Implementation of Second-Order Combined Particle-Element Method (CPEM) in the Elastic-Plastic Impact Computations (EPIC) code

Gerlach, Charles (Southwest Research Institute)

Beissel, Stephen

Computational Structure Mechanics

Efficiently simulating large-deformation impacts with Lagrangian methods would ideally use higher-accuracy finite-element formulations in regions of small deformation, and only use the more expensive but more robust meshless particle methods where they are truly needed, in the regions of large deformation. The Combined Particle-Element Method (CPEM) is designed to be a means of allowing integration points to use finite-element shape functions until they achieve a user-specified equivalent strain, at which point they switch to using the meshless Moving-Least-Squares (MLS) shape functions, without re-locating any integration points or mass nodes. Previously, CPEM was implemented with first-order finite-elements and MLS shape functions constructed with a linear basis. This work has expanded CPEM to use second-order finite-elements, which will convert into MLS shape functions with a quadratic basis. The new shape functions are demonstrated on several problems with different conversion strains.