Simulation of high speed impact, penetration and fragmentation problems on locally refined Cartesian grids

Techniques are presented to solve problems involving high speed material interactions that can lead to large deformations followed by fragmentation. To simulate such problems in an Eulerian framework on a fixed Cartesian mesh, interfaces (free surfaces as well as interacting material interfaces) are tracked as levelsets; to resolve shocks and interfaces, a quadtree adaptive mesh is employed. This paper addresses issues associated with the treatment of all interfaces as sharp entities by defining ghost fields on each side of the interface. Collisions between embedded objects are resolved using an efficient collision detection algorithm and appropriate interfacial conditions are supplied. Key issues of supplying interfacial conditions at the precise location of the sharp interface and populating the ghost cells with physically consistent values during and beyond fragmentation events are addressed. Numerous examples pertaining to impact, penetration, void collapse and fragmentation phenomena are presented along with careful benchmarking to establish the validity, accuracy and versatility of the approach.