CAREER: Bridging Experiments and Multiscale Modeling of Size- and Temperature-dependent Phenomena in Polycrystalline Plasticity

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This Faculty Early Career Development Plan (CAREER) proposes a new multiscale modeling and simulation methodology, integrated with experiments, in fundamental studies of defect-mediated deformation and fracture in crystalline solids at small length scales. The objectives are to investigate the combined effects of material length scales (e.g. grain size) and structural length scales (e.g. device dimensions) on temperature-dependent fracture transitions and creep. Brittleness and creep are important reliability issues in small-scale devices and nanostructured metallic materials. Central to modeling is a mesoscale framework based on the dynamics of defects, which will deliver: (i) scale- and temperature-dependent mechanical response; and (ii) microcrack nucleation criteria for use in continuum modeling of fracture transitions. This mesoscale framework will serve as the hyphen in information passing from the atomic scale, with on-demand calls to molecular dynamics simulations for targeted dislocation-interface interactions, all theway to the continuum scale, where model predictions can be validated with experiments.Societal benefits of small-scale devices, such as micro/nano-electro-mechanical systems and electronic devices, stem from their pervasiveness in the emerging technologies that are affecting the ways in which we work, communicate, learn, treat diseases, and are even entertained. The proposed activities will help improve our understanding of plasticity at nano- and micro-scales, which has direct applications to structural components in small-scale devices. Multiscale modeling of plasticity will play a key role to reduce development costs and manufacturing times of new devices and materials and to assess their reliability and mechanical integrity. Integration of research and education is achieved through the development of a materials nanomechanics graduate course, involvement of undergraduates in research, an international exchange program with universities in North-Africa and use of visualization in outreach activities to help students with different backgrounds and learning paths retain a physically intuitive comprehension of crystal defects.