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弛豫机制。研究方法是用最近开发的场位错力学模型来补充传统的多晶塑性公式，该模型以机械严谨的方式解释内应力和可观察到的极性位错密度的演变（在所需的分辨率尺度上）。该理论被应用于理解载荷路径变化时的屈服这一技术上的重要问题，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。该项目提供了一种低成本的方法来预测屈服和反向屈服，分别适用于任何选择的加载和卸载路径方向。该结果将提供一种模拟能力，包括加工过程中的大块晶体滑移、卸载过程中的非弹性以及最终产品强度的预测。通过使用铝合金来实现汽车的轻量化仍然是减少温室气体排放以及提高燃油效率的一种经济有效且及时的手段。这两个问题都对国家和国际经济和环境产生重大影响。了解冲压铝板的回弹和应力松弛对于设计轻量化汽车车身板的生产工具至关重要。通过对研究生的教育，增强了科研队伍，丰富了教材。这项与工业界学术联络的资助机会（GOALI）为卡内基梅隆大学和一个工业合作伙伴ABAQUS公司（罗德岛州）之间的联合研究提供了机会。该项目以研究生指导的形式利用ABAQUS公司的专业知识，并将我们的研究成果与商业有限元软件包ABAQUS集成在一起。

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.