DOCSLIB.ORG

On the Interaction of Creep and High-Cycle Fatigue in CM 247 LC

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
On the Interaction of Creep and High-Cycle Fatigue in CM 247 LC University of Central Florida STARS Electronic Theses and Dissertations, 2020- 2021 On the Interaction of Creep and High-Cycle Fatigue in CM 247 LC Thomas Bouchenot University of Central Florida Part of the Mechanical Engineering Commons Find similar works at: https://stars.library.ucf.edu/etd2020 University of Central Florida Libraries http://library.ucf.edu This Doctoral Dissertation (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Electronic Theses and Dissertations, 2020- by an authorized administrator of STARS. For more information, please contact [email protected]. STARS Citation Bouchenot, Thomas, "On the Interaction of Creep and High-Cycle Fatigue in CM 247 LC" (2021). Electronic Theses and Dissertations, 2020-. 475. https://stars.library.ucf.edu/etd2020/475 ON THE INTERACTION OF CREEP AND HIGH-CYCLE FATIGUE IN CM 247 LC by THOMAS S. BOUCHENOT B.S. University of Central Florida, 2013 M.S. University of Central Florida, 2015 A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Mechanical and Aerospace Engineering in the College of Engineering and Computer Science at the University of Central Florida Orlando, Florida Spring Term 2021 Major Professor: Ali P. Gordon © 2021 Thomas S. Bouchenot ii ABSTRACT Industrial gas turbines constitute a considerable portion of global power generation, from large engines for centralized grids, to smaller frames for decentralized demand. Power output, efficiency, and reliability are chief criteria regarding the development of next-generation turbines, whose components are expected to operate in ever harsher environments. Turbine blades are subjected to high temperatures, an array of mechanical loads, and dynamic fluid fields, all contained within a non-isothermal profile, making creep and high-cycle fatigue critical aspects of turbine blade design. Current analysis tools and methods have resulted in the development of many successful components; however, improved life prediction models with even greater accuracy are needed to maintain today’s product reliability under the extreme environments associated with next-generation operating conditions. The combination of creep and high-cycle fatigue produces a synergistic interaction effect, whose explicit consequence to turbine life remains unaccounted for by current, decoupled life prediction models, which traditionally incorporated such interaction effects into design safety factors. The continued development of high fidelity analytical tools, unique cooling technologies, and advanced materials has propelled turbine design to higher efficiencies and tighter margins. Improved lifing models capable of capturing these effects are now needed in order to maintain current reliability standards in these ever-expanding, future operating conditions. Combined creep and high-cycle fatigue has been the subject of very little research; however, sufficient knowledge is available in literature to guide the formation of a comprehensive study. This research study identifies the life-limiting aspect of a combined high-cycle fatigue and creep response in conventionally cast Ni-base superalloy CM 247 LC, and captures the interaction of the two loads in two novel candidate life prediction frameworks. The frameworks iii are created from a comprehensive collection of experimental data obtained using a conventional high-cycle fatigue test method and an unconventional two-part test method, where test specimens pre-deformed to a prescribed creep strain are fatigue loaded at an elevated temperature and high frequency until failure. A variety of temperatures, creep strains, and fatigue loading conditions are be explored to ensure that the resulting model is applicable to the myriad of potential turbine blade operating conditions. Additional tests are also be carried out to determine the contribution of high temperature aging on the combined failure and to evaluate the effect of material grain size. Rigorous metallographic assessments accompanying each test are leveraged to create the microstructurally-informed combined life prediction frameworks. iv To my wife and parents v ACKNOWLEDGEMENTS The assistance and support of many co-workers, friends, and family were critical to the completion of this disseration. Several individuals deserve special acknowledgement. My success as an engineer and researcher must largely be credited to the mentorship of Dr. Ali P. Gordon. His guidance, hard work and dedication as an advisor, teacher, and role model has been the foundation of my academic and professional career. I cannot thank him enough. I would like to thank Dr. Seetha Raghavan, Dr. Kevin Mackie, Dr. Ranajay Ghosh, and Dr. Felipe Viana for serving as my disseration committee members. I would also like to thank Siemens Energy for the opportunity and funding to conduct the research utilized in this dissertation. In particular, I would like to thank my manager at Siemens, Mandy Goltsch, and the lifing methods manager at Siemens, Sachin Shinde. I would not have been able to complete my dissertation without their invaluable support. Ronnie Bladh will always have my gratitude and respect. His mentorship in the field of aeromechanics and applied gas tubine high-cycle fatigue life prediction have been a great influence and learning experience. I also want to think Kirtan Patel for always supplying his expert recommendations on material characterization. My discussions with Allister James and Phillip Draa have also been a great help with regards to understanding superalloy microstructure. I am also thankful for the support of my other past and present Siemens colleagues, including Zach Dyer and Kyle Smith. I would also like to express my deepest thanks to the technicians and engineers at Siemens Casselberry lab for their significant contributions to the completion of this dissertation. I am especially grateful for the assistance of Dillon Ryan and David Kosich for conducting many vi of the experiments used in this study, as well as the help and expertise of Tom Brumley, without whom the post-test fracture analysis could not have been completed. I am also thankful for the help of Brooke Sarley for keeping the project on schedule by interfacing with the test vendors and coordinating the specimen preparation. I would also like to thank all the past and present friends and colleagues in the Mechanics of Materials Research Group (MOMRG) at the University of Central Florida (UCF). I have learned a substantial amount from them over the years as both an undergraduate and graduate student. Collaborations and discussions with Justin Karl, Scott Keller, Steven Kraft, Calvin Stewart, Kevin Smith, Jonathan Torres, Nathan O’Nora, Sanna Saddiqui, Bassem Felemban, Firat Irmak, and the numerous other lab members have helped me grow as a engineer and researcher. I could not have achieved so much without the support of my family. The care and encourgement of my parents and brother have been driving force in my education and development. I would never have finished my doctorate without the love and compassion of my wife, Jenny. She has always been there to cheer me on when I was starting to lose sight of the finish line, and always convinced me to take a break whenever I would begin to wear out. Knowing that she will always be there for me has made a tremendous difference on my graduate career and my life as a whole. vii TABLE OF CONTENTS LIST OF FIGURES ...................................................................................................................... xii LIST OF TABLES ..................................................................................................................... xxiii LIST OF NOMENCLATURE .................................................................................................... xxv CHAPTER 1 INTRODUCTION .................................................................................................... 1 CHAPTER 2 MATERIAL ............................................................................................................ 10 2.1 Processing ........................................................................................................................... 10 2.2 Microstructure ..................................................................................................................... 12 2.2.1 Composition ................................................................................................................. 12 2.2.2 Grain Details ................................................................................................................ 14 2.3 Elastic and Tensile Response .............................................................................................. 16 CHAPTER 3 LITERATURE REVIEW ....................................................................................... 22 3.1 High-Cycle Fatigue ............................................................................................................. 22 3.1.1 The HCF Load Cycle ................................................................................................... 24 3.1.2 HCF Testing ................................................................................................................. 26 3.1.3 Presenting HCF Results ............................................................................................... 27 3.1.4 Classical HCF Failure Criteria ....................................................................................
Load more

Recommended publications
  • Deformation Twinning in Metals and Ordered Intermetallics-Ti and Ti-Aluminides M
    Deformation twinning in metals and ordered intermetallics-Ti and Ti-aluminides M. Yoo, C. Fu, J. Lee To cite this version: M. Yoo, C. Fu, J. Lee. Deformation twinning in metals and ordered intermetallics-Ti and Ti- aluminides. Journal de Physique III, EDP Sciences, 1991, 1 (6), pp.1065-1084. 10.1051/jp3:1991172. jpa-00248626 HAL Id: jpa-00248626 https://hal.archives-ouvertes.fr/jpa-00248626 Submitted on 1 Jan 1991 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. (1991) Phys. 1065-1084 J. 1991, III1 1065 PAGE JuiN Classification Physics Abstracts 61.70N 62.20F 62.20D twinning intermetallics-Ti ordered Deformation metals and in Ti-aluminides and (1) C. Fu K. Yoo, H. and J. M. L. Lee (2) Ridge, 37831,6115, Ridge Laboratory, Division, Oak TN Oak National Metals Ceranlics and U-S-A- 1990) (Received19 accepted September 1990, 4 June cons6quences maclage ductilitd des la ddformation de fracture Rksumk.-Los la la et par sur cristallographie, intermdtalliques fonction alliages ordonnds dtudides de de mdtaux la et sont en systdmatique l'dnergie cindtique maclage. analyse ddformations dtd faite de des Une la et a par en comparaison systdmes Ti~Al, consid6rant Ti, TiAl moddles.
    [Show full text]
  • Tensile Deformation, Toughness and Crack Propagation Studies of Alloy 617
    UNLV Retrospective Theses & Dissertations 1-1-2007 Tensile deformation, toughness and crack propagation studies of alloy 617 Vikram Marthandam University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Marthandam, Vikram, "Tensile deformation, toughness and crack propagation studies of alloy 617" (2007). UNLV Retrospective Theses & Dissertations. 2792. http://dx.doi.org/10.25669/5x53-uv5y This Dissertation is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Dissertation has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. TENSILE DEFORMATION, TOUGHNESS AND CRACK PROPAGATION STUDIES OF ALLOY 617 by Vikram Marthandam Bachelor of Engineering in Mechanical Engineering University of Madras, India Master of Science in Mechanical Engineering, 2004 University of Nevada, Las Vegas, Las Vegas, NV 89154 A dissertation submitted in partial fulfillment of the requirements for the Doctor of Philosophy Degree in Mechanical Engineering Department of Mechanical Engineering Howard R. Hughes College of Engineering Graduate College University of Nevada, Las Vegas May 2008 UMI Number: 3319132 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted.
    [Show full text]
  • Temperature Dependence of Deformation Behavior in a Co–Al–W-Base Single Crystal Superalloy
    Materials Science & Engineering A 620 (2015) 36–43 Contents lists available at ScienceDirect Materials Science & Engineering A journal homepage: www.elsevier.com/locate/msea Temperature dependence of deformation behavior in a Co–Al–W-base single crystal superalloy L. Shi, J.J. Yu n, C.Y. Cui, X.F. Sun Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China article info abstract Article history: Tensile properties of a single-crystal Co–Al–W–Ni–Cr–Ta alloy with low tungsten content have been Received 18 June 2014 studied within the temperatures ranging from 20 to 1000 1C at a constant strain rate of 1.0 Â 10 À4 sÀ1. Received in revised form The alloy exhibits comparable yield strength with that of Co–Al–W-base alloys containing more 17 September 2014 tungsten. From 600 1Cto8001C, a yield strength anomaly is observed, probably due to the cross-slip Accepted 18 September 2014 of superdislocations from the octahedral plane to the cube plane. TEM analysis demonstrates that Available online 26 September 2014 stacking faults (SFs) appear both in γ channels and γ0 precipitates in a wide temperature range. These SFs Keywords: are responsible for the obvious strain hardening observed in stress–strain curves. From room – – Co Al W-base alloy temperature to 900 1C, the deformation is dominated by dislocations shearing γ0 particles. At 1000 1C, Tensile behavior 0 the main deformation mechanism is dislocations bypassing γ particles. Dislocation structures & 2014 Elsevier B.V. All rights reserved. Stacking fault 1. Introduction that the addition of Cr makes against the improvement of γ0 solvus temperature.
    [Show full text]
  • Mechanical Behaviour and Simulation of Alloys Used in Jet Engines
    Universidad Politécnica de Madrid Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos Mechanical Behaviour and Simulation of Alloys Used in Jet Engines Tesis doctoral Rafael Sancho Cadenas Ingeniero de Materiales 2020 Departamento de Ciencia de Materiales Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos Universidad Politécnica de Madrid Mechanical Behaviour and Simulation of Alloys Used in Jet Engines Tesis doctoral Rafael Sancho Cadenas Ingeniero de Materiales Director: Francisco Gálvez Díaz-Rubio Dr. Ingeniero Aeronáutico Catedrático de Universidad 2020 A mis padres I II Contents AgradecimientosV Abstract VII AbbreviationsIX NotationXI 1 Introduction and Objectives1 1.1 Introduction ............................. 1 1.2 Motivation and objectives ..................... 5 2 State of the art 9 2.1 Introduction to plastic deformation ................ 9 2.2 Computational plasticity in the continuum framework . 12 2.2.1 Macroscopic plasticity ................... 13 2.2.2 Crystal plasticity ...................... 14 2.2.3 Polycrystal homogenization . 16 2.3 The Johnson-Cook model ..................... 20 2.4 Yield-strength anomaly in superalloys . 21 2.5 The split-Hopkinson bar ...................... 27 2.5.1 Pochhammer-Chree oscillations . 29 3 A model for the yield-strength anomaly 33 3.1 Constitutive model ......................... 33 3.1.1 Time discretization ..................... 37 3.2 Cobalt-base superalloys ....................... 39 III Contents 3.2.1 Numerical simulations ................... 43 3.3 VascoMax C-250 .......................... 51 3.3.1 Numerical simulations ................... 55 3.4 MAR-M247 ............................. 59 3.4.1 Experiments ......................... 60 3.4.2 Numerical simulations ................... 68 4 CP modelling of MAR-M247 DS 73 4.1 Crystal plasticity model ...................... 73 4.1.1 Time discretization ..................... 77 4.2 Finite-element modelling .....................
    [Show full text]
  • Anna University , Chennai
    www.Vidyarthiplus.com Anna University , Chennai AE2354 HIGH TEMPERATURE MATERIALS TWO MARKS WITH ANSWERS UNIT-1 CREEP 1. Define creep Creep is large plastic deformation of material on application of stress or elevated temperature or a combination of both applied for a prolonged time. A material subjected to a constant stress may fail well below its yield stress if load is applied for prolonged time. 2. Define creep formation It involves time-dependent deformation and high temperature creep cracking generally develops in an intercrystalline manner in components of engineering importance that fail over an extended time. 3. What is meant by diffusion process? At low stress and high temperature atoms diffuse from sides to the top and bottom. The grain becomes longer as the applied stress does work. Atomic diffusion in one direction is same as vacancy diffusion in opposite direction. 4. Why the rate of creep is more at elevated temperature? Creep is one of the most serious high temperature damage mechanisms. As temperature increases mobility of atom increases, frequently increasing the diffusion mechanism and has significantly influence on high temperature mechanical properties like creep and fracture. So the rate of creep is more at elevated temperature. 5. What are the problems associated with materials used at elevated temperature? Generally a material subjected to high temperature reduces the strength of the material and failure mechanisms affecting the functional life of components are totally different. At high temperature the strength of material has strong dependence on time. 6. What are the factors influencing functional life of components at elevated temp? 1) Creep 2) Corrosion 3) High temperature fracture 4) Thermo mechanical Fatigue 5) Interaction of all above with each other 6) Metallurgical ageing and metallurgical stability 7) Micro structural changes SRINIVASAN ENGINEERING COLLEGE www.Vidyarthiplus.com www.Vidyarthiplus.com 7.
    [Show full text]
  • Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys
    Orientation and Alloying Effects on Creep Strength in Ni-Based Superalloys DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Timothy Michael Smith Jr. Graduate Program in Materials Science and Engineering The Ohio State University 2016 Dissertation Committee: Dr. Michael Mills, Advisor Dr. Hamish Fraser Dr. Yunzhi Wang Dr. Andrew Wessman Dr. Bern Kohler © Copyright by Timothy Michael Smith Jr. 2016 Abstract The creep deformation mechanisms present during creep at intermediate stress and temperatures in ME3 were further investigated using diffraction contrast imaging. Both conventional transmission electron microscopy and scanning transmission electron microscopy were utilized. Distinctly different deformation mechanisms become operative during creep at temperatures between 677-815ºC, and at stresses ranging from 274- 724MPa. Both polycrystalline and single crystal creep tests were conducted. The single crystal tests provide new insight into grain orientation effects on creep response and deformation mechanisms. Creep at lower temperatures (760C) resulted in the thermally activated shearing modes such as microtwinning, stacking fault ribbons and isolated superlattice extrinsic stacking faults (SESFs). In contrast, these faulting modes occurred much less frequently during creep at 815ºC under lower applied stresses. Instead, the principal deformation mode was dislocation climb bypass. In addition to the difference in creep behavior and creep deformation mechanisms as a function of stress and temperature, it was also observed that microstructural evolution occurs during creep at 760C and above, where the secondary coarsened and the tertiary precipitates dissolved. Based on this work, a creep deformation mechanism map is proposed, emphasizing the influence of stress and temperature on the underlying creep mechanisms.
    [Show full text]
  • A Diffraction Based Study of the Deformation Mechanisms In
    A DIFFRACTION BASED STUDY OF THE DEFORMATION MECHANISMS IN ANOMALOUSLY DUCTILE B2 INTERMETALLICS A Dissertation Presented to The faculty of the School of Engineering and Applied Science University of Virginia In Partial Fulfillment of the requirements for the Degree Doctor of Philosophy (Materials Science and Engineering) by Rupalee Prashant Mulay December 2011 APPROVAL SHEET This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Materials Science and Engineering) This dissertation has been read and approved by the examining Committee: ~San~ R. Agn .. ~ uJZ d(i ~) &tb~ William A. Soffa on) Richard P. Gangloff J~~ . ~ Accepted for the School of Engineering and Applied Science: an, School of En Applied Science December, 2011 i Abstract For many decades, the brittle nature of most intermetallic compounds (e.g. NiAl) has been the limiting factor in their practical application. Many B2 (CsCl prototypical structure) intermetallics are known to exhibit slip on the <001>{110} slip mode, which provides only 3 independent slip systems and, hence, is unable to satisfy the von Mises (a.k.a. Taylor ) criterion for polycrystalline ductility. As a result, inherent polycrystalline ductility is unexpected. Recent discovery of a number of ductile B2 intermetallics has raised questions about possible violation of the von Mises criterion by these alloys. These ductile intermetallic compounds are MR (metal (M) combined with a rare earth metal or group IV refractory metal (R)) alloys and are stoichiometric, ordered compounds. Single crystal slip trace analyses have only identified the presence of <100>{011} or <100>{010} slip systems. More than 100 other B2 MR compounds are known to exist and many of them have already been shown to be ductile (e.g., CuY, AgY, CuDy, CoZr, CoTi, etc.).
    [Show full text]
  • The Flow Stress Anomaly in Fe–43At%Al Single Crystals
    Intermetallics 14 (2006) 607–619 www.elsevier.com/locate/intermet The flow stress anomaly in Fe–43at%Al single crystals U. Messerschmidt *, M. Bartsch, Ch. Dietzsch Max Planck Institute of Microstructure Physics, D-06120 Halle/Saale, Germany Received 24 January 2005; received in revised form 21 October 2005; accepted 24 October 2005 Available online 20 December 2005 Abstract Fe–43at%Al single crystals were deformed in compression between room temperature and 700 8C. The strain rate sensitivity of the flow stress was measured by stress relaxation tests. The dislocation structure of the deformed samples was studied in a high-voltage transmission electron microscope. In addition, micro-tensile specimens were deformed in situ in this microscope to directly observe the dynamic behaviour of the dislocations. The specimens show a flow stress anomaly accompanied with an ‘inverse’ dependence of the strain rate sensitivity on the strain rate. Both the in situ experiments and the transmission electron micrographs of macroscopically deformed samples indicate the occurrence of climb at temperatures in and above the anomaly range. In the in situ experiments, viscously moving dislocations are straight and crystallographically oriented. The phenomena related to the flow stress anomaly are interpreted by the decomposition of the cores of dislocations with h111i Burgers vectors. q 2005 Elsevier Ltd. All rights reserved. Keywords: A. Iron aluminides, based on FeAl; B. Plastic deformation mechanisms; D. Defects: dislocation geometry and arrangement; Electron microscopy, F. transmission; F. Mechanical testing 1. Introduction after the observation that the anomaly occurs only in specimens in which the high excess vacancy concentration Within a certain temperature range, many intermetallic originating from the crystal preparation is annealed out by alloys show a flow stress anomaly, i.e.
    [Show full text]
  • Deforemation and Dislocation Tem Image Simulation in L10-Fepd
    DEFOREMATION AND DISLOCATION TEM IMAGE SIMULATION IN L10-FEPD by Amal A. Al Ghaferi BE, United Arab Emirates University, 2000 Submitted to the Graduate Faculty of School of Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2006 UNIVERSITY OF PITTSBURGH SCHOOL OF ENGINEERING This dissertation was presented by Amal A. Al Ghaferi It was defended on December, 4 , 2006 and approved by Dr. John A. Barnard, Professor, Department of Mechanical Engineering and Materials Science Anthony J. DeArdo, Professor, Department of Mechanical Engineering and Materials Science Ian Nettleship, Associate Professor, Department of Mechanical Engineering and Materials Science Jean R. Blachère, Associate Professor Emeritus, Department of Mechanical Engineering and Materials Science Dr. J.M.K. Wiezorek, Associate Professor , Department of Mechanical Engineering and Materials Science, Dissertation Director ii Copyright © by Amal A. Al Ghaferi 2006 iii DEFORMATION AND DISLOCATIONS TEM IMAGES SIMULATION OF L10 FEPD Amal A. Al Ghaferi, PhD University of Pittsburgh, 2006 A yield strength anomaly has been observed in intermetallic L10-ordered FePd alloys between about 300-700K. However, previous work did not provide clear explanations regarding the microstructural or mechanistic origins for this observation. FePd and γ-TiAl have the same crystal sturtucre. YSA was studied intensively in γ-TiAl system and its origin was related for the dislocation fine structure. In TiAl, the dissociation of the superdislocation [10-1] play an important role in the YSA phenomena and the existence of Yoo torque promote dissociated shockly partial to cross slip to another slip plane. This forms KW lock which is the reason of YSA in TiAl.
    [Show full text]
  • Modeling the Temperature Dependence of Tertiary Creep Damage of a Ni-Based Alloy
    Modeling the Temperature Dependence of Tertiary Creep Damage of a Ni-Based Alloy To capture the mechanical response of Ni-based materials, creep deformation and rup- ture experiments are typically performed. Long term tests, mimicking service conditions at 10,000 h or more, are generally avoided due to expense. Phenomenological models such as the classical Kachanov–Rabotnov (Rabotnov, 1969, Creep Problems in Struc- Calvin M. Stewart tural Members, North-Holland, Amsterdam; Kachanov, 1958, “Time to Rupture Process Under Creep Conditions,” Izv. Akad. Nauk SSSR, Otd. Tekh. Nauk, Mekh. Mashin., 8, pp. Ali P. Gordon 26–31) model can accurately estimate tertiary creep damage over extended histories. Creep deformation and rupture experiments are conducted on IN617 a polycrystalline Department of Mechanical, Materials, and Ni-based alloy over a range of temperatures and applied stresses. The continuum damage Aerospace Engineering, model is extended to account for temperature dependence. This allows the modeling of University of Central Florida, creep deformation at temperatures between available creep rupture data and the design Orlando, FL 32816-2450 of full-scale parts containing temperature distributions. Implementation of the Hayhurst (1983, “On the Role of Continuum Damage on Structural Mechanics,” in Engineering Approaches to High Temperature Design, Pineridge, Swansea, pp. 85–176) (tri-axial) stress formulation introduces tensile/compressive asymmetry to the model. This allows compressive loading to be considered for compression loaded gas turbine components such as transition pieces. A new dominant deformation approach is provided to predict the dominant creep mode over time. This leads to development of a new methodology for determining the creep stage and strain of parametric stress and temperature simulations over time.
    [Show full text]
  • Yield (Engineering) - Wikipedia, the Free Encyclopedia
    Yield (engineering) - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Proof_stress Yield (engineering) From Wikipedia, the free encyclopedia (Redirected from Proof stress) A yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible. In the three-dimensional space of the principal stresses (), an infinite number of yield points form together a yield surface. Knowledge of the yield point is vital when designing a component since it generally represents an upper limit to the load that can be applied. It is also important for the control of many materials production techniques such as forging, rolling, or pressing. In structural engineering, this is a soft failure mode which does not normally cause catastrophic failure or ultimate failure unless it accelerates buckling. Contents 1 Definition 2 Yield criterion 2.1 Isotropic yield criteria 2.2 Anisotropic yield criteria 3 Factors influencing yield stress 3.1 Strengthening mechanisms 3.1.1 Work hardening 3.1.2 Solid solution strengthening 3.1.3 Particle/Precipitate strengthening 3.1.4 Grain boundary strengthening 4 Testing 5 Implications for structural engineering 6 Typical yield and ultimate strengths 7 See also 8 References 8.1 Notes 8.2 Bibliography Definition It is often difficult to precisely define yielding due to the wide variety of stress–strain curves exhibited by real materials.
    [Show full text]
  • Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems
    Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Department of Mechanical and Materials Engineering of College of Engineering and Applied Science University of Cincinnati by Xingshuo Wen M.S., University of Cincinnati, Ohio, USA, 2009 B.S., Shaanxi University of Science and Technology, Shaanxi, China, 2005 March, 2014 Committee: Dr. Vijay K. Vasudevan (Chair) Dr. Relva C. Buchanan Dr. Rodney D. Roseman Dr. Vesselin N. Shanov Abstract The Very High Temperature Reactor (VHTR) is one of the leading concepts of the Generation IV nuclear reactor development, which is the core component of Next Generation Nuclear Plant (NGNP). The major challenge in the research and development of NGNP is the performance and reliability of structure materials at high temperature. Alloy 617, with an exceptional combination of high temperature strength and oxidation resistance, has been selected as a primary candidate material for structural use, particularly in Intermediate Heat Exchanger (IHX) which has an outlet temperature in the range of 850 to 950°C and an inner pressure from 5 to 20MPa. In order to qualify the material to be used at the operation condition for a designed service life of 60 years, a comprehensive scientific understanding of creep behavior at high temperature and low stress regime is necessary. In addition, the creep mechanism and the impact factors such as precipitates, grain size, and grain boundary characters need to be evaluated for the purpose of alloy design and development.
    [Show full text]