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

Abstract

The coexistent phenomenon of deformed and transformed adiabatic shear bands (ASBs) is analyzed using Johnson-Cook model and gradient-dependent plasticity for heterogeneous ductile metal material. The size of deformed ASB is described by the internal length reflecting the heterogeneity of material. Microstructural effect leads to a nonuniform distribution of temperature rise in deformed ASB. When the peak temperature in deformed ASB exceeds the transformation temperature, a transformed ASB appears at the center of deformed ASB. With a decrease of flow shear stress, the width of transformed ASB increases until its upper bound, i.e., the size of deformed ASB, 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, later occurrence 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 shear deformation in the boundaries of transformed ASB is higher; the flow shear stress that corresponds to transformation is higher; earlier occurrence of transformation and higher peak shear stress will be expected.