A MULTI-SCALE CRYSTAL PLASTICITY FINITE ELEMENT MODELING FRAMEWORK FOR PREDICTING STRAIN-RATE SENSITIVE DEFORMATION OF HEXAGONAL METALS

Abstract

This work presents improvements to the methods used in crystal plasticity simulations. It shows how these improvements can be used to accurately predict the deformation behavior of two magnesium alloys, WE43, and AZ31. The first improvement to the methodology is guidance on the type of finite elements to use in explicit grain crystal plasticity simulations. This study found that quadratic tetrahedral and linear hexahedral elements are the most accurate element types included in the study. The study also concluded that tetrahedral elements are more desirable due to fast mesh generation and flexibility to describe geometries of grain structures. The second improvement made was the addition of a numerical scheme to enable the use of any rate sensitivity exponent in the fundamental power-law representation of the flow rule in crystal visco-plasticity. While allowing the use of even very large exponents that many materials exhibit, this numerical scheme adds little to no increase in computational time. This crystal plasticity model was used to accurately predict the deformation behavior of both WE43 and AZ31 under quasi-static and high rate deformation, predicting the stress-stain response and the evolution of texture, twinning and the relative activities of the various deformation modes