Simulation of multiple shear-bands in collapsing cylinder experiments Z. Lovinger and Y. Partom RAFAEL, P.O.B 2250, Haifa 31021, Israel Abstract. This work presents 2D numerical simulations of shear-band formation in collapsing thick walled cylinder experiments with 304L stainless steel. We use a simple shear-failure model which incorporates a positive feedback mechanism. Both the global behavior and the shear band evolution are examined. The calculated global behavior compares well with the experimental results. The calculated shear-bands follow the patterns of self organization demonstrated in experiments, with a good quantitative agreement with the observed final spatial configuration. The calculations reveal a clear spacing between initiation sites at the inner surface of the cylinder. The evolving shear-bands, having a width of several mesh elements in which strength decreases to zero, develop outwards in spiral paths while maintaining an angle of 45 degrees to the radial direction. Interactions between shear-bands, either by direct contact or through relief waves, result in competi- tive growth, eventually leading to a typical distribution of lengths and spacing. The spacing at the initiation stage and at the matured developed stage is quantitatively compared with existing analy- tical models. 1. INTRODUCTION Shear localization in the form of Adiabatic Shear Bands (ASB) is a dominating failure mechanism at high strain rates, acting as a precursor to fracture. Under high rate plastic shear deformation, a high power of dissipated heat is generated. As the characteristic time for heat conduction is much larger than the time for heat dissipation, a positive feedback mechanism is formed: the heat generated causes elevated temperatures, causing thermal softening and strength reduction which then results in further intense plastic deformation. In [1], Nesterenko and Bondar show a controlled and repeatable way to create multiple shear bands and study their properties and conditions for their evolution. They use a cylindrical geometry in which the Thick Walled Cylinder (TWC) sample is sandwiched between two cylindrical copper shells (Figure 1). The shells are driven inwards by an exploding cylindrical shell of explosive. The outer copper shell is a tamper and the inner copper shell controls the extent of collapse of the sample. The diagnostics are post-mortem: after the test, the sample is cut to reveal the shear bands. TWC experiments were conducted for different materials such as metals [2–5], ceramics [6] and reactive media [7]. In all of these experiments the spatial distribution of the ASBs are characterized at an early stage of formation and at late stages of propagation. To better understand the mechanics and evolution of multiple ASBs, it is necessary to be able to simulate the TWC experiments, including the ASBs. Some recent papers present efforts to simulate multiple ASBs in TWC experiments [8, 9], yet only in a qualitative manner. In what follows, we describe 2D numerical simulations of shear-band formation in collapsing TWC experiments with 304L Stainless Steel (SS). We use our shear-failure model described in [10] to represent the thermal softening and the positive feedback mechanism in evolving shear bands. We report the global behavior of the sample and the shear bands’ dynamics, and obtain good quantitative agreement with data given in [3]. DYMAT 2009 (2009) 1601–1607 Ó EDP Sciences, 2009 DOI: 10.1051/dymat/2009226