Effect of Nonsmooth Nose Surface of the Projectile on Penetration Using DEM Simulation

Abstract

The nonsmooth body surface of the reptile in nature plays an important role in reduction of resistance and friction when it lives in a soil environment. To consider whether it was feasible for improving the performance of penetrating projectile we investigated the influence of the convex as one of nonsmooth surfaces for the nose of projectile. A numerical simulation study of the projectile against the concrete target was developed based on the discrete element method (DEM). The results show that the convex nose surface of the projectile is beneficial for reducing the penetration resistance greatly, which is also validated by the experiments. Compared to the traditional smooth nose structure, the main reason of difference is due to the local contact normal pressure, which increases dramatically due to the abrupt change of curvature caused by the convex at the same condition. Accordingly, the broken particles of the concrete target obtain more kinetic energy and their average radial flow velocities will drastically increase simultaneously, which is in favor of decreasing the interface friction and the compaction density of concrete target around the nose of projectile. InstructionThe penetrating problem of the projectile against geological target has already been the focus of research for a long time. It has been found that there are many factors that influence the penetration performance. The nose of the projectile, named shape function in cavity-expansion theory, could determine the impact pressure [1] and the interface friction [2] between projectile and target. Therefore, as one of the most important factors, it can affect the penetrating resistance directly.In the process of natural evolution, the reptile, such as lizard, dung beetle, and pangolin, has its special body surface morphology, which is classified into five types: groove, rib, scale, convex, and concave according to different shapes. The bionic research has discovered that these specific structures can play important roles in reducing soil resistance and friction when the reptile lives in the geological environment [3]. At present, the explanation for this above phenomenon is attributed to the following aspects [4-6].(i) When the reptile moves in the soil, the nonsmooth surface can decrease the real contact area, resulting in the reduction of friction accordingly. (ii) The nonsmooth surface of the reptile is able to change the movement pattern of the contact soil particle from sliding to rolling. Therefore, it decreases the friction force and has ability of antiwear correspondingly. (iii) The soil compacted density around the reptile could decrease because the groove and concave nonsmooth surface can hold a certain amount of the soil fragments.Inspired by the nonsmooth surface structure, the question is can it be applied to design the projectile nose to deduce the penetration resistance and abrasion? We think it is essential to research the difference of penetration caused by the convex surface.Since the discrete element method (DEM) was developed ...