Adaptive FEM computation of geometric and material nonlinearities with application to brittle failure

Abstract

A model is presented for the dynamic finite element analysis of large-strain, high strain rate deformation behavior of materials. A total Lagrangian formulation is used in the derivation of discrete equations of motion. Both an isochoric finite deformation plasticity model, including rate and temperature effects, for metals, and a multiple-plane microcracking model for ceramics are introduced. In addition, algorithms are presented for correcting finite element mesh distortion through mesh rezoning, optimization, and refinement. A surface-defined multibody contact algorithm designed to handle large relative displacements between bodies, with addition for friction, is included. Extensions of the mechanical contact to account for heat fluxes between sliding bodies and the treatment of body interfaces with cohesive strength are presented within a unified framework. Two test examples are examined, simulating a modified Taylor rod impact experiment, in which an aluminum anvil strikes a confined or unconfined ceramic rod. Axial and radial velocities are computed at the free end of the ceramic and at 30 mm from the impact surface, respectively. Comparisons with experimental traces reveal that the simulations produce the same overall features observed in the experimental data.