| Realistic numerical analysis of dynamic failure process has long been a challenge in the field of computational mechanics. The challenge consists of two aspects: a realistic representation of fracture criteria, and its efficient incorporation into a viable numerical scheme. This study investigates the dynamic failure process in a variety of materials by incorporating a Cohesive Zone Model (CZM) into the finite clement scheme, The CZM failure criterion uses both a finite cohesive strength and work to fracture in the material description. Based on crack initiation criteria, CZMs can be categorized into two groups, i.e., intrinsic and extrinsic. This study focuses on extrinsic CZMs, which eliminates many of the inherent drawbacks present in the intrinsic CZMs. The extrinsic CZM approach allows spontaneous and adaptive insertion of arbitrary cracks in space and time, i.e., where needed and when needed. To that effect, a novel topology-based data structure is employed in the study, which provides both versatility and robustness, and allows adaptive insertion of cohesive elements as required by simulation. Both two-dimensional and three-dimensional problems are analyzed. A series of dynamic fracture phenomena, including spontaneous crack initiation, dynamic crack micro-branching and crack competition, are successfully captured by the CZM simulations. To better analyze mesh size dependence of the numerical scheme, an investigation of cohesive zone size is also presented, which indicates limitations of conventional cohesive zone size estimates in dynamic and rate-dependent problems. |
