Modeling spontaneous adiabatic shear band formation in electro-magnetically collapsing thick-walled cylinders

Abstract

The ability to simulate shear bands evolution in thick-walled-cylinder (TWC) experiments is required to understand their spontaneous formation and propagation. Recently we presented experiments on electro-magnetically collapsing metallic cylinders (Lovinger et al., 2015). Here we present numerical simulations that reproduce the experimental results for multiple shear bands in those TWC's. We present a detailed study of the initiation and propagation of the shear bands and their mutual interactions, which replicates many of the experimental observations. We investigate the influence of initial perturbations and pressure history on the initiation and final stages of the process using an energy-based failure model which incorporates a positive feedback mechanism. The numerical model is calibrated for four different materials to reconstruct the number of shear bands and their experimentally determined distribution. The results indicate that the number of shear bands is related to deformation micromechanisms operating in the material, such as twinning and martensitic transformations, which may hold back and eventually stall the shear bands evolution. The numerical simulations provide a reliable quantitative description of the shear bands distribution and spacing, thus paving the way for future predictive work of this failure mode.