CAREER: Understanding Grain Level Residual Stresses Through Concurrent Modeling and Experiments

Purdue University, West Lafayette IN

Investigators

Abstract

Polycrystalline materials such as metals, alloys and ceramics dominate the infrastructure of modern society in terms of both tons of raw material usage and in the breadth of applications, which span energy, transportation, defense, and other sectors. Stresses introduced during the processing of these materials, known as residual stresses, are ubiquitous in all materials and can have tremendous effects on performance. Despite their presence and critical role in component life, many analysis efforts cannot account for residual stresses. This Faculty Early Career Development (CAREER) award supports the method development to characterize residual stresses at the micron level within polycrystalline materials. The research will lead to the development of a computational framework to account for residual stresses, and faithfully predict their distributions. The research leverages recent advances in High Energy Diffraction Microscopy through collaboration with the Advanced Photon Source (APS) at Argonne National Laboratory. This award also supports an innovative educational program that is twofold. First, a series of continuing education courses will be developed focusing on the treatment of residual stress analyses produced in this research, specifically targeted towards the design systems, structural analysis, and manufacturing communities (i.e. non-materials) across professional societies. Second, hands-on learning activities will be introduced within Purdue's Space Day, an existing grade-school outreach program, which will focus on residual stresses in aerospace materials. In order to establish a basic understanding of residual stresses, the research team will: (i) develop a modeling framework to initialize and evolve residual stresses based on a backstress formulation present on individual slip systems, (ii) measure residual stresses and their development at the grain and sub-grain length scales within polycrystalline aggregates via high energy x-ray diffraction microscopy, (iii) develop techniques to map dislocation arrangements within the bulk of structural alloys, and (iv) produce validation datasets for crystal plasticity models containing state dependent variables that were previously impossible to measure. The work is predicated on a synergy between state-of-the-art experiments and simulations at the same length scale. The results will unequivocally elucidate the role of residual stresses across length scales in polycrystalline materials, in order to develop more accurate lifetime predictions of the alloys and fabricate tailored components that offer either minimal or beneficial residual stresses and therefore are more resistant to failures.