Instantiation of Poly crystal Plasticity Models to Predict Heterogeneous Straining in Aluminum Alloys

摘要

A methodology for incorporating a description of material structure into a finite element formulation is presented.This modeling framework was used to study the development of deformation induced surface roughening in thin sheets machined from AA 7050 thick plate.Predicting this roughening phenomenon necessitates the quantification and representation of processes that exist over several size scales.This work describes an experiment/simulation-based study focused on the deformation behavior of thick AA 7050 aluminum plate.EBSD(Electron Back Scatter Diffraction)experiments were used for the material structure characterization,which included crystallographic texture,distributions in grain sizes,and a distribution in internal grain misorientation.These distributions in structure were used to create digital microstructures which represented virtual specimens composed of finite element-discretized crystals,whose size,orientation and intra-grain misorientations were chosen to match experimentally measured crystal distribution statistics.A continuum slip-polycrystal plasticity model was employed with hardening parameters determined by matching the macroscopic stress-strain response,and the digital microstructures were employed to study the differences in roughening seen in specimens deformed along the Rolling Direction(RD)and Transverse Direction(TD)of the plate material.In general,the trends in the surface roughening were well predicted using the digital microstructures.The TD specimen roughened more than the RD specimen,and the TD roughness appeared to have more directionality.However,the magnitude of the roughening features was less accurately captured,as the model over-predicted the height of the surface roughening.The success of these simulations build additional insight into how to incorporate material structure into deformation simulations,and build representative virtual specimens that can study the complicated processes that underlie the deformation mechanics in polycrystalline materials.