Self organization of shear bands in stainless steel

The spatial distribution of shear bands was investigated in 304L stainless steel through the radial collapse of a thick-walled cylinder under high-strain-rate deformation (similar to10(4)s(-1)). The shear-band initiation and propagation were also examined. Self-organization of multiple adiabatic shear bands was observed. The effect of grain size on spacing of shear bands was investigated at four different grain sizes: 30 mum, 50 mum, 140 mum and 280 mum. A single crystal with a similar composition was also tested. The experimental results show only a modest variation of shear-band spacing within the investigated grain size range. Three principal mechanisms are considered to be active in initiation: (a) momentum diffusion by stress unloading, (b) perturbation in the stress/strain/temperature fields, (c) microstructural inhomogeneities. The observed shear-band spacing is compared with existing theories; Grady-Kipp and Wright-Ockendon-Molinari theories. These are one-dimensional theories that do not consider the evolution in spacing as the shear bands grow. A discontinuous growth mode for shear localization under periodic perturbation is applied and predicts spacings in good agreement with observations. Self-organized initiation and propagation modes are discussed in relation to the interaction among the nucleus and well-developed shear bands. (C) 2004 Elsevier B.V. All rights reserved.