Development of shear bands in dynamic plane strain compression of depleted uranium and tungsten blocks

Abstract

We study the initiation and growth of shear bands in prismatic bodies of rectangular cross-section made of either depleted uranium or tungsten and deformed in plane strain compression at a nominal strain-rate of 5000 s −1. It is assumed that defects are distributed symmetrically with respect to the two centroidal axes and each quadrant has up to 300 randomly distributed defects in the form of a weaker material; the flow stress for the weaker material in a quasistatic simple compression test is taken to be 5% lower than that for the original material. It is found that, in the deformed configuration, shear bands in depleted uranium blocks are inclined at approximately 42.5° counterclockwise from the horizontal axis, those in tungsten are inclined at nearly 135°. When shear bands initiate, the total compressive force required to deform the body drops sharply for the uranium blocks but gradually for the tungsten blocks. After a shear band has developed, dead zones form in both uranium and tungsten blocks; the size of the dead zone in the tungsten block is more than that in the uranium block. When the shear modulus for the tungsten is artificially changed so as to equal that for the uranium, the angle of inclination for the shear bands in tungsten blocks changes to that found for the uranium blocks. This suggests that the value of the shear modulus plays a noticeable role in the development of shear bands. We have also studied the effect, on the initiation of shear band, of modeling the defects as either very weak or very strong material.