DYNAMIC ADIABATIC SHEAR BAND DEVELOPMENT IN A BIMETALLIC BODY CONTAINING A VOID

We study the problem of the initiation and subsequent growth of a shear band in a thermally softening viscoplastic prismatic body of square cross-section and containing two symmetrically placed thin layers of a different viscoplastic material and an elliptical void at the center. The yield stress of the material of the thin layer in a quasistatic simple compression test is taken to be either five times or one-fifth that of the matrix material. The body is deformed in plane strain compression at a nominal strain rate of 5,000 s-1. These deformations are assumed to be symmetrical about the centroidal axes. It is found that shear bands initiate from the ends of the major axes of the ellipsoidal void and propagate in the direction of the maximum shear stress. These bands are arrested by the strong virtually rigid material of the thin layer, but pass through the weaker material of the thin layer rather easily. Other shear bands originate from points where the thin layers meet the free boundaries and propagate into the matrix material along the direction of maximum shearing when the material of the thin layer is stronger, but propagate into the thin layer when its material is weaker than the matrix material. The band in the weaker material of the thin layer bifurcates into two bands that propagate into the matrix material in the direction of the maximum shearing stress.