Advanced algorithms for computer simulation of hypervelocity impact

Abstract

Presented are several algorithms that allow a Lagrangian hydrodynamic computer code to simulate hypervelocity impact. Such impacts typically involve very large material deformations and ordinarily can be handled only by Eulerian codes, in which the materials flow through a stationary grid. In Lagrangian codes, the mesh is attached to the material and deforms with it; in problems involving severe distortions, the mesh can become tangled, resulting in loss of accuracy or even a breakdown of the computational scheme. However, Lagrangian codes present several advantages in economy, ease of programming and use, and interpretation of results. This paper describes several modifications of the DEFEL code ( Flis, Miller, and Clark, 1984). This code, a descendant of EPIC-2 ( Johnson, 1976), was originally developed to simulate low- to medium-velocity impact and explosive-metal interaction. Modifications include automatic rezoning, a surface-erosion model, and treatment of fracture (cracking) by automatic introduction of sliding lines between elements. These fractures allow DEFEL to handle a variety of problems in the hypervelocity regime. Included are discussions of several example problems.