Meshfree Penetration of Projectiles into Rock

Abstract

ABSTRACT: The penetration of projectiles into soil and rock has many applications, both military and civilian. In this research we are concerned with depth of penetration of projectiles at formerly used munitions sites. We examine here a numerical framework for analyzing such penetration. Because the penetration problem includes large deformation, fracture, fragmentation, and other phenomena, standard finite elements cannot adequately capture the interaction. In this research, we employ a semi-Lagrangian Reproducing Kernel Particle Method (RKPM) framework. This meshfree technique updates the influence functions for each particle with deformation, naturally extremely large deformation, particle rearrangement, separation, and contact. The method has recently been updated with improved nodal integration for enhanced stability and accuracy. At this a stage a Drucker-Prager with damage model is used the capture the hardening and softening of the material. The damage function is modified to only include damage in tension. 1. INTRODUCTION Penetration of projectiles into rock and soil is of interest in many applications. These include protection of sensitive underground structures, projectile design, nuclear waste disposal, investigate of properties of remote sites, and mining. The ultimate goal in this research is the prediction of penetration depths at formerly used munitions sites, in order to detect buried projectiles and remediate the sites. While there are many empirical, analytical, and numerical approaches to this problem, it remains a challenging endeavor. Reasons for this include uncertainty in material properties, complicated physics of interaction between projectile and rock, and limitations of numerical methods. In the last case, challenges include large deformation inelastic behavior of the material, multiple discontinuities, and tracking of complex evolving contacts among the interacting projectile and rock mass. Standard finite elements struggle with penetration problems, due to the basic assumption of continuous deformation. While many enhancements have been created to handle fracturing [1-6] and large deformation [7-8], the problem of multiple rapidly changing contacts of parts creates a computationally intense problem. Discrete elements [9-11] can handle separation and contact more easily but are computationally expensive.