Numerical modelling to reproduce fragmentation of a tungsten heavy alloy projectile impacting a ceramic tile: Adaptive solid mesh to the SPH technique and the cohesive law

This paper presents an innovative approach for 3D Lagrangian finite element modelling of the fragmentation of a blunt shaped projectile (BSP) made of a tungsten heavy alloy impacting against a ceramic Alumina tile. The aim of this work is to develop an alternative way of modelling the fragmentation of both the projectile and the ceramic tile, with respect to the classical approach of the deletion of the finite elements. In particular, the projectile is made of an assembly of pre-fragmented sub-parts, without the possibility of deletion of the finite elements, with a cohesive law that allows the separation of the sub-parts when the suitable failure criterion is met. The ceramic tile model adopts the transformation of the finite elements into SPH (smooth particle hydrodynamics) elements when the failure criterion is met. Both these approaches are adopted to conserve the mass and to avoid discontinuities of the contacts between the parts. The heat generation by plastic work and the rate dependent properties of the materials are reproduced in the analyses. The model is compared with experimental data from the literature, in particular validating its performance in predicting the residual velocity and the residual mass of the projectile; an analysis of the wave propagation and damage morphology has also been carried out.