Steady state penetration of elastic perfectly plastic targets

Steady state axisymmetric deformations of an elastic perfectly plastic target being penetrated by a fast moving rigid cylindrical rod have been analyzed by the finite element method. The target is assumed to obey the yon Mises yield criterion and the associated flow rule. Contact between target and penetrator has been assumed to be smooth. A mixed formulation, in which two components of the velocity and four components of the deviatoric stress tensor at each node point, and the hydrostatic pressure at the centroid of an element are taken as unknowns, is employed. This should give a better estimate of tractions acting on the penetrator nose, and hence of the axial resisting force experienced by the penetrator. The effect of the penetrator speed, its nose shape and the elasticity of the target material on the target deformations, and the axial force experienced by the penetrator has been studied. The consideration of elastic effects helps delineate the elastic-plastic boundary in the target.