X-FEM Analysis of dynamic crack growth under transient loading in thick shells

This paper is devoted to the modeling of crack propagation under impact loadings in thick shells composed of metallic materials using X-FEM. The proposed thick shell element is based on the existing Q4 gamma 24 4-node shell element for fast transient loadings that is enriched in the present work using X-FEM. The shell is considered to be always cut by a through the thickness crack. This element is hence enriched only with jump Heaviside functions on all degrees of freedom (displacements as well as rotations). The mass matrix corresponding to all added DOF is simply a copy of the usual continuous DOF diagonal mass matrix. The crack is discretized explicitly with a simple 1D mesh that lives on the shell's mid-surface and independently of the finite element mesh. Plasticity as well as stress field used for crack propagation criterion is evaluated using 5 Simpson points across the thickness. The crack propagation criterion is based on the measure of an equivalent stress at the crack tip and can predict both tensile and shear driven fracture as well as transitions between those two regimes. Comparisons with elastoplastic crack propagation experiments involving fracture under transient loadings show that the method is able to reproduce experimental fracture quite well.