Numerical analysis for the abnormality of protective properties of a thin shield under oblique impact

A numerical analysis is performed to explain the abnormal effect observed in experiments investigating the protective properties of a thin shield under high-velocity impact at different angles. Within the framework of the model of a viscoelastic Maxwell-like body, in which fracture is taken into account, we solve three problems: the problem of perpendicular impact and that of impact at a 60$^\circ$ angle to the surface in the planar formulation, and the problem of perpendicular impact in the axisymmetrical case. The analysis has shown that under the given specific conditions the peculiarities of the projectile-target interaction in the case of the oblique impact give a decrease in the level of breaking loads as compared with the breaking loads appearing at the perpendicular impact and, as a consequence, lead to less fragmentation of the projectile. Ultimately, this decreases the protective properties of the shield.