Investigation into the penetration mechanism of a rigid long rod into a semi-infinite metallic target

Metallic materials are widely employed as armor target materials, making the investigation of their penetration mechanisms critically important. In this study, we develop a novel theoretical model of rigid projectile penetrating into semi-infinite metal target. The model constructs a two-dimensional velocity field in the target material based on the mass conservation equation, while incorporating the effects of strain hardening, strain rate, and thermal softening into the radial stress formulation within the plastic region. Using the above mentioned velocity field, the momentum equation is accurately solved in the elastic and plastic region, the stress field is obtained, the force exerted on the projectile is approximated, and the equation of motion is solved numerically to ultimately determine the penetration depth. Subsequently, the theoretical predictions of the proposed approximation method are compared with experimental data on normal penetration in metal target. The results demonstrate that the calculations using the explicit Johnson–Cook constitutive relationship exhibit excellent agreement with the experimental penetration depths of ogive–nosed rigid long rods penetrating into semi–infinite metal targets. Moreover, a comparison of different constitutive models in the plastic region reveals their influence on the deformation resistance. When the θ₀ related to nose shape correlation parameter, falls within the range 0^∘<θ₀≤90^∘, the effect of strain rate on deformation resistance increases with θ₀, whereas the effect of thermal softening first decreases and then increases slightly as θ₀ increases. In addition, the proposed theoretical model proves that the inertial effect of the rigid projectile penetrating the semi-infinite metal target is negligible. However, a significant nonlinear correlation is observed between the penetration resistance and the impact velocity, the physical mechanism of which arises from the strain rate effect in the target material.