An Enhancement of LS-DYNA® XFEM Shells for Dynamic Ductile Failure Analysis

This paper presents an enhancement of LS-DYNA XFEM shell method [30] for dynamic ductile failure in shell structures. The XFEM shell formulation adopts the finite element continuous-discontinuous approach. The continuum damage model based on continuous displacements is used in the continuous stage to describe the diffuse micro-cracking in ductile failure before a macro-crack is formed. In the context of first-order shear deformable shell finite element method, a nonlocal modelling procedure based on a projection of mid-plane reference surface is introduced to regularize the element-wise strain fields induced by the continuum damage model. In the discontinuous stage, an incorporation of velocity discontinuities in shell finite elements is pursued by XFEM method when the damage variable exceeds a critical value and the transition from a continuous to a discontinuous model is permitted. A phantom-node approach [17] is employed in XFEM method to simplify the numerical treatment of velocity discontinuities in the shell finite element formulation. Several numerical benchmarks are examined using the explicit dynamics analysis and the results are compared with the experimental data to demonstrate the effectiveness and accuracy of the numerical method.