Monday, 11 October 2004 - 9:15 AM

This presentation is part of : Metal Forming I

A comparative study of slip hardenings for 3D rate-dependent single crystals

Xianwu Ling, Center for Advance Vehicular Systems, Mail Stop 9618, 200 Research Blvd., Mississippi State University, Starkville, MS 39759 and Mark F. Hortemeyer, CAVS, Starkville, MS 39759.

The polycrystalline responses at large deformations are determined by the single crystal behaviors. At the single crystal level, the material can be characterized by the crystal orientations (which specify the crystal geometrically), the flow rules (which specify the instantaneous strain-stress relationships for the slip systems), and the slip hardening laws (which specify on one hand the self- and inter- actions among the slips, and on the other hand, the history dependent resistance of each slip system). The slip hardening laws are of paramount importance in determining the crystal behaviors. Yet, existing laws are essentially empirical, no single model appears to provide a full description of enhanced material behaviors over any other models

In the present work, the effects of different schools of hardening laws on the crystal reorientation and stress responses are studied. These include R. Asaro's law, D. Peirce's law, K. S. Havner's law, J. Bassani's law, G. Weng's law, and M. Hortemeyer's hardening-recovery law. For each law under study, seven representative initial crystal reorientation are chosen from the standard triangle. The calculations are based on a rate-dependent crystal plasticity algorithm proposed by the present authors. From the results, it is seen that isotropic hardening largely determines the stress levels, while the anisotropic hardening strongly affects the crystal reorientation. Although all the hardening laws under study give similar trends of crystal reorientation, the stress responses can be quite different. Lastly, the tensile axis tends to move forward to the nearest high density directions.

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