Combined continuum damage-embedded discontinuity model for explicit dynamic fracture analyses of quasi-brittle materials

SUMMARY: In this paper, a novel constitutive model combining continuum damage with embedded discontinuity is developed for explicit dynamic analyses of quasi-brittle failure phenomena. The model is capable of describing the rate-dependent behavior in dynamics and the three phases in failure of quasi-brittle materials. The first phase is always linear elastic, followed by the second phase corresponding to fracture-process zone creation, represented with rate-dependent continuum damage with isotropic hardening formulated by utilizing consistency approach. The third and final phase, involving nonlinear softening, is formulated by using an embedded displacement discontinuity model with constant displacement jumps both in normal and tangential directions. The proposed model is capable of describing the rate-dependent ductile to brittle transition typical of cohesive materials (e.g., rocks and ice). The model is implemented in the finite element setting by using the CST elements. The displacement jump vector is solved for implicitly at the local (finite element) level along with a viscoplastic return mapping algorithm, whereas the global equations of motion are solved with explicit time-stepping scheme. The model performance is illustrated by several numerical simulations, including both material point and structural tests. The final validation example concerns the dynamic Brazilian disc test on rock material under plane stress assumption.