13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- Clearly, there is a link between the anisotropy in the deformation process and the development of damage and fracture processes in the three sheet materials. Microcrack formation in AZ31 sheets, for example, is strongly related to the twin formation as a result of the inability of textured AZ31 sheet to deform by dislocation mechanisms alone. IF steel on the other hand deforms by dislocation mechanisms which produce vacancies at high strains, leading to void formation which grow and coalesce to drive the material to failure. AA5754 sheets deform by dislocation mechanisms but voids form not from vacancy condensation at large strains as in IF steel but because of matrix-particle interactions in the sheet which then quickly develops to rupture. The above results suggest the need for developing microscale models that account for these differences in the microstructure and deformation mechanisms between different materials. It is expected that the quantitative data provided above can serve as a starting point for linking the anisotropic deformation with damage processes using a multi-scale (micro and macro scale) simulation strategy. 4. Conclusions In this paper, we report the dependence of shear localization and fracture on plastic anisotropy of three types of automotive sheet materials, namely IF steel (BCC structure), AA5754 aluminum alloy (FCC) and AZ31 magnesium alloy (HCP). The results show that both narrowing and thinning of the tensile sample occur in IF steel, while only thinning occurs in AA5754 and only narrowing occurs in AZ31. These differences arise from the differences in the plastic anisotropy of the three materials, as measured by their r-values. Even though all three materials exhibit ductile fracture, the damage and fracture processes in the three materials differ from each other – mainly void mechanisms arising due to dislocation interactions in IF steel, premature void formation influenced by particle distribution in AA5754 sheets and premature crack initiation caused by twinning in textured AZ31 sheets. The need for micro-macro model development to link material anisotropy with fracture processes is identified for numerical model development. Acknowledgements The authors are grateful for the continuous financial support from Natural Sciences and Engineering Council of Canada (NSERC), General Motors Canada and Initiative for Automotive Manufacturing Innovation (iAMi). JK thanks the support from CanmetMATERIALS, Natural Resources Canada. Valuable technical discussions with scientific staff members in GM R&D Center, Warren, MI, U.S.A. are acknowledged. References [1] J. Kang, D. S. Wilkinson, M. Jain, J. D. Embury, A. J. Beaudoin, S. Kim, R. Mishra, A. K. Sachdev, On the sequence of inhomogeneous deformation processes occurring during tensile deformation of strip cast AA5754. Acta Materialia, 54(2006), 209-218. [2] Z. Marciniak, K. Kuczynski, Limit strains in the process of stretch-forming sheet metal, International Journal of Mechanical Sciences, 9(1967), 600-620. [3] J. Kang, D.S.Wilkinson, R.K.Mishra, W. Yuan, R.S. Mishra, Effect of inhomogeneous deformation on anisotropy of AZ31 magnesium sheet. Materials Science and Engineering A (in press, http://dx.doi.org/10.1016/j.msea.2012.08.117). [4] Z. Gao, D.S. Wilkinson, J. Kang, Microstructural stability of magnesium alloys during high
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