Rate Independent Crystal Plasticity

The problem of non-uniqueness in the selection and determination of the amount of shear on the active slip systems has plagued the rate-independent crystal plasticity theories for several years. A new large deformation rate-independent crystal plasticity theory is fromulated which overcomes this long standing problem. The model has been implemented in a commerical finite element program ABAQUS/Implicit and ABAQUS/Explicit. The accuracy of the model has been evaluated by comparing the results for simple tensile deformation on f.c.c single crystals and a simple compression experiment on polycrystalline OFHC copper against the results of the rate-dependent model of Kalidindi, Bronkhorst and Anand (1992) in the rate-independent limit. Our calculations show that the results from the rate-independent model are in excellent aggreement with those of the rate-dependent model in the rate-independent limit. Thesis Supervisor: Dr. Lallit Anand Title: Professor Acknowledgments I would like to express my sincere thanks to all those people, whose input and advice over the past three years has been invaluable. First and foremost, I am indebted to my advisor and mentor, Prof. Anand, for his guidance, patience, encouragement and financial support without which this work would not have been possible. I owe all my confidence and the ability in dealing with problems, not just in research, to him. I am very grateful to him for that. He has helped me lay a foundation on which I hope to complete my ph.d and build a successful career. I would also like to thank him for letting me incorporate parts of his paper into my thesis. I would like to thank Christine Allan, my mentor in experimental work, for her invaluable help and guidance. I am very grateful to my colleagues Fred Haubensak, Srihari, Chuang Chia, Brian, Ganti, Clarence, Omar, Apostollos, Jian and John for the fruitful discussions on research as well as on other "issues". I have learnt a lot from them and significantly improved my experimental and computational skills. Thanks to my parents, my brother and my sister who have always been a source of inspiration and support during difficult times.