Shear band development in dynamic loading of a viscoplastic cylinder containing two voids

We presume that plane strain state of deformation prevails when the interior of a long gun barrell or a cylindrical pressure vessel is dynamically loaded. The viscoplastic material of the body-is taken to exhibit strain-rate hardening and thermal softening. Two thin ellipsoidal voids located symmetrically on the horizontal axis and near the center of the cylinder wall act as nuclei for the initiation of shear bands. We note that deformations of the cylinder are nonhomogeneous even in the absence of the voids. I t is therefore interesting to investigate when the bands initiate from the void tips and the interaction, if any, among them. I t is found that shear bands initiate first at void tips closer to the center of the cylinder. These bands propagate faster to the inner surface of the cylinder as compared to those initiating from the other void tips which propagate towards the outer bounding surface of the cylinder. Whereas contours of constant maximum principal logarithmic strain originating from the outer void tips spread out laterally in both directions as they propagate into the cylinder, those originating from the inner void tips spread out in only one lateral direction as they propagate into the body.