EFFECT OF VISCOPLASTIC FLOW RULES ON STEADY-STATE PENETRATION OF THERMOVISCOPLASTIC TARGETS

Steady state thermomechanical deformations of a thick viscoplastic target being penetrated by a fast moving long rigid cylindrical penetrator are analysed by the finite element method. Two different constitutive relations, the Bodner-Partom flow rule, and the Litonski-Batra flow rule, are used to model the viscoplastic response of the material. The two flow rules are calibrated to give essentially similar shear stress-shear strain curves during the overall adiabatic simple shearing deformations of a block deformed at an average strain-rate of 3300 s-1. For the Bodner-Partom flow rule, the effect on target deformations of the penetrator nose shape, penetrator speed, and the variation in the values of material parameters of the target is also studied.