Self-organization of shear bands in stainless steel

Abstract

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 (∼10 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 m, 50 m, 140 m and 280 m. 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.

Suppression of repeated adiabatic shear banding by dynamic large strain extrusion machining

“…2b-e). The previous works have demonstrated that the shear band spacing increases as the shear band evolves (Meyers et al, 2001;Xue et al, 2002Xue et al, , 2004Ye et al, 2013;Zhou et al, 2006aZhou et al, , 2006b. Therefore, the shear band spacing decreases with CEF increasing, our experimental results are in coincidence with this prediction.…”

“…According to the solid lines, the predicted shear band spacing by the present momentum diffusion theory is more consistent with the experimental results. The discussions about the difference in predicting shear band spacing between the momentum diffusion theory and the perturbation theory have been made by several researchers (Meyers et al, 2001;Xue et al, 2002Xue et al, , 2004; Wei, 2006, 2007); (Molinari, 1997(Molinari, , 2013; (Chen et al, 2013;Ye et al, 2013).…”

“…The mechanism of multiple shear bands in HSM is different from that in simple shear because the materials convection exists in the former. The detailed discussions on multiple shear banding in simple shear can be found in several books and reviews (Bai and Dodd, 1992;Batra and Wei, 2006;Dodd and Bai, 2012;Grady and Kipp, 1987;Meyers, 1994;Meyers et al, 2001;Molinari, 1997;Wright, 2002;Wright and Ockendon, 1996;Xue et al, 2002Xue et al, , 2004Zhang and Clifton, 2003;Zhou et al, 1996aZhou et al, , 1996b. As for the multiple shear bands in serrated chips during machining, Huang and Aifantis put forward a laconic method to predict the shear band spacing in serrated chip formation by multiplying the chip flow speed by the characteristic instability time Aifantis, 1997, 2007).…”

“…The scaling laws in serrated chip formation were obtained in their numerical and dimensional analysis. Meyers and co-workers made a systematic experimental study and found that in many cases the shear band spacing was different at different loading stages (Meyers et al, 2001;Xue et al, 2002Xue et al, , 2004. In order to consider the later stage of shear localization, Ye et al not only considered the momentum diffusion and material convection (due to chip flow), but also took into account the shear band evolution in the prediction of segment spacing for serrated chip formation (Ye et al, 2013).…”

The chip-flow behaviors and formation mechanisms in the orthogonal cutting process of Ti6Al4V alloy

“…This implies that heat conduction is one of the crucial factors that influence the chip flow process in low cutting-speed processes. The experimental results of Meyers et al (2001) and Xue et al (2002Xue et al ( , 2004 demonstrate that both the perturbation theory Fig. 19.…”