Cohesive-force embedded damage model and its application to crack propagation analyses

A cohesive-force embedded damage model is proposed in this study to realize both crack nucleation and propagation. As in the existing smeared crack model and rotating crack model, the crack opening is introduced at each material point, but is treated as an internal variable to be determined implicitly. To work with the proposed damage model in crack propagation analyses, the Nested Tangent Secant Method (NTSM) is proposed as a proper alternative to the method with approximate tangent moduli. After verifying that the proposed model provides equivalent performance to the traditional cohesive zone models for cracking behavior under uniform tensile loading, we demonstrate its superiority over them in simulating crack nucleation and propagation in a plate with hole and in a beam-like structure subjected to bending. Here, the superiority of the NTSM over the Explicit Secant Method (ESM) is also discussed. Also, we studied the characteristics of the exiting cohesive zone models that do not have the crack opening as an internal variable and pointed out their limitation in history-dependent problems by taking the mixed-mode condition crack propagation analysis as an example.