Description of Strengthening through Internal Stress Development in Rolled Structured Metals

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The objective of this research is to study the internal stress and relaxation mechanisms in the plasticity of polycrystalline metals. The research approach is to complement traditional formulations of polycrystal plasticity with a recently developed model of field dislocation mechanics that accounts for the internal stress and evolution of the observable polar dislocation density (at the desired scale of resolution) in a mechanically rigorous manner. The theory is applied to the technologically important problem of understanding yield upon load path change to enable predictive modeling of springback and in-service stress relaxation in rolled metal products. This project provides a new step in providing a low-cost means of predicting yield and reverse yield for any choice of loading and unloading path direction, respectively. The result will give a simulation capability embracing bulk crystallographic slip in processing, inelasticity in unloading, and prediction of strength in the final product. Light weighting of automobiles through use of aluminum alloys remains a cost-effective and timely means of reducing greenhouse gas emissions as well as improving fuel efficiency. Both issues have significant national and international economic and environmental ramifications. Understanding of the springback and stress relaxation in stamped aluminum sheet is essential to design of tooling for production of autobody panels leading to light weighting. The research enhances the scientific workforce through the education of graduate students and enriches education materials.This Grant Opportunities for Academic Liaison with Industry (GOALI) grant provides an opportunity for a joint research effort between Carnegie Mellon University and an industrial partner, ABAQUS, Inc (Rhode Island). The project leverages expertise from ABAQUS, Inc. in the form of graduate student advising and integration between our research result and the commercial FEM software package, ABAQUS.