Thermal-mechanical analysis on the mass loss of high-speed projectiles penetrating concrete targets

The significant mass loss of the kinetic energy (KE) projectile has been observed in the high-speed penetration (usually v0 > 1 km/s) into concrete target, resulting in nose abrasion, bending, and trajectory deviation as well as great drop of the Depth of Penetration (DOP). The thermoplastic failure of material peeling from the thin exterior interface between the projectile and the concrete is the main mechanism of the mass loss. Combining the heat generated from the friction work and the plastic deformation work during the high-speed penetration process, a discrete iterative method is proposed to investigate the movement and the nose shape variation on the basis of thermoplastic instability of the material. Utilizing the temperature-based failure criterion and the Johnson-Cook (J-C) constitutive model, the receding displacements of the discrete points are determined by the gradient distribution of the temperature change along the depth from the surface of a projectile, which result in blunting of the projectile nose. The predictions of the nose shape, the percentage of the mass loss and the DOP were validated against the experimental data. Then further studies are conducted to investigate the critical velocity of mass loss and the “secondary peak” deceleration. The onset of the mass loss and the occurrence of the distinct pulse of the deceleration in the tunnel stage are regarded as the symbol of the lower and upper velocity limits of the nondeformable penetration regime. In addition, through the comparison of the percentages of heat generated with different mechanisms at different locations of the projectile, the dominant mechanism of the mass loss between the friction and plastic deformation is analyzed to get an insight into the high-speed penetration process.