Influence of specimen geometry on adiabatic shear instability of tungsten heavy alloys

Finite element simulations are carried out for the deformation and instability of truncated-conic tungsten heavy-alloy specimens subjected to impact loading. A two-dimensional axis-symmetric adiabatic model is introduced in the simulations and the Johnson-Cook model is employed to describe the thermo-viscoplastic behavior of the material. In order to obtain detailed information of the deformation and instability of specimens in different scales, two meshes are used in the simulations. A coarse mesh is used to gain a general picture of the global deformation. Then, a locally refined mesh with a minimum element dimension of 10 pm is used to analyze the initiation and propagation of the adiabatic shear band (ASB). The results obtained by the present numerical simulations agree well with experimental observations. Finally, three truncated-conic specimens with different geometry are simulated. It is found that the specimen geometry as well as the surface friction has significant effect on the sensitivity of ASB formation. (C) 2002 Elsevier Science Ltd. All rights reserved.