Unified modelling of adiabatic shear banding and subsequent micro-voiding driven dynamic failure of viscoplastic solids

Abstract

Adiabatic shear bands (ASBs) are intense shear localisation zones resulting from thermomechanical instability in dynamically loaded, high strength structural materials. In the wake of the ASB, Micro-voids (MVs) have been observed which coalesce and ultimately rupture the material. ASBs thus favour premature MV induced damage and further material failure. In the present work, the coupled effects of ASB+MV on the representative volume element (RVE) are reproduced in a unified model within irreversible thermodynamics framework considering a large scale postulate. The influence of the softening mechanisms such as thermal softening and/or DRX induced softening on the ASB onset is accounted for. The model is numerically implemented as a user material subroutine into the engineering finite element (FE) computation code LS-DYNA and its feasibility and performances are assessed on both RVE and structural scales. The dynamic shear compression loading of a hat shaped structure is simulated for that purpose. The respective contributions of ASB and MV on the progressive material deterioration can be clearly identified.