Effects of Temperature and Strain Rate on the Evolution of Thickness ofTransformed Adiabatic Shear Band

摘要

The coexistent phenomepon of deformed and transformed adiabatic shear bands (ASBs) isanalyzed using Johnson-Cook model and gradient-dependent plasticity for heterogeneous ductilemetal material. The size of deformed ASB is described by the internal length reflecting theheterogeneity of material. Microstructural effect leads to a nonuniform distribution of temperaturerise in deformed ASB. When the peak temperature in deformed ASB exceeds the transformationtemperature, a transformed ASB appears at the center of deformed ASB. With a decrease of flowshear stress, the width of transformed ASB increases until its upper bound, i.e., the size of deformedASB, is reached. The effects of initial temperature and strain rate on the occurrence of transformation,evolution of the thickness of transformed ASB, distributions of local temperature and plastic shear deformation in ASB are investigated. Lower initial temperature results in higher peak shear stress, later occurrence of shear strain localization, lower shear stress when transformation occurs, lateroccurrence of transformation, thinner transformed ASB, lower peak temperature in ASB, and lower value of local plastic shear deformation in the boundaries of transformed ASB. At higher strain rates,the transformed ASB is wider; the peak temperature in ASB is higher; the value of local plastic sheardeformation in the boundaries of transformed ASB is higher; the flow shear stress that corresponds totransformation is higher; earlier occurrence of transformation and higher peak shear stress will beexpected.