Description of Strengthening through Internal Stress Development in Rolled Structured Metals

本研究的目的是研究多晶金属塑性中的内应力和松弛机制。研究方法是用最近发展的场位错力学模型来补充传统的多晶塑性公式，该模型以机械严格的方式解释了可观察到的极位错密度的内应力和演化(在所需的分辨率范围内)。该理论被应用于了解载荷路径变化时的屈服这一重要技术问题，从而能够对轧制金属产品的回弹和使用中的应力松弛进行预测建模。该项目提供了一个新的步骤，提供了一种低成本的方法，分别预测装卸路径方向的任何选择的产量和反转产量。模拟结果将包括加工过程中的块状晶体滑移、卸载时的非弹性以及对最终产品强度的预测。通过使用铝合金使汽车轻量化仍然是减少温室气体排放和提高燃料效率的一种经济有效和及时的手段。这两个问题都对国家和国际经济和环境产生重大影响。了解铝合金冲压件的回弹和应力松弛现象，对于设计轻量化车身覆盖件模具具有重要意义。这项研究通过研究生的教育加强了科学队伍，丰富了教育材料。这项与工业的学术联系机会(GOALI)赠款为卡内基梅隆大学和工业合作伙伴Abaqus，Inc.(罗德岛)之间的联合研究工作提供了机会。该项目利用了ABAQUS，Inc.的专业知识，以研究生咨询的形式，并将我们的研究成果与商业有限元软件包ABAQUS相结合。

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.