Low-Velocity penetration of a rigid, hemispherical nose projectile in incompressible, elastoplastic, strain-hardening Mises media

A core-cavity model for steady, low-velocity penetration of a rigid, hemispherical nose projectile in elastoplastic, strain-hardening Mises media is presented. The target response is modelled by two distinct regions. The first region is an incompressible, elastoplastic flow field core around the projectile nose. The second region, outside the plastic core, is an incompressible, elastoplastic material response, which is induced by an internally pressurized spherical cavity. The analytical analysis has led to a closed-form expression for the penetration resisting pressure, for an arbitrary target material stress-strain curve with a definite yield point, which depends on the extent of the plastic core. This expression reduces to the quasi-static spherical cavitation pressure when a plastic core does not exist and it matches with well-known results for the resisting pressure of a perfectly-plastic Mises solid. The strain hardening effect on the penetration resisting pressure is found to be significant when compared to elastic/perfectly-plastic target response. Comparison with available numerical results has revealed that a relatively large flow field core, with the outer boundary at the elastic region, should exist around the hemispherical nose. By further comparison to penetration depth experiments, the core outer boundary location is found to be identical to the elastic/plastic interface location of a quasi-static cylindrical cavitation in incompressible Mises media under plane-strain conditions.