报告题目：A Multiscale Crystal Defect Dynamics and Simulations of Dislocation and Fracture
报告人：李少凡教授
时间：2013年12月9日15:00
地点：西六楼五楼雷电会议室
邀请人：陈志军副教授
报告摘要：
A Multiscale Crystal Defect Dynamics and Simulations of Dislocation and Fracture
Shaofan Li
Department of Civil and Environmental Engineering
The University of California, Berkeley, California 94720
shaofan@berkeley.edu
A multiscale crystal defect dynamics has been developed for an alternative to simulate dislocations and other defect motions at small scale. The multiscale crystal defect dynamics is based on an atomistic based dual lattice process zone model. In this approach, coarse grain models are adopted for both the bulk medium and material process zone. In bulk elements the first order Cauchy-Born rule is adopted, so that we can formulate an atomistic enriched continuum constitutive relation to describe the material behaviors. All the nonlinear deformation is assumed to be confined inside the interface process zone, and the interphase zone between two bulk media is remodeled as a finite-width strip whose lattice constants and atomistic potential may be the same or different from those of the bulk medium. Inside the process zone, the higher order Cauchy-Born rules are adopted, and a strain gradient-type coarse grain constitutive model is derived, which may capture the size-effect at the small scales. Different process zones are constructed such that they can represent various defects in the crystal such as void, slip planes, dislocation loops in the lattice space.
The multiscale crystal defect dynamics model has been applied to simulate dislocation nucleation; dynamics crack propagation, and fragmentation during impact and penetration in both single crystals and polycrystals. Crack branching and void formation have been found possible for different element mesh stacking fault energies, which are dictated, by the effective lattice structure or microstructure in the process zone elements.
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土木工程与力学学院
2013年12月6日
