Recent Development of LS-DYNA® XFEM Shells for Dynamic Ductile Failure Analysis: XFEM with GISSMO Damage Model

This paper presents a coupling of LS-DYNA XFEM shell method [30] and GISSMO damage model for dynamic ductile failure in shell structures. The XFEM shell formulation adopts the finite element continuous-discontinuous approach with the phantom-node technique [17] employed to incorporate velocity discontinuities in standard shell finite element formulations. The generalized incremental stress-state dependent damage model (GISSMO) adds damage and failure to most material models in LS-DYNA that do not allow failure. With the stress-triaxiality dependent failure criterion provided in GISSMO model, XFEM can better simulate material failure and crack propagation in mixed modes and under more complicated loading conditions. The option of element-size dependent regularization factor in GISSMO model removes the strain localization existing in the standard continuum damage model and suppresses the element-size sensitivity of ductile fracture, which is similar to the regularization zone approach in our original XFEM shell method for ductile fracture [30-32]. Unlike element erosion, when an element fails after certain number of integration points reach failure criterion, a crack (discontinuity)is inserted into the element with its direction depending on the stress state or other propagation option, and the element becomes an XFEM element comprised of two phantom elements. XFEM formulation allows crack propagation across elements without the sensitivity on mesh discretization and maintains the conservations of mass and momentum. Several numerical benchmarks and examples are tested using the explicit dynamics analysis to demonstrate the effectiveness and accuracy of the method described in this paper.