Factors in Laser-Peened M(T) Samples Anoop Vasu, American Axle and Manufacturing, Detroit, MI, United States #862: Framework to Conduct Re-Laser Peening for Maximum Fatigue Life
12:00 – 12:15 pm Poster Introductions (#868, #869, #871, #874)
12:15 pm Collect Box Lunch...... 4th Floor, TUC
12:30 – 9:00 pm Visit to National Museum of the US Air Force and Engineers Club...... Dayton, Ohio (see page 14 for more details) Wednesday, May 13
7:30 am – 5:00 pm Conference Registration...... 4th Floor TUC
7:30 – 8:00 am Light Breakfast...... Great Hall, TUC
SESSION 6: PREDICTIVE MODELING AND SIMULATIONS Chair: Ramana Grandhi, Wright State University, United States 8:00 – 8:30 am Keynote Presentation...... Great Hall, TUC Dr. Craig McClung, Southwest Research Institute, United States #937: A Framework for Verification and Validation of Models for Laser Peening 8:30 – 10:20 am Oral Presentations INVITED Robert Brockman, University of Dayton Research Institute, United States #840: LSP Process Simulation and Data Interpretation
6 INVITED José L. Ocaña, Polytechnical University of Madrid and UPM Laser Center, Madrid, Spain #825, #826: Simulation-Guided Induction of Through-Thickness Compressive Residual Stresses and Application of Laser Shock Processing to the Mitigation of the Effect of Surface Defects on the Fatigue Life of Thin Metal Plates Arif Malik, Saint Louis University, United States #855: A Reliability-Based Framework to Efficiently Optimize Laser Peening Parameters Hamidreza Karbalaian, Center of Advanced Systems and Technologies (CAST), Iran #878: A Novel Approach for Simulation of Laser Shock Peening Using a Finite DomainRobert Cory Seidel, Saint Louis University, United States #905: Application of a Reliability-Based Laser Peening Design Framework to Friction-Stir Weld Test Specimens
10:20 – 10:30 am Break...... Great Hall, TUC
SESSION 7: FUNDAMENTAL MECHANISMS AND MODELING Chair: Arif Malik, St. Louis University, United States 10:30 – 12:00 pm Oral Presentations Dong Qian, Innova Engineering, CA and University of Texas at Dallas, United States #891: Simulation-Based Optimization of Laser Shock Peening Parameters for Improved Fatigue Performance Marianna Sticchi, Helmholtz-Zentrum Geesthacht, Germany #828: A Parametric Study of the Peen Size and Coverage on the Laser Shock Peening induced Residual Stress Profiles in thin AA2024 Samples Suraiya Zabeen, Coventry University, United Kingdom #927: Correlation Between Residual Stress and Nanohardness Generated by Laser Shock Peening in AL-2624 Aerospace Alloy Daniel Glaser, University of the Witwatersrand, South Africa #861: The Effect of Cavitation during the Laser Shock Peening Process
12:00 – 12:15 pm Poster Introductions (#877, #883)
12:15 – 1:15 pm Lunch...... 400 ABC, TUC
SESSION 8: RELATED PROCESSES AND PHENOMENA Chair: Vijay K. Vasudevan, University of Cincinnati, OH, United States 1:15 – 1:45 pm Keynote Presentation...... Great Hall, TUC Professor Hitoshi Soyama, Tohoku University, Japan #832: Surface Mechanics Design by Cavitation Peening
1:45 – 3:25 pm Oral Presentations INVITED Tomokazu Sano, Osaka University, Japan #901: Femtosecond Laser Peening without Sacrificial Overlay under Atmospheric Conditions Hongchao Qiao, Shenyang Institute of Automation Chinese Academy of Sciences, China #857: Study and Development of High Peak Power Short Pulse Nd:YAG Laser for Peening Applications INVITED Laurent Berthe, CNRS, France #841: Shock Produced by Laser for Adhesion test of Coatings and Multi-layered Materials Yongxiang Hu, Shanghai Jiao Tong University, China #829: Applicability of Laser Peen Forming for the Bending of Fiber Metal Laminates Hitoshi Soyama, Tohoku University, Sendai, Japan #817: Preventing Hydrogen Embrittlement in Stainless Steel by Means of Compressive Stress Induced by Cavitation Peening 7 3:25 – 3:40 pm Break...... Great Hall, TUC
SESSION 9: FUNDAMENTAL MECHANISMS AND PROPERTIES Chair: Y. S. Choi, Pusan University, South Korea 3:40 – 5:45 pm Oral Presentations Tomokazu Sano, Osaka University, Japan #902: Ultrafast Lattice Dynamics of Femtosecond Laser-driven Shocked Iron Probed with XFEL Fatigue Life Xiaoxu Deng, Shanghai Jiao Tong University, China #836: Investigation on the Pressure of Laser-induced Shock Wave with Condensed Matter Analytical Method José L. Ocaña, Polytechnical University of Madrid and UPM Laser Center, Madrid, Spain#824: #824: Analysis of Induced Surface Modifications Effects on the Electrochemical Behaviour of LSP- Treated Metallic Alloys INVITED Uroš Trdan and Janez Grum, Faculty of Mechanical Engineering, Ljubljana, Slovenia #896: Enhancement of Microstructural, Mechanical and Tribological Properties of Al-Mg-Si alloy by LSP Process Hitoshi Soyama, Tohoku University, Sendai, Japan #837: Suppression of Crack Propagation of Duralumin by Cavitation Peening
5:45 pm Bus to return to Kingsgate Conference Center
6:15 pm Bus to depart Kingsgate Cincinnati Reds Baseball Game (Optional) Thursday, May 14
8:00 am – 5:00 pm Conference Registration...... 4th Floor, TUC
8:00 – 8:30 am Light Breakfast...... Great Hall, TUC
SESSION 10: RELATED PROCESSES AND PHENOMENA Chair: Hitoshi Soyama, Tohoku University, Sendai, Japan 8:30 – 9:00 am Keynote Presentation...... Great Hall, TUC Professor Young-Sik Pyun, Sun Moon University, Republic of Korea #870: Fatigue Characteristics of UNSM-treated SAE52100 Bearing Steel
9:00 – 10:20 am Oral Presentations INVITED Auezhan Amanov, Sun Moon University, Republic of Korea #872: A Comprehensive Review of Nanostructured Materials by Ultrasonic Nanocrystal Surface Modification Technique Seky Chang, Korea Railroad Research Institute, Republic of Korea #820: Wear and Fatigue Behavior of Rail By UNSM Treatment Young-Sik Pyun, Sun Moon University, Republic of Korea #875: Rotary Bending Fatigue Properties of Inconel 718 Alloys by Ultrasonic Nanocrystal Surface Modification Technique Michael Kattoura, Vijay Vasudevan, University of Cincinnati, United States #1017: Effects of UNSM and LSP on Fatigue Life of IN718+ Superalloy
10:20 – 10:45 am Break...... Great Hall, TUC
8 SESSION 11: FUNDAMENTAL MECHANISMS, MICROSTRUCTURE AND PROPERTIES Chair: Tomokazu Sano, Osaka University, Japan 10:45 am – 12:10 pm Oral Presentations
INVITED Yiliang Liao, Department of Mechanical Engineering, Purdue University, NV, United States #1008: The Mechanisms of Thermal Engineered Laser Shock Peening for Enhanced Fatigue Performance Vijay Vasudevan, University of Cincinnati, United States #936: Microstructure, Residual Stress and Property Changes in Metallic Alloys Induced by Advanced Mechanical Surface Treatments Kristina Langer, AFRL/RQSV, United States #893: Laser Peening for Surface Enhancement of Thin Aluminum Structures Sun Yaofei, Shanghai Jiao Tong University, China #873: Experimental Study of Laser Shock Peening on ASME SA240 Type 304 Stainless Steel Subjected to Different Initial States
12:10 – 12:15 pm Poster Introductions (#884, #895)
12:15 – 1:15 pm Lunch...... Stadium View Cafe
SESSION 12: ENGINEERING APPLICATIONS AND LIFE PREDICTION Chair: Dr. Kristina Langer, Air Force Research Laboratory, United States 1:15 – 1:45 pm Keynote Presentation...... Great Hall, TUC Pete Caruso, Lockheed Martin Aeronautics Company, United States #930: Structural Certification of Laser Peening for Safety Critical Aluminum Forgings
1:45 – 3:10 pm Oral Presentations INVITED Dong Qian, University of Texas at Dallas, United States #892: A Simulation Study on Enhanced High Cycle Fatigue Life of LSP using Extended Space-Time Finite Element Method Thomas Spradlin, Air Force Research Laboratory, United States #894: Predictive Crack Growth Technique for Laser Peening Process Development Mitchell Leering, University of the Witwatersrand, South Africa #851: Laser Shock Peening to Recover Fatigue Life of Flawed Friction Stir Welded Joints Niall Smyth, Coventry University, Coventry, United Kingdom #934: Effect on Fatigue Life of LSP Induced Residual Stress in the C(T) Specimen: experiments and prediction models
3:10 – 3:30 pm Break...... Great Hall, TUC
SESSION 13: FUNDAMENTAL MECHANISMS AND PROPERTIES Chair: Janez Grum, Faculty of Mechanical Engineering, Ljubljana, Slovenia 3:30 – 4:50 pm Oral Presentations INVITED Daniel Glaser, University of the Witwatersrand, South Africa #860: Laser Shock Peening for Stress Relaxation of Laser Beam Welded AA6056-T4 Mohammad Karim, University of Texas at Dallas, United States #890: Integrated Multiscale Simulation Approach to Laser Shock Peening Process Hamidreza Karbalaian, University of Tehran, Iran #881: Investigation on Effects of Thickness and Boundary Layer Conditions in Laser Shock Peening by FEM
9 Stefano Coratella, Coventry University, United Kingdom #839: Evaluation of Residu al Stresses in Double Peened Thin Samples with Hole-Drilling and Synchrotron X-Ray Techniques
5:00 pm Bus to return to Kinsgate Conference Center
5:45 – 9:30 pm Bus to depart for B&B Riverboat Dinner Cruise...... B&B Riverboats Friday, May 15
8:30 am – 1:00 pm Conference Registration...... 4th Floor, TUC
8:30 – 9:00 am Light Breakfast...... Great Hall, TUC
SESSION 14: ENGINEERING APPLICATIONS AND CORROSION PROPERTIES Chair: Seetha Ramaiah Mannava, University of Cincinnati, United States 9:00 – 9:30 am Keynote Presentation...... Great Hall, TUC Paul Crooker, EPRI, United States #1016: Peening Surface Stress Improvement to Mitigate Stress Corrosion Cracking in Pressurized Water Reactors
9:30 – 11:00 am Oral Presentations Uroš Trdan and Janez Grum, Faculty of Mechanical Engineering, Slovenia #897: Investigating the LSP effects on initiation and propagation of pitting corrosion by means of acoustic emission and electrochemical methods Abhishek Telang, University of Cincinnati, United States #939: Effects of Laser Shock Peening on SCC behavior of Alloy 600 in Tetrathionate Solution and High Temperature Pure Water Norihito Sibuya, SINTOKOGIO, LTD, Japan #946: The Effect of Peening for Stress Corrosion Cracking on Hot Work Tool Steel R. Sundar, Raja Ramanna Centre for Advanced Technology, India #865: Oblique Laser Peening of Interior of 304 Stainless Steel Tube for Enhanced Stress Corrosion Cracking Resistance
11:00 – 11:15 am Break...... Great Hall, TUC
SESSION 15: FUNDAMENTAL MECHANISMS AND PROPERTIES Chair: Y S. Choi, Pusan University, South Korea 11:15 – 12:15 pm Oral Presentations Michael Fitzpatrick, Coventry University, Coventry, United Kingdom #818: Use of Neural Networks in Laser Peening Rohit Jagtap, Vijay Vasudevan, University of Cincinnati, United States #950: The Effect of Ultrasonic Nanocrystal Surface Modification on Residual Stress, Microstructure and Fatigue Properties of a Low-Modulus Beta Titanium TNTZO Alloy Marco Pavan, Coventry University, United Kingdom #899: Neutron Diffraction Evaluation of Residua Stress in a PH13-8Mo Round Bar after Laser Shock Processing
12:15 – 1:15 pm Closing Panel...... Great Hall, TUC
1:15 – 2:00 pm Tour CEAS LSP Center (Optional)...... Meet at 4th Floor Lobby, TUC 10 Posters
Monday, May 11 - Thursday, May 14 Great Hall, TUC
Yongxiang Hu, Shanghai Jiao Tong University, China # 830: Modeling of Laser Peen Forming with Prestress by Eigenstrain Method
Gilberto Gomez Rosas, Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Mexico #843: The Effect of Laser Shock Peening on the Low Cycle Fatigue Behavior of Superferritic Stainless Steel
Bilal Ahmad, Open University, United Kingdom #847: Hardness and Surface Profiles of Laser Peened Marine Butt Welds
Hongchao Qiao, Shenyang Institute of Automation, Chinese Academy of Sciences, China #856: The Effect of Laser Peening on Fatigue Life of Ti17 Titanium Alloy
Gilberto Gomez Rosas, Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Mexico #868: Laser Shock Processing to Improve Ti6AL-4V Surface Properties
Auezhan Amanov, Sun Moon University, South Korea #869: State-of-the-Art and Perspectives: Ultrasonic Nanocrystal Surface Modification Technique towards Improving Surface Properties of Hard Ceramics
Chang-Min Suh, Kyungpook National University, South Korea #871: Fatigue Characteristics of UNSM and SP-treated Aluminum A895lloy (A7075-T651) using Ultrasonic (20 kHz) and Rotary Bending (53 Hz) Fatigue Testing Machines
In-Sik Cho, Ambrosia Research Team of EBH Group, Republic of Korea #874: Fatigue Lifetime of AlBC3 Alloy by Ultrasonic Fatigue Testing Machine
Muhammad Kashif Khan, Sichuan University, China #877: Effect of Ultrasonic Nanocrystal Surface Modification on Characteristics of Ti6Al4V up to Very High Cycle Fatigue
In-Sik Cho, Pusan University, Republic of Korea #883: Effect of UNSM on Deformation Behaviors of As-Rolled AZ31 Magnesium Sheet
Young-Sik Kim, Andong National University, Republic of Korea #884: Stress Corrosion Cracking of Alloy 600 for Nuclear Power Plant and UNSM Treatment
Gilberto Gomez Rosas, Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Mexico #895: Laser shock Processing Effects Using Focalized Spot on Duplex Stainless Steel Properties
11 Committee
Chairpersons Conference Related Phenomena Lead Seetha Ramaiah (Manny) Mannava Dr. Hitoshi Soyama University of Cincinnati, OH, USA Tohoku University, Sendai, Japan
Professor Vijay K. Vasudevan Dr. Young-Sik Pyun University of Cincinnati, OH, USA Sun Moon University, Cheonan-Asan, S. Korea
Conference Secretary and Technical Chair Conference Program Committee Professor Michael Fitzpatrick Dr. Domenico Furfari Coventry University, Coventry, UK Airbus GmbH, Hamburg, Germany
Conference Industry Lead Professor, Dr. José L. Ocaña Professor Ramana Grandhi Centro Láser UPM, Madrid, Spain Wright State University, OH, USA Dr. Yuji Sano Conference Events Lead Toshiba, Yokohama, Japan Dr. Kristina Langer Air Force Research Laboratory, WPAFB, Dayton, OH, USA Dr. Tomokazu Sano Osaka University, Osaka, Japan Conference Sponsorship and Exhibits Lead Professor Arif Malik Dr. Janez Grum St Louis University, MO, USA University of Ljubljana, Ljubljana, Slovenia
Conference Administrator Dr. Omar Hatamleh Mrs. Katy Marston NASA, Houston, TX, USA University of Cincinnati, OH, USA
12 13 General Information & Social Events
Sunday, May 10 must be on the boat by 6:30 p.m. Opening Welcome Reception If you prefer to drive to the cruise, the address is: BB The opening welcome reception will be held in the Riverboats, 101 Riverboat Row, Newport, KY 41071. The Grand Ballroom, Salon A located on the 2nd floor of the phone number is, 1-800-261-8586. The Belle of Kingsgate Conference Center from 5: 00 – 7:00 p.m. Cincinnati will dock at 9:30 p.m. Busses will take you Refreshments and a bar will be available. back to the Kingsgate Conference Center.
National Air Force Museum & Dinner at the Engineers Free Apps that are useful to Guide you through Club of Dayton, Tuesday, May 12 Cincinnati: Immediately after morning sessions, attendees should pick up a box lunch from the 4th floor lobby, TUC. You UC Mobile may choose to eat your lunch in the Great Hall or on the Cincinnati.com Things to Do bus. The bus will depart from McMicken Circle at 12:30 Downtown Cincinnati p.m. for the Air Force Museum. The bus will depart the Air Force Museum at 5:00 p.m. and take you to the UCGUEST - Wireless Connection Engineers Club of Dayton for a reception and dinner. The Visitors to the university should select the “UCGuest” reception will begin as soon as you arrive and end at wireless connection. See the IT Knowledge Base articles 6:15 p.m. Dinner will be served at 6:15 p.m. The bus will at listed below for “UCGuest” set-up instructions. depart the Engineers Club of Dayton at approximately 7:30 p.m. The bus will arrive at Kingsgate at 8:45 p.m. 1) From your mobile device or laptop computer, locate the network settings for your device. Wednesday, May 13 2) A list of available wireless network SSID’s will appear; Reds v.s Braves Baseball Game select “UC Guest.” The game will be held at the Great American Ballpark 3) You will be redirected to the “UC Guest Portal” page. beginning at 7:10 p.m. Transportation will be provided 4) On the portal page, input your name and a valid email to and from the ball game. The buses will depart from address. The email address will be your username. Click the Kingsgate Conference Level Lobby located on level 1 the Checkbox to accept the terms of use policy and then on Goodman Street. The bus will begin to depart at 6:15 click “Register.” p.m. If you prefer to drive to the ballpark the address is: 5) You will be redirected to the receipt page. Click “Log In.” Great American Ballpark, 100 Joe Nuxhull Way, Cincinnati, 6) You will be redirected to http://www.uc.edu Ohio 45202. The game will end at approximately 10:00 7) You are now connected to the UC Guest wireless p.m. The bus will depart after the game at the corner of network! 3rd and Main Street. Please note: access is allowed for 8 hours. After the eight Thursday, May 14 hour session expires, the registration process will need Ohio Riverboat Dinner Cruise to be repeated. Enjoy an evening on the Belle of Cincinnati. The flagship of BB Riverboats, the Belle of Cincinnati is a majestic and If you have any questions or require assistance, please ornate beauty. Transportation will be provided to and contact the IT@UC Service Desk at (513)556-4357 or via from. The buses will depart from Kingsgate Conference email at: [email protected] or online instructions at Center on Conference Level Lobby located on level 1 on https://kb.uc.edu/KBArticles/UCGuest-Mobile.aspx Goodman Street. The buses will depart at 5:45 p.m. The Belle of Cincinnati sail time is at 7:00 p.m. All attendees 14 THANK YOU TO OUR SPONSORS
PLATINUM PREMIER
Sintokogio, LTD.
GOLD RESERVE
Airbus
American Stress Technologies, Inc.
Coventry University
DesignMecha
University of Cincinnati CEAS
THANK YOU TO OUR EXHIBITORS
RPMC Lasers Inc.
University of Cincinnati Research Institute 15 ORAL Abstract #1015 Laser Shock Peening as Surface Technology to extend Fatigue Life in Metallic Airframe Structures
Domenico Furfari1, Nikolaus Ohrloff1, Elke Hombergsmeier2, Ulrike C. Heckenberger2, Vitus Holzinger2 1Airbus Operations GmbH, Germany 2Airbus Group Innovations, Germany
The use of surface technologies inducing residual stresses can be employed in aeronautical industry as technologies to ensure salvage for identified hot spots in terms of fatigue and crack growth performance. Degradation processes, such as fatigue, limit service lives of aircraft structures. Technologies and methodologies that improve the resistance of structures to these degradation processes are of benefit to the aircraft industry in terms of extending the service life of the structure and thus reducing maintenance costs. An emerging technology is Laser Shock Peening, which can be used in lieu of conventional Shot Peening to introduce residual compressive stresses to a metallic structure. This engineering field can be identified as Residual Stresses Engineering aiming at improving the economical and ecological impact of an aging fleet as well as of future aircraft structures by controlling the residual stresses. This paper provides an overview how this technology can enhance fatigue and crack growth for different metallic materials commonly used in aircraft structures: ranging from Al alloys (2024-T351, 7010-T7451, 7050-T7451) to Precipitation Hardened Stainless Steel X3CrNiMoAl13-8-2. The depth of the compressive residual stresses is controlled by the laser peening parameters to obtain the “desirable” residual stress profile with the aim to inhibit fatigue crack initiation and crack propagation as function of the thickness. Through thickness compressive residual stresses can be obtained treating the two opposite surfaces of Al sheets (i.e. Al2024 and Al7050) up to a thickness of 6mm, controlling the extension of the tensile residual stresses (auto balanced stresses) outside the processes areas to avoid undesirable increase of stresses at other critical locations. Both Al2024- T351 clad and unclad material (2mm thick) where laser peened and fatigue tested under constant amplitude loading showing the capability to slow down through thickness crack growth when the crack front crossed the compressive residual stress field. It was possible to obtain through thickness compressive stresses firing the laser directly onto the Al clad layer at the surface of the specimens without prior clad layer removal. The residual stress field induced by the laser shock peening process was characterized with hole drilling technique as well as non-destructive testing such as X-Ray Diffraction and Synchrotron diffraction. Tests on CCT (Centre Crack Tension) specimens made of Al2024-T351 have shown a dramatic reduction of the crack propagation rates (an order of magnitude compared with reference material) at a stress intensity factor ranging from 30MPam1/2 to 50MPam1/2. Most works on LSP have utilized a Neodym-YAG laser with its fundamental wavelength of 1064 nanometers in the near infrared or Neodym glass lasers (fundamental wavelength at 1054 nanometers) in combination with an applied absorption/insulation layer (usually a thin aluminum foil). This additional Al layer, which vaporizes during the laser pulse forming the plasma pressure and the consequent pressure shock wave travelling into the material, is also used to prevent the surface from melting or being damaged during peening (as a sort of sacrificing layer). When the laser process was used without the prior application of the Al ablative layer (i.e. laser peening onto bare material) the status of the surface was studied and it was found that the thermally affected layer caused by the high temperature during the peening (although only for a duration of 20 nanoseconds) left the first 5-10µm of material without compressive residual stress or slightly in tension. A laser peening coverage above 300% brought back the compressive residual stresses at the near surface of the treated material. For high production rates or to make the application of laser shock peening in some specific aircraft components economical more attractive it could be a valid solution to carry out the treatment without ablative coating which is normally a manual operation slowing down the manufacturing rate significantly. Surface treatments such as Chromic Acid Anodizing (CAA) and Tartaric Sulfuric Anodizing (TSA) are typical surface protections applied in Al structures to prevent from corrosion damages. Structural coupons made of Al7050-T7451 and Al7010-T7451 of 30 mm
1 16 ORAL Abstract #852 Laser Shock Peening for Fatigue Crack Retardation in Airframe Structures
D. van Aswegen1,2, C. Polese1,2, S. Taddia3, and E. Troiani3 1 School of Mechanical, Industrial and Aeronautical Engineering, 2 DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, 2000, South Africa 3 University of Bologna, Via Fontanelle 40, Forlì, 47121, Italy
Fatigue damage and the consequences thereof on metallic airframe structures is a serious structural design and maintenance concern. One possible method of controlling the growth rates of fatigue cracks in metal structures and hence extending fatigue life is to introduce a compressive residual stress field into key areas of highly stressed components.
The Laser Shock Peening (LSP) process was used to introduce compressive residual stress fields in 1.2mm thick AA2024-T4 sheet to test edge crack configurations. However, the LSP treatment also causes balancing tensile stresses. For this reason the residual stress field needed to be engineered precisely. Laser parameters (Power Intensity [GW/cm2] and Coverage [spots/cm2]) as well as the peened region geometry (rectangular strip of 10mm or 20mm width) and proximity of the LSP centerline to the plate edge (between 10mm and 20mm) and to the initial crack tip need to be varied to determine the effects on the resulting residual stress field. Power intensities between 1.5GW/cm2 and 2.5GW/cm2 and coverages of 100-500 spots/cm2 were selected based on initial processing trial runs on the same material. Initial analytical models were used to determine possible effective geometric parameters, assuming a Terada residual stress profile [1]. Samples were also processed on the front and back surfaces to determine the effect of single and double sided peening.
The residual stress fields have then been characterised using the Synchrotron X-Ray Diffraction (XRD) facilities at Elettra, Italy. Residual stresses were measured across the peened strip in order to characterise the residual stress profile experienced by the crack tip as it propagates through the plate. The stresses were measured at three energy levels (12, 15, and 18 keV) providing stress data at 40, 80, and 120 micron depths below the front and back surfaces of the samples.
(a) LSP Region Plate Edge (b) LSP End Plate Edge 80 40 60 20 40 0 20 0 -15 -10 -5 -20 0 5 10 15 -20 0 1 2 3 4 5 6 7 8 9 10 -40 -40 -60 -60 -80 -80 Single Sided Front -100 Single Sided Back -100 -120 -120 -140 Double Sided Front 12keV [40micron depth] -140 -160 Double Sided Back 15keV [80micron depth] -180 -160 18keV [120micron depth] Resdiual Stress [MPa] -200 -180 -220 Distance from LSP Centerline [mm] -240 Distance from LSP Centerline [mm]
Fig.1. (a) Residual stress profile across a 10mm wide LSP strip at 3 depths (stresses measured perpendicular to the crack path). (b) Residual stress profiles for the front and back surfaces of single and double sided LSP processed samples, from the LSP centreline to the plate edge. Figure The analytical model indicates that Terada stress fields created with selected parameters will slow down the growth rate of a crack propagatingFigure through the peened region. The measured stress profiles were similar to these Terada estimates, therefore similar results were obtained when the experimental stresses were input into the model. As expected a higher magnitude compressive residual stress showed to have a greater effect on slowing the growth of a fatigue crack. However the initial proximity of the peened region to the crack tip can play a major role in fatigue life due to the crack being accelerated in the tensile region. Experimental fatigue crack propagation tests have also been carried out to validate the analytical fatigue life predictions.
[1] H. Terada, “Stress Intensity Factor Analysis and Fatigue Behavior of a Crack in the Residual Stress Field of Welding”, Journal of ASTM International, vol. 2, no. 5 (2005).
17 ORAL Abstract #1012 Smart Surface Technology Development for Aerospace, Industrial and Biomedical Systems
1 1 1 1 1 S. R. Mannava , Vijay K. Vasudevan , Abhishek Telang , Amrinder Gill , Gokul Ramakrishnan , 1 1 2 3 3 4 Sagar Bhamare , Yixiang Zhao , Chang Ye , Dong Qian , Zhong Zhou , Hitoshi Soyama , Y-S. 5 Pyun 1Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA 2Department of Mechanical Engineering, University of Akron, Akron, OH 3Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 4Department of Nanomechanics, Tohoku University, Sendai, Japan 5Department of Mechanical Engineering, Sun Moon University, Cheonan-Asan, S. Korea
Main author email address: [email protected]
Laser shock peening (LSP), ultrasonic nanostructure surface modification (UNSM) and cavitation shot less peening (CSP) are some of the latest novel surface treatment technologies. An Ohio Center for Laser Shock Processing for Advanced Materials and Devices (UC LSP Center) has been established at University of Cincinnati to explore these technologies for industrial applications. The center’s vision is to advance the state-of-the art in surface engineering to enhance the reliability and service lives of critical components in aerospace, industrial and biomedical systems and create a pipeline of trained scientists and technologists for industries. The center is fully equipped with LSP, SP and UNSM equipment to generate favorable compressive residual stresses and near-surface microstructural changes; and the systems to characterize the processed surfaces to establish topography, residual stress, micro/nano hardness, microstructure and electro-chemistry; and also systems to establish the effects of these processes in fatigue, corrosion, SCC, corrosion & SCC fatigue, fretting fatigue, fretting wear and galling. The center is managed by a team of experts in materials science, processes and simulations & modeling. To date we have graduated several PhD and Master’s students. We are actively engaged on several industrial research and Government funded projects. During presentation industry collaborative research opportunities will be discussed.
18 ORAL Abstract #907 Fatigue strength of high strength Al alloy in high humidity condition
Y.Kobayashi1, T. Tsuji1, andN. Kawagoishi2 1SINTOKOGIO, LTD. Blast business division Blast technology group, Process technology team 180-1, Komaki, Ohgicho, Toyokawa, Aichi, Japan 2Faculty of Engineering, Daiichi Institute of Technology, Japan
email address: [email protected]
Aluminum alloy are using for aircraft and auto motive parts. Because, it has good mechanical property such as high strength and light weight.But, aluminum alloy are easy to corrode in high humidity condition. As a result, in the case of air craft cabin, high humidity condition is never permit. Thus, the passenger must endure unpleasant environment.If we obtain higher fatigue strength on aluminum alloy, we can get comfortable environment on long fright. Therefore, we investigate the peening effect to aluminum alloy and the fatigue strength of aluminum alloy in high humidity condition. In this research, the residual stress distributions are reported that are obtainedvariouscondition of shot peening and laser peening on A7075. In addition, fatigue strength is investigated on A2017in high humidity condition.
Fig. 1 Residual distribution by shot peening and laser peening. 㻌 Fig.2 S-N curve in High humidity condition㻌
Fig.1 shows residual distribution of peened A7075 that were applied several conditions of shot peening and laser peening. The maximum residual stress of laser peened specimen is 1.5times of shot peened specimen. And, the crossing point was deeper than shot peened specimen.
Fig.2 shows result of fatigue strength on shot peened material in various humidityconditions [1]. On the EP specimen, the fatigue strength is significantly down in high humiditycondition.In the comparison with shot peened specimen, the fatigue strengthis significantly increasing. In addition, the fatigue strength of shot peened specimen does not depend on humidity value. As a result, peening technology affect to fatigue strength in fatigue strength effectively.
[1] N. Kawagoishi and Q. Chen, K. Kariya, T. Nagano, “Effect of humidity on fatigue properties of shot-peened High Strength Al Alloy,”The Twelfth International Conference on Shot Peening (2014).
19 ORAL Abstract #1009 Fatigue crack retardation in Laser Shock Peened high strength steel
E. Hombergsmeier1, V. Holzinger1, U. Heckenberger1, W. von Bestenbostel1, D. Furfari2, N. Ohrloff2 1Airbus Group Innovations, Airbus Defence and Space GmbH, 81663 Munich, Germany 2Airbus Operations GmbH, 21129 Hamburg, Germany
Highly loaded aircraft components have to fulfil strict fatigue and damage tolerance requirements. For some components besides the crack initiation mainly the fatigue crack propagation behaviour is the driving design criteria. To improve the crack propagation behaviour of a component several methods are known or have been described in literature. For thick structures mainly the introduction of compressive residual stresses is beneficial.
In this paper the potential of compressive residual stresses induced by Laser Shock Peening (LSP) is investigated using high strength steel (PH 13-8Mo). The effect of the deep compressive stress profile, that LSP provides, up to a depth of 20 % of the material thickness, results in a significant benefit especially in crack propagation after LSP treatment. This was proven under spectrum loading and the retardation effect of a factor of six was confirmed as shown in Fig. 1. The specimens used for this type of test were round bar coupons with a stress concentration factor of 2 subjected to four point bending fatigue at variable amplitude loading condition. The fatigue crack was initiated from an EDM semi-circular surface notch with a depth of 1.27 mm.
as machined LSP
Fig. 1: Crack propagation curve under spectrum fatigue; as machined versus LSP
Additionally the effect of laser shock peening without ablative coating and subsequent fine surface machining as well as peening with ablative layer without surface machining has been investigated assessing the fatigue behavior of un-notched flat coupons.
Furthermore the effect of machining after laser shock peening to improve the surface quality and obtain tight tolerances and the possibility of relaxation of residual stresses during fatigue cycling was analysed. Finally the crack retardation was confirmed by striation counting on the fracture surface. The measurement of residual stresses was performed on the surface by X-ray diffraction and the depth profile by incremental hole drilling as well as by neutron diffraction.
20 ORAL Abstract #853 Reduction of Cavitation Erosion by Laser Peening* Lloyd Hackel1, Serena Marley, andAlexander Rubenchik2 1Curtiss Wright Corporation, 7655 Longard Rd., Livermore CA 94551 2Lawrence Livermore National Laboratory, Livermore CA [email protected]
Cavitation, the collapse of air bubbles, is a mechanismin fluidsthatgeneratesundesiredmaterialerosion in propellers, rudders, pumpimpellers and valves andpiping. As liquids flow throughregions of low pressure bubblescanform due to the concentration of dissolvedgases and the reduced pressure. As theliquidre-enters areas of higher pressure the bubbles collapse non-symmetrically on the surface generatingfast jets of liquidwhichimpingeon nearby surfaces and aftermany impactsbegin to fatigue-spall the surfaceresulting in materialerosion. The generallyacceptedexplanation of cavitation damage isthus as follows [1-3] : Repetitive stresses due to the bubble collapse cause local surface flexing and eventuallyresult in local cracking and fatigue failuremanifested as the detachment or flaking off of smallpieces of material. The erosiongenerates stress risers leading to broaderfatigue cracking and more rapiderosion.
Figure 1 Laser peening biases stress to anegativestarting Figure 2. Weightlossrate of a laser peened sampleof Ti-6/4 point therebyreducing the operational stress when a exposed to ultrasonic cavitation erosionisreduced by 400% vs component isloaded an unpeened sample.
When asampleis laser peened the imprinted compressive stress effectivelyincreases the ultimatetensile stress as illustrated inFigure 1 with a resultingincrease in incubation time (number of pulsesbeforeerosionbegins). Laser peeningplasticallydeforms and leavesresidual compressive stress deepinto the metal’ssubsurface. This deep stress greatlysuppresses fatigue failure and since cavitation erosionis a fatigue drivenphenomenonreducedtensile stress reduces the erosion rate. Figure 2 shows results of twocavitated 12 mm x 60 mm x 5 mm samples of Ti6/4. One samplewas laser peened at an irradiance of 10 GW/cm2, pulse duration 18 ns, 10 ns pulse rise time and with one layer of peening. The peening wasdonewithout use of an ablative layerresulting in a thin (10-20 m) recast layer thatisrapidlyremoved by the cavitation process. The othersamplewasleft as fabricatedwithout peening.The sampleswerealternatelyimmersed in a water tank and exposedat astandoff of 0.240 inchesto the cavitation generated by anultrasonicallydriven tip for equalperiods of time and with respective tipsoperatedwithidenticalrun scenarios. Figure 2 shows the 400% differenceobservedbetween the weightlossrates of the laser peened vs.unpeenedsamples. Weattributesome of the initial weightloss to ultrasoniccleanup of eachspecimen and suggestthatthe rate-of-lossis a betterindicator of the longertermerosion and thusbenefit of the compressive stress generated by the laser peening. We are currently running longertermexposures and othermaterialsincluding Ni-Al-Bronze an important material for marine applications.
*Work performed in part underthe auspices of USDOE by the Lawrence Livermore National Laboratory, Contract DE-AC52-07N
REFERENCES: 1.C.Brennen .Cavitation and bubbledynamics. Oxford UniversityPress 1995 2. R.Knapp,J.Daily and F.Hammit Cavitation. McGrow Hill, New York 1970 3. G.SpringerErosion by the liquid impact. J. Wiley& Sons 1976
21 ORAL Abstract #827 Effects of Laser Peening on Friction Characteristics of Aluminum Alloy
J. S. Park, I. K. Yeo, andS. H. Jeong School of Mechatronics, Gwangju Institute of Science and Technology 1 Oryong-dong Buk-gu, Gwangju 500-712, Republic of Korea
Email: [email protected]
This paper reports the experimental results of laser peening ofan aluminum alloy using a Nd:YAG laser (wavelength=532 nm, pulse width=8 ns, repetition rate=10 Hz, diameter=11 mm). The laser beam was focused with a plano-convex lens (focal length=140 mm) to a spot diameter of 2.1 or 1.6 mm at the sample surface, depending on the laser irradiance used in experiments, and each spot was irradiated with 50% overlapping. No coating was applied on the aluminum surface. The hardness of laser peened surface was found to increase up to about 17% (irradiance=4 GW/cm2) from that of original material. The friction characteristics of laser peened aluminum surface was tested using a friction-wear tester (straight motion, frequency=15 Hz, stroke=10.8 mm, lubrication=SAE 5W 30, load= 50~150 N normal, duration=61 min). The results showed that friction coefficient of laser peened surface is significantly lower than that of the original surface, 20~40% depending on applied load. Also, the roughness of laser peened surface decreased after friction-wear test, whereas that of the original surface increased significantly. When the particles produced during the friction-wear test was collected and filtered, it was found that large particles of 10~40 m size were produced from the original surface while particles less than 10 m size only were produced from the peened sample (see Fig.1) after friction-wear test. The particle size is considered to be closely related to the hardness of sample surface [1]. The relation between friction characteristics of the peened surface and the measurement results including hardness, surface roughness, particle size are to be discussed.
(a) (b)
Fig. 1. Scanning electron micrographs of the particles produced from the (a) original and (b) laser peened samples after friction test.
[1] D.H.Hwang, D. E. Kim and S. J. Lee, “Influence of wear particle interaction in the sliding interface on frictionof metals,”Wear, vol. 225-229, 427-439 (1999).
22 ORAL Abstract #933 The DiPOLE Laser –Efficiently Delivering Very High Energy Pulses with High Average Power
Dr Ric Allott
Business Development Manager, Central Laser Facility, STFC Rutherford Appleton Laboratory, UK
There is increasing demand for efficient pulsed lasers operating at high energy and high repetition rate for a range of applications including, pump sources for high-intensity PW-class amplifiers and direct sources for materials processing techniques such as Laser Peening or exploring high energy density physics phenomena. To meet this demand, the Central Laser Facility (CLF) is developing an efficient high pulse energy diode-pumped solid-state laser (DPSSL) architecture (called DiPOLE) based on cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier technology, capable of amplifying ns pulses to kJ pulse energies. Recently, a scaled-down prototype amplifier has met its design specification delivering 10 J pulses at 1030 nm and 10 Hz repetition rate with an optical-to-optical conversion efficiency of 21%. Furthermore, long term shot-to-shot energy stability of 0.5% rms at 7 J output was demonstrated during extended operation over 48 hours, corresponding to almost 2 million shots. Following on from this success a larger scale laser, DiPOLE100, is being built at the CLF that will confirm the scalability of the cryo- cooled amplifier concept. The current laser system is being built for the HiLASE project in the Czech Republic and will deliver 100 J temporally-shaped ns pulses at 10 Hz with a fully integrated control system.
Laser peening represents a market in which the DiPOLE system can offer a real benefit. The high energy and high repetition rate of the DiPOLE lasers (pulse energy of 100J and a pulse rate of 10Hz), allows for very large shot per area processing. Thus use of the DiPOLE laser can significantly increase throughput and quality. Furthermore due to the use of diode pumping these lasers offer an increased lifespan, reduced power requirements and lower maintenance.
This paper describes the key features and benefits of DiPOLE and provides performance results from DiPOLE100, with particular emphasis on the active temporal and spatially-shaped front end, intermediate 10 J cryogenic amplifier and the main 100 J cryogenic power amplifier.
23 ORAL Abstract #864 ImPACT: A Newly-funded Japanese National Program to Realize Ultra-compact Power Lasers
Y. Sano1 1Impulsing Paradigm Change through Disruptive Technologies Program (ImPACT) c/o Japan Science and Technology Agency (JST) K's Gobancho, 7, Gobancho, Chiyoda-ku, Tokyo, 102-0076 Japan
The Japanese Government has established ImPACT (Impulsing Paradigm Change through Disruptive Technologies) program constituting “a new system that will create disruptive innovation bringing about change in society” with the purpose of transforming mindsets of the R&D community, converting from introversion to the spirit of challenge, and from a go-it-alone orientation to open innovation. Twelve program managers (PMs) were designated last year and each proposed a five-year program through Japanese FY2018 (http://www.jst.go.jp/impact/en/index.html). As shown in Fig. 1, the developments toward the realization of ultra-compact power lasers and their applications are the key elements of the program entitled “ubiquitous power laser for achieving a safe, secure and longevity society”. The microchip lasers will extend the horizons of laser applications such as peening, forming, cleaning, laser- ultrasonics, etc. and the compact XFELs will be used for the real-time diagnosis of their processes. The outline of the ImPACT program, R&D structure, schedule, current status, etc. will be presented.
Fig. 1. R&D structure of the ImPACT program, “ubiquitous power laser for achieving a safe, secure and longevity society” (http://www.jst.go.jp/impact/en/program03.html).
24 ORAL Abstract #831 New possibilities of efficient peening by using diode-pumped kW-class lasers
J. Brajer1,2, R. Svabek1, D. Rostohar1, T. Mocek1 J. Madl2, Z. Pitrmuc2 1HiLASE Centre, Institute of Physics ASCR, Za Radnici 828, 25241 Dolni Brezany, Czech Republic, Europe 2Department of Machining, Process Planning and Metrology, Czech Technical University in Prague, Technicka 4, 166 07 Prague 6 Dejvice, Czech Republic, Europe
The aim of the HiLASE project is to serve as a platform for development of new lasers based on thin-disk laser amplifiers and cryogenically cooled multi-slab laser amplifiers as well as to build state of the art application laboratory. In this paper, some of preliminary selected applications are mentioned. The application laboratory, nevertheless, will be open for any advance investigations selected by scientific community or by industrial applications. Efficient application of lasers in the surface treatment of metals requires lasers with high power density over a big spot size and repetition rate [1]. A fully diode-pumped 10 J cryogenically cooled Yb:YAG multislab laser system (with further amplification to 100 J) with pulse duration of 2-10 ns, 10 Hz repetition rate and spot size of 21*21mm2 , developed as a part of the HiLASE project, is expected to start a new era in the laser surface treatments. In this paper, we present the conceptual design of this laser system among others. Additionally, the beam delivery and a further experimental station for material processing, which will be established around this laser, are also discussed. New opportunities of LSP technique offered by the new laser system for the large scale processing are also mentioned. Moreover, the quality and properties of treated surface in the future will be possible to characterize by different methods through very close cooperation with the Czech Technical University in Prague. While station for the LSP treatment in the Czech Republic is still under construction, the cooperation with the institutes which are involved in this technology is established. Our strongest cooperation is with Centro Láser de la Universidad Politécnica de Madrid, Alma Mater University of Bologna and Raja Ramanna Centre for Advanced Technology, Indore, India.
Fig. 1. Comparison of existing and future high energy DPSSL facilities [1].
[1] M. Sawicka, M. Divoky, J. Novak, A. Lucianetti, B. Rus, and T. Mocek, JOSA B, Vol. 29, Issue 6, pp. 1270-1276 (2012) [2] M. Chyla, T. Miura, M. Smrz, P. Severova, O. Novak, S. S. Nagisetty, A. Endo, T. Mocek, Proc. of SPIE, vol. 8780, 87800A-1 (2013) [3] D.C. Brown, I.E.E.E. Journal of Sel. Top. In Quantum Electronics, vol.11, pp. 587-599 (2005) [4] O. Slezak, A. Lucianetti, M. Divoky, M. Sawicka, and T. Mocek, I.E.E.E. Journal of Quantum Electronics, Vol. 49, pp. 960-966 (2013)
25 ORAL Abstract #866 New High Power Laser Peening System
Jeff Dulaney
LSP Technologies, President and CEO, 6145 Scherers Pl, Dublin, Ohio 43016
LSP Technologies has a history of firsts in the laser peening industry. LSPT was the first company to commercially provide laser peening services and the first company to design and deliver laser peening equipment to an OEM. LSP Technologies began providing laser shock peening job shop services using an LSPT, custom-designed, 50J, 5W system in 1996. We delivered four laser peening systems to GEAE in Cincinnati in the late 90s, which GEAE used to be the first company in history to adopt laser peening commercially. LSPT continued to improve the speed and efficiency of our laser peening systems over the years, introducing a 50J, 20W system in 1998 and a 50J, 40W system in the early 2000s. This year, LSP Technologies is introducing another first in the industry: a diode-pumped 10J, 200W LSP system, the Procudo™ 200 (illustrated below).
The new Procudo™ 200 has been installed at LSP Technologies’ facility in Dublin, Ohio and interfaced to a dual- robot peening cell. Photos and video of the system in operation will be presented. Sample performance data will be presented, showing key processing parameters. Operational features and capabilities of the control system will be discussed.
The Procudo™ 200 continues LSPT’s mission to proliferate laser peening technology around the globe by providing high-quality industrial equipment to end users, while reducing processing costs for our job shop customers. This new LSP system is available for purchase or lease.
Procudo™ 200 Laser Peening System
26 ORAL Abstract #1014 Assessing Laser Shock Peening for Stress-Corrosion Cracking and Fatigue Resistance Enhancement of Launchers External Structures
Ghidini, T*.
*ESA, European Space Agency, Product Assurance and Safety Department, Materials Technology Section
Stress corrosion cracking (SCC) has been an issue in the space industry since the days of the Apollo program. Many cases where structural failures of space hardware were caused by stress-corrosion cracking at launch sites can be found in the literature, occurring both in both American and European space programs, and generating substantial costs and delays. Atmospheric water condensation, exposure to coastal environment, typically at launch sites, and the presence of chemical substances such as cleaning fluids or accidentally released substances (e.g. hydrazine, cleaning solvents and hydraulic fluids) can promote stress-corrosion cracking in launchers structures and subsystems. Laser Shot Peening (LSP) is an emerging technique that has been successfully used to introduce compressive residual stresses (therefore minimizing the risk of SCC and improving the fatigue life of the processed materials) into metallic structures with a wide range of possible applications (including aircraft engines and structures, panel forming, nuclear power reactors, steel bridges and medical implants). LPS can be applied as highly repeatable process on aluminum, titanium, high strength steels as well as stainless steels. The present activity has the primary objective of identifying and optimizing the ideal LPS process for improving SCC and fatigue life performances of susceptible materials commonly used for launchers external structures, by introducing quantified, controlled and repeatable compressive residual stresses. It can be used as a suitable method for enhancing, repair or protect from SCC failures sensitive external structures exposed to coastal environment during integration and launch phases. Moreover, the possibility of enhancing the fatigue life of critical structures could lead to significant mass savings and costs reduction especially in recurring products such as launchers. LSP is one of the technologies developed within the frame of a larger program in ESA on Advanced Manufacturing which will also be presented here.
27 ORAL Abstract #859 Residual Stress Improvement of Nickel Base Superalloy Alloy 706 by Laser Peening
I. Chida1, R. Sumiya2, D. Saito2, T. Sawa2, Y. Yoshioka3, D. Kobayashi4, A. Ito4, M. Miyabe4 and Y. Kagiya5
1Toshiba Corporation, 8 Shinsugita-Cho, Isogo-Ku, Yokohama, 235-8523 Japan 2Toshiba Corporation 3Ehime University (ex-Toshiba Corporation) 4Chubu Electric Power Co.,Inc 5Chubu Plant Service Co.,Inc (ex- Chubu Electric Power Co.,Inc)
The first stage wheel discs in 1300℃ gas turbine rotors had an accident in 2003, and inter-granular cracking were observed under highly stressed and damage sensitive locations with less potential for oxidation[1]. This accident was investigated and concluded that main cause was due to the phenomena of stress accelerated grain boundary oxidation, hold-time cracking [2]. However the details were not disclosed yet. Peening process is one of the effective methods to improve the creep and creep-fatigue lives of Alloy 706 by introducing compressive residual stress on the material surface [3]. In this study, laser peening was developed to improve fatigue properties of Ni-base superalloy Alloy 706, and the effects on the material properties were examined. Laser peening is a novel process to induce compressive residual stress on material surface by irradiating focused high-power laser pulses. In this experiment, laser peening was performed under the condition as follows; pulse energy of 200 mJ/pulse, spot size of 0.6mm, pulse number density of 45 pulses/mm2. Several durability tests, such as thermal aging treatment test shown in Fig. 1 and stress aging test shown in Fig.2, were performed under thermal power plant operation conditions, and the effectiveness of laser peening treatment was confirmed.
Fig. 1 Relationship between residual stress and aging time Fig.2 Surface residual stress after thermal and stress aging test
[1] D. Kobayashi, A. Ito, M. Miyabe, Y. Kagiya, Y, Yoshioka, “Crack Initiation Behavior and Its Estimation For a Gas Turbine Rotor Based on the EBSD Analysis”, Proceedings of ASME Turbo Expo 2012, GT2012-68226, Copenhagen, Denmark (2012). [2] Y. Yoshioka, D. Saito, R. Sumiya, K. Ishibashi, S. Ito, D. Kobayashi, A. Itou, M. Miyabe, Y. Kagiya, “Effects of environments and surface conditions on creep and creep-fatigue behaviors of Ni-base superalloy Inconel® Alloy 706”, Proceedings of ASME Turbo Expo 2012, GT2012-68313, Copenhagen, Denmark (2012). [3] R. Sumiya, T. Tazawa, Y. Yoshioka, I. Chida, K. Ishibashi, “ Stress relaxation behavior of laser peened test specimen under thermal aging treatment”, Proceedings of the 3rd International Conference on Laser Peening and Related Phenomena,
28 ORAL Abstract #846 Residual Stresses in Laser and Shot Peened Marine Butt Welds
B. Ahmad1 and M. E. Fitzpatrick2 1Department of Engineering and Innovation, The Open University, Milton Keynes, MK7 6AA, UK 2Faculty of Engineering and Computing, Coventry University, Priory Street, Coventry, CV1 5FB, UK [email protected]
This paper focuses on improvement of the residual stress at the weld toe of marine butt welds made of DH275 steel. In the as-welded condition the weld crown toe of these specimens is identified as the region most susceptible to fatigue cracks [1]. Laser and shot peening was applied to improve the fatigue life of these specimens. Laser peening was examined with respect to the influence of ablative tape and the number of peen layers. Residual stresses are characterised in the longitudinal direction of specimens by the contour method and synchrotron X-ray diffraction.
The contour method provided 2D stress maps at the weld crown toe locations of single V-butt welded specimens. The contour method results were corrected by taking into account the cutting artefacts from the wire electro- discharge machining. Figure 1 shows a contour method stress map for a specimen laser peened with three layers of peening. Synchrotron X-ray diffraction enabled measurement of near surface stresses. Figure 2 shows the average stress profiles as measured by synchrotron X-ray diffraction across the weld near the center width of the specimens. Weld root side
X
Weld crown side
Fig. 1. Contour method stress map along the weld crown toe of a laser peened butt welded specimen.
Fig. 2. Residual stress line profiles measured by synchrotron X-ray diffraction across the weld of laser and shot peened butt welded specimens.
Contour method results showed that laser peening introduced a greater depth of compressive stress as compared to shot peening. Also it indicated the influence of the number of peening layers as well as the importance of measurement location on quality of contour method results. Synchrotron X-ray diffraction results of laser peened specimens showed that the ablative tape in laser peening has increased surface compressive stress which is contrary to the case when laser peening was performed without ablative tape covering. In-addition a variation of residual stress profile across laser peen spots as well as across and along the weld was noticed.
[1] B. Ahmad, M. E. Fitzpatrick, D. Howarth, H. Polezhayeva, J. Przydatek and A. Robinson, ‘‘Residual Stress Measurements and Fatigue Testing of Butt Welds Subjected to Peening Treatments’’, International Institute of Welding, Document Number XIII-2497-13 (2013).
29 ORAL Abstract #821 Effect of Elasto-plastic Material Behaviour on Determination of Laser Shock Peening induced Residual Stress Profiles using the Hole Drilling Method
S. Chupakhin1, N. Kashaev1, and N. Huber1
1Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, Max-Planck-Str. 1, D-21502 Geesthacht, Germany
The Integral Method is widely accepted technique for determination of non-uniform residual stress profiles using relaxation data from hole drilling measurements [1-2]. This Method assumes linear elastic material behavior and is therefore limited to the measurement of residual stresses below 60% of the yield stress [3]. The aim of this study is to investigate effects of elastic-plastic material behavior on the determined residual stress profile when the residual stresses exceed the given 60% limit. To this end, typical compressive residual stress profiles induced by laser shock peening are investigated using finite element simulations followed by an analysis with the Integral Method. The obtained results from the analysis are compared with the residual stress profiles that have been applied to the finite element simulation. An evaluation of the deviation between these two profiles gives detailed insight into the expected error as function of hole drilling depth for residual stress distributions exceeding the commonly assumed limit of 60% of the yield stress. As an additional benefit of the presented approach, it also gives an indication at which range of depth for which the residual stress profile should be corrected to reduce measurement error.
Fig. 1. Equivalent plastic strain distribution created by the presence of the hole
[1] G. Schajer, “Measurement of Non-Uniform Residual Stresses Using the Hole-Drilling Method. Part 1 – Stress Calculation Procedures,” ASME Journal Engineering and Materials and Technology, 110, 338-343 (1988). [2] G. Schajer, “Measurement of Non-Uniform Residual Stresses Using the Hole-Drilling Method. Part 2 – Practical Application of the Integral Method,” ASME Journal Engineering and Materials and Technology, 110, 334-349 (1988) [3] G. Schajer, “Advances in Hole-Drilling Residual Stress Measurements,” Experimental Mechanics, 50, 159-168(2010)
30 ORAL Abstract #858 Effects of laser peening on deformation microstructure evolution and residual stress in TiAl alloy
Qiao Hongchao1, Zhao Jibin1, Lu Ying1, and Zhao Yixiang2 1 Shenyang Institute of Automation Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China 2 Institute of Metal Research Chinese Academy of Sciences, Shenyang, Liaoning 110016, China
Email address: [email protected]
Laser peening is a novel surface treatment process that generates deep compressive residual stresses and microstructural changes and thereby dramatically improves fatigue strength of critical metal aircraft engine parts [1- 5]. The present study was undertaken to develop a basic understanding of the effects of LSP parameters on the deformation microstructural changes, residual stress distributions and texture evolution in TiAl alloy. The microstructure and surface modification of laser shock peened sample are outlined in terms of laser shock peening processing parameters. Depth-resolved characterization of the residual stresses and strains was achieved using X-ray diffraction as well as by hardness. Furthermore, using the whole pattern fitting method the Structure-Texture- Phase- Stress combined analysis can be performed based on the X-ray diffraction patterns collected by area detector. The results showing the relationship between laser peening parameters, microstructure, texture, residual stress distributions and hardness are presented and discussed.
Fig. 1. Reconstructed pole figures of the (001), (110) and (111) reflections fitted on the virgin sample and 9J laser peened sample.
[1] Fairand B P, A.H. Clauer A H, “Laser generation of high-amplitude stress waves in materials,” Journal of Applied Physics, 50, 1497-1502 (1979). [2] Peyre P, Fabbro R, Merrien P, et al., “Laser shock processing of aluminium alloys. Application to high cycle fatigue behaviour,” Materials Science and Engineering A, 210, 102-113 (1996). [3] Rubio-Gonzalez C, Ocana J L, Gomez-Rosas G, et al, “Effect of laser shock processing on fatigue crack growth and fracture toughness of 6061- T6 aluminum alloy,” Materials Science and Engineering A, 386, 291-295 (2004). [4] Montross C S, Wei T, Ye L, et al., “Laser shock processing and its effects on microstructure and properties of metal alloys: a review,” International Journal of Fatigue, 24, 1021-1036 (2002). [5] Cellard C, Retraint D, Francois M, et al., “Laser shock peening of Ti-17 titanium alloy: Influence of process parameters,” Materials Science and Engineering A, 532, 362-372 (2012).
31 ORAL Abstract #844 Physical understanding of the water confined plasma regime for laser shock processing
D. Courapied1, L. Berthe1, P. Peyre1, S. Costil², R. Kromer², J. Cormier3, M. Boustie3
1 PIMM – UMR 8006 CNRS – Arts et métiers ParisTech, 151 Bd de l’Hôpital, 75013 PARIS, France 2 IRTES-LERMPS Institute, UTBM, Belfort Cedex, 90010, France 3 Institut Pprime - Mechanics and Materials Science Laboratory UPR CNRS 3346, ISAE-ENSMA, Téléport 2, 1, avenue Clément ADER BP 40109 86961 CHASSENEUIL – FUTUROSCOPE, FRANCE
When a nanosecond laser irradiation is focused on a metallic target, the laser-matter interaction leads to an intense plasma formation [1-3]. As a response to the plasma expansion, a shock wave is imparted through the target. To improve the pressure load transmitted to the target, a water confinement is the most convenient solution. This additional water layer constrains the plasma expansion and allows the generation of 5 to 10 times higher pressure loads [2, 3]. This water confined regime (WCR) configuration and the resulting shock wave system transmitted to the targets, have already proven their efficiency for material surface processing [4] and, more recently, for laser adhesion test [5].
As the main characteristics of the shock wave (pressure amplitude, time maintain) depend on several parameters, such a pulse shape and duration, energy, wavelength, or water thickness, it is of the higher importance to be able to develop dedicated experiments for characterizing the laser-matter interaction and the resulting shock wave generation in confined regime.
This paper presents recent investigations to describe the physical processes involved during the laser matter interaction in water confinement regime, with a specific focus on the plasma behavior, which is a key-point for optimizing laser-shock driven techniques. Different diagnostics were implemented to observe physical phenomena involved. For instance, a transverse visualization was carried out to observe the plasma time- expansion in WCR whereas VISAR (Velocimetry Interferometer system for Any Reflector) measurements allowed determining the pressure loading P=f(t) generated by the plasma expansion. Disrupting phenomena like plasma breakdown appearance (Fig. 1.) were clearly identified and correlated with pressure levels. It can be concluded that dedicated experimental diagnostics to investigate confined plasmas and laser-shock generation in WCR are an important mean for improving the understanding of LSP, and expanding the range of experimental conditions.
Fig. 1: Cross-section viewing of the WCR interaction area for two different laser intensities [3].
[1] R. Fabbro et al., Physical study of laser produced plasma in confined geometry J. Appl. Phys.68, 775-784, (1990). [2] L. Berthe et al., Shock waves from a water confined laser-generated plasma, Journal of Applied Physics, Vol. 82, n°6, 2826-2832, (1997) [3] A. Sollier et al., Laser-matter interaction in laser shock processing", Proc. SPIE 4831, First International Symposium on High-Power Laser Macroprocessing, 463 (March 3, 2003); doi:10.1117/12.497617; [4]P. Peyre, R. Fabbro, L. Berthe, and C. Dubouchet, J. Laser Appl.8, 135, (1996). [5]L. Berthe, M. Arrigoni, M. Boustie, J. P. Cuq-Lelandais, C. Broussillou, G. Fabre, M. Jeandin, V. Guipont, M. Nivard (2011), State-of- the-art laser adhesion test (LASAT), Nondestructive Testing and Evaluation. 32 ORAL Abstract #823
Hα-Line Characterization of Electronic Density in Plasmas Generated by Laser Shock Processing
C. Moreno-Díaz1, J.A. Porro2,3, A. Alonso-Medina1, C. Colón1 and J.L. Ocaña2,3
1Department of Applied Physics, ETSIDI, Universidad Politécnica de Madrid, Ronda de Valencia 3, 28012, Madrid, Spain. 2Department of Applied Physics and Materials Engineering, ETSII, Universidad Politécnica de Madrid, C/ José Gutiérrez Abascal 2, 28006, Madrid, Spain 3UPM Laser Centre, Universidad Politécnica de Madrid, Ctra. Valencia, km. 7.3, 28031 Madrid, Spain
Main author email address: [email protected] Corresponding author email address: [email protected]
Laser Shock Processing (LSP) is based on the application of a high intensity pulsed Laser beam (I>109 W/cm2; τ<50 ns) on a metallic target forcing a sudden vaporization of its surface into a high temperature and density plasma that immediately develops inducing a shock wave propagating into the material [1]. The reported LSP treatments were performed using a Q-switched Nd:YAG laser with a wavelength of 1064 nm, 10 ns pulse length and 2.5 J per pulse, focused onto a Al 2024 sample.
We report test measurements of the plasma electron density utilizing spectral analysis to the emitted Hα-line. We have compared our results with those obtained in similar experiments in the absence of water. In both cases, the measurements have been made in a range of 2-8 μs after laser pulse at a distance from target of 2 mm. In the last case, the electron density from the optically thin Al II line at 281.62 nm was measured in parallel from the same spectra [2]. As example, in Figure 1 (a), where we present the emission obtained with a time delay of 5 μs after laser pulse, the presence of the hydrogen Hα-line in all conditions studied is observed. In the experiments carried in air, for obtained an estimation of the temperature, were used Boltzmann´s plots, with different species (Mg I, Mg II, Cu I, Cu II,...). See Figure 1 (b).
(a) (b)
Fig. 1. (a) Hα-line emission at 5 μs after laser pulse (b) A section of typical spectra for 278 -286 nm range in air at 5 μs after laser pulse
The agreement between the measured electron density from both the Hα-line and the Al II-line would confirm the reliability of utilizing the Hα-line as an electron density standard reference line in LSP. We have obtained a 17 16 -3 temperature in a range of 17000-11000 K and an electron density in a range of 10 -10 cm at longer delay time.
[1] J.L. Ocaña et al.,”Physical Characterization of Laser Interaction and Shock Generation in Laser Shock Processing: Coupled Theoretical-Experimental Analysis”, AIP Conf. Proc. 1464, 209-218, (2012). [2] C. Colón, G. Hatem, E. Verdugo, P. Ruiz and J. Campos, “Measurement of the Stark broadening and shift parameters for several ultraviolet lines of singly ionized aluminum”, Journal of Applied Physics, 73(10), 4752-4758, (1993).
33 ORAL Abstract #850 Predicting Stress Intensity Factors in Laser-Peened M(T) Samples
D.O. Busse1, P.E. Irving1, and S.Ganguly1
1School of Aerospace, Transportation and Manufacturing, Cranfield University, Cranfield Beds MK 43 0AL
As commonly known the major damage and consequent failure of aircraft damage-tolerant structures are from fatigue crack initiation and propagation. For damage tolerant structures the fatigue crack propagation rate determines the life of a structure corresponding to an inspection interval and presently research in this area is focussed on introduction of compressive residual stress field which would reduce the crack propagation rate and improve the overall life cycle cost of a structure. Compressive stresses reduce the effective stress intensity factor (SIF) range, which according to Elber [1] is the major factor for crack growth rate, and thus significantly retard the crack growth. There are several ways to introduce compressive stress field in a material and laser shock peening [2-18 ] has been identified and explored as the most promising technique to introduce large magnitude near surface and through thickness compressive residual stress state which can have very significant influence on crack retardation and thereby life enhancement. Laser shock peening , is a surface treatment in which short duration laser pulses are impinged on the surface of a metallic sample confined in a laser transparent medium, causing local plastic deformation on and the near surface region of the sample. This constrained localised plastic deformation causes formation of compressive residual stress state near the surface as the elastically deformed region around the plastically deformed zone pushes back. This emerging technology is of great interest especially for the aerospace industry to enhance the structural durability and efficiency of advanced airframes during design and/ or during Maintenance, Repair and Overhaul (MRO). Management of “engineered” RSFs would lead to cost effective advanced airframes structures through weight saving and increase operational lifetime which also will generate potential savings from reduction of non- and recurring costs for the operator. This paper explores the application of laser peening induced “engineered” residual stresses to achieve the greatest reduction of SIFs which would lead to maximising crack propagation life. An extensive study will be performed where the variation of the M(T) samples’ dimensions, applied load level and the location, size and the number of laser peened areas (refer to Figure 1) will be correlated
Figure 2 FE modelling of SIF variation vs. crack length in a laser peened M(T) sample to stress intensity factors for various crack lengths (refer to Figure 2). For this purpose, a detailed Finite Element Model (FEM) of a quarter M(T) sample have been developed and SIFs are calculated by predicting Strain Energy Release Rates (SERR) using the Modified Virtual Crack Closure Technique (MVCCT) [13], including non-linear contact definition between the crack flanks [14] and residual stress field introduction capability. Prior to residual stress field introduction into the SIF MVVCT model, a methodology of reconstructing a complete residual stress field in Abaqus FEA software from limited experimentally determined residual stress data will be Figure 1. M(T) evaluated. The outcome of this study will be analysed in light of a potential effect on the crack life of such specimens. sample and parameters [1] ELBER W (1970), "FATIGUE CRACK CLOSURE UNDER CYCLIC TENSION", Engineering Fracture Mechanics, vol. 2, no. 1, pp. 37-.45 investigated by [2] Peyre, P., Fabbro, R., Merrien, P. and Lieurade, H. P. (1996), "Laser shock processing of aluminium alloys. Application to high cycle fatigue behaviour", Case Study Materials Science and Engineering A, vol. 210, no. 1-2, pp. 102-113. [3] Rubio-González, C., Ocaña, J. L., Gomez-Rosas, G., Molpeceres, C., Paredes, M., Banderas, A., Porro, J. and Morales, M. (2004), "Effect of laser shock processing on fatigue crack growth and fracture toughness of 6061-T6 aluminum alloy", Materials Science and Engineering A, vol. 386, no. 1-2, pp. 291-295. [4] Gomez-Rosas, G., Rubio-Gonzalez, C., Ocaña, J. L., Molpeceres, C., Porro, J. A., Chi-Moreno, W. and Morales, M. (2005), "High level compressive residual stresses produced in aluminum alloys by laser shock processing", Applied Surface Science, vol. 252, no. 4, pp. 883-887. [5] Rubio-González, C., Felix-Martinez, C., Gomez-Rosas, G., Ocaña, J. L., Morales, M. and Porro, J. A. (2011), "Effect of laser shock processing on fatigue crack growth of duplex stainless steel", Materials Science and Engineering A, vol. 528, no. 3, pp. 914-919. [6] Smith, P. R., Shepard, M. J., Prevéy III, P. S. and Clauer, A. H. (2000), "Effect of power density and pulse repetition on laser shock peening of Ti-6Al-4V", Journal of Materials Engineering and Performance, vol. 9, no. 1, pp. 33-37. [7] Fairand, B. P., Clauer, A. H., Jung, R. G. and Wilcox, B. A. (1974), "Quantitative assessment of laser-induced stress waves generated at confined surfaces", Applied Physics Letters, vol. 25, no. 8, pp. 431-433. [8] Ocaña, J. L., Porro, J. A., Morales, M., Iordachescu, D., Díaz, M., Ruiz De Lara, L., Correa, C. and Gil-Santos, A. (2013), "Laser shock processing: An emerging technique for the enhancement of surface properties and fatigue life of high-strength metal alloys", International Journal of Microstructure and Materials Properties, vol. 8, no. 1-2, pp. 38-52. [9] Rubio-González, C., Gomez-Rosas, G., Ocaña, J. L., Molpeceres, C., Banderas, A., Porro, J. and Morales, M. (2006), "Effect of an absorbent overlay on the residual stress field induced by laser shock processing on aluminum samples", Applied Surface Science, vol. 252, no. 18, pp. 6201-6205. [10] Gomez-Rosas, G., Rubio-Gonzalez, C., Ocaña, J. L., Molpeceres, C., Porro, J. A., Morales, M. and Casillas, F. J. (2010), "Laser Shock Processing of 6061-T6 Al alloy with 1064 nm and 532 nm wavelengths", Applied Surface Science, vol. 256, no. 20, pp. 5828-5831. [11] Sánchez-Santana, U., Rubio-González, C., Gomez-Rosas, G., Ocaña, J. L., Molpeceres, C., Porro, J. and Morales, M. (2006), "Wear and friction of 6061-T6 aluminum alloy treated by laser shock processing", Wear, vol. 260, no. 7-8, pp. 847-854. [12] Tan, Y., Wu, G., Yang, J. -. and Pan, T. (2004), "Laser shock peening on fatigue crack growth behaviour of aluminium alloy", Fatigue and Fracture of Engineering Materials and Structures, vol. 27, no. 8, pp. 649-656. [13] Krueger, R., “The Virtual Crack Closure Technique: History, Approach and Applications”, 2002, NASA/CR-2002-211628 ICASE Report No. 2002-10, ICASE, NASA Langley Research Center Hampton, Virginia [14] Schnubel, D. and Huber, N. (2012), "The influence of crack face contact on the prediction of fatigue crack propagation in residual stress fields", Engineering Fracture Mechanics, vol. 84, pp. 15-24.
34 ORAL Abstract #862 Framework to Conduct Re-Laser Peening for Maximum Fatigue Life
A. Vasu1, K. Gobal2, and R. Grandhi2 1American Axle and Manufacturing, One Dauch Dr, Detroit, Michigan 2Wright State University, Dayton, Ohio
Email: [email protected]
Surface enhancement techniques, such as laser peening, have wide applications in the aerospace industry. They increase the structural component’s life by imparting compressive residual stresses around the critical locations where the cracks are likely to initiate and later propagate leading to component failure. However, the compressive residual stresses can relax due to the loading conditions and reduce the laser peening effectiveness. Under such a condition, re-peening or re-laser peening a component already in service can further increase its component life. This research develops a method to predict the optimum re-peening time for maximum fatigue life under realistic loading conditions. The framework for the proposed method is shown in Figure 1.
Fig. 1. Re-Peening Optimization Framework [1]
An optimization problem is set up to illustrate the application of this method to an aircraft lug problem. Results from the investigation indicate that re-peening this component ~50-55% of its expected fatigue life maximizes the component’s fatigue life. The proposed approach, proven to be able to obtain optimal process parameters for improving the fatigue resistance of the component, can significantly reduce the costs for experimental testing.
[1] Vasu, Anoop, Koorosh Gobal, and Ramana V. Grandhi. "A computational methodology for determining the optimum re-peening schedule to increase the fatigue life of laser peened aircraft components." International Journal of Fatigue 70 (2015): 395-405.
35 ORAL Abstract #937 A Framework for Verification and Validation of Models for Laser Peening
R. C. McClung1, B. H. Thacker1, and V. Bhamidipati1 1Southwest Research Institute, P. O. Drawer 28510, San Antonio, Texas 78228-0510
Main author email address: [email protected]
Engineered residual stress methods such as laser peening (LP) have demonstrated great potential to enhance the structural integrity and reliability of safety-critical components in a variety of industrial applications. LP methods have already been used with great success in some applications, and extensions to other applications are being actively considered. In most cases, the successful methods have been developed empirically through systematic trial and error, evaluating the performance of a range of LP parameters with expensive experimental investigations. The broader use of LP methods will depend on the development of predictive models that can be used to optimize the LP parameters and to quantify the resulting benefits in specific applications.
Predictive LP models have been under development for many years. These models are inherently complex, because the physical phenomena being addressed are highly complex. Taking advantage of rapidly growing computational power, some current models employ highly detailed numerical representations of shock wave propagation and material deformation. The critical question, however, is whether these complex models are credible for decision- making: can they be trusted to determine the expenditures of large sums of money in support of hardware systems where failure can have catastrophic consequences?
Model Verification and Validation (V&V) is an enabling methodology for the development of computational models that can be used to make predictions with quantified confidence [1[1]. Verification is the process of determining that a model implementation accurately represents the developer’s conceptual description of the model and its solution. Validation is the process of determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model. In short, verification is a mathematics issue, whereas validation is a physics issue. Model V&V can reduce the time, cost and risk associated with component and full-scale testing of products, materials, and processes. Quantifying the confidence and predictive accuracy of a model provides the decision-maker with the information necessary for making a risk-informed decision.
This presentation will outline a framework for V&V of the predictive capabilities of LP models. A preliminary V&V plan was developed to scope the problem, assess the state-of-practice, and define the overall objectives and requirements. A hierarchical model of the analysis process was developed to map out the actual V&V process by decomposing the LP model into its fundamental submodels and identifying their interrelationships. A Phenomenon Identification and Ranking Table (PIRT) was constructed to identify and prioritize the critical submodels.
The V&V methodology must also consider the experimental and measurement uncertainties that are associated with the data used for development, calibration, and validation of the model. The uncertainties associated with three of the most commonly used laboratory methods for determining surface and subsurface residual stress fields—X-ray diffraction with layer removal, the slitting method, and the contour method—were explored. Preliminary hierarchal diagrams of potentially significant uncertainties at steps in each measurement/analysis process were constructed.
Finally, the predictive capability of LP models must also be considered in the larger framework of models for structural integrity and reliability. V&V issues associated with this larger framework, and their relationship to LP modeling issues, will be briefly discussed.
[1] ASME, V&V 10-2006 Guide for Verification and Validation in Computational Solid Mechanics, American Society of Mechanical Engineers, New York, NY (2006).
36 ORAL Abstract #840 LSP Process Simulation and Data Interpretation
R.A. Brockman1, S.E. Olson1, W.R. Braisted3, and K. Langer2 1University of Dayton Research Institute, Dayton, Ohio, USA 2AFRL Aerospace Systems Directorate, AFRL/RQSV, Wright-Patterson AFB, Ohio, USA
Improved simulation capabilities for laser peening processes are needed both for designing and optimizing processing conditions, and for understanding the resulting residual stress states, which typically exhibit a high degree of variability [1]. This paper presents several elements of an overall strategy for LSP process simulation that allows consideration of complex LSP procedures, and provide insight into the spatial variability of the residual stress field. The finite element modeling methodology is based on Abaqus/Explicit, using alternating shock and relaxation phases for the LSP shot sequence that can be interrupted and restarted as necessary in a variety of computing environments [2]. The most useful data reduction procedures produce statistical distributions of stress components, plastic strains, and other data at depths or positions of interest, based on the variability observed throughout the computational model. While the finite element results provide valuable information about the possible variability of local stress fields, comparisons with experimental data can be difficult. Accordingly, results can be averaged over appropriate patches of area for comparison with x-ray diffraction or other measurements, for validating the computations, and methods have been developed for this purpose. Selected experiments done to validate the results of simulations for aluminum and titanium workpieces are described as well. One novel series of tests involves the collection of x-ray diffraction measurements on a finely-spaced (0.75 mm) grid of overlapping points, to determine if the degree of stress variability predicted in finite element simulations is realistic (Figure 1a). Examples of the interpretation of depthwise stress distributions obtained from the computational models using simple statistical measures are discussed (Figure 1b). These comparisons illustrate the value of the detailed simulation data, in terms of understanding worst-case conditions in LSP-processed parts. Finally, some current challenges and problems in the simulation of practical LSP processes are discussed, including processing details and material modeling requirements for thin sections, process optimization, detailed characterization of LSP-induced pressure loading, particularly near spot boundaries, and prediction of relaxation of the LSP residual stress field.
(a) (b)
Fig. 1. (a) Comparison of XRD measurements with 0.75 mm spacing and finite element predictions for a thick aluminum specimen processed at 4 GW/cm2 intensity; circular outlines show the LSP shot pattern. Finite element results are averaged over patches the same size as the LSP spots. (b) Finite element predictions of residual stress CDF versus depth, compared with XRD depth measurements and simplified analytical model [3].
[1] S.A. Martinez, S. Satish, M.P. Blodgett, and M.P. Shepard, Residual stress distribution on surface-treated Ti-6Al-4V by x-ray diffraction, Exp. Mechanics, 43(2), 141-147 (2003). [2] R.A. Brockman, W.R. Braisted, S.E. Olson, R.D. Tenaglia, A.H. Clauer, K. Langer, and M.J. Shepard, Prediction and characterization of residual stresses from laser shock peening, Int. J. Fatigue 36, 96-108 (2012). [3] W.R. Braisted, Prediction of Residual Stresses from Laser Shock Peening, Ph.D. Dissertation, University of Dayton (2000).
37 ORAL Abstract #825 Simulation-Guided Induction of Through-Thickness Compressive Residual Stresses in Thin Al2024-T351 Plates by LSP
C. Correa, J.A. Porro, D. Peral, A. García-Beltrán and J.L. Ocaña
UPM Laser Centre, Universidad Politécnica de Madrid, Ctra. Valencia, km. 7.3, 28031 Madrid, Spain
Main author email address: [email protected] Corresponding author email address: [email protected]
With the aid of the calculational system developed by the authors [1], the analysis of the problem of LSP treatment for induction of residual stress fields for fatigue life enhancement in relatively thin sheets in a way compatible with reduced overall workpiece deformation due to spring-back self-equilibration has been envisaged. Numerical results directly tested against experimental results have been obtained confirming the critical influence of the laser energy and irradiation geometry parameters.
Plane rectangular specimens (160 mm x 100 mm x 2 mm) of Al-cladded (∼80 µm) Al2024-T351 were considered both for LSP experimental treatment and for corresponding numerical simulation.
In figure 1, numerical simulation results are shown of the final residual stress state (in both perpendicular x and y directions) in a middle transverse cut (y direction) of the considered geometry after treatment with the appropriate irradiation parameters. It is clearly observed how the plate front (direct laser beam incidence) is in compressive residual stress and how the rear part of the plate is also under compressive residual stress (in both components), what in practice demonstrates the possibility of induction of the desired through-thickness compressive residual stress field.
Figure 1. Colorscale representation of σx and σy components of the residual stresses fields in a treated specimen under selected parametric conditions.
Provided that the reported results have been fully confirmed by experimental measurements, these are considered to provide a firm basis for the design of LSP treatments able to confere a broad range of residual stresses fields to thin components aiming the extension of their fatigue life, a relevant field in which the authors are currently working.
[1] OCAÑA, J.L., MORALES, M., MOLPECERES, C., TORRES, J.: “Numerical simulation of surface deformation and residual 38 stresses fields in laser shock processing experiments”. Applied. Surface Science, 238, 242-248 (2004). ORAL Abstract #826 Application of Laser Shock Processing to the Mitigation of the Effect of Surface Defects on the Fatigue Life of Thin Metal Plates
C. Correa, J.A. Porro, M. Díaz, L. Ruiz de Lara, A. García-Beltrán and J.L. Ocaña
UPM Laser Centre, Universidad Politécnica de Madrid, Ctra. Valencia, km. 7.3, 28031 Madrid, Spain
Main author email address: [email protected] Corresponding author email address: [email protected]
The application of the LSP technique has been envisaged as a potential method for the mitigation of the deleterious effects induced by surface defects on the fatigue life of thin components. It is reasonably expected that the induction of compressive residual stress fields by means of the LSP treatment can overcome the effect of enhanced crack aperture occasioned by such superficial defects.
The principle for such improvement has been both theoretically and experimentally analyzed and successfully demonstrated. With the aid of the calculational system developed by the authors [1], the analysis of the problem of LSP treatment for induction of residual stress fields for fatigue life enhancement in relatively thin sheets with induced superficial defects has been envisaged. Numerical results directly tested against experimental results have been obtained confirming the possibility of effective improvement of the fatigue life of these specimens by means of different LSP treatment strategies.
Plane standard dogbone specimens 400 mm long of 2 mm thickness Al-cladded (∼80 µm) Al2024-T351 with a central triangular notch of 150 µm maximum depth transversal to the elongation direction were considered for comparative analysis in the pristine and LSP treated conditions. The practical LSP irradiation system consisted in a Q-switched Nd:YAG laser operating at 10 Hz with a wavelength of 1064 nm, 9.4 ns pulse length and 2.8 J per pulse energy level.
Figure 1 presents a numerical simulation result showing the way in which the fields of residual stresses is induced in the sample specimen by the LSP treatment in one of the reported sweeping options, total or partly overcoming the effect of the induced notch.
Figure 1. Colorscale representation of σx and σy components of the residual stresses fields induced by LSP in an initially notched plate.
In view of the results reported in this paper, that deal with the appropriate experimental implementation of the treatments in order to get an advantageous result on the tested specimens, the capability of LSP to overcome the effect of superficial defects in thin plates is to be considered as fully demonstrated, thus settling a relevant path for protection and repair of damaged structural components.
[1] OCAÑA, J.L., MORALES, M., MOLPECERES, C., TORRES, J.: “Numerical simulation of surface deformation and residual stresses fields in laser shock processing experiments”. Applied. Surface Science, 238, 242-248 (2004). 39 ORAL Abstract #855 A Reliability-Based Framework to Efficiently Optimize Laser Peening Parameters
P. Hasser1, A. Malik1, K. Langer2, and T. Spradlin2 1Parks College of Engineering, Aviation and Technology, Saint Louis University, St. Louis, Missouri 63103 2Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433
A simulation framework for efficiently performing reliability-based design optimization of laser peening parameters is presented [1]. Described is an auxiliary tool that can reduce experimental testing in identifying suitable laser peening parameters that meet minimum required fatigue-life reliability. The framework includes non-parametric probability density estimation, surrogate modeling using finite element simulations, and reliability analysis with correlated random variables. To provide efficient finite element modeling of laser peening, a new approach termed Single Explicit Analysis using Time-dependent Damping (SEATD) is described, which can reduce simulation times by a factor of six over recent 2N+1 methods [2]. A reliability-based optimization (vs. a deterministic one [3]) is applied to simulate laser peened fatigue performance of a ‘candy bar’ test coupon. Optimum values are estimated for the maximum peening pressure and spot overlap that minimize number of laser spots required, while attaining the target fatigue life reliability. The computed reliability accounts for several uncertainties, including maximum peening pressure, spatial pressure profile, component elastic modulus, and Johnson-Cook material constitutive parameters. Case study simulations reveal that fatigue reliability significantly affects optimal laser peening treatment design, since 52 laser spots are needed for 99% reliability, versus only 44 spots for 95%. Framework Initial Analysis Block Start Flowchart Rank correlated Orthogonal Yes Are any RVs No LHS of LHS of correlated? design space design space
Run FEA at all sample designs Format FEA output for surrogate model
Build response surface Run FEA at optimal (surrogate model) point and surrounding points
Use optimizer to obtain RV values for best design 2N+1 SEATD Sufficient Total Simulation Time (H:MM:SS) 5:52:11 0:41:56 convergence No between iterations? Time in Analysis 1:38:56 0:36:01 Time in Pre-/Post-Processing 4:13:15 0:05:55 Yes Analysis Time Per LP Shot 0:11:00 0:04:00 Optimization Block Design point Pre-/Post-Process Time Per LP Shot 0:28:08 0:00:39
a) b)
Fig. 1. (a) Flowchart of the Reliability-Based Design Optimization process for Laser Peening. (b) Log plot of strain energy history for three 2N+1 constant damping values and SEATD oscillatory damping; and table comparing simulation times for 2N+1 and SEATD methods.
[1] P. Hasser,“An Efficient Reliability-Based Simulation Framework for Optimum Laser Peening Treatment,” MS Thesis, St. Louis Univ. (2014). [2] R. Brockman, W. Braisted, S. Olson, R. Tenaglia, A. Clauer, K. Langer, M. Shepard, “Prediction and Characterization of Residual Stress from Laser Shock Peening,” International Journal of Fatigue, Vol. 36, No. 3, pp. 96-108 (2012). [3] G. Singh, R. Grandhi, “Mixed-Variable Optimization Strategy Employing Multifidelity Simulation and Surrogate Models,” AIAA Journal, Vol. 48, No. 1, 215-223 (2010).
40 ORAL Abstract #878 A novel approach for simulation of laser shock peening using a finite domain
H.R. Karbalaian1, A. Yousefi-Koma1,M. Karimpour1, S.S. Mohtasebi1, M.H. Soorgee1 1School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Laser shock peening (LSP) is one of the advanced surface treatments in which compressive residual stresses are imparted on and near the surface by a short and intense laser pulse. In this process, the laser pulse irradiated on the surface of the part, vaporizes the surface and forms a high pressure and short duration plasma. As the plasma expands, shock waves are generated and propagate through the part which cause plastic deformation [1]. After initial deformation, the wave would travel into the part and is then reflected from boundaries and may cause part yield again. After all plastic deformations occur and waves diminish, residual stress is left on the surface. This process improves fatigue life and corrosion resistance in addition to strength and hardness [2,3]. Recent studies show that in LSP surface layer of the material could be nanostructure [4]. The finite element method (FEM) has been known as an effective tool to analyze practical laser shock peening. Effects of various parameters and details of the process such as complex geometry, multiple and overlapping laser pulses, laser spot shape and size, laser intensity, on the resulting residual stress have been investigated using FEM [5,6]. In most of the researches, a non-reflecting boundary (or semi-infinite models) has been used to simplify the model and reach equilibrium faster. In these cases, investigation of the effects of size and interaction of waves on residual stresses is not possible. Others used finite models with symmetry in simulating of two sided laser peening. Under these conditions, interaction of waves would be simply modeled and effect of size may be observed. However in these cases, one challenge is damping of the waves in material to see the residual stress field. In 2011, Brockman et.al, done a simulation considering the interaction of waves [6]. They defined a long enough step so that all plasticity including interaction of waves takes place and a secondary step with heavy damping is utilized to return the system to near equilibrium. In the current study, finite domain for one sided laser peening is presented and different approaches are investigated to return the system to near-equilibrium and then the best method which has the lowest computational cost is determined. This model is based on the work done by Ballard [7]. The specimen material was 35CD4 30HRC steel which was modeled using an axisymmetric setup with a diameter of 30mm and height of 15mm. Moreover ABAQUS/Explicit was used to analyze the model. It is determined that alpha has a very low effect on damping of waves. Beta significantly decreases the kinetic energy however stable time decreases in explicit analysis and thus computational cost increases. Linear and quadratic bulk viscosities cause minor changes to kinetic energy and also reduce stable time increment. Viscous pressure rapidly decreases the kinetic energy to about 1% of its initial value but after that it changes slowly. For decreasing kinetic energy for example to 0.001% of its initial value, the best method is to apply viscous pressure with a very low beta value. It was observed that in the finite model, total plastic energy is about 11% more than semi-infinite model. Comparing to Ding’s work, results have better agreement with the experimental data. Moreover in this method, and comparing with the work done by Brockman et al. computational cost has been greatly reduced.
[1] W. Braisted and R. Brockman, “Finite element simulation of laser shock peening,” Int. J. Fatigue, 21, 719-724(1999). [2] C. S. Montross, T. Wei, L. Ye, G. Clark and Y. Mai, “Laser shock processing and its effects on microstructure and properties of metal alloys: a review,” Int. J. Fatigue, 24, 1021-1036 (2002). [3] P.Peyre, X. Scherpereel, L. Berthe, C.Carboni, R.Fabbro, G. Be´ranger, and C.Lemaitre, “Surface modifications induced in 316L steel by laser peening and shot-peening. Influence on pitting corrosion resistance”. Materials Science and Engineering A, 280, 294-302 (2000). [4]C. Zhigang, Y.Jie, G.Shuili, C.Ziwen, Z.Shikun and X.Haiying, “Self-Nanocrystallization of Ti-6Al-4V Alloy Surface Induced by Laser Shock Processing,” Rare Metal Materials and Engineering, 43, 1054-1060 (2014). [5] K. Ding and L. Ye, “Simulation of multiple laser shock peening of a 35CD4 steel alloy,” Journal of Materials Processing Technology, 178, 162–169 (2006) [6] R. Brockman, W. Braisted, S.E. Olsen, R.D. Tenaglia, A.H. Clauer, K. Langer and M.J. Shepard, “Prediction and characterization of residual stresses from laser shock peening” Int. J. Fatigue, 36, 96-108 (2012) [7] P. Ballard, “Residual stresses induced by rapid impact-applications of laser shocking,”Ph. D. Dissertation, Ecole Polytechnique, France (1991).
41 ORAL Abstract #905 Application of a Reliability-Based Laser Peening Design Framework to Friction-Stir Weld Test Specimens
C. Seidel1, J. Moulton1, H. Alsadah1, P. Hasser2, M. Hatamleh2, A. Malik3, and K. Langer4
1Undergraduate Student, 2Graduate Student, 1-3Parks College of Engineering, Aviation and Technology, Saint Louis University, St. Louis, Missouri 63103 4Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433
Application of a reliability-based design framework to determine optimum laser peening parameters for a 7075 Al friction-stir weld test specimen is presented [1]. Aim of the design framework in this work is reduce experimental testing in identifying suitable laser peening parameters to obtain target fatigue life reliability of the friction stir weld test specimens. Initial residual stresses for a ‘dog-bone’ specimen cut from materials joined using full penetration friction stir welding at 500 rpm weld speed and 71 in/min spindle-speed is considered. The reliability framework includes a new, efficient finite element modeling approach known as Single Explicit Analysis using Time-dependent Damping (SEATD) [2]. Comparisons of laser peening patterns for different target fatigue reliabilities are made, as well as comparisons of fatigue life for the friction stir weld specimens with and without laser peening treatment. Simulations to determine fatigue life reliability of laser peened specimens account for several uncertainties relating to maximum peening pressure, spatial pressure profile, component elastic modulus, and Johnson-Cook material constitutive parameters. A python tool programming script, developed for the reliability framework, is utilized to reduce the time, cost, and complexity in simulating widely varying laser peening patterns on complex parts.
Fig. 1. Top left: Friction stir weld process [1]; Bottom left: Image of weld cross section; Top right: Reliability framework for laser peening design [2]; Bottom right: finite element model and photo of test specimen.
[1] O. Hatamleh, J. Lyons, R. Forman, “Laser and shot peening effects on fatigue crack growth in friction stir welded 7075-T7351 aluminum alloy joints,” International Journal of Fatigue, Vol. 29, 421–434 (2007) [2] P. Hasser, “An Efficient Reliability-Based Simulation Framework for Optimum Laser Peening Treatment,” MS Thesis, St. Louis Univ. (2014).
42 ORAL Abstract #891 Simulation-based Optimization of Laser Shock Peening Process for Improved Fatigue Performance
Sagar Bhamare1, G. Ramakrishnan2, S. R. Mannava2, K. Langer3, V. K. Vasudevan2 and D. Qian4
1Innova Engineering, Inc. Irvine, CA 92614
2 Department of Mechanical and Materials Engineering University of Cincinnati Cincinnati, OH 45211
3Air Force Research Laboratory Wright Patterson Air Force Base Fairborn, OH 45433
4Department of Mechanical Engineering University of Texas at Dallas Richardson, TX 75080
Laser shock peening (LSP) is a surface process technique for improving the high cycle fatigue behavior of certain metals and alloys by incorporating compressive residual stresses. Residual stress distribution is influenced by various laser parameters (energy, laser pulse width, and spot diameter), the geometry, the material and the laser shot sequencing. By exploring the parametric space, a numerical approach based on 3D nonlinear finite element method [1] is employed to optimize the residual stress distribution. This methodology is applied to the thin coupon of Ti-6Al-2Sn-4Zr-2Mo alloy to improve the bending fatigue life. Effect of laser parameters and laser shot sequencing on final residual stress distribution is studied by performing full scale simulations of LSP patches constituting large number of laser shots. Based on simulation studies, optimal set of parameters is obtained that produces through thickness compression eventually improving the bending fatigue life. Fatigue testing results support the recommendations made based on simulation results.
References
[1] S. Bhamare, G. Ramakrishnan, S. R. Mannava, K. Langer, V. K. Vasudevan, and D. Qian, "Simulation- based optimization of laser shock peening process for improved bending fatigue life of Ti-6Al-2Sn-4Zr- 2Mo alloy," Surface & Coatings Technology, vol. 232, pp. 464-474, Oct 2013.
43 ORAL Abstract #828 A Parametric Study of the Peen Size and Coverage on the Laser Shock Peening induced Residual Stress Profiles in thin AA2024 Samples
M. Sticchi1, Y. Sano2, N. Huber1 and N. Kashaev1 1 Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Material Mechanics, Max-Planck-Straße 1, D- 21502 Geesthacht, Germany 2 Toshiba Corporation, Power and Industrial Systems Research and Development Center,8 Shinsugita-cho, Isogo- ku, 235-8523 Yokohama, Japan
Laser shock peening is a mechanical surface treatment using laser energy to induce compressive residual stress in the first outer layers of metallic components. This work describes the variations of the introduced residual stress field with peen size and coverage. The purpose of the research was to investigate the influence of different parameters (i.e. peen size and coverage) on the residual stress distribution for thin metal samples treated with under- water laser shock peening [1]. The specimens under investigation were of Al alloy AA2024-T351, with dimensions 40 mm x 40 mm x 1.9 mm. The surface of the specimens was laser peened on an area with dimension 20 mm x 20 mm. The residual stresses were measured by the use of the hole drilling with electronic speckle interferometer. Of particular interest are the effects of the above mentioned parameters on (A) the zero-depth value (the value at which the stresses turn from compressive to tensile) which gives an indication of the amount of residual stress through the thickness (Figure 1(a)), on (B) the maximum value of the compressive stresses which gives an indication of the magnitude of residual stress after peening, and on (C) the maximum value of the tensile stresses which gives an estimation of the reaction of the material to the introduced compression field. Figure 1 (b) shows the peen size effect for a given coverage. Both of the figures show the measured σyy stresses. The peening treatment has been accomplished along the x direction. (a) (b)
Fig. 1. Residual stress profiles measured in laser shock peened AA2024-T351: Max. compression, zero-depth and max. tension points (a). Peen size effect on max compression, zero-depth and max tension, for a given coverage (b).
The compendium based on the performed measurements is shown in this work, aiming to give a trend of the residual stress introduced in thin aluminum samples via under-water laser shock peening. A finite element based approach for a preliminary estimation of the stress field trend is also presented.
[1] Y. SANO, K. Akita, K. Masaki, Y. Ochi, I. Altenberger, B. Scholtes, J. Laser Micro/Nanoengineering Vol. 1, No. 3 (2006) 161-166
44 ORAL Abstract #927 CORRELATION BETWEEN RESIDUAL STRESS AND NANOHARDNESS GENERATED BY LASER SHOCK PEENING IN AL-2624 AEROSPACE ALLOY
S. Zabeen1, K. Langer2, and M. E. Fitzpatrick1
1 Coventry University, Faculty of Engineering and Computing, Gulson Road, Coventry, CV1 2JH 2Air Force Research Laboratory, Wright Patterson Air Force Base, Dayton, OH 45433, USA
Email: [email protected]
Deep and stable compressive residual stresses introduced by laser shock peening (LSP) enhance the fatigue performance of aerospace structural components. In order to obtain a desired life benefit from the material through a known level of residual stress, it is essential to have a mechanistic understanding of the influence of the LSP process parameters on the plastic deformation of the material that causes hardening and residual stress generation.
In this study the effect of two important laser peening parameters, namely laser energy and number of peening layers, was investigated on the residual stress and nanohardness profiles. An aerospace structural material, Al-2624 alloy was used for this study in two heat treatment conditions: T-351 and T-39. The specimens were peened by Metal Improvement Company (MIC), UK. In contrast to the commercial peening method where a component is peened in patterns using multiple overlapping laser spots to introduce direction-dependent stress profiles, the specimens were peened with single laser spots.
The residual stresses have been measured by high energy synchrotron X-ray diffraction at ESRF, France, and incremental hole drilling (ICHD). It is evident from the results that the magnitude of the maximum compressive residual stresses increases with increasing peening energy and the number of peening layers (as shown in Figure 1). Nanohardness profiles were obtained using an MTS Nanoindenter XP system with a Berkovich indenter tip. Since the two tempering conditions have different yield strengths and hardening capability, a significant variation in nanohardness profiles was observed between two alloys. The results will provide a basic understanding of the relationship between the residual stress and nanohardness generated at different peening parameters and will be used to develop and validate a predictive model for hardening and consequent residual stress generation.
Figure 1: Residual stress profiles measured by incremental hole drilling technique showing the effect of number of peening layers in two heat treatment conditions: (a) for T-351 alloy and (b) T-39 alloy.
45 ORAL Abstract #861 The Effect of Cavitation during the Laser Shock Peening Process
D. Glaser1, C. Polese1,2 1 School of Mechanical, Industrial and Aeronautical Engineering, 2 DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, 2000, South Africa
Recent research activities have revealed that cavitation may occur during the Laser Shock Peening (LSP) process [1- 4]. In addition, it has been suggested that cavitation during LSP generates a secondary pressure pulse comparable to the primary pulse from the laser driving the peening process [2, 3]. In terms of mechanical engineering, cavitation is typically considered a detrimental process, and is usually associated with the damage of hydrodynamic machinery. However, it has also emerged that hydrodynamic cavitation has been successfully applied as a beneficial peening process [5]. Therefore, in order to establish whether or not cavitation is a desirable occurrence, it is necessary to obtain a deeper understanding of the mechanical effect in the context of LSP.
This research first quantifies the conditions that dictate the occurrence of a cavitation event during the LSP process. A strong dependence has been found on the energy of the laser pulse and water layer thickness, since coalescence of the vapour bubble to the air-water interface precludes the impulsive collapse of the cavitation bubble. Fig. 1a shows an image taken from a high speed video using shadowgraph photography at some time after a single laser pulse. In Fig. 1a, no cavitation event occurs, as the bubble from the target surface coalesces with a bubble emanating from the air-water interface. However, in the instance when the cavitation bubble collapses, a shock wave is emitted through the water, as seen in Fig. 1b showing a hemispherical shock wave. An experimental framework has been devised which allows for deliberate occurrence or non-occurrence of an impulsive cavitation bubble collapse after a single identical laser pulse, therefore allowing for investigation of cavitation in the context of LSP.
(a) (c)
(b)
Fig. 1 (a) Non-impulsive cavitation event due to cavitation bubble coalescence with the air-water interface. (b) An impulsive cavitation collapse emitting a hemispherical shock wave. (c) A 3D surface map of a single LSP event showing the surface indentation.
The pressure generated by a single LSP event creates a surface indentation of several microns, which is measured using surface mapping as shown in Fig. 1c. Essentially, if the surface indentation depth and geometry is altered after a cavitation event, further plastic deformation would have occurred, implying that cavitation would have some effect on the local residual stress field. Therefore, three different aluminium alloys, specifically selected for differences in yield strength, have been investigated as the magnitude of pressure generated by the cavitation event is unknown. In addition to the single shot samples, samples with a 5 by 5 array of laser pulses (with and without cavitation) have been created for determination of surface residual stress using X-Ray Diffraction. The single shot samples will also formulate the foundation of an experimental benchmark for future FEA activity.
[1] L. Martí-López, R. Ocaña , and J. A. Porro, “Laser Peening Induced Shock Waves and Cavitation Bubbles in Water Studied by Optical Schlieren Visualization”, Physics Procedia, vol. 12, 442–451 (2011). [2] T. Nguyen, R. Tanabe, and Y. Ito, “Laser-induced shock process in under-liquid regime studied by time-resolved photoelasticity imaging technique”, Applied Physics Letters 102, 124103 (2013). [3] T. Takata1, M. Enoki1, A. Matsui, “Evaluation of Optimal Condition in Laser Shock Peening Process by AE Method”, 13th International Conference on Fracture, China (June 2013). [4] C. Polese, D. Glaser and R. Bedekar, “Water Confinement Influences on the Laser Shock Peening process”, 30th International Congress on High-Speed Imaging & Photonics, South Africa (2012). [5] H.Soyama, T.Kusaka and M.Saka, “Peening by the Use of Cavitation Impacts for the Improvement of Fatigue Strength”, Journal of Materials Science Letters, vol. 20, 1263-1265 (2001).
46 ORAL Abstract #832 Surface Mechanics Design by Cavitation Peening
H. Soyama1 1Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai, Japan
Cavitation normally causes noises, vibrations and severe damage in hydraulic machinery such as pumps and valves. However, impacts induced by shock wave at cavitation bubble collapse can be utilized for mechanical surface treatment in the same way as laser peening and shot peening. In view point of use of shock wave, cavitation peeing is similar phenomena to laser peening. The peening method using cavitation impacts is called “cavitation shotless peening” as shots are not required, or named simply “cavitation peening” [1-3]. Cavitation peening can be utilized for surface mechanics design, which controls mechanical properties in surface modified layer such as residual stress, yield stress, surface roughness was proposed as shown in Fig. 1. Although cavitation can be generated by ultrasonic or pulse laser, in the case of conventional cavitation peening, cavitation is generated by injecting a high sped water jet into a water filled chamber. This sort of the jet is called a cavitating jet in water. A cavitating jet in air was realized by injecting a high speed water jet into a low speed water jet which was injected in air [4, 5]. The cavitating jet in air can introduce relative large compressive residual stress at the surface, and the cavitating jet in water can introduce the compressive residual stress in deeper region [6]. Note that “cavitation peening” and “water jet peening” in which droplets impacts were used can be distinguished by considering cavitation number and standoff distance [7]. As arc height of Almen strip is conventional indicator to show peening intensity of shot peening, Fig. 2 illustrates the arc height of Almen strip peened by the cavitating jet in air and water to demonstrate peening capability of cavitation peening.
Water jet Ultrasonic Pulse laser 0.3 Droplet Cavitation Abrasion
Liquid collision Shock wave 0.2 mm A Cavitating jet in water Impacts h
Local Plastic Deformations Arc height 0.1 Dislocation density Arc height Grain size Young’s modulus Cavitating jet in air Residual stress Tensile strength 0 Yield stress Roughness 0 5 10 15 20 Hardness Processing time per unit length tp s/mm Fracture toughness Fig. 2. Arc height of Almen strip of A-gage (Cavitating jet in water : Surface Mechanics Design inpection pressure of high speed jet pH = 30 MPa, nozzle diameter d = 2 mm, standoff distance s = 262 mm; cavitating jet in air : injection pressure of high Delayed fracture Fretting fatigue speed jet pH = 30 MPa, nozzle of high speed jet dH = 1 mm, injection pressure Fatigue strength Hydrogen embrittlement of low speed jet pL = 30 MPa, nozzle of high speed jet dL = 30 mm, standoff Fig. 1. Surface mechanics design by cavitation peening distance s = 56 mm)
[1] H. Soyama, K. Saito and M. Saka, “Improvement of Fatigue Strength of Aluminum Alloy by Cavitation Shotless Peening,” Trans. ASME, Journal of Engineering Materials and Technology, vol. 124, 135-139 (2002). [2] H. Soyama and Y. Sekine, “Sustainable Surface Modification Using Cavitation Impact for Enhancing Fatigue Strength Demonstrated by a Power Circulating-Type Gear Tester,” International Journal of Sustainable Engineering, vol. 3, 25-32 (2010). [3] H. Soyama, “The Use of Cavitation Peening to Increase the Fatigue Strength of Duralumin Plates Containing Fastener Holes,” Materials Sciences and Applications, vol. 5, 430-440, (2014). [4] H. Soyama, “Introduction of Compressive Residual Stress Using a Cavitating Jet in Air,” Trans. ASME, Journal of Engineering Materials and Technology, vol. 126, 123-128, (2004). [5] H. Soyama, “High-Speed Observation of a Cavitating Jet in Air,” Trans. ASME, Journal of Fluids Engineering, vol. 127, 1095-1101, (2005). [6] H. Soyama, “Surface Mechanics Design of Metallic Materials for Automotive Lightweight Technology,” Proceedings of 1st International Conference on Modern Auto Technology and Services (MATS 2014), (2014). [7] H. Soyama, “Surface Mechanics Design of Metallic Materials on Mechanical Surface Treatments,” Mechanical Engineering Reviews, vol. 2, (2015), in press.
47 ORAL Abstract #901 Femtosecond Laser Peening without Sacrificial Overlay under Atmospheric Conditions
Tomokazu Sano1, Takayuki Eimura1, Syouhei Iwata1, Norihiro Matsuyama1, Ryota Kashiwabara1, Tomoki Matsuda1, Yutaro Isshiki1, Akio Hirose1, Kazuto Arakawa2, Tadafumi Hashimoto3, Seiichiro Tsutsumi4, Kiyotaka Masaki5, and Yuji Sano6 1Division of Materials and Manufacturing Science, Osaka University,2-1 Yamada-oka, Suita, Osaka 565-0871, Japan 2Interdisciplinary Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan 3Hashimoto Iron Works Co., Ltd. 3-156 Kaisan-cho, Sakai-ku, Sakai, Osaka 590-0982, Japan 4Joining and Welding Research Institute, Osaka University, 11-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan 5Okinawa National College of Technology, 905 Henoko, Nago, Okinawa 905-2192, Japan 6Power and Industrial Systems Research and Development Center, Toshiba Corporation, Yokohama, Kanagawa 235-8523, Japan
We achieved peening of 2024-T351 aluminum alloy using femtosecond laser pulses without a sacrificial overlay such as a plasma confinement medium in the air. The surface region with several tens of m thickness was hardened and the induced compressive residual stress was almost equal to the 0.2 % proof stress of 2024-T351 aluminum alloy. The fatigue strength of the femtosecond laser irradiated alloy increased compared with that of the base material. The femtosecond laser has a potential to increase the applicability of peening treatments.
48 ORAL Abstract #857 Study and development of high peak power short pulse Nd:YAG laser for peening applications
Qiao Hongchao Shenyang Institute of Automation Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China
Email address: [email protected]
For short pulse Nd:YAG laser of nanosecond pulse-width and high peak power has a unique capability to improve the mechanical properties of metal parts[1-4], a study on the development of high peak power short pulse from Nd:YAG laser along with its peening application has been performed. Design scheme of laser and characteristic of laser beam transmission are presented and discussed. A pulse energy of 25J with 15ns pulse-width and a maximum peak power of 1660 kW laser system which used one oscillation and eight amplifiers has been achieved. Laser beam has a max divergence angle of 0.3mrad, a pulse-to-pulse pulse-width stability of ±1ns, and the pulse-to-pulse energy stability factors were less than ±28%. A low value of divergence means easier for the modification of a nearly hat-top laser beam intensity profile and the transmission of laser beam. To evaluate the performance of the laser system, several metal materials were processed. Laser peening quality and efficiency have been analyzed by using optical microscope, transmission electron microscope, and X-ray diffraction device. The processed results show that performance of the laser system is excellent.
Original sample Laser peened with 7J
Fig. 1. The microscopic structure of Ti17 specimens before and after laser peening.
[1] Bagherifard S, Gernaadez I, Ghelichi R, et al., “Effect of severe shot peening on microstructure and fatigue strength of cast iron,” International Journal of Fatigue, 65, 64-70 (2014). [2] Achintha M, Nowell D, Fufari D, et al., “Fatigue behavior of geometric features subjected to laser shock peening: experiments and modelling,” International Journal of Fatigue, 62, 171-179 (2014). [3] Chang Y, Sergey S, Fei X L, et al., “Bimodal nanocrystallization of NiTi shape memory alloy by laser shock peening and post-deformation annealing,” Acta Materialia, 59, 7219-7227 (2012). [4] Cellard C, Retraint D, Francois M, et al., “Laser shock peening of Ti-17 titanium alloy: Influence of process parameters,” Materials Science and Engineering A, 532, 362-372 (2012).
49 ORAL Abstract #841 Shock produced by laser for adhesion test of coatings and multi-layered materials
L. Berthe1, P. Peyre1, D. Courapied1, M. Boustie2, F. Touchard2, R. Ecault2, R. Kromer3, S. Costil3, J. Cormier2
1PIMM – UMR 8006 CNRS – Arts et métiers ParisTech, 151 Bd de l’Hôpital, 75013 PARIS, FRANCE 2Institut Pprime - Mechanics and Materials Science Laboratory UPR CNRS 3346, ISAE-ENSMA, Téléport 2, 1, avenue Clément ADER BP 40109 86961 CHASSENEUIL – FUTUROSCOPE, FRANCE 3IRTES-LERMPS Institute, UTBM, Belfort Cedex, 90010, FRANCE
Laser shock processing consists in irradiating targets with laser in the power density range of GW/cm2 to produced plasma. Pressure generated up to 5 GPa can reinforce surface material (Laser Shock Peening). Since 2000', the adhesion test of interfaces emerges as new application for shock produced by laser. Indeed, playing on the propagation of shock wave inside multilayered material, interfaces can be sollicitated by tensile stress to evaluate their adhesion [1]. First developpements have been concerned unique coating. Results demonstrate the sensitivity of the technique to interfaces properties. But, laser sources capability limits the use of technique to a narrow range of thickness depending on pulse duration. This paper presents recent results on this promising scope. Current research progresses on the selective adhesion test of complex and multilayered materials using new generation of laser technologie allowing profilable pulses. For example, a major effort has been done on the bonding test of Carborn Fiber Renforced Polymer(CFRP). It has been demonstrated that sollicitation can be located inside the material and the sensitivity of the test to surface properties before assembling. Besides, numerical simulation can reproduce shock wave propagation to evaluate stresses field along interfaces [2]. New configurations have been also developped coupling shock waves produced by two delayed laser pulses. It allows for the same laser source the selective adhesion test for multilayered material and for thick coatings
[1] L. Berthe, M. Arrigoni, M. Boustie, JP, Cuq-Lelandais, C. Broussillou, G. Fabre, “State-of-the-art laser adhesion test (LASAT)” .Nondestructive Testing and Evaluation, 26(3-4), 303-317. (2011) [2] E. Gay, L. Berthe, M.. Boustie, M. Arrigoni, M. and E. Buzaud, “Effects of the shock duration on the response of CFRP composite laminates” Journal of Physics D: Applied Physics, 47, 455303 (2014) [3] R. Ecault , M. Boustie , L. Berthe , F. Touchard , L. Chocinski-Arnault , H. Voillaume , B. Campagne, "Development of the laser shock wave adhesion test on bonded CFRP composite", International Journal of Structural Integrity, Vol. 5 Iss: 4, pp.253 – 261 (2014) [4] D. Courapied, L. Berthe, P. Peyre, F. Coste, J-P Zou, Laser-Delayed Double Shock-wave generation in water confinement Regime, submitted to Journal of Laser Application, 2014.
50 ORAL Abstract #829 Applicability of laser peen forming for the bending of fiber metal laminates
Yongxiang Hu1, Mingshen Luo1, Xingwei Zheng2 1 State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China 2Shanghai Aircraft Manufacturing Co., Ltd
Main author email address: [email protected] (Yongxiang Hu)
Fiber-metal laminates (FMLs) has demonstrated success primarily as a substitute to high strength aluminum alloy to reduce the weight of aircraft structures due to their excellent fatigue and impact properties [1]. Laser peen forming (LPF) is a process that utilizing laser pulses to form complex shape of metal alloy with pure mechanical shock loading [2]. It is characterized by non-contact, tool-free, high efficiency and compressive residual stressed on two side surfaces. To overcome the drawback of the expensive and time-consuming manufacturing processes, forming FMLs parts from flat FMLs by LPF to generate complex shape could provide a novel and economical option to decrease the labor cost because it can be deformed plastically like metal sheets.
The objective of this study is to assess the possibility of FMLs forming by LPF. Two types FMLs of Glare 2 and Glare 3 are prepared by the standard bonding technology with different prepreg orientations between 2024-T3 aluminum alloy sheets. The strips with the dimension of 70 × 16 mm2 and thickness of about 1.4 mm were laser- peened with different layer to find the saturation of bending curvatures. The experiments results show that all samples are bent away from the laser beam with different convex curvatures. It can be observed that the curvature radii for all three kinds of samples are decreased by the increase of laser-peening layers and then become saturated. Compared the results for different FMLs under the same laser-peening layers, the FMLs of GLARE 2-0° has maximum radius of bending curvature, while GLARE 2-90° is most easily deformed with smallest radius due to the different prepreg orientations respect to the length direction of samples. It can also be found from Fig.1 that the radii of bending curvature tend to increase when the laser-peening layer is more than five, especially for the layers of six and eight. This phenomenon should be attributed to the failure of delamination generated to dissipate the elastic bending strain. Further analyse by the stereo microscopes were performed to analyze the delamination inside the samples as shown in Fig. 2. The delamination is observed not generating as expected at the first interface of aluminum sheet and the fibre laminate, but at the second interface because the shear embedded zone can be found at the first interface.
400 GLARE 2-0° 350 GLARE 2-90° 300 GLARE 3 250 200 (a) 150 100 50 Curvature Radius (mm) 0 0 1 2 3 4 5 6 7 8 9 Laser-peening Layers (b)
Fig.1 Radii of bending curvature for FMLs under different laser- Fig.2 Delamination of formed FMLs under different laser-peening peening layers layers: (a) 8 layers; (b) 5 layers.
References [1] S.U. Khan, R.C. Alderliesten, and R. Benedictus, 2009, "Post-Stretching Induced Stress Redistribution in Fibre Metal Laminates for Increased Fatigue Crack Growth Resistance," Composites Science and Technology, 69(3–4), pp. 396-405. [2] Y. Hu, X. Xu, Z. Yao, and J. Hu, 2010, "Laser Peen Forming Induced Two Way Bending of Thin Sheet Metals and Its Mechanisms," Journal of Applied Physics, 108(7), pp. 073117.
51 ORAL Abstract #817 Preventing Hydrogen Embrittlement in Stainless Steel by Means of Compressive Stress Induced by Cavitation Peening
O. Takakuwa1 and H. Soyama1 1Tohoku University,6-6-01, Aoba, Aramaki, Aoba-ku, Sendai, Japan
Main author email address: [email protected]
Hydrogen in metal affects mechanical properties [1] and promotes fatigue crack propagation around a crack tip, i.e., hydrogen embrittlement [2].In order to construct hydrogen society based on usage of hydrogen as an energy carrier, hydrogen embrittlement should be prevented. In the past report, it has been demonstrated that cavitation peening utilizing impact caused by cavitation bubble collapsing can prevent hydrogen-assisted fatigue crack propagation in austenitic stainless steel [3] and hydrogen concentration around a crack tip can also be mitigated due to compressive stress by a numerical simulation [4].Those studies did not reach to evaluate actual hydrogen content in untreated and treated samples. Therefore, in this study, the actual hydrogen content in austenitic stainless steel with and without cavitation peening employing a cavitating jet in air has been evaluated using thermal desorption analysis to reveal the effect of cavitation peening on the hydrogen absorption behavior. Figure 1 (a) and (b) plot the hydrogen content normalized by the hydrogen content for untreated sample, CH/CH0, as a function of the processing time per unit length, tp, and CH/CH0 as a function of the area of compressive residual stresswith respect to depth, S, respectively. As shown in Fig. 1(a), the CH/CH0 was being decreased as processing time, tp, was increasing. The CH/CH0fortp = 2 s/mm was 0.146. The hydrogen content for tp = 2 s/mm became seventh part of the untreated sample. In Fig. 1(b), the CH/CH0 was being decreased as S was increasing. From the result, the compressive residual stress plays a role to prevent the hydrogen absorption from the surface because of narrowing atomic spacing and increasing potential energy for hydrogen entry from external environment. Also, the compressive residual stress may affect diffusion constant of hydrogen in metals.
1 1
0.8 0.8
0 0 H 0.6 H 0.6 C C / /
H H C 0.4 C 0.4
0.2 0.2
Normalized Hydrogen content Hydrogen Normalized Normalized Hydrogen content Hydrogen Normalized 0 0 0 0.5 1 1.5 2 0 20 40 60 80 Area of compressive residual stress Processing time per unit length tp s/mm with respect to depth Ss MPa・mm Fig. 1. Preventing the hydrogen absorption by cavitation peening. (a) The decrease in the hydrogen content along with the processing time per unit length of cavitation peening. (b) The decrease in the hydrogen content along with the area of compressive residual stress introduced by cavitation peening with respect to depth from the surface.
[1] O. Takakuwa, Y. Mano and H. Soyama, “Increase in the local yield stress near surface of austenitic stainless steel due to invasion by hydrogen,”International Journal of Hydrogen Energy, vol. 39, 6095-6103 (2014). [2]W.H. Johnson, “On some remarkable changes produced in iron and steel by the action of hydrogen and acids Title of paper,”Proceedings of Royal Society of London, vol. 23, 168-179 (1874). [3] O. Takakuwa and H. Soyama, “Suppression of hydrogen-assisted fatigue crack growth in austenitic stainless steel by cavitation peening,” International Journal of Hydrogen Energy, vol. 37, 5268-5276 (2014). [4] O. Takakuwa, M. Nishikawa and H. Soyama, “Numerical simulation of the effects of residual stress on the concentration of hydrogen around a crack tip,”Surface and Coatings Technology, vol. 206, 2892-2898 (2014).
52 ORAL Abstract #902 Ultrafast Lattice Dynamics of Femtosecond Laser-driven Shocked Iron probed with XFEL
Tomokazu Sano1, Tomoki Matsuda1, Mitsuru Ohata1, Tomoyuki Terai1, Akio Hirose1, Hiroyuki Uranishi2, Norimasa Ozaki2, Ryosuke Kodama2, Toshinori Yabuuchi2, Kazuo A. Tanaka2, Tomonao Hosokai3, Takeshi Matsuoka3, Kazuto Arakawa4, Yoshinori Tange5, Tomoko Sato6, Toshimori Sekine6, Tsutomu Mashimo7, Yukio Sano8, Yuji Sano9, Yuichi Inubushi10, Takahiro Sato10, Makina Yabashi10, Tadashi Togashi11, Kensuke Tono11, and Osami Sakata12
1Division of Materials and Manufacturing Science, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan. 2Division of Electrical, Electronic and Information Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan. 3Photon Pioneers Center, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan. 4Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan. 5Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan. 6Department of Earth and Planetary Systems Science, Hiroshima University, 1-3-1 Kagami-yama, Higashi-Hiroshima, Hiroshima 739- 8526, Japan. 7Institute of Pulsed Power Scinece, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan. 8Faculty of Maritime Sciences, Kobe University, 5-1-1, Fukae-minamimachi, Higashinada-ku, Kobe, Hyogo 658-0022, Japan. 9Power and Industrial Systems Research and Development Center, Toshiba Corporation, Yokohama, Kanagawa 235-8523, Japan. 10RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan. 11Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan. 12Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
Understanding of the physics under shock compression has been an important subject over the past century. Many experimental results have revealed that the shock-compressed material initially behaves as a purely elastic medium, and finally results in plastic deformation. However, the details of the transition between these two states has not been fully understood. We directly observed transient structural dynamics of iron induced by shock wave using brilliant X-ray Free Electron Laser (XFEL) pulses with a duration less than 10 femtoseconds. We found that the shock at an early stage produces an elastic strain corresponding to a stress of 22 GPa. We suggest that the giant elasticity induces generation of dislocations causing a high density of lattice defects inside the material, and that the plastic deformation without dislocations occurs, which was theoretically predicted but has not been observed. Our findings elucidate mechanisms of ultrafast phenomena under extreme conditions driven by shock compression, and promote to emerge novel characteristics in matters.
53 ORAL Abstract #836 Investigation on the pressure of laser-induced shock wave with condensed matter analytical method
Xiaoxu Deng*, Rui Miao
Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
*Corresponding author: [email protected]
Based on the equation of state for condensed matter, shock pressures generated by the water-confined regime in laser shock peening were investigated with homogenous rectangular laser pulse at power density of a few GW/cm2. The shock pressures are functions of not only the laser power density, but also the shock velocities, the densities and adiabatic exponents of the target material and confined water which are considered to be condensed matter other than “solid” or “perfect gas”. Performed on aluminium alloy, the laser-induced shock wave was measured by the polyvinylidene fluoride (PVDF) transducer which was directly attached to the rear face of the target material.
Figure 1 The Oscilloscope tracesof the laser-induced shock wave measured by PVDF transducer.
The proposed analysis was found to fit with the experimental results much better than that using“solid” or “perfect gas” theories(shown in table 1).
Table 1 The experimental laser-induced shock wave pressure and theoretical analysis with different model. Laser power Experimentallaser-induc Proposed theory in this “Solid”theory “Perfect gas” theory density ed shock wave pressure paper (GPa) (GPa) (GW·cm-2) (GPa) (GPa) 1.728 0.812 1.1765 0.5338 0.917 2.841 1.151 1.5085 0.7436 1.278
3.481 1.416 1.6698 0.8514 1.463
54 ORAL Abstract #824 Analysis of Induced Surface Modifications Effects on the Electrochemical Behaviour of LSP-Treated Metallic Alloys
J.A. Santiago, J.A. Porro, L. Ruiz de Lara, M. Díaz and J.L. Ocaña
UPM Laser Centre, Universidad Politécnica de Madrid, Ctra. Valencia, km. 7.3, 28031 Madrid, Spain
Main author email address: [email protected] Corresponding author email address: [email protected]
The influence of Laser Shock Processing (LSP) on the electrochemical behaviour of AA2024-T3, AISI 316L and Ti-6Al-4V in a chloride environment was evaluated. The application of LSP induces modifications on the surface topography, on the microstructure, as well as on the integrity of the passive film formed in chloride electrolytes that were investigated, as they seem to have beneficial effects on the corrosion behaviour [1,2].
The reported LSP treatments were performed using a Q-switched Nd:YAG laser operating at 10 Hz with a wavelength of 1064 nm, 9.4 ns pulse length and 2.8 J per pulse energy level. Several pulse densities were used: 900 pulses/cm2, 1600 pulses/cm2, 2500 pulses/cm2 and 5000 pulses/cm2. Water was the confining medium and the process was made without protective layer. The residual stress distribution was determined by the hole drilling method according to the ASTM E837 Standard. The techniques to determine the effects on microstructure include scanning electron microscopy (SEM) and an energy dispersive X-ray spectrometer (EDX) was used to analyze the chemical composition in surface. The surface topography was evaluated with confocal microscopy, extracting the 2D parameter Sa as a roughness measurement.
Electrochemical behaviour was studied by means of cyclic polarization (CP) curves and electrochemical impedance spectroscopy (EIS). CP measurements were used to characterize the generalized and localized attack for these materials and EIS analysis allowed us to develop an understanding of passive film behaviour in the as-received state, as well as after laser shock processing. A variety of interfacial impedance models have been explored for fitting the obtained data.
Fig. 1. (a) Cyclic polarization (CP), (b) Electrochemical Impedance Spectroscopy (EIS) of AA2024-T3 in 3,5% NaCl at room temperature
Cyclic polarization has shown that LSP increases localized corrosion potentials due to the large compressive stress and work hardening levels. Surface roughness also plays an important role, especially in repassivation potentials. Electrochemical impedance spectroscopy has enabled the effects of LSP on passive film structure and stability to be understood more fully than otherwise possible. Increases in the amplitude of the complex impedance at low frequency (below 1,000 Hz) are correlated with increased modification of the surface by LSP, which appears to cause a denser and more stable protector layers, thereby enhancing the resistance of the passive films, along with the corrosion resistance.
[1] U. Trdan et al., Corrosion Science 82 (2014) 328-338 [2] Y. Sano et al., Materials Science and Engineering A 417 (2006) 334-340 [3] JL. Ocaña et al, Applied Surface Science 238 (2004) 501-505
55 ORAL Abstract #896 Enhancement of microstructural, mechanical and tribological properties of Al-Mg-Si alloy by LSP process
U. Trdan1, M. Skarba2, J.A. Porro3, J.L. Ocaña3 and J. Grum1 1Faculty of Mechanical Engineering, Askerceva 6, 1000 Ljubljana, Slovenia 2Faculty of Materials Science and Technology in Trnava, Paulínska 16, 917 24 Trnava, Slovak Republic 3Centro Láser U.P.M., Carretera de Valencia km. 7,300, 28031 Madrid, Spain
The aim of this study is to assess the effects of laser shock peening without coating (LSPwC) parameters on the microstructural, mechanical and tribological properties of wrought Al-Mg-Si alloy. The alloy used in the study (AA6082), is the strongest in the 6XXX group and is widely used in the marine, automotive, aerospace and construction industries due to its low cost, good weight/strength ratio, high corrosion resistance and welding ability by the friction stir welding process. The influence of surface ablation and ultra-high plastic strain deformations induced by the LSPwC on the micro- and nano-structures and dislocation configurations were analysed using optical, confocal, polarized light and transmission electron microscopy. Moreover, LSPwC effect on the mechanical state was also evaluated via analyses of residual stresses and microhardness distribution. Tribological behaviour under dry contact conditions was studied in air, in accordance with the ASTM G99-04 standard, using a ball-on-disc configuration with an AISI 52100 ball (diameter 3mm). Test parameters were selected as following: sliding speed 0.0785 m/s, sliding distance 1000 m and a normal load of 5 N, which corresponds to a maximum Hertzian contact pressure of 1.22 GPa (mean value 0.81 GPa). During the experiments several variables were recorded, such as wear, sliding speed, friction force, friction coefficient, etc. Surface morphology and wear volume were characterized by the SEM and confocal microscope, respectively.
Fig.1. (a-b) Bright-field TEM images of the LSPwC treated specimens: (a) dense dislocations and cell structures, (b) shear bands with SAD pattern inset taken from the centre region and (c) wear trace of unpeened specimen.
TEM results confirmed an exceptional increase in dislocation density after LSPwC treatment with various dislocation configurations and greatly refined microstructure with ultra-fine and nano grains. In addition, a good agreement between the dislocation density measurements and residual stresses were obtained. Results of the present study also revealed that despite the general increase of surface roughness after LSPwC, lower wear rate and friction coefficient can be achieved due to the modified surface condition and compressive residual stresses.
[1] A.H. Clauer et al., Effects of laser induced stress waves on metals, Met. Trans. 675-702 (1981). [2] U. Trdan and J. Grum, “SEM/EDS characterization of laser shock peening effect on localized corrosion of Al alloy in a near natural chloride environment,” Corrosion Science, vol. 82, 328-338 (2014). [3] C. Correa, L. Ruiz de Lara, M. Díaz, J.A. Porro, A. García-Beltrán, J.L. Ocaña, “Influence of pulse sequence and edge material effect on fatigue life of Al2024-T351 specimens treated by laser shock processing”, International Journal of Fatigue, vol. 70, 196–204 (2015). [4] U. Trdan, M. Skarba and J. Grum, “Laser shock peening effect on the dislocation transitions and grain refinement of Al–Mg–Si alloy”, Materials Characterization, vol. 97, 57–68 (2014).
56 ORAL Abstract #837 Suppression of Crack Propagation of Duralumin by Cavitation Peening
H. Soyama1, N. Kumagai1, L. Xu1, O. Takakuwa1, and F. Takeo2 1Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai, Japan 2Hachinohe National College of Technology, 16-1 Uwanotai, Tamonoki, Hachinohe, Japan
Shock wave induced by cavitation bubble collapse can be used for mechanical surface treatment in the same way of laser peening. The peening method using cavitation is called “cavitation peening” [1, 2] or “cavitation shotless peening” [3], as shots are not used. Although improvement of fatigue strength of duralumin plate with a hole was already demonstrated [2], the characteristics of crack propagation were not clear. In the present paper, the crack propagation of duralumin was investigated by using a load controlled plate bending fatigue tester which was developed by the authors [4]. In the present experiment, duralumin Japanese Industrial Standards JIS A2017-T3 was used as tested material, as the same material was tested at the fatigue test [2]. The geometry of the specimen was same as in the report and the thickness of the duralumin plate was 4 mm [4]. The both surfaces of the fatigue specimen was treated by cavitation peening. A cavitating jet in water was used for the cavitation peening. The injection pressure of the jet was 30 MPa, the nozzle throat diameter was 2 mm, and the standoff distance was 262 mm. The processing time per unit length was 4 s/mm. After cavitation peening, the notch was introduced on the surface of one side by a milling machine. The depth, width and length of the notch were 0.25 mm, 0.5 mm and 5 mm, respectively. Figure 1 reveals the crack length 2a with the number of cycles N of the bending fatigue test for the non-peened specimen and cavitation peened specimen. As shown in Fig. 1, the non-peened specimen was broken at N = 18,291 cycles. On the other hand, the fractured cycles of cavitation peened specimen was 78,225 cycles. Namely, the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In order to investigate effect of cavitation peening on crack propagation rate, Fig. 2 illustrates the relation between the stress intensity factor range K and the crack propagation rate da/dn. As shown in Fig. 2, the crack propagation rate was reduced by cavitation peening. For example, da/dN was 3.3 × 10-7 m/cycle at 14.4 MPa for non-peened and 4.0 × 10-8 m/cycle at 14.5 MPa for cavitation peening. It was concluded that cavitation peening suppressed the crack propagation of the duralumin. √� √�
-4 20 10
-5 mm mm 15 10 a Non peened 10-6 10 Non peened
m/cycle 10-7
5 da/dN -8 2 length Crack 10
Cavitation peening rate Crack propagation Cavitation peening 0 10-9 0 25,000 50,000 75,000 100,000 5 10 15 20 25 30 Number of cycles at fatigue test N cycles Stress intensity factor range K MPa
Fig. 1. Crack length as a function of number of cycles at fatigue test Fig. 2. Reduction of crack propagation rate by cavitation√� peening
[1] H. Soyama and Y. Sekine, “Sustainable Surface Modification Using Cavitation Impact for Enhancing Fatigue Strength Demonstrated by a Power Circulating-Type Gear Tester,” International Journal of Sustainable Engineering, vol. 3, 25-32 (2010). [2] H. Soyama, “The Use of Cavitation Peening to Increase the Fatigue Strength of Duralumin Plates Containing Fastener Holes,” Materials Sciences and Applications, vol. 5, 430-440, (2014). [3] H. Soyama, K. Saito and M. Saka, “Improvement of Fatigue Strength of Aluminum Alloy by Cavitation Shotless Peening,” Trans. ASME, Journal of Engineering Materials and Technology, vol. 124, 135-139 (2002). [4] H. Soyama, “Evaluation of Crack Initiation and Propagation of Stainless Steel Treated by Cavitating Peening Using a Load Controlled Plate Bending Fatigue Tester,” Metal Finishing News, vol. 15, no. 4, 60-62 (2014).
57 ORAL Abstract #870 Fatigue Characteristics of UNSM-treated SAE52100 Bearing Steel
Y.S. Pyun1, C.M. Suh2,J.H. Kim1, A. Amanov1, S.H. Nahm3 and M.S. Suh4 1Department of Mechanical Engineering, Sun Moon University, Asan 336-708, Korea 2School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea 3Korea ResearchInstitute of Standards and Science, Daejeon 305-600, Korea 4Korea Institute of Energy Research, Daejeon 305-343, Korea
Main author email address: [email protected]
Ultrasonic nanocrystal surface modification (UNSM) technology is a novel surface modification technologythat can improve the mechanical and tribological properties of interacting surfaces in relativemotion. UNSM treatment was utilized to improve the fatigue strength of slim bearings made of SAE52100 bearing steel without damaging the raceway surfaces. In this study,fatigue results that were subjected to different impact loads of the UNSM treatment wereinvestigated and compared with those of the untreated specimens. The hardness of the UNSM-treatedspecimens increased by about 20%, higher than those of the untreated specimens. TheX-ray diffraction analysis showed that a compressive residual stress of more than 1 GPa wasinduced after the UNSM treatment. Also, electron backscatter diffraction analysis was used to studythe surface structure and nano-grain refinement.
The rotary bending fatigue results showed that the strength of the UNSM-treated specimens increased by about 31%, compared to those of the untreated specimens. These results may beattributed to the increased hardness, the induced compressive residual stress, and the presence of nanocrystalstructure after the UNSM treatment. In addition, the fracture surface analysisshowed that the fish-eye crack initiation phenomenon was observed after the UNSM treatment.
58 ORAL Abstract #872 A Comprehensive Review of Nanostructured Materials by Ultrasonic Nanocrystal Surface Modification Technique
A. Amanov and Y.S. Pyun 1Department of Mechanical Engineering, Sun Moon University, Asan 336-708, South Korea
Main author email address: [email protected]
It is well known that the nanostructured materials with a grain size of 100 nm or less are considered the material of the future. Nanostructured materials possess superior properties to those of conventional coarse-grained materials. Hence designing and producing potentially cost-efficient and environmentally products with better performance and efficiency are on demand. This paper gives a comprehensive review about the most recent progress in production, characterization, fundamental understanding and the performance of nanostructured materials by ultrasonic nanocrystalline surface modification (UNSM) technique. In this review, we demonstrate a detailed description of the literature on the subject as well as highlighting challenges for the production of nanostructured materials by UNSM technique. Practical applications of UNSM technique in various industries are also considered and discussed.
59 ORAL Abstract #820 Wear and Fatigue Behavior of the Rail by UNSM
S. Chang1 and Y.S. Pyoun2
1Korea Railroad Research Institute, Uiwang, Gyeonggi-do, Korea 2Sunmoon university, Asan, Choongcheongnam-do, Korea
email address: [email protected]
The railway track is repeatedly overstressed and damaged by the increase of passing tonnage as well as the numerous contact cycles of train wheels and rail especially at corner tracks[1-2]. In order to secure the safety of train operation, rail surface needs regular inspection and maintenance. Surface hardening of the rail was attempted by using ultrasonic nanocrystal surface modification (UNSM). Two types of rails, normal rail and heat treated rail, were prepared for surface modification. Some changes in the surface properties were detected with respect to hardness and residual stress. Wear and rolling contact fatigue tests were performed with the rail materials after UNSM. Wear amount was measured to estimate the effect of UNSM with static loads and revolution speeds of the wear test. The data obtained from the test showed the effect of UNSM on surface hardening of the rail materials.
Fig. 1. Basic mechanism of UNSM
[1] M. Vidaud and W. Zwanenburg, "Current situation on rolling contact fatigue - a rail wear phenomena", Swiss Transport Research Conference (2009) [2] J. Brouzoulis, “Wear impact on rolling contact fatigue crack growth in rails”, Wear 314 (2014)
60 ORAL Abstract #875 Rotary Bending Fatigue Properties of Inconel 718 Alloys by Ultrasonic Nanocrystal Surface Modification Technique
J.H. Kim1, C.M. Suh2, A. Amanov1, H.D. Kim1 and Y.S. Pyun1 1Department of Mechanical Engineering, Sun Moon University, Asan 336-708, Korea 2School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea
Main author email address: [email protected]
This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM) technique on fatigue properties of SAE AMS 5662 (solution treatment) and SAE AMS 5663 (hardening treatment) of Inconel 718 alloys. The fatigue properties of the specimens were investigated using a rotary bending fatigue (RBF) tester. Results revealed that the UNSM-treated specimens showed longer fatigue lifetime in comparison with those of the untreated specimens. The improvement in fatigue lifetime of the UNSM-treated specimens is attributed mainly to the induced compressive residual stress, increased hardness, reduced roughness and refined grains at the top surface. Fractured surfaces were analyzed using a scanning electron microscopy (SEM) in order to give insight into the effectiveness of UNSM technique on fracture mechanisms and fatigue life.
61 ORAL Abstract #1017 Effect of UNSM on the Fatigue Life of IN718+
Micheal Kattoura1, Abhishek Telang1, Dong Qian2, Seetha Ramaiah Mannava1, Vijay K.Vasudevan1 1Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH45221-0072, USA 2 Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080-3021, USA
Email address: [email protected]
Fatigue experiments on Allvac 718 Plus (IN718+) are conducted to study the improvement in the fatigue life after Ultrasonic Nano-crystal Surface Modification (UNSM). UNSM uses vibration energy by striking the material surface at the rate of several thousand strikes per second (20–40 KHz) as a constant pressure is applied. Stress controlled uniaxial fatigue tests were conducted on the as-received, heat treated, and UNSM treated samples to determine the improvement in fatigue life through the stress-life (S-N) curves. The effects of UNSM on residual stresses, microstructure changes and hardness is investigated. For the samples subjected to UNSM treatment with static loads of 20N, the surface compressive residual stresses around -1600 MPa and the hardness increase from 680 Hv to 920 Hv. The residual stress and hardness profiles through the depth of the UNSM samples are studied and the depth of effect is determined. In addition, changes in the micro-structure were characterized using the classical Optical Microscopy (OP), and Scanning Electron Microscopy (SEM). The surface compressive residual stresses and hardening induced by UNSM led to improvement in fatigue life.
62 ORAL Abstract #1008 The mechanisms of thermal engineered laser shock peening for enhanced fatigue performance
Yiliang Liao1, and Gary J. Cheng2 1Department of Mechanical Engineering, University of Nevada, Reno, Reno, NV, 89557, USA 2Department of Industrial Engineering, Purdue University, West Lafayette, IN, 47906, USA
Email Address: [email protected]
Abstract
Thermal engineered laser shock peening (LSP) is a technique combining warm laser shock peening (WLSP) with subsequent post-shock tempering treatment to optimize the surface strength and fatigue performance of metallic materials. This technique integrates the advantages of LSP, dynamic strain aging (DSA), dynamic precipitation (DP) and post-shock tempering to obtain optimized microstructures for extending fatigue life, such as nanoprecipitates and highly dense dislocations. In this work, AISI 4140 steel is used to evaluate the thermal engineered LSP process. The resulting microstructures as well as mechanical properties are studied under various processing conditions. The mechanism underlying the improvements in fatigue performance is investigated. It is found that the extended fatigue life is mainly caused by the enhanced cyclic stability of compressive residual stress as well as surface strength. This improved material stability and reliability are attributed to the enhanced dislocation pinning effect corresponding to the number density, size and space distribution of nanoprecipitates, which could be tailored by manipulating the WLSP processing conditions and by post-shock tempering. The effects of the precipitate parameters on the precipitation kinetics as well as on the dislocation pinning strength are discussed [1-2].
[1] Y. L. Liao, C. Ye, S. Suslov, G. J. Cheng, “The mechanisms of Thermal Engineered Laser Shock Peening for Enhanced Fatigue Performance”,Acta Materialia, 60, 4997–5009 (2012). [2] Y. L. Liao, G. J. Cheng, “Controlled precipitation by thermal engineered laser shock peening and its effect on dislocation pinning: Multiscale dislocation dynamics simulation and experiments”, Acta Materialia, 61, 1957-1967 (2013).
63 ORAL Abstract #936 Microstructure, Residual Stress and Property Changes in Metallic Alloys Induced by Advanced Mechanical Surface Treatments
Amrinder Gill,1 Abhishek Telang,1 Chang Ye,1 Zhong Zhou,3 Gokul Ramakrishnan,1 Yixiang Zhao,1 Sagar Bhamare,1 Hitoshi Soyama,4, Y-S. Pyun,5 S. R. Mannava,1 Dong Qian3 and Vijay K. Vasudevan1 1Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA 2Department of Mechanical Engineering, University of Akron, Akron, OH 3Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 4Department of Nanomechanics, Tohoku University, Sendai, Japan 5Department of Mechanical Engineering, Sun Moon University, Cheonan-Asan, S. Korea
Main author email address: [email protected]
Laser shock peening (LSP), ultrasonic nanostructure surface modification (UNSM) and cavitation shotless peening (CSP) are novel surface treatment processes that generate varying degrees of favorable compressive residual stresses and near-surface microstructural changes, thereby leading to dramatic improvements in fatigue strength, crack propagation and corrosion resistance of alloys and components. In this talk, we will present results of the effects of LSP, UNSM and CSP on the behavior of aerospace alloys like IN718, IN718+, Ti-6Al-4V and Ti6242 as well as nuclear alloys like alloy 600 and 304 austenitic stainless steel. Coupons of these alloys were surface-treated at a range of process conditions. Depth-resolved characterization of the residual strains, stresses and texture was achieved using high-energy synchrotron x-ray diffraction as well as by conventional XRD. The near-surface and through-the-depth changes in microstructure (i.e., nanostructures, dislocations, metastable phases, etc) were studied using complete pattern x-ray diffraction analysis, EBSD/OIM, PED and by TEM of thin foils fabricated using both FIB and traditional methods. Local property changes were examined using nanoindentation, microhardness and micropillar compression tests. Fatigue tests were also conducted and experiments were also performed to assess the thermal stability of induced microstructural changes and residual stress. Finally, controlled experiments and analytical and finite element modeling and simulation were utilized to predict the surface-treatment-induced residual stress and thermal relaxation of residual stress. The results showing the relationship between process parameters and the near-surface microstructure, residual strain/stress distributions, texture, hardening, thermal stability, mechanical properties, including plasticity, hardening and fatigue, corrosion and stress corrosion cracking behavior, will be presented and discussed.
64 ORAL Abstract #893 Laser Peening for Surface Enhancement of Thin Aluminum Structures
K. Langer1, T. J. Spradlin1, and M. E. Fitzpatrick2 1Air Force Research Laboratory, AFRL/RQVS, 2790 D Street, Wright-Patterson Air Force Base, OH 45433 US 2Coventry University, Faculty of Engineering & Computing, Priory Street, Coventry CV1 5FB UK
The use of laser peening (LP) to induce favorable distributions of compressive stress in very thin structural sections (on the order of about 2-3 mm or less, such as an aircraft skin) without detrimental side effects can be challenging. Not only are thin structures prone to distortion [1, 2], but as demonstrated experimentally by Dorman et al [3] in aluminum plates and Cellard et al [4] in titanium plates, near-surface tensile stresses can develop, extending into the component to depths as great as 0.5 mm. Although various techniques have been developed to mitigate these effects, such as two-sided peening or the application of special acoustic backing materials, these procedures are not feasible for in situ components in which the far side of the section is inaccessible.
In this paper, three-dimensional non-linear finite element modeling is used to investigate the effects of laser peening on thin aluminum plates. The basic model was validated using the experimental findings in [1], and then expanded to explore the relationships between peen parameters, spot patterning, and plate thickness. The objective was to better understand the effects of one-sided processing on the resulting residual stress state. Effects of modeling assumptions were explored to minimize the influence of computational factors (e.g., time incrementation and element size) and key differences between the peening of thin and thick structures were identified.
As will be discussed, LP-induced residual stresses in thin sections are strongly driven by spot overlap and patterning, with some peening schemes producing significantly more favorable distributions than others (Figure 1). Also, for the special case of applying peen spots in a line configuration, such as in the surface repair of a scratch or scribe mark, it is confirmed that the stress state is strongly biaxial (as shown in [1]), with the near-surface stresses transverse to the peen line generally less conservative than for a single laser shot. The paper concludes with a list of recommendations for inducing favorable residual stress distributions in thin aluminum sections.
Fig. 1. The effects of peen patterning on the induced residual stress in a thin aluminum plate. Three patterns were simulated each at 300% coverage but with varying amounts of overlap. (a) Cross-section illustrating transverse residual stresses through the center of the peen line. The red and orange regions represent tensile stresses; all other regions are compressive. (b) Transverse stresses through the plate thickness.
[1] A. H. Claure and D. F. Lahrman, “Laser shock processing as a surface enhancement process,” Durable Surface, 197, 121-142 (2001). [2] M. B. Toparli and M. E. Fitzpatrick, “Residual stresses induced by laser peening of thin aluminium plates,” Materials Science Forum, 681, 504-509 (2011). [3] M. Dorman, M. B. Toparli, N. Smyth, A. Cini, M. E. Fitzpatrick, and P. E. Irving, “Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects,” Materials Science and Engineering A, 548, 142-151 (2012). [4] C. Cellard, D. Retraint, M. François, E. Rouhaud, and D. Le Saunier, “Laser shock peening of T-17 titanium alloy: influence of process parameters,” Materials Science and Engineering A, 532, 362-372 (2012).
65 ORAL Abstract #873 Experimental Study of Laser Shock Peening onASME SA240Type 304 Stainless SteelSubjected toDifferent Initial States
Yaofei Sun1, Zhenqiang Yao1,2, andYongxiang Hu1,2 1School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 China 2State Key Laboratory of Mechanical System and Vibration,Shanghai Jiao Tong University, Shanghai 200240 China
The beneficial effects of laser shock peening (LSP)on austenitic stainless steel and it’s fabrications like weldmentshave been demonstrated by several investigators [1-3].In order toinvestigate the relations betweeninitial state of material and LSP effects,and then improve the understanding of the mechanism of LSP.Experimental study was performed onASME SA240 Type 304 stainless steel thick plate and three typical initial states: (a) solution annealed, (b) welded and (c) surface machined were selected as the representatives.The states (b) and (c)were got from state (a) by additional processing to eliminate individual differences.LSP was performedby Nd:YAGlaser with 532nm output wavelength and 10ns short pulseon constant state samples for each condition. Subsequently surface roughness, micro-hardness,residual stress and microstructurewas studied by roughness tester, micro-hardness tester, X-ray Diffraction (XRD) technology,optical microscope (OM) and scanning electron microscope (SEM).Some main factors were discussed in detail.Experimental results show that LSPcandecrease surface roughness, improve micro- hardness, refine grains.As for the residual stress distribution,LSP processed solution annealed samples and surface machined sampleswereuniform and welded sampleswere not so uniform because of residual stress rebalancing.Thus,LSP is an effective way to improvethe performances of ASME SA240 Type 304 stainless steelparts and optimized parameters should be usedin parts of different initial states.
[1] Lu, J.Z., K.Y. Luo, D.K. Yang, X.N. Cheng, J.L. Hu, F.Z. Dai, H. Qi, L. Zhang, J.S. Zhong, Q.W. Wang, and Y.K. Zhang, Effects of laser peening on stress corrosion cracking (SCC) of ANSI 304 austenitic stainless steel,Corrosion Science, 60,145-152 (2012). [2] Sano, Y., M. Obata, T. Kubo, N. Mukai, M. Yoda, K. Masaki, and Y. Ochi, Retardation of crack initiation and growth in austenitic stainless steels by laser peening without protective coating, Materials Science and Engineering A, 417(1-2), 334-340 (2006). [3] Roman, I.B., M.H. Tierean, J.L. Ocaña, and C. Munteanu, Microstructural characterization and friction coefficient after the laser shock processing treatment on AISI 316 L stainless steel welds, Journal of Optoelectronics and Advanced Materials, 15(7-8), 645-649 (2013). [4] Julan, E., S. Taheri, C. Stolz, P. Peyre, and P. Gilles,Numerical simulation of laser shock peening in presence of weld for fatigue life design,ASME 2014 Pressure Vessels and Piping Conference, PVP 2014, American Society of Mechanical Engineers (ASME), 2014.
66 ORAL Abstract
#930 Structural Certification of Laser Peening for Safety Critical Aluminum Forgings
P.J. Caruso1, M.S.Edghill1, G.T. Kerrick2, andP.C. Gross2
1Lockheed Martin Aeronautics Company, 1 Lockheed Blvd, MZ 6516, Fort Worth, TX 76108, USA 2Lockheed Martin Aeronautics Company, 1 Lockheed Blvd, MZ 6502, Fort Worth, TX 76108, USA
Pete Caruso, [email protected]
The effect of laser shock peening (LSP) in the crack initiation and damage tolerance behavior of 7085-T7452 forgings was investigated. The F-35B (STOVL variant) utilizes very large 7085-T7452 forgings for wing carry-thru bulkheads that have experienced fatigue cracking prior to 1 lifetime of full scale durability test as shown in Figure 1 [1].Additional fatigue cracking has occurred between 1 and 2 lifetimes of cycling [2]. A comprehensive structural certification plan has been developed to qualify laser shock peening (LSP) torestore F-35B aircraft service lifefor fielded aircraft and apply in new production. LSP lessons learned during qualification of safety critical titanium bulkheads have been applied to reduce the certification risk [3]. Three test phases shall be performed to qualify the LSP process for safety critical aluminum forgings. Phase 1 is the LSP process characterization testing conducted at the coupon level. Representative cross-section details shall be laser peened and residual stress measurements shall verify finite element predictions. Test spectra truncation and marker band methods shall be verified in coupon level tests. Phase 2 is the element level durability and damage tolerance testing to characterize the variability of the LSP process on mechanical properties. Element durability tests shall develop the crack initiation life improvement benefit.Element damage tolerance tests shall develop crack growth rate data in the presence of artificial flaws introduced preceding and subsequent to the LSP process. Phase 3 is the subcomponent level durability test to verify the LSP process. A critical step is to develop acceptable baseline (unpeened) fatigue test results to verify the durability test set-up. The LSP subcomponent durability test results shall be used to certify the safety critical aluminum forgings.LSP expected benefits are to restore the durability and damage tolerance life of delivered and new F-35B aircraft. Lessons learned from the LSP certification testing shall be applied to improve the life of F-35A and F-35C variants, if warranted from interpretation of full scale airframe test results.
(a)
(b)
Crack
Up
© 2014 Lockheed Martin Corporation © 2014 Lockheed Martin Corporation Inbd
(a) Lower airframe surface with test anomaly (b) Crack location in structural detail
Fig. 1. Carry-thru bulkhead crack location [1]
[1] M.E. Christian and R.J. Burt, “Overview of the Full Scale Durability Tests on F-35 Lightning II Program,”USAF Aircraft Structural Integrity Conference(2012). [2]M.E. Christian and R.J. Burt, “Overview of the Full Scale Durability Tests on F-35 Lightning II Program,”USAF Aircraft Structural Integrity Conference(2014). [3] M.R. Hill, A. DeWald, J. VanDalen, J. Bunch, S. Flanagan, K. Langer, “Design and Analysis of Engineered Residual Stress Surface Treatments for Enhancement of Aircraft Structure,” USAF Aircraft Structural Integrity Conference (2012).
© 2015 Lockheed Martin Corporation. All Rights Reserved. 67 ORAL Abstract #892 A Simulation Study on Enhanced High Cycle Fatigue Life of LSP using Extended Space-Time Finite Element Method
Sagar Bhamare1, Z. Zhou2, R. Zhang2, S. R. Mannava3, V. K. Vasudevan3 and D. Qian2
1Innova Engineering, Inc. Irvine, CA 92614
2Department of Mechanical Engineering University of Texas at Dallas Richardson, TX 75080
3 Department of Mechanical and Materials Engineering University of Cincinnati Cincinnati, OH 45211
Safe-life and damage-tolerance approaches have been widely used for fatigue life predictions of LSP- related applications. However, these methods have some limitations due to their empirical nature. Finite element method based on semi-discrete approaches, currently used for simulating the structural response under dynamic conditions have time-step limitations making HCF simulation an elusive task. An extended space-time method (XTFEM) based on the time discontinuous Galerkin formulation [1, 2] is proposed to handle the time-scale issues in fatigue problems. This method is stable for any large time-step and accurately handles high frequency loadings. Advantages of our XTFEM in handling practical fatigue loading histories over semi-discrete methods are presented. XTFEM is coupled with the two-scale continuum damage mechanics model [3] for evaluating fatigue damage accumulation, with a damage model governing the fatigue crack-initiation and propagation as the simulation progresses. HCF simulations are performed using the proposed methodology on a specimen subjected to LSP. Results obtained for the total fatigue life of specimen (fatigue crack initiation and propagation) under different loading conditions are presented. Proposed simulation can serve as the robust tool for predicting the life of structural components processed by LSP and other surface mechanical treatments.
References
[1] S. U. Chirputkar and D. Qian, "Coupled atomistic/continuum simulation based on extended space-time finite element method," Cmes-Computer Modeling In Engineering & Sciences, vol. 24, pp. 185-202, Feb 2008. [2] S. Bhamare, T. Eason, S. Spottswood, S. Mannava, V. Vasudevan, and D. Qian, "A multi-temporal scale approach to high cycle fatigue simulation," Computational Mechanics, pp. 1-14, 2013/08/29 2013. [3] R. Desmorat, A. Kane, M. Seyedi, and J. P. Sermage, "Two scale damage model and related numerical issues for thermo-mechanical High Cycle Fatigue," European Journal of Mechanics - A/Solids, vol. 26, pp. 909-935, 2007.
68 ORAL Abstract #894 Predictive Crack Growth Technique for Laser Peening Process Development
T.J. Spradlin1 and K. Langer1 1Air Force Research Laboratory, AFRL/RQVS, 2790 D Street, Wright-Patterson AFB, OH 45433 US
Extending the service life of military aircraft components using residual stresses has been well documented over the past 50 years. One residual stress treatment technique, laser peening (LP), has shown excellent fatigue life extension in numerous tests with typical treatments garnering 2-4 times the fatigue performance of an untreated component [1]. This extension requires careful planning, taking into consideration the material, geometry, and intended loading of the component. Initially, large test programs were implemented to determine the best LP parameters for a given scenario, eventually being augmented by physics-based modeling due to the large design space available to the LP process. Approval for these processes continues to be on a case-by-case basis, contingent on multiple factors: cost, applicability, time, % fatigue life extension, and ability to track crack growth. Because LP induces compressive residual stresses in the near surface region, the compensatory tensile residual stresses are shifted sub-surface. While an axial tensile load would be mitigated by surface compressive stresses, sub-surface a crack can propagate rapidly via tensile stresses in what is known as crack tunneling [2]. Current predictive methods lack the ability to track this sub-surface behavior, limiting the accuracy of fatigue crack growth predictions throughout the various design stages of an LP treatment. This work seeks to combine currently available tools to predict any crack tunneling behavior a given LP treatment might produce, limiting or avoiding crack tunneling as a major crack growth mechanism, and expediting LP process approval. This work is comprised of three separate efforts; the first is experimental measurement of potential LP treatments on feature plates; the second simulates the fatigue crack growth behavior of a feature plate using the measured residual stresses; and the third is experimental testing to validate the crack growth predictions. Replicates of a simple specimen fabricated from Al 2024-T351 (specimens are 10” X 4” X 0.5” with a 1.0” centered hole machined with 0.002” tolerances on all dimensions) have been treated using three different LP processes. The vendor was allowed to choose three distinct sets of parameters that included spot size, percentage overlap between both spots and layers, laser energy density (variable between layers), and spot pattern layout with a target goal of 4x fatigue life extension over an untreated specimen. Contour Method residual stress measurements have been made across the supposed crack plane of each LP treated specimen. Next, a 3D model of the feature plate geometry will be created in a finite element (FE) code and then loaded with the residual stress field from each of the Contour Method measurements as an initial condition. 2D cracks will then be grown across the assumed crack plane by iterating between the FE code and a commercial crack growth analysis program. Finally, the crack growth rate predictions and simulated crack front morphology will be validated through experimental testing using standard crack growth techniques and marker banding.
[1] C. Montross, et al., “Laser Shock Processing and Its Effects on Microstructure and Properties of Metal Alloys: A Review,” International Journal of Fatigue, Vol. 24, No. 10, 1021–1036 (2002). [2] M.A. James, and J.C. Newman Jr., “The effect of crack tunneling on crack growth: experiments and CTOA analyses”, Engineering Fracture Mechanics, Vol. 70, 457-468 (2003).
69 ORAL Abstract #851 Laser Shock Peening to Recover Fatigue Life of Flawed Friction Stir Welded Joints
M. Leering1, C. Polese1, 2 1School of Mechanical, Industrial and Aeronautical Engineering, 2DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, 2000, South Africa
Friction Stir Welding (FSW) is a solid state thermo-mechanical joining process which is a novel welding technique utilised on materials such as aluminium, steel and titanium. During this process, a rotating welding tool is plunged between two sheets, locally heating the material and further stirs them together forming a solid bond once cooled. A possible flaw which may occur during this welding is known as Lack of Penetration (LOP). LOP can occur due to slight misalignment of the welding tool, variations in sheet thickness and inaccuracies in assembly tolerances which are possible issues in the industrial domain [1]. These flaws are commonly recognised as cracks, which originate from the root of the weld. An example of extreme LOP is shown in Fig. 1a. The effects of LOP were investigated by intentionally introducing controlled offsets of the welding tool whilst FSW occurs using aluminium alloy 6082-T6, 3mm thick sheets. LOP was found to reduce the tensile load carrying capability by as much as 20%, depending on the magnitude and position of the crack.
2.5 1 GW/cm21 GW/cm2 2 GW/cm22 GW/cm2 3.53.5 GW/cm2 GW/cm2 5.55.5 GW/cm2 GW/cm2 2
1.5
1 Deflection [mm] 0.5
0 0 5 10 15 20 Coverage [spots/mm2]
Fig.1. (a) Micro CT scan of FSW with 2.5mm horizontal tool offset. (b) Deflection of aluminium samples, with varying LSP parameters.
Laser Shock Peening (LSP) is a process whereby a pulsing laser interacts with the surface of a metal material resulting in compressive residual stresses being introduced into the component. LSP has already been utilised in the mitigation of unfavourable tensile residual stress, characteristic of FSW, and showed to improve the fatigue performance of the unflawed joints [2, 3]. LSP was used in the present work to alter the tensile residual stress in controlled flawed FSW joints, in order to reduce the rate at which the initiated cracks (LOP) propagate throughout the weld. This ideally rectifies the detrimental effects of LOP on the fatigue life and general strength of the FSW joints. LSP parameters were initially optimised by investigating the effects of varying laser power intensities (1-5.5 GW/cm2) and processed coverage (0.5-20 spots/mm2) on the deflection, hardness, and residual stress of both base and FSW materials, as for example shown in Fig. 1b for the measured deflection of the LSP base material. Static testing, bending fatigue testing, and fracture surface analysis were then used to show that LSP has a beneficial effect on these flawed joints. Successful demonstrations of using LSP for this purpose would result in a reduced need for strict material quality control, welding assembly tolerances, post-welding testing and the eventual scrapping of irrecoverable welds.
[1] C. Mandache, D. Levesque, “Non-destructive detection of lack of penetration defects in friction stir welds”, Science and Technology of Welding and Joining, vol. 17, 295-303 (2012). [2] Y. Sano, K. Masaki, “Improvement in fatigue performance of friction stir welded A6061-T6 aluminum alloy by laser peening without coating”, Materials & Design, vol. 36, 809-814 (2012). [3] O. Hatamleh, “A comprehensive investigation on the effects of laser and shot peening on fatigue crack growth in friction stir welded AA 2195 joints,” International Journal of Fatigue, vol. 31, 974-988 (2009). 70 ORAL Abstract #934 Effect on fatigue life of LSP induced residual stress in the C(T) specimen: experiments and prediction models
N. Smyth1, and M.E. Fitzparick1 1Coventry University, Priory Street, Coventry, CV1 5FB
Laser shock peening (LSP) is an emerging surface treatment used to enhance the fatigue properties of safety critical components and structures. This is achieved through creation of near surface compressive residual stress that inhibits fatigue crack initiation and reduces fatigue crack growth rate (FCGR). Although the effect on FCGR of tensile residual stress fields is general well understood further effort is required to understand fully the effect on FCGR in the presence of compressive residual stress fields. In this work compact tension specimens made from 2624-T39 aluminum of thickness 4 and 12.4 mm and were treated using LSP. The peening was applied on both sides of the samples in a 15×15 mm square patch ahead of the notch tip. The induced residual stress fields were measured using the incremental hole drilling method and X-ray diffraction. Constant amplitude fatigue tests were performed and crack growth rate was measured using optical and DCPD based methods. The effect of the induced residual stress fields on fatigue crack closure, that is the premature contact of the opposing crack faces prior to the minimum applied load being reached during unloading, was monitored using compliance based methods. The effect of the residual stress field on the crack front shape evolution during crack growth was studied by inspection of the fracture surfaces using SEM. A residual stress based FCG model is presented to predict the observed behaviour. The model used 2D FE analysis and included the measured residual stress fields. Based on the experiments and modelling results an optimum residual stress field to enhance the fatigue life in the compact tension specimens is proposed. Also 3D finite element analysis was used to study the effect on the crack front shape evolution as the crack advanced through the residual stress fields, as demonstrated in figure 1 below. Proper understanding of this effect is vital if LSP is to be applied successfully to complicated geometries and structures. Unpeened crack front Peened crack front 3.80
2.85
1.90
0.95 Through Thickness (mm) Thickness Through 0.00 13 14 15 16 17 18 19 20 21 22 23 Crack Length (mm) Fig. 1. Effect on crack front shape evolution of LSP induced residual stress field predicted using FEA
71 ORAL Abstract #860 Laser Shock Peening for Stress Relaxation of Laser Beam Welded AA6056-T4
D. Glaser1, C. Polese1,2 1 School of Mechanical, Industrial and Aeronautical Engineering, 2 DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, 2000, South Africa
The South African Laser Shock Peening research initiative is focused on LSP without an ablative protective coating for the use on airframe structural applications. Conventionally, the skin and stringer joints of integral airframe structures are riveted together, however Laser Beam Welding (LBW) has been identified as a potential improved joining process in terms of production costs, weight reduction, and maintenance [1]. The thermal LBW process generates tensile residual stresses in the component, therefore LSP is investigated as a possible stress relaxation solution. The work conducted has been on a weldable 3.2mm AA6056-T4 alloy developed for airframe structural joints.
Investigations were first conducted on the base material only to determine a suitable range of LSP parameters. The primary parameters analysed were power intensity and coverage (or spot overlap) whereby the process is applied using a thin water layer and a laser wavelength of 1064nm. The different LSP parameter combinations have been evaluated using different residual stress measurement techniques, such as of X-Ray Diffraction (with hard X-Rays from Synchrotron radiation), the incremental hole-drilling technique, and Neutron diffraction. Due to the resource intensive nature of residual stress characterization, an “Almen Strip” methodology has also been evaluated as an effective method to practically distinguish between LSP parameter configurations. The “Almen Strip” approach shows that sample deflections are well correlated to residual stress measurements found with XRD, and can therefore effectively distinguish optimal parameter combination performance.
(a) (b) 0,6 0,4 0,2 Normalized 0 Longitudinal ‐0,2 Stress ‐0,4 ‐0,6 LBW + LSP ‐0,8 LSP region LBW only ‐1 0 5 10 15 Weld only Weld + LSP Distance from Weld Centre (mm)
Fig. 1 (a) LBW and LBW +LSP samples. (b) XRD residual stress results for the Laser Beam Weld before and after application of LSP.
Once the optimal LSP performance envelope had been identified, the selected LSP configuration was applied to LBW butt welds of the same aluminium alloy. As shown in Fig. 1b, the XRD results for the welded coupons show a tensile residual stress as expected, and after LSP treatment, the measurements reveal a successful relaxation of the tensile stress state to a beneficial state of compressive residual stress under the region treated by LSP. Bending fatigue trials have also been conducted for the different sample types combining LSP with the welded and base samples only. Firstly, the LSP treatment of the un-welded base material showed an enhancement in fatigue life. As expected, the LBW samples revealed a reduced fatigue life compared to the base metal due to the tensile residual stress. However, after LSP treatment of the LBW samples, preliminary results indicate that the fatigue life can be restored to levels beyond that of the un-welded base material. Therefore, it has been demonstrated that LSP can successfully be engineered as a stress relaxation tool after the LBW process.
[1] M. Pacchione, J. telgkamp, “Challenges of the Metallic Fuselage”, 25th International Congress of the Aeronautical Sciences (2006)
72 ORAL Abstract #890 Integrated Multiscale Simulation Approach to Laser Shock Peening Process
D. Qian1, M. R. Karim1, S. R. Mannava2 and V. K. Vasudevan2
1Department of Mechanical Engineering University of Texas at Dallas 800 Campbell Road, Richardson, TX 75080
2 Department of Mechanical and Materials Engineering University of Cincinnati Cincinnati, OH 45211
There is a continuing interest in exploring the fundamental mechanisms of laser shock peening (LSP) process in improving the mechanical performance of a wide range of applications. Unlike many other mechanical surface treatments, LSP involves the complex mechanisms of laser-material interaction. Furthermore, the unique spatial and temporal profiles of the LSP-induced pressure generated lead to microstructural evolutions in the materials that are not well-understood based on a single scale modeling approach. In this context, a multiscale simulation method that integrates the atomistic with continuum representations was established with a goal to link the relevant length scales. Efforts in applying the multiscale framework for LSP will be presented. The work is based on the so-called bridging scale approach that was developed in [1, 2]. Following a brief introduction of the bridging scale methodology, the detailed implementation on the modeling of laser pressure and material responses will be presented. In particular, we highlights the ability of the multiscale methodology in incorporating critical experimental observations and providing detailed answers on the link among the LSP process parameters, coupon/parts configurations and material responses.
References
[1] G. J. Wagner and W. K. Liu, "Coupling of atomistic and continuum simulations using a bridging scale decomposition," Journal of Computational Physics, vol. 190, pp. 249-274, Sep 1 2003. [2] D. Qian, G. J. Wagner, and W. K. Liu, "A multiscale projection method for the analysis of carbon nanotubes," Computer methods in applied mechanics and engineering, vol. 193, pp. 1603-1632, 2004 2004.
73 ORAL Abstract #881 Investigation on effects of thickness and boundary conditions in laser shock peening by FEM
H.R. Karbalaian1, A. Yousefi-Koma1, M. Karimpour1, S.S. Mohtasebi1, M.H. Soorgee1 1School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Laser shock peening (LSP) is one of the advanced surface treatments that causes favorable compressive residual stresses imparted on and near the surface that causes the material to have better mechanical properties such as fatigue life, hardness and strength [1,2]. Because of severity of loading, LSP is capable of transforming the surface of the material to resemble a nano-structure [3]. However due to its complexity, it is crucial to understand accurately the effect of parameters and details of the process on the resulting material properties. Due to the significant cost and time necessary to conduct the necessary experimental studies, the numerical alternative has been chosen for estimation of enhanced properties and the effect of process parameters. It was shown that finite element method (FEM) is capable of providing models which have good agreement with the available experimental data [4,5]. Up until now the effects of various parameters and details such as complex geometry, multiple and overlapping laser pulses, laser spot shape and size, laser intensity, on the resulting residual stress have been investigated using FEM [5,6]. However, the effects of size and boundary condition of the part have not been reported yet in the case of one sided laser peening since all the models were semi-infinite. The LSP modeled in this paper, was carried out by Ballard. In that work 35CD4 steel specimen with cylindrical form and a diameter of 30mm and height of 15mm was subjected to 150J laser pulse [7]. In this study, the effects of size and boundary condition on residual stress, induced by LSP have been investigated using FEM. For evaluation of the effect of the size, different aspect ratios which are defined as the ratio of radius to height, were modeled. The results are shown in figure 1. Significant changes can be observed caused by varying thickness beyond aspect ratio=0.1. To evaluate the effect of boundary condition, three different boundary conditions were considered. Results show that the boundary condition has limited effect on surface residual stress.
Fig. 1. Residual stress S11 on the surface of material
[1] C. S. Montross, T. Wei, L. Ye, G. Clark and Y. Mai, “Laser shock processing and its effects on microstructure and properties of metal alloys: a review,” Int. J. Fatigue, 24, 1021-1036 (2002). [2] P.Peyre, X. Scherpereel, L. Berthe, C.Carboni, R.Fabbro, G. Be´ranger, andC.Lemaitre, “Surface modifications induced in 316L steel by laser peening and shot-peening. Influence on pitting corrosion resistance”. Materials Science and Engineering A, 280, 294-302 (2000). [3]C. Zhigang, Y.Jie, G.Shuili, C.Ziwen, Z.Shikun and X.Haiying, “Self-Nanocrystallization of Ti-6Al-4V Alloy Surface Induced by Laser Shock Processing,” Rare Metal Materials and Engineering, 43, 1054-1060 (2014). [4] W. Braisted and R. Brockman, “Finite element simulation of laser shock peening,” Int. J. Fatigue, 21, 719-724(1999). [5] K. Ding and L. Ye, “Simulation of multiple laser shock peening of a 35CD4 steel alloy,” Journal of Materials Processing Technology, 178, 162–169 (2006) [6] R. Brockman, W. Braisted, S.E. Olsen, R.D. Tenaglia, A.H. Clauer, K. Langer and M.J. Shepard, “Prediction and characterization of residual stresses from laser shock peening” Int. J. Fatigue, 36, 96-108 (2012) [7] P. Ballard, “Residual stresses induced by rapid impact-applications of laser shocking,”Ph. D. Dissertation, Ecole Polytechnique, France (1991).
74 ORAL Abstract #839
Evaluation of Residual Stresses in Double Peened Thin Samples with Hole-Drilling and Synchrotron X-Ray Techniques Stefano Coratella1, a, Michael E. Fitzpatrick1,b 1Faculty of Engineering and Computing, Coventry University, Priory Street, Coventry CV1 5FB, UK [email protected]; [email protected]
Laser Shock Peening is a relatively new technology that allows introducing deep compressive residual stresses (RS) inside metallic components. While several studies have shown the possibility to increase the fatigue life by introducing RS in metallic alloys, more studies are needed on the thin samples in order to understand how the RS is distributed after the surface treatment. In order to fill this gap, twelve aluminum alloy 2024-T351 samples 2 mm thick were treated: six of them were laser shock peened only on one side; while the other six were laser peened with two coincident strips, one each face of the sample. In order to measure the RS and find the correlation between the laser parameter settings and the RS distribution, incremental hole-drilling measurements were carried out in different positions on each plate. In order to complement the data from the hole-drilling technique, which is reliable only to 1 mm in depth, some through-thickness measurements were carried out using synchrotron X- ray diffraction at the Argonne Photon Source facility, USA.
Fig. 1 The through-thickness RS profile for the stress component aligned along the direction of the peening
As Fig. 1 shows, with the diffraction methods it was possible to obtain the though-thickness RS profile in a sample 2-mm-thick with a laser peening treatment on both faces. Further results from the hole-drilling showed how the increase of both the laser spot diameter and the overlapping distance can be beneficial for the RS in terms of higher and deeper compression, while in the double peened samples it was possible to obtain the same RS profile in both the stress direction aligned to the laser peened strip and the perpendicular to it.
75 ORAL Abstract #1016 Peening Surface Stress Improvement to Mitigate Stress Corrosion Cracking in Pressurized Water Reactors
P. Crooker1, G. White2, and W. Sims3 1EPRI, 3420 Hillview Avenue, Palo Alto, CA 94304 USA 2Dominion Engineering, Inc., 12100 Sunrise Valley Dr., Suite 220, Reston, VA 20191 USA 3Entergy, 1340 Echelon Parkway, Jackson, MS 39213 USA [email protected]
Laser peening and water jet (i.e., cavitation) peening are surface stress improvement methods that are available to mitigate primary water stress corrosion cracking (PWSCC) of Alloy 600/82/182 nickel-base alloy components in nuclear power pressurized water reactors (PWRs) (Fig. 1). These peening methods generate compressive residual stresses at the wetted surface, preventing future initiation of PWSCC and arresting the growth of any existing cracks located in the compressive stress zone. PWSCC of pressure boundary components made using Alloy 600 and its weld metals Alloys 82 and 182 has been a major materials degradation concern affecting PWRs. PWSCC cracking and leakage concerns have necessitated costly inspections, repairs, replacements, and lost power production.
Fig. 1. Candidate Alloy 600/82/182 Locations in PWR Reactor Vessels for Peening Mitigation of Stress Corrosion Cracking.
Beginning in 1999, in-service peening has been extensively applied in Japanese boiling water reactors and PWRs to mitigate stress corrosion cracking. The first peening mitigation applications in the U.S. are planned for 2016 and 2017. EPRI has developed a detailed technical basis demonstrating the effectiveness of peening to mitigate PWSCC without adverse effects. The technical basis, which includes extensive data generated by peening vendors as well as confirmatory testing sponsored by EPRI, is now being used to support acceptance by the ASME Boiler & Pressure Vessel Code and U.S. regulator of appropriate relaxation of inspection intervals for peened components. In this approach, in order to justify inspection relief, a set of performance criteria must be met to ensure that minimum stress parameters are achieved (compressive stress magnitude, depth, and coverage), that the minimum stress condition is maintained for the life of the component, and that there are no unacceptable adverse effects. The technical basis work includes a combination of mockup testing and analyses to demonstrate that the intended stress effect is achieved under operating conditions. Corrosion testing including with simulated PWR primary coolant confirms the effectiveness of the peening mitigation. The long-term performance is demonstrated by testing for thermal stress relaxation and stress shakedown due to load cycling.
A Monte Carlo probabilistic simulation model was developed to assess the benefit of peening mitigation in reducing the risk of pressure boundary leakage or rupture during future operation. Key model elements include the residual stress profile induced by peening, the sustainability of the compressive peening stress with operation, crack initiation, fracture-mechanics-based crack growth, and crack detectability via non-destructive examination (NDE), including visual examinations for evidence of leakage. The approach emphasizes modeling of multiple flaw initiation to address the possibility of flaws of various depths being present when peening is performed.
76 ORAL Abstract #897 Investigating the LSP effects on initiation and propagation of pitting corrosion by means of acoustic emission and electrochemical methods
U. Trdan and J. Grum Faculty of Mechanical Engineering, Askerceva 6, 1000 Ljubljana, Slovenia
Corrosion damage represents one of the most important problems in existing structural parts. Although aluminium alloys covers a broad field of various applications owing to low weight, good mechanical properties and high corrosion resistance, in aggressive environment these alloys undergo a localized corrosion and stress corrosion cracking [1,2]. However, localized forms of corrosion are rather complex and consists various steps and electrochemical reactions. In this aspect, implementation of non-destructive acoustic emission (AE) method enables early detection with ameliorated understanding of corrosion phenomena [3,4]. Thus, in-situ monitoring of acoustic emission (AE) during accelerated potentiostatic corrosion measurements in a chloride environment was used to study localised corrosion phenomena of unpeened and Laser Shock Peened without coating (LSPwC) Al alloy. Correlations between LSwC parameters, anodic current density and characteristics of AE events were observed and analysed.
(a) (b) (c)
Fig. 1. (a) Number of AE events inside the specific amplitude level during PS corrosion test, (b) evolution of AE burst waveform and (c) spectrograph of AE population -3-.
The results revealed three different populations of AE events during the potentiostatic sweep, which differ significantly in the waveform, amplitude, signal duration and rise time. This effect is mainly attributed to the different acoustic emission sources, or to say different direction of energy release. First population of AE bursts, with low emissivity originated from the initiation step of pitting corrosion attack. The second population with higher amplitude and longer duration of AE bursts appeared due to the propagation of pitting corrosion, in which the most vivid difference between untreated and LSPwC treated specimens could be observed. However, the most emissive source was found to be population -3- (Fig. 1), due to the evolution of hydrogen bubbles, with highest amplitude and the longest duration of AE signals.
Moreover, results of the present work confirmed high employability of in-situ AE monitoring technique for the early detection, propagation and characterization of localised corrosion attack even at extremely accelerated corrosion tests. Moreover, obvious beneficial effect of preliminary LSPwC treatment was confirmed, with reduction of both, i.e. current density and AE activity, indicating improved corrosion resistance in an aggressive chloride environment.
[1] U. Trdan and J. Grum, Corrosion Science, vol. 82, 328-338 (2014). [2] U. Trdan and J. Grum, Corrosion Science, vol. 59, 324–333 (2012). [3] M. Boinet, J. Bernard, M. Chatenet, F. Dalard, S. Maximovitch, Electrochimica Acta, vol. 55, 3454–3463 (2010). [4] Y.P. Kim, M. Fregonese, H. Mazille, D. Feron, D. Santarini, Corrosion Science, vol. 48, 3945–3959 (2006).
77 ORAL Abstract #939 Effects of Laser Shock Peening on SCC behavior of Alloy 600 in tetrathionate solution and high temperature pure water Abhishek Telang1, Sebastien Teysseyre2, Xingshuo Wen1, S.R. Mannava1, Vijay K. Vasudevan1 1Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221-0072 2Idaho National Laboratory, Materials Properties and Performance, Idaho Falls, ID 83415-2218
Abstract Surface treatments like Laser Shock Peening (LSP) are being explored to improve the stress corrosion cracking (SCC) resistance of austenitic stainless steels, Ni-based Alloy 600 and their welds. In this study, the effects of LSP on SCC behavior of Alloy 600 in tetrathionate solution and high temperature pure water were investigated. Depth and magnitude of LSP induced compressive residual stresses and changes in the near surface microstructure were characterized. The effects of LSP on SCC susceptibility of Alloy 600 in tetrathionate solution were evaluated using slow strain rate tests (SSRT) and constant load tests. The decreased susceptibility to SCC in tetrathionate solutions after LSP was attributed to the deep compressive residual stresses and changes in the near surface microstructure. Results from U bend tests, constant load tests and SSRT of LSP treated Alloy 600 in simulated PWR environment will also be presented.
78 ORAL Abstract #946 The effect of peening for stress corrosion cracking on hot work tool steel
N.Shibuya1, Y. Kobayashi2 and T. Tsuji2 1 SINTOKOGIO, LTD. Mass and Precision Finishing Business division Development group 72-2, Tsukeda, Nishijo, Oharu-cho, Ama-gun, Aichi, Japan 2SINTOKOGIO, LTD. Blast business division Blast technology group, Process technology team 180-1, Komaki, Ohgicho, Toyokawa, Aichi, Japan
Email address: [email protected]
Die-casting method are using in automotive industry and aero craft industry that have good property on high strength and high precision. Fracture of die-casting die can separate two types. One is heat checking on cavity surface, another one is stress corrosion cracking on the surface of water cooking hole that is located on back of die in order to cool die. The residual stress that is induced in near the surface by shot peening or laser peening is famous to prevent the stress corrosion cracking [1]. By the way, there are many literatures about stainless steel for nuclear parts [2]. However, there are few studies on steel for dies. Then, we investigate the effect of peening for stress corrosion cracking on typical material of hot work tool steel JIS SKD61.
Fig.2 Tensile stress state of specimen. Table.1 Result of stress corrosion cracking test. Bend radius×750hr (Load stress[MPa]) R=100 R=200 R=400 (2180) (1090) (545) Non-treatment Fracture Fracture Non-Fracture Cast steelφ0.1 Fracture Fracture Non-Fracture Conditioned cut wire φ0.3 Fracture Non-Fracture Non-Fracture Fig.1 Residual stress distribution by shot peening. Conditioned cut wire φ0.6 Fracture Non-Fracture Non-Fracture
Fig.1 shows residual stress distribution by various kind of shot peening conditions on JIS SKD61. The larger shot diameter is, the deeper crossing point is. Fig.2 shows loaded condition of tensile stress for specimen. Shot peened specimens are prepared for stress corrosion cracking experiment. Specimens that are applied tensile stress like Fig.2 are dipped in hot water. The temperature is 98 degrees Celsius. Table 1 shows the result of stress corrosion cracking experiment after 750 hours. In the case of R=200, stress corrosion cracking occurred in Φ0.1mm shot peening specimen. However, stress corrosion cracking did not occur in Φ0.3mm shot peening specimen. Therefore, it is supposed deeper crossing point is effective for stress corrosion cracking. For the result, we consider that laser peening specimen gotten deep crossing point are obtained better resistance of stress corrosion cracking than shot peening specimen.
[1] Y. Kobayashi and A. Matsui, “Shot Peening to Prevent Cracking in the Water Cooling Hole for Die-Casting Die,” The Twelfth International Conference on Shot Peening , p463-p469 (2014). [2] Y. Sano, K. Masaki, K. Akita, T. Kubo, M. Sato and K. Kajiwara, “Nondestructive evaluation of laser-peened materials by high-energy synchrotron radiation,” The Japanese Society for Synchrotron Radiation Research, p270-p278 (2008)
79 ORAL Abstract #865
Oblique laser peening of interior of 304 stainless steel tube for enhanced stress corrosion cracking resistance
R. Sundar, R. K. Gupta, P. Ganesh, D. C. Nagpure, K. Ranganathan, R. Kaul, K. S. Bindra, L. M. Kukreja and S. M. Oak
Raja Ramanna Centre for Advanced Technology, Indore 452013 INDIA
Laser shock peening (LSP) has emerged as a powerful surface treatment for enhancing performance characteristics of engineering components, particularly operating under fatigue and stress corrosion cracking (SCC) conditions. Stress corrosion cracking in austenitic SS is one of the serious metallurgical problems in high temperature high pressure devices. In a recently concluded study, significant suppression of SCC susceptibility of machined 304 L stainless steel (SS) sheet specimens has been demonstrated through normal incidence LSP. However, in actual applications, SCC damage is mostly encountered on internal surface of tubular components and life enhancement of such components demand peening on their internal surfaces. Major challenges involved in LSP internal tubular surfaces include (i) difficulty in maneuvering laser beam in small space, (ii) protecting beam steering optics from dielectric damage due to intense laser pulse and (iii) maintaining proper water flow while protecting associated focusing and bending optics from water splashes generated by irradiation of specimen’s surface with high intensity laser beam. These limitations make the task of normal incidence LSP on internal surface of tubular components extremely difficult. The present investigation evaluates a new approach of oblique LSP (O- LSP) for enhancing SCC resistance of internal surface of type 304 SS tube. To the best of our knowledge it is the first attempt to exploit O-LSP for a potential industrial application. Oblique-LSP experiments were performed with an indigenously developed 2.5 J/8 ns Nd:YAG laser system on type 304 SS tube (OD = 111 mm; ID = 101 mm). Internal surface of SS tube was machined and the tube was wire cut into six equal longitudinal sections to facilitate residual stress measurements on their internal surfaces. The cut sections were reassembled to form the tube by mounting them on a suitable jig. The jig was mounted on computer-controlled rotation and translation stage, while using a 125 µm thick black PVC-based tape as the sacrificial coating and water as plasma-confining medium. The experiments employed a 400 mm focal length lens to focus the laser beam while keeping the specimen at a distance of 380 mm from the lens. O-LSP was performed at 62 angle of incidence (AOI - angle between laser beam and surface normal) which provides maximum peening length of ~150 mm in the given tube. AOI of 62º was selected on the basis of a related sub-study aimed at determining the maximum AOI yielding a uniform distribution of surface compressive stress. Machined internal surface of SS tube displayed high magnitude of tensile stress along machining marks i.e. in circumferential direction. O-LSP effectively introduced compressive residual stress on the machined surface, as shown in Fig.1. The Accelerated SCC testing of partly peened SS tube specimens carried out as per ASTM G36 in boiling MgCl2 solution for 8 hrs, demonstrated significant suppression of SCC susceptibility of internal surface of SS tube, as shown in Fig. 2. On machined surface, the fraction of SCC-damaged area accounted for ~25% whereas on O-LSP surface, the corresponding effect was confined to 1-2%. The paper presentation shall include effect of processing parameters on SCC susceptibility of peened surface. The technique of O-LSP, in spite of its inherent limitations on length of peened region being limited by tube ID and the need for access from both sides, presents a simplified approach for peening internal surface of small tubular components.
Machined O-LSP
Fig.1: Surface profiles of residual stress Fig.2: Machined (left) and O-LSP(right) surfaces after SCC test. across O-LSP region Some of the SCC damaged regions marked with red arrows 80 ORAL Abstract #818 Use of Neural Networks in Laser Peening
M. Burak Toparli1, Michael E. Fitzpatrick2 1Defense Industries Research and Development Institute, (TÜBİTAK SAGE), P.K. 16, 06261, Mamak, Ankara, Turkey 2Faculty of Engineering and Computing, Coventry University, Priory Street, Coventry CV1 5FB, UK
Inspired by biological nervous systems, Neural Networks or Artificial Neural Networks are mathematical models used to link complex interactions: i.e. the interactions between multiple input and output parameters having complex relationships between them. Linear and non-linear functions connected by nodes can be considered in a similar manner as neurons connected at synapses in a human nervous system. The technique employs “training” data (for example experimental data) to “learn” the interaction between input and output parameters employing functions connected by nodes. The “trained” model can be used to interpolate any input parameters to obtain predicted output parameter(s). Neural Network is widely used in many disciplines including engineering applications like selection of powder metallurgy process parameters for material production [1].
Fig. 1. Schematic of the Neural Network used in this study
Laser peening can induce a significant amount of distortion when applied to materials having thin sections, as shown by the authors previously [2]. In this study, 10 different peened patches were investigated in terms of the amount of distortion induced after laser peening. Laser peening was carried out using different laser energy, laser spot size and number of laser shots, and these became the input parameters for the Neural Network. The amount of distortion arising from the laser peening was measured by a Coordinate Measuring Machine: this was the desired output from the Neural Network. Based on the measured experimental data, a Neural Network was created (Fig. 1), so that the model learnt the interaction between input and output parameters. Using the Neural Network, the effects of the individual input parameters – laser energy, laser spot size and number of shots – were investigated for their effect on the output parameter, distortion. According to the created Neural Network, as number of shots increases, amount of distortion also increases, as can be expected. However, the overall effect of laser energy and laser spot size was found to be more complex.
[1] R.P. Cherian, L.N. Smith and P.S. Midha, “A neural network approach for selection of powder metallurgy materials and process parameters,” Artificial Intelligence in Engineering, 14., 39-44 (2000). [2] M.B. Toparli and M.E. Fitzpatrick, “Through thickness residual stress measurements by neutron diffraction and hole drilling in a single laser- peened spot on a thin aluminium plate,” Materials Science Forum, 772., 167-172 (2014).
81 ORAL Abstract #950 The Effect of Ultrasonic Nanocrystal Surface Modification on Fatigue Behavior of a Low Modulus Beta Titanium Alloy
Rohit Jagtap1, Abhishek Telang1, Henry Rack2, S.R.Mannava1 and Vijay K.Vasudevan1 1Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA 2Material Science & Engineering Department, Clemson University, Clemson, SC, USA
Email address: [email protected]
In this paper, the effects of mechanical surface treatment, known as Ultrasonic Nanocrystal Surface Modification (UNSM) on residual stress, near0surface microstructure, local properties and fatigue behavior of a low-modulus beta Titanium alloy Ti-35Nb-7Zr-5Ta-0.3O (wt %) alloy was studied. At first, the samples were solution treated at 850º C for 1 hour and water quenched to obtain a single phase β structure. These samples were subjected to UNSM treatment with two different static loads (20N and 50N) and characterized by X-ray diffraction for residual stresses and by optical and scanning electron microscopy for microstructure. Nanoindentation tests were used to determine local properties like hardness with distance from the treated surface. The UNSM treated samples shows more refined microstructure with plastic deformation at the top surface, compressive residual stresses as high as -1600 MPa and significant increase in surface hardness from 400Hv to 600Hv. Fatigue tests were also performed and the results for UNSM treated samples were compared with non-treated samples. The improvement in fatigue life is mainly resulted from nanostructured surface, increase in surface hardness caused by severe plastic deformation and high magnitude of compressive residual stresses.
82 ORAL Abstract #899 Neutron Diffraction Evaluation of Residual Stress in a PH13-8Mo round bar after Laser Shock Peening
M. Pavan1, S. Coratella2, and M. E. Fitzpatrick 3 1Coventry University, Priory Street, Coventry, United Kingdom, CV1 5FB
Laser Shock Peening (LSP) is a relatively new technology [1] able to induce a deep compressive residual stress (RS) field into metallic materials, improving fatigue life [2], resistance to fretting fatigue and resistance to stress corrosion cracking. Extensive measurement and modelling work has been undertaken recently on the application of LSP to aerospace aluminium parts, and this study extends this research to a high-strength steel sample for aerospace applications. The specimen is a round bar made of a martensitic precipitation-hardened stainless steel (PH13-8Mo), laser shock peened uniformly as shown in Figure 1(a) with the following laser parameters: 10 GW/cm2 as laser power density, 18 ns pulse time of each laser shot and 3 layers of treatment at each point. To increase the measurement accuracy close to the surface, the Z-scan method [3] has been applied to calculate the strain in the Hoop and Axial directions. The radial strain component has been measured with a regular scan, corrected then for the spurious strains introduced by the partial filling of the gauge volume.
(a) (b)
Fig. 1. (a) PH13-8Mo round bar measurement line P1 and in red the LSP treatment area (b) Residual stress results through the thickness along P1
The results presented in Figure 1 (b) show compression in both the axial and hoop directions starting from 100 µm depth as expected. Despite an S-shaped profile in the first half millimetre, probably caused by the turning machining process after peening, the RS trends highlight the presence of a beneficial compressive stress field up to 7 millimetres depth.
[1] Allan H. Clauer, C.T.W., and Stephan C. Ford, “THE EFFECTS OF LASER SHOCK PROCESSING ON THE FATIGUE PROPERTIES OF 2024-T3 ALUMINUM”, in Lasers in Materials Processing, 1983, Los Angeles. [2] H. Luong and M. R. Hill, "The effects of laser peening and shot peening on high cycle fatigue in 7050-T7451 aluminum alloy," Mater. Sci. Engineering: A, vol. 527, pp. 699-707, 2009. [3] Edwards, L. (2003). Near-surface stress measurement using neutron diffraction. In Analysis of Residual Stress using Neutron and Synchrotron Radiation, M.E. Fitzpatrick, and A. Lodini, eds. Taylor & Francis, pp. 233-248.
83 Poster Abstract #830 Modeling of Laser Peen Forming with Prestress by Eigenstrian Method
Yongxiang Hu, Xiongchao Yu, Zhi Li, Zhenqiang Yao State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Main author email address: [email protected] (Yongxiang Hu)
Laser peen forming, is a purely mechanical forming method achieved through the use of laser energy to form large- scale metal sheet with small curvatures. The prestressing LPF is proposed as an effective and useful method to improve its formability of thick metal sheets [1]. Besides experiments to analyze the role of prestress on bending, numerical modeling of prestressing LPF can provide an effective way to predict the deformed shape. Hu et al proposed an eigenstrain-based numerical method for the efficient prediction of LPF without any prestress [2]. In prestressing LPF, the existed prestress state would affect the eigenstrain field after laser shocks. But it has not been taken into account in the previous numerical model and requires further work.
The objective of the present work is to investigate the effect of elastic prestress on the deformed shape in LPF through numerical modeling. An eigenstrain-based numerical model is developed to simulate the prestressing LPF. An explicit-infinite plate model is first used to determine the eigenstrain under different prestress conditions. As shown in Fig.1, the boundary conditions of displacements from a simple bending with plain strain are proposed to define to include the prestress effect in the explicit model. By incorporating the eigenstrain, an implicit elastic model is developed to predict the defomred shape efficiently.The model predictions of deformed shape are compared with the corresponding experimental results as shown in Fig.2. The numerical model is validated to be an effective and efficient tool for the predictions of deformed shape. The reason for different bending deformation under prestress is further analyzed from the point of eigenstrain. The increase of bending deformation by the prebending curvature is found because of the increase of in-plane plastic strains. The forming with prestress makes the plastic strain much earlier to generate with higher amplitude during the shock loading.
(a) y (b)
1400 Infinite Mesh BC3 BC2
h s e M e t i n i F Region 1
z y 1200 Region 2 x x 2R o 2R Region 3 1000
Region 4 l 1 BC2 800 l =l +2R BC3 2 1 Scanning Path BC1 Experiment Rx Experiment Ry σ z x 600 Model Prediction Rx σ ≠ 0 M σy y Model Prediction Ry εy = 0 M Bending curvature radius (mm) x 400 o -0.5 0.0 0.5 1.0 1.5 2.0 -1 Prebending curvature, 1/Rpb (m ) l Fig. 1 Explicit-infinite plate model with displacement boundary Fig. 2 Experimental and model predicted relationship between radii of conditions from a simple bending problem in plain strain bending curvature and prebending curvatures
References: [1] L. Hackel, and F. Harris, 2002, Pre-loading of components during laser peen forming, U.S. Patent [2] Y. Hu, and R.V. Grandhi, 2012, "Efficient Numerical Prediction of Residual Stress and Deformation for Large-Scale Laser Shock Processing Using the Eigenstrain Methodology," Surface and Coatings Technology, 206(15), pp. 3374-3385.
84 Poster Abstract #843 The effect of laser shock peening on the low cycle fatigue behavior of superferritic stainless steel
S. Hereñú1,*, L. Spadaro2, R. Bolmaro3, G. Gomez-Rosas4, A. Chavez-Chavez4, C. Rubio-González5
1 Instituto de Física Rosario-CONICET, UTN-FRSN, Bv.27 de febrero 210 bis, 2000 Rosario, Argentina. 2 Universidad Tecnológica Nacional. Facultad Regional San Nicolás, Argentina. 3 Instituto de Física Rosario-CONICET, UNR-FCEIA, Bv.27 de febrero 210 bis, 2000 Rosario, Argentina 4 Departamento de Fisica, CUCEI, Universidad de Guadalajara, Blvd. Marcelino Garcia Barragan 1421, 44430 Guadalajara, Jal, México. 5 Centro de ingeniería y desarrollo industrial, Av. Playa Pie de la Cuesta 702, Querétaro, México. *[email protected]
The laser shock peening (LSP) is a new technique that improves the fatigue life of metals components by inducing deep compressive residual stresses through the surface [1]. However, the beneficial effects of LSP depend on the persistence and stability of such residual stress fields under cyclic loading and temperature [2, 3]. Moreover, if absorbent coatings (typically a black paint) are not used in LSP operation, thermal effects can occur on the metallic substrate [1, 4].
The effectiveness of LSP for improving the high cycle fatigue (HCF) performance in many materials, such as aluminum, steel, Ti, Ni and its alloys, is well documented [1-2,5-7]. On the other hand, no available reports are found in literature evaluating the influence of LSP on materials tested under the low cycle fatigue (LCF) regime.
The purpose of this work is to study in a superferritic stainless steel UNS S 44600 the effect of LSP, without protective coating, on the low cyclic fatigue behavior at room temperature. The laser source is a Q switched Nd:YAG operating at 10 Hz. The FWHM of the generated pulses is 6 ns; the maximum pulse energy is 1 J/pulse with a wavelength of 1064 nm. Three pulse densities are used: 1600, 2500 and 5000 pulses/cm2. In samples with and without LSP, LCF tests have been conducted at room temperature under fully reversed plastic strain control, with plastic strain ranges of Δεp = 0.1% and Δεp = 0.3%. The steel microstructure is analysed by optic, transmission (TEM) and scanning electron microscopy (SEM) equipped with electron diffraction spectroscopy (EDS). Residual stresses are measured by X-Ray diffraction and the hole drilling method. The micro-hardness profiles is also presented.
In the present steel, LSP produces beneficial compression residual stresses that agree with an increase in both the dislocation density and hardness. However, the thermal effects of the LSP without coating cause intergranular corrosion that generates a stress concentration where fatigue cracks easily nucleate.
Acknowledgements The authors are grateful to the project supported by MINCYT–CONACYT (MX/11/12).
[1] C. S. Montross, T. Wei, L. Ye, G. Clark, Y-W Mai, International Journal of Fatigue 24, 1021-1036 (2002). [2] I. Nikitin, I. Altenberger, Materials Science and Engineering A 465 176–182 (2007). [3] C. Rubio-González, A. Garnica-Guzmán, G. Gómez-Rosas, Revista Mexicana de física 55 (4) 256–261(2009). [4] Y.Y. Xu, X. Dong Ren, Y. K. Zhang, J. Z Zhou, X. Q. Zhang, Key Engineering Materials, 353-358 1753-1756 ( 2007). [5] C. Rubio-González, J .L. Ocaña, G. Gomez-Rosas, C. Molpeceres, M. Paredes, A. Banderas, J. A. Porro, M. Morales, Materials Science and Engineering A 386 291–295 (2004). [6] C. Rubio-González, C. Felix-Martinez, G. Gomez-Rosas, J.L. Ocaña, M. Morales, J.A. Porro, Materials Science and Engineering A 528 914– 919 (2011). [7] P. Peyre, L. Berthe, X. Scherperreel, R. Fabbro, Journal of Materials Science 33 1421-1429 (1998).
85 Poster Abstract #847 Hardness and Surface Profiles of Laser Peened Marine Butt Welds
B. Ahmad1 and M. E. Fitzpatrick2 1Department of Engineering and Innovation, The Open University, Milton Keynes, MK7 6AA, UK 2Faculty of Engineering and Computing, Coventry University, Priory Street, Coventry, CV1 5FB, UK [email protected]
Residual stress is often considered as the main criterion during laser peening (LP) to affect the fatigue life improvement. In-addition to residual stresses other important factors for laser peening are changes in material hardness and surface finish. These two aspects are investigated in this paper for marine butt welded steel DH275. Vickers hardness map was determined through micro-indentation, and the surface displacement profile was measured using a co-ordinate measurement machine (CMM).
Figure 1 shows the Vickers hardness map on the cross section of a laser peened butt-welded specimen. The specimen was peened onto the weld and shows different levels of hardness depending upon initial hardness before peening. Fig. 2 shows the surface displacement profile. The plotted surface profile was measured from parent metal to weld crown toe location. A curved shape profile is seen in the parent metal, which was depressed in the laser peened region and at the weld toe where it reached at its highest level. Peened length HV Weld crown
Distance Parent Peened parent Weld from root metal metal of weld Y (mm)
Weld root X
Length (mm) Fig. 1. Vickers hardness map of a laser peened butt welded specimen.
Peened Parent metal parent metal
Weld toe
X (mm) Y (mm) Fig. 2. Surface displacement profile of a laser peened butt welded specimen.
During laser peening distortion can be significant, as has been noted for thin plates [1]. It is noted that the surface displacement profiles can provide significant information about the impact of the number of laser peening layers and the geometry of the specimen after welding. A comparative study was also performed between LP specimens.
[1] M. Dorman, M. B. Toparli, N. Smyth, A. Cini, M. E. Fitzpatrick and P. E. Irving, ‘‘Effect of Laser Shock Peening on Residual Stress and Fatigue Life of Clad 2024 Aluminium Sheet Containing Scribe Defects’’, Materials Science and Engineering A, Volume 548, pp. 142–151.
86 Poster Abstract #856 The effect of laser peening on the fatigue life of Ti17 titanium alloy
Qiao Hongchao Shenyang Institute of Automation Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China
Email address: [email protected]
To investigate the effect of laser peening on the fatigue life of Ti17 titanium alloy, different process parameters of laser peening are used to Ti17 alloy. And the influence of process parameters on mechanical properties and microstructure of Ti17 titanium alloy are optimized and summarised. With the increase of impact times and pulse energy, the hardness of specimens will be enhanced, but when the impact times reaches 3 times, the effect of laser peening will be saturated, with the increasing of impact times, the hardness will not be changed any more when going on processing. With regard to the improvement of the median fatigue life of Ti17 alloy, the best process parameter is 7J and impacting twice, the median fatigue life can be improved nearly 3 times. For the improvement of the low fatigue life of Ti17 alloy, when impacted twice, the surface of the material will be intensified completely, and the low fatigue life can be improved more than 10 times. With the increase of impact times and pulse energy, the plastic deformation of specimens’ surface and the dislocation density of its subsurface will be improved, but when the impact times reaches 3 times, the plastic deformation and the dislocation density will not be increased. At the same time, laser peening can form strengthening layer and residual compressive stress on the surface of titanium alloys. In the strengthening layer, grain refinement is happened obviously. According to the experiment and the analysis above, the increasing of the dislocation density and grain refinement will be taken place due to the plastic deformation of titanium alloy surface, so the increasing of the dislocation density and grain refinement are the strengthening mechanism of enhancing the surface hardness of titanium alloys. At the same time, because of the plastic deformation of titanium alloy surface, the forming of fine-grain strengthening layer and residual compressive stress are the strengthening mechanism of prolonging the fatigue life of titanium alloys [1-4].
(a) (b)
Fig. 1. The fracture surface of fatigued specimens. (a) The fracture surface of fatigued specimens without laser peening. (b) The fracture surface of fatigued specimens with laser peening.
[1] Mu Z, Li H, and Li M Q, “The microstructure evolution in the isothermal compression of Ti17 alloy,” Materials Science and Engineering A, 582, 108-116 (2013). [2] Vasu A, Gobal K, and Grandhi R V, “A computational methodology for determining the optimum re-peeing schedule to increase the fatigue life of laser peened aircraft components,” International Journal of Fatigue, 70, 395-405 (2015). [3] Trdan U, Skarba M, and Grum J, “Laser shock peening effect on the dislocation transitions and grain refinement of Al-Mg-Si alloy,” Materials Characterization, 97, 57-68 (2014). [4] Ganesh P, Sundar R, and Kumar H, et al., “Studies on fatigue life enhancement of pre-fatigued spring steel specimens using laser shock peening,” Materials and Design, 54, 734-741 (2014).
87 Poster Abstract #868 LASER SHOCK PROCESSING TO IMPROVE Ti6Al4V SURFACE PROPERTIES
Cesar A. Reynoso-Garcia1, Gilberto Gómez Rosas2, Oscar Blanco Alonso2, Carlos Rubio Gonzalez3, Arturo Chávez Chávez2, E. Castañeda1
1Posgrado en Ciencia de Materiales, CUCEI, Universidad de Guadalajara Jose Guadalupe Zuno # 48, 45100. Núcleo Universitario los Belenes, Zapopan, Jalisco; México 2Departamento de Física, CUCEI, Universidad de Guadalajara Blvd. Marcelino García Barragán # 1421, 44430, Guadalajara, Jalisco; México 3Centro de Ingeniería y Desarrollo Industrial Av. Playa Pie de la Cuesta # 702, 76130. Desarrollo San Pablo Querétaro, Querétaro; México.
Abstract
The laser shock processing (LSP) is a technique of surface treatment that improves the mechanical, physical and chemical properties of metallic materials [1-5]. This treatment is based on high-energy laser pulses that impact the surface metal inducing a shock wave into the material. The shock wave generates a pressure due to the expansion of the plasma. Plasma is formed by the interaction of matter - energy. Ti6Al4V titanium alloy has an important value in the aeronautical, aerospace and medical industries. It is due to its low density, high melting point and its high resistance to corrosion [6].
The effect of laser shock processing (LSP) on the surface properties of Ti6Al4V alloy has been studied [7-9]. A high-energy pulse Q-switched Nd:YAG laser, operating in 1064 nm and 532 nm wavelengths, was used. The laser power density was 9 GW/cm2 and 7 GW/cm2, with pulse duration of 6 ns and 5 ns, respectively. The pulse density was 2500 pulses/cm2. The confining mode was water jet without ablative protection (LPwC). The results were supported by analysis of compressive residual stresses by the hole drilling technique. A pin on disk test was used to determine the friction coefficient. The hardness was determined by Vickers micro-indentation. The surface roughness was analyzed by confocal microscopy. The microstructure and wear debris were analyzed by scanning electron microscope (SEM). In this work we present a friction coefficient reduction, an increment in the hardness, an induced high field compressive residual stress and an increase in surface roughness in the treated surface of a Ti6Al4V alloy.
[1] Rubio-Gonzalez, C., et al. Effect of laser shock processing on fatigue crack growth of duplex stainless steel J. A. Mater. Sci. Eng. A 528, 914-919, (2011). [2] Sano,Y., et al., Retardation of crack initiation and growth in austenitic stainless steels by laser peening without protective coating Mater. Sci. Eng. A. 417, 334-340, (2006). [3] Sanchez-Santana, U. et al., Wear and friction of 6061-T6 aluminum alloy treated by laser shock processing” Wear 260, 847-854, (2006). [4] Peyre, Patrice et al., Influence of thermal and mechanical surface modifications induced by laser shock processing on the initiation of corrosion pits in 316L stainless steel” J. Mater. Sci. 42, 6866-6877, (2007). [5] Huyntaeck, L. et. al. Improvement of surface hardness of duplex stainless steel by laser shock hardening for the application to seawater desalination pump Desalin. Water Treat. 15, 43-47, (2010). [6] Trtica, M., et al. Surface modifications of a titanium implant by a picosecond Nd: YAG laser operating at 1064 and 532 nm Appl. Surf. Sci. 253, 2551-2556, (2006). [7] Khosroshahi, M. E., Characterization of Ti6Al4V implant surface treated by Nd:YAG laser and emery paper for orthopaedic applications” Appl. Surf. Sci. 253, 8772–8781, (2007). [8] Rozmus, M., Surface Modifications of a Ti6Al4V Alloy by a Laser Shock Processing Acta Phys. Polonica A 117-5, 808-811, (2010). [9] Ziwen, C., et al. Surface Profiles and Residual Stresses on Laser Shocked Zone of Ti6Al4V Titanium Alloy Rare Metal Mat Eng. 40- S4, 190-193, (2011).
88 Poster Abstract #869 State-of-the-Art and Perspectives: Ultrasonic Nanocrystal Surface Modification Technique towards Improving Surface Properties of Hard Ceramics
A. Amanov and Y.S. Pyun 1Department of Mechanical Engineering, Sun Moon University, Asan 336-708, South Korea
Main author email address: [email protected]
This paper is intended as an introduction to the newly developed ultrasonic nanocrystalline surface modification (UNSM) technique. In principle, this technique produces nanostructured materials (NMs) that are produced through the application of severe plastic deformation (SPD) to conventional coarse-grained (CG) materials [1]. This paper focuses on the state-of-the-art and perspectives of UNSM technique with recent mechanical and tribological experimental results of hard sintered ceramics. Possible mechanisms of friction and wear behavior of silicon carbide (SiC) and silicon nitride (Si3N4) with different counter surfaces under various environments are also discussed.
The combination of high hardness, high strength and high resistance to high temperature gives hard ceramics excellent capabilities for service in a wide range of applications [2]. However, despite these outstanding properties, pores in sintered ceramics cannot be fully eliminated and their mechanical and tribological properties are still poor, which restrict to work at conditions required for wear resistant technological applications. Fig. 1 shows the AFM images of residual indent impressions on the untreated and UNSM-treated SiC specimens with a depth of 2.33 µm and 2.01 µm, respectively. The fracture toughness quantified was found to be 2.62 MPa × m1/2 and 7.18 MPa × m1/2 for the untreated and UNSM-treated specimens, respectively. The findings of this paper confirm that the UNSM treatment insures a stronger and denser ceramics and hence enables superior mechanical and tribological properties than the conventional available sintered ceramics.
(a) (b) Pore
Pores
Fig. 1. AFM images of indent impressions on the untreated (a) and UNSM-treated (b) SiC specimens.
[1] A. Amanov, Y.S. Pyun, and S. Sasaki, “Effects of ultrasonic nanocrystalline surface modification (UNSM) technique on the tribological behavior of sintered Cu-based alloy,” Tribology International, vol. 72, 187-197 (2014). [2] A. Amanov, Y.S. Pyun, J.H. Kim, and S. Sasaki, “The usability and preliminary effectiveness of ultrasonic nanocrystalline surface modification technique on surface properties of silicon carbide,” Applied Surface Science, vol. 311, 448-460 (2014).
89 Poster Abstract #871 Fatigue Characteristics of UNSM and SP-treated Aluminum Alloy (A7075-T651) using Ultrasonic(20kHz) and Rotary Bending(53Hz) Fatigue Testing Machines
C.M. Suh1,S.H. Nahm2, M.S. Suh3, Y.S. Pyun4, J.H. Kim4and C.H. Suh5 1School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Korea 2Korea ResearchInstitute of Standards and Science, Daejeon 305-600, Korea 3Korea Institute of Energy Research, Daejeon 305-343, Korea 4Department of Mechanical Engineering, Sun Moon University, Asan 336-708, Korea 5Daegu Mechatronics & Materials Institute, Daegu 704-240, Korea
Main author email address: [email protected]
The VHCF Fatigue characteristics of A7075-T651 aluminum alloy were studied and compared with surface treatment of UNSM (ultrasonic nano-Crystal surface modification) technology and SP(shot peening) treatment. Fatigue characteristics of those are unearthed by using fatigue testing machines of followings; the ultrasonic fatigue testing machine (UFT, 20kHz), and the multi-spindles (cantilever type) rotary bending fatigue testing machines (RFT, 53Hz). The improvement of fatigue life was confirmed for rotary bending fatigue testing machines with the specimens treated under UNSM-30N and SP-35psi. The fatigue strength of ultrasonic fatigue test, UFT, 20kHz shows relatively lower than that of the rotary bending fatigue testing, RFT, 53Hz. However, in the 5x108 up to the regime of VHCF, both fatigue characteristic became similar. The general mechanical characteristics including hardness and fatigue strength of RFT specimen were improved by the UNSM and SP surface modification, nevertheless the effects of surface modification was not prominent under ultrasonic fatigue testing machine.
90 Poster Abstract #874
Fatigue Lifetime of AlBC3 Alloy by Ultrasonic Fatigue Testing Machine
I.S. Cho1, A. Amanov2, H.C.Noh3, T.H. Park3 and I.G. Park3
1Mbrosia Research Team of EBH Group, Asan 336-708, South Korea 2Department of Mechanical Engineering, Sun Moon University, Asan 336-708, South Korea 3Department of Hybrid Engineering, Sun Moon University, Asan 336-708, South Korea
Main author email address: [email protected]
The reliability for offshore structures is very important since they operate under harsh operating conditions for a long time. Material damage in seawater involves not only physical damage due to cavitation, but also fatigue damage; thus, seawater deteriorates the mechanical performance and lifetime of propellers. In this study, the influence of ultrasonic cavitation on the fatigue properties of AlBC3 alloy was investigated. The fatigue properties of the untreated and treated specimens were assessed using a ultrasonic fatigue testing (UFT) machine which was recently developed by Mbrosia Co., Ltd. [1]. The treated specimens exhibited longer fatigue life in comparison with those of the untreated specimens, which may attributed to the plastically deformed layer at the top surface of the treated specimen as shown in Fig. 1(b). Also, fracture analysis was also studied using a scanning electron microscopy (SEM) to shed light on the fracture mechanisms of the specimens.
(a) (b)
Fig. 1. Comparison of OM images for the untreated (a) and treated (b) AlBC3 specimens by ultrasonic cavitation.
[1] Information on http://www.mbrosia.co.kr
91 Poster Abstract #877 Effect of Ultrasonic Nanocrystal Surface Modification on Characteristics of Ti6Al4V up to Very High Cycle Fatigue
M. K. Khan1, 3, Y. L. Yongji1, Q. Y. Wang1, Y. S Pyoun2, A. Amanov2 1Department of Mechanics and Engineering Science, Sichuan University, Chengdu, 610065, China. 2Department of Mechanical Engineering, Sun Moon University, Asan, 336-708, Korea. 3Department of Mechanical Engineering, DHA Suffa University, DHA, 75500, Karachi, Pakistan
Email: [email protected]
Fatigue cracking is the most common damage mechanism in materials and structures under dynamic loading. The fatigue cracks initiate from stress concentration regions in the structures and may limit the service life significantly. Due to the economic concerns many aerospace, automotive, locomotive and wind energy structures are expected to have fatigue life beyond 107 cycles. Hence, improvement of the fatigue life up to 109 to 1010 cycles is gaining continuous attraction. The concept of energy transfer in to the material through mechanical work to improve the surface properties and fatigue life of the materials has been proved very successful. The techniques like laser shock peening (LSP), shot peening (SP), ultrasonic shot peening (USP) and ultrasonic nanocrystal surface modification (UNSM) have shown substantial effectiveness in improvement of the fatigue life. However, most studies have focused on fatigue life improvement up to 107 fatigue cycles only. There are no such studies which discuss the effectiveness of these surface treatment techniques in improvement of the fatigue life up to very high fatigue cycles. In this study, the UNSM was used to improve the fatigue life of Ti6Al4V. Two different impact forces and feed rates of UNSM process were used. The S-N curve of the materials showed substantial improvement in the fatigue life in all specimens. The specimens showed surface cracking up to 107 cycles and beyond that subsurface cracking with fish eye was observed. The depth of crack initiation in the subsurface of the specimens continuously increased with failure cycles. The UNSM treatment increased the hardness of material by 25%. The effects of UNSM process parameters on crack initiation depth and fatigue life improvement have also been discussed. It was concluded that suitably chosen UNSM process parameters may increase the fatigue life of materials substantially, up to VHCF.
92 Poster Abstract #883 Effect of UNSM Treatment on Deformation Behaviors of As-Rolled AZ31 Magnesium Sheets
M.S. Kang1, J.H. Kim2, Y.S.Pyun2 andY.S. Choi1 1School of Materials Science and Engineering, Pusan National University, Busan 609-735, Korea 2Department of Mechanical Engineering, Sun Moon University, Asan 336-708, Korea
Main author email address: [email protected]
Mechanical behaviors of Mg alloys have been subject to numerous studies because of their superior specific strength. In particular, the production of rolled Mg alloys opens more opportunities for the wide application of Mg alloys for structural parts that require weight reduction. However, the rolled Mg alloy sheets exhibit anisotropy in plastic deformation, which sometimes limits their processibility [1-5]. Recently, a UNSM (ultrasonic nanocrystal surface modification) technique receives spotlights as a new surface enhancement technology [6-10]. Compared to the conventional shot peening technique, the UNSM technique allows more precise and controllable surface modification (or enhancement).
In the present study, a basic research was performed in order to understand the deformation behavior (including plastic anisotropy) of an as-rolled Mg alloy (particularly, AZ31 alloy) when it is subject to the UNSM treatment. The UNSM treatment was applied to as-rolled AZ31 sheets with four different sheet thicknesses (1mm, 0.5mm, 2mm and 3mm, respectively). Through-thickness microstructures were compared between UNSM-treated and untreated AZ31 sheets using the optical microscopy (OM), scanning electron microscopy (SEM) and electron back- scattered diffraction (EBSD) mapping techniques. Tensile tests were also performed to UNSM-treated and untreated AZ31 sheets along the rolling direction (RD), the diagonal direction and the transverse direction (TD), and the resulting flow curves and plastic anisotropy R-values were compared. Based upon these results, the effect of the UNSM treatment on the deformation behavior of as-rolled AZ31 sheets was quantitatively analyzed as a function of the sheet thickness.
[1]Shujin Liang, Hongfei Sun, Zuyan Liu, and Erde Wang, “Mechanical properties and texture evolution during rolling process of an AZ31 Mg alloy”, Journal of Alloys and Compounds, 472., 127-132 (2009). [2]HyungLae Kim, Won Kyu Bang, and Young Won Chang, “Deformation behavior of as-rolled and strip-cast AZ31 magnesium alloy sheets”, Materials Science and Engineering A, 528., 5356-5365 (2011). [3]LiliGuo, Zhongchun Chen, and Li Gao, “Effects of grain size, texture and twinning on mechanical properties and work-hardening behavior of AZ31 magnesium alloys”, Materials Science and Engineering A, 528., 8537-8545 (2011). [4] N.V. Dudamell, I. Ulacia, F. Gálvez, S. Yi, J. Bohlen, D. Letzig, I. Hurtado, and M.T. Pérez-Prado, “Twinning and grain subdivision during dynamic deformation of a Mg AZ31 sheet alloy at room temperature”, ActaMaterialia, 59., 6949-6962 (2011). [5]Jidong Kang, David S. Wilkinson, Raja K. Mishra, Wei Yuan, and Rajiv S. Mishra, “Effect of inhomogeneous deformation on anisotropy of AZ31 magnesium sheet”, Materials Science and Engineering A, 567., 101-109 (2013). [6]AuezhanAmanov, In-Sik Cho, Dae-Eun Kim, and Young-SikPyun, “Fretting wear and friction reduction of CP titanium and Ti-6Al-4V alloy by ultrasonic nanocrystalline surface modification”, Surface and Coatings Technology, 207., 135-142 (2012). [7] Bo Wu, Pangpang Wang, Young-ShikPyoun, Jianxun Zhang, andRi-Ichi Murakami,“Effect ofultrasonicnanocrystal surface modification on the fatigue behaviors of plasma-nitrided S45C steel”, Surface and Coatings Technology, 213., 271-277 (2012). [8] AuezhanAmanov, Oleksiy V. Penkov, Young-SikPyun, andDae-Eun Kim, “Effects of ultrasonic nanocrystalline surface modification on the tribological properties of AZ91D magnesium alloy”, Tribology International, 54., 106-113 (2012). [9] AuezhanAmanov, Shinya Sasaki, Dae-Eun Kim, Oleksiy V. Penkov, and Young-SikPyun, “Improvement of triboloical properties of Al6061- T6 alloy under dry sliding conditions”, Tribology International, 64., 24-32 (2013). [10] Amrinder Gill, Abhishek Telang, S.R. Mannava, Dong Qian, Young-ShikPyoun, Hitoshi Soyama, and Vijay K. Vasudevan, “Comparison of mechanisms of advanced mechanical surface treatments in nickel-based superalloy”, Materials Science and Engineering A, 576., 346-355 (2013).
93 Poster Abstract #884 Stress Corrosion Cracking of Alloy 600 for Nuclear Power Plant and UNSM Treatment
J.H.Lee, H.W.Cho,J.H. Choi, K.T. Kim, N.I. Kim andY.S. Kim Materials Research Center for Energy and Green Technology, Andong National University, Andong 760-749, Korea
Main author email address: [email protected]
In pressurized water reactor, the reactor and pressurizer yield the primary water with high temperature and high pressure and then the steam was generated in steam generator (S/G) by heat transfer from the primary water to the secondary water. Its steam operates the turbine and thus generates the electric power. Many problems including wastage, denting, pitting, fretting, SCC (Stress Corrosion Cracking), intergranular attack have occurred in nuclear power plant because of high pressure, load, and temperature. Among these problems, SCC is main corrosion damage. SCC means the brittle fracture as the materials suffer tensile stress in special corrosion environments. The occurrence of SCC may induce a radiation accident and shut-down and the economic loss as like the increased maintenance, and thus SCC is very important mechanism.
Steam generators of pressurized water reactors have used Alloy 690 as the tubing. Alloy 690 meets the requirement of design and shows good corrosion resistance. However, since the facilities have been operated in continuous and long time working, S/G tubing was suffered by SCC and repaired by means of sleeving and plugging and steam generator was exchanged in extreme case. Therefore it needs the new technology to monitor and control the corrosion damage including SCC in the sites of power plants. Also, SCC occurs when tensile stress is subjected to the materials in some environments. Therefore, there are many methods to reduce the possibility of SCC in the industry including nuclear power plants. UNSM (Ultrasonic NanocrystalSurface Modification) treatment is one of powerful methods to reduce the residual tensile stress of the materials.
Since nuclear power plants are operating under high temperature and pressure, on-line monitoring technique could be more effective than off-line method in shut-off period. In this condition, electrochemical noise method can be suitable to monitor the corrosion. Electrochemical noise methods was developed by Iverson in 1968 [1] and it could give useful information about electrochemical reaction. Also, during last 10 years, electrochemical technique could afford the beneficial effect on the energy-related industry including oil and gas, fossil fuel, nuclear power plants which are exposed in aggressive corrosive environments and many efforts to improve the accuracy and applicability of electrochemical noise method have been on-going [2].Stress corrosion cracking tests include constant load test, slow strain rate test(SSRT) and constant strain tests(C-ring, U-bending). Using the electrochemical noise method, the difference between stress corrosion cracks and mechanical cracks of 304 stainless steel in sodium thiocyanate solution was reported [3], and IASCC(Irradiation-Assisted Stress Corrosion Cracking) of sensitized 304 stainless steel in 288oC, BWR environment was done by electrochemical noise method during the SSRT testing.
As reviewed at the above, the many studies on pitting and SCC by electrochemical noise method were reported but there are few about the relation between the cracking and electrochemical noise signal, and also there are little reports for the effect of UNSM treatment to SCC. Therefore, this paper aims the analysis on the relation between the cracking and electrochemical noise signal of Alloy 600 under U-bending and the evaluation of the effect of UNSM treatment on the resistance to SCC.
[1]J. J. Kim, “Stress Corrosion Cracking in the Pre-Cracked Specimens of Type 403 Stainless Steel” Corros. Sci. Tech., vol.3, 14-19 (2004). [2]J. R. Keams, J. R. Scully, P. R. Roberge, D. L. Reichert, and J. L. Dawson, Eds., “Electrochemical Noise Measurement for Corrosion Applications”American Society for Testing and Materials, ASTM STP 1277, ASTM (1996). [3]C. C. Lee and F. Mansfeld, “Analysis of Electrochemical noise data for a passive system in the Frequency Domain” Corros. Sci., vol.40, 959- 962 (1998).
94 Poster Abstract #895 Laser shock processing effects using focalized spot on duplex stainless steel properties
1 2 3 2 1 E. Castañeda , G. Gómez-Rosas , C. Rubio-González , A. Chávez-Chávez , and C.A. Reynoso-García
1Posgrado en Ciencia de Materiales, Centro Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, José Guadalupe Zuno 48, Zapopan, Jalisco; México. 2 Departamento de Física, Centro Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Blvd. Marcelino García Barragán 1421, Guadalajara, Jalisco; México. 3 Centro de Ingeniería y Desarrollo Industrial, Pie de la Cuesta 702, Desarrollo San Pablo, Querétaro, Querétaro; México.
The Laser Shock Processing (LSP) is a surface treatment technique that uses high-energy pulsed lasers. In LSP the laser impact generates a shock wave due to the produced pressure according to plasma expansion; this plasma is forming when the interaction between the laser pulse and the material surface occurs [1-6]. Duplex stainless steels combine some of the best features of both austenitic and ferritic kinds of stainless steels, due to that are materials with almost equal amount mixed of ferrite and austenite phases in its composition. Generally, these are used in the chemical processing industry, desalination plants, petrochemical plants, the pulp industry, and among others [7-9].
In this work, LSP effects on 2205 duplex stainless steel (DSS2205) were evaluated. The profiles of residual stresses, hardness, and wear for DSS2205 with and without LSP are presented. In addition, the characterization of the surface and the wear mechanisms using the microscopy techniques confocal and scanning electron respectively were obtained. DSS2205 specimens of 50 mm x 50 mm x 9 mm, machined and polished with SiC sandpaper grit 80 were used. The LSP setup used in this work consisting of a Q-Switched Nd:YAG laser, Quantel Brilliant b model, emitting with fundamental wavelength of 1064 nm, 850 mJ pulse energy, 10 Hz repetition rate, and pulse width duration of 6 ns. In addition, a device for the water jet supply, a 2D precision motorized system (x-y stage) for moving the specimens and an optical system to deliver and focus the laser pulse were used. Fig. 1 shows a diagram of experimental setup.
Fig. 1. Schematic of the experimental setup for LSP treatment on DSS2205.
[1] Daly J.J., et al; “New Laser Technology Makes Lasershot Peening Commercially Affordable” The 7th International Conference on shot peening (ICSP7); Institute of Precision Mechanics; Warsaw Poland; (1997-1998). [2] Sokol David W.; “Laser Shock Processing Technical Bulletin No. 1” LSP Technologies, Inc.6145 Scherers Place Dublin, OH 43016-1284. [3] Montross C.S., et al; “Laser shock processing and its effects on microstructure and properties of metal alloy: a review” Int. J. Fatigue, 24, 1021-1036, (2002). [4] Peyre P., et al; “Influence of thermal and mechanical surface modifications induced by laser shock processing on the initiation of corrosión pits in 316L stainless steel” J.Mat.Sci., 42 (16), 6866-6877, (2007). [5] Sano Y., et al; “Laser peening without coating as a surface enhancement technology” JLMN, 1 (3), 161-166, (2006). [6] Ocaña J.L., et al; “Improvement of mechanical properties and life extensión of high reliability structural components by laser shock processing” in SPIE Eco-Photonics (2011), Proc of SPIE Vol. 8065 80650V-1-80650V-11, (2011). [7] Ibarra-Echeverria M., Nuñez-Solis E., Huerta-Ibañez J.M., “Manual de Aceros Inoxidables” (INDURA S.A.); Chile (2010). [8] Lim H., et al; “Enhancement of abrasion and corrosion resistance of duplex stainless steel by laser shock peening” J. Mat. Process. Tech., 212, 1347–1354, (2012). [9] Rubio-Gonzalez C., et al; “Effects of laser shock processing on fatigue crack growth of duplex stainless steel” Mat. Sci. Eng. A-Structural Materials Properties Microestructure and Processing, 528 (3), 914-919, (2011).
95 Abstract Index
LAST, FIRST, ABSTRACT #, PAGE #
Allott,Ric, #933...... 23 Leering, Mitchell, #851...... 70 Amanov, Auezhan, #872...... 59 Liao, Yiliang, #1008...... 63 Amanov, Auezhan, #869...... 89 Malik, Arif, #855...... 40 Berthe, Laurent, #841...... 50 Mannava, Seetha Ramaiah, #1012...... 18 Brajer, Jan, #831...... 25 McClung, Craig, #937...... 36 Brockman, Robert, #840...... 37 Ocaña, José L, #826...... 39 Busse, David, #850...... 34 Ocaña, José L, #825...... 38 Caruso, Pete, #930...... 67 Ocaña, José L, #824...... 55 Chang, Seky, #820...... 60 Ocaña, Jose L, #823...... 33 Chida, Itaru, #859...... 28 Pavan, Marco, #899...... 83 Cho, In-Sik, #874...... 91 Pyun, Young-Sik, #870...... 58 Choi, Yoon-Suk, #883...... 93 Qian, Dong, #892...... 68 Chupakhin, Sergey, #821...... 30 Qian, Dong, #891...... 43 Coratella, Stefano, #839...... 75 Qiao, Hongchao, #858...... 31 Courapied, Damien,# 844...... 32 Qiao, Hongchao, #857...... 49 Crooker, Paul, #1016...... 76 Qiao, Hongchao, #856...... 87 Deng, Xiaoxu, #836...... 54 Rosas, Gilberto Gomez, #843...... 85 Dulaney, Jeff, #866...... 26 Rosas, Gilberto Gomez, #868...... 88 Fitzpatrick, Michael, #846...... 29 Rosas, Gilberto Gomez,. #895...... 95 Fitzpatrick, Michael, #847...... 86 Sano, Tomokazu, #902...... 53 Fitzpatrick, Michael, #818...... 81 Sano, Tomokazu, #901...... 48 Furfari, Domenico, #1015...... 16 Sano, Yuji, #864...... 24 Ghidinl, Tommaso, #1014...... 27 Seidel, Cory, #905...... 42 Glaser, Daniel, #861...... 46 Shibuya, Norihito, #946...... 79 Glaser, Daniel, #860...... 72 Smyth, Niall, #934...... 71 Hackel, Lloyd, #853...... 21 Soyama, Hitoshi, #837...... 57 Hombergsmeier, Elke, #1009...... 20 Soyama, Hitoshi, #832...... 47 Hu, Yongxiang, #830...... 84 Soyama, Hitoshi, #817...... 52 Hu, Yongxiang, #829...... 51 Spradlin, Thomas, #894...... 69 Jagtap, Rohit, #950...... 82 Sticchi, Marianna, #828...... 44 Jeong, Sungho, #827...... 22 Suh, Chang-Min, #871...... 90 Karbalaian, Hamidreza, #881...... 74 Sundar, R., #865...... 80 Karbalaian, Hamidreza, #878...... 41 Telang, Abhishek, #939...... 78 Karim, M.R, #890...... 73 Trdan, Uroš, #897...... 77 Kattoura, Michael, #1017...... 62 Trdan, Uroš, #896...... 56 Khan, Muhammad Kashif, #877...... 92 van Aswegen, Dean, #852...... 17 Kim, Young-Sik, #884...... 94 Vasu, Anoop, #862...... 35 Kim, Jun-Hyong, #875...... 61 Vasudevan, Vijay, #936...... 64 Kobayashi, Yuji, #907...... 19 Yaofei, Sun, #873...... 66 Langer, Kristina, #893...... 65 Zabeen, Suraiya, #927...... 45
96 Notes
97 Notes
98 Notes
99 Notes
100 LOBAL NE G SINT O O
Peening Solutions For AEROSPACEBrand D e AUTOMOTIVEsign Guidelin eMEDICALs POWERブランドデ GENERATIONザインガイドライン
Now with Contract Visit us at International Conference Peening Resources! on Laser Peening May 10-15, 2015 Cincinnati, Ohio
TM
NATIONAL PEENING SINTOKOGIO, LTD SINTOKOGIO GROUP Nagoya Intercity, Japan Tel 336-302-4492 Tel +81 52 582 9216 www.nationalpeening.com www.sinto.com