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Prediction and Reduction of Defects in Sheet Metal Forming Dissertation

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PREDICTION AND REDUCTION OF DEFECTS IN SHEET METAL FORMING DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University Ali Fallahiarezoodar M. S. Graduate Program in Industrial and Systems Engineering The Ohio State University 2018 Dissertation Committee: Taylan Altan, Advisor Farhang Pourboghrat Jerald Brevick Copyright by Ali Fallahiarezoodar 2018 ABSTRACT Sheet metal forming as process of forming a metal blank into a useful part is a major metal forming process. The overall objective of the sheet metal forming process is to form the part within the required tolerances without any defects. Defects in sheet metal forming appeared as tearing, necking, wrinkling, and springback. In the last decade, the advanced high strength steels (AHSS) and high strength aluminum alloys are increasingly used in automotive industry to satisfy the demands for improved safety, fuel efficiency and low-emission of greenhouse gas. However, in general, in high strength materials, low formability and high springback are observed. Therefore, forming of these materials is more challenging than normal mild steels. Several parameters affect the quality of the final part. Blank and tool material, friction and lubrication, and process parameters such as forming speed and temperature can significantly affect the result. Determination of material properties and formability is necessary for tooling and process design. The common methods for determination of material properties required for designing and simulating the sheet metal forming process are reviewed. Also, forming limit diagram as an indication of material formability is studied. The limitations of the forming limit diagram are presented and a practical method for developing the forming limit diagram is presented. Friction and lubrication play an important role in providing high quality parts from a deep drawing process. Friction conditions depend on sheet and tool material, surface qualities, the type of the lubricant and process conditions such as contact pressure, sliding velocity, and temperature. Laboratory tests for evaluating deep drawing lubricants should be designed to emulate the conditions of actual forming processes. The cup drawing test and twist compression test are compared for evaluating metal stamping iii lubricants. Effects of contact pressure and sliding velocities on lubricant performance are evaluated. Also, numerical simulations are developed to predict the temperature increase in the part during each test. Results showed that the testing condition in the cup drawing test is closer to actual deep drawing operations and this test is more proper for evaluating metal stamping lubricants compared to the twist compression test. Springback affects the dimensional accuracy and final shape of stamped parts. Accurate prediction of springback is necessary to design dies that produce the desired part geometry and tolerances. Springback occurs after stamping and ejection of the part because the state of the stresses and strains in the deformed material has changed. To accurately predict springback through finite element analysis, the material model should be well defined for accurate simulation and prediction of stresses and strains after unloading. Despite the development of several advanced material models that comprehensively describe the Bauschinger effect, transient behavior, permanent softening of the blank material, and unloading elastic modulus degradation, the prediction of springback is still not satisfactory for production parts. Dies are often recut several times, after the first tryouts, to compensate for springback and achieve the required part geometry. Material properties which affect the springback are studied and effect of each property is investigated. Results showed that the E-modulus is the most important material property defining the elastic recovery of the material and springback. A methodology for determination of an average E-modulus that can provide accurate springback prediction is presented. The method is expanded to determine the variation of E-modulus with plastic strain to simulate the springback in real industrial part and obtain reasonably accurate springback prediction before manufacturing a real die. Finally, effect of post-stretching method on reduction of springback is investigated both experimentally and numerically. iv DEDICATION To my beloved family v ACKNOWLEDGMENTS First and foremost, I would like to thank God Almighty for giving me the strength, knowledge, ability and opportunity to undertake this research study and to persevere and complete it satisfactorily. Without his blessings, this achievement would not have been possible. I would like to thank my advisor, Dr. Taylan Altan, for providing me the value of science with continuous assistance and support. He was the Key to my success. I am also grateful to Dr. Brevick and Dr. Pourboghrat for the constant support to improve my dissertation. I wish to thank the sponsors of the following research: Honda America, Shiloh, Posco, Nucor, Aida America, GM, and the other CPF member companies, as well as all of the personnel of those companies which assisted me. I also thank my fellow coworkers and friends of the Center for Precision Forming (CPF). Adam Groseclose, Suraj Appachu Palecanda Krishna, Tingting Mao, Ruzgar Peker, David Diazinfante Hernandez, Pedro Stemler, Fabian Bader, Advaith Narayanan, Berk Aykas, Tanmay Gupta, Aanandita Katre, Pratik Mehta, Josh Hassenzahl, and Linda Anastasi, as well as many others, all helped me more than they can possibly imagine. Lastly, I would like to thank my parents, whose love and guidance are with me in whatever I pursue. They are the foundation to which my education is built on and will continue to push me to bigger and better things. Most importantly I wish to thank my loving and supportive wife, Mina who provides unending inspiration. vi VITA Master of Science (Mechanical Engineering) .................................................. September 2010 Bachelor of Engineering (Mechanics of Agricultural Machines) ..................... June 2008 PUBLICATIONS 1. A. Fallahiarezoodar, R. Peker, T. Altan, Temperature Increase in Forming of Advanced High- Strength Steels – Effect of Ram Speed Using a Servodrive Press, Journal of Manufacturing Science and Engineering, Vol 138, pp 094503-1-94503-7, 2016. 2. A. Fallahiarezoodar, A. Katre, T. Altan, Predicting springback when bending AHSS and aluminum alloys, Part I, Stamping journal, pp 12-13, November/December 2016. 3. A. Fallahiarezoodar, Z. Yin, T. Altan, Controlling material flow in drawing operations CNC hydraulic cushions help improve drawability, Stamping journal, pp 16-17, May/June 2016. 4. A. Fallahiarezoodar, K, Drotleff, M. Liewald, T. Altan, Lightweighting in automotive industry using sheet metal forming-advances and challenges, 5th international conference on accuracy in forming technology, Chemnitz, 2015. 5. A. Fallahiarezoodar, L. Ju, T. Altan, Use of FE simulation and servo press capabilities in forming of AHSS and aluminum alloys, Key engineering materials, Vol 639, pp 13-20, 2015. 6. A. Fallahiarezoodar, T. Altan, Determining flow stress data by combining uniaxial tensile and biaxial bulge test, Stamping journal, pp 16-17, September/October 2015. 7. A. Fallahiarezoodar, R, Peker, T. Altan, Heat generation in forming of AHSS, Stamping journal, pp 12-13, March/April 2015. 8. A. Fallahiarezoodar, J. Dykeman, T. Altan, Using the frictionless dome test to determine flow stress data, Stamping journal, pp 14-15, November/December 2014. 9. A. Fallahiarezoodar, M.R. Abdul Kadir, M. Alizadeh, Sangeetha Naveen, T. Kamarul, Geometric variable designs of cam/post mechanisms influence the kinematics of knee implants, Knee Surgery, Sports Traumatology, Arthroscopy Volume 22, Issue 12, pp 3019-3027, 2014. 10. M. Heydari, M. R. Abdulkadir, J. Kashani, A. Fallahiarezoodar, M. Alizadeh, Influences of rheumatoid arthritis on elbow: A finite element analysis, Journal of Advanced Science Letters, Volume 19, Number 11, pp. 3219-3222(4), November 2013. vii 11. M Ailzaadeh, M.R. Abdul Kadir, M. Mohd Fadhil, A. Fallahiarezoodar, B. Azmi, M. R. Murali, T. Kamarul, The use of X shaped cross-link in posterior spinal constructs improves stability in thoracolumbar burst fracture: A finite element analysis, Journal of Orthopaedic Research, 31(9):1447-54, 2013 Sep. 12. M. Heydari, M. R. Abdulkadir, A. Fallahiarezoodar, Muhamad Noor Harun, Mina Alizadeh, and Jamal kashani., Biomechanical assessment of unconstrained elbow prosthesis after total elbow replacement: A finite element analysis. Journal of Applied Mechanics and Materials, Vol. 234, pp 7-10, 2012. FIELDS OF STUDY Major Field: Industrial and Systems Engineering Specialization: Manufacturing viii TABLE OF CONTENTS Abstract ................................................................................................................................................. iii Dedication ............................................................................................................................................. v Acknowledgements ............................................................................................................................... vi Vita ........................................................................................................................................................ vii List of Figures ......................................................................................................................................
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