Cell model for nonlinear fracture analysis - II. Fracture-process calibration and verification

A cell endowed with the micro-separation characteristics of the material is critical to formulating a predictive tool for nonlinear fracture mechanics analysis. This companion article addresses the second step in a two-step calibration scheme, namely, the calibration of the fracture-process parameters D and f(o). The discrete, three-dimensional nature of a cell element enables it to capture important features of (i) interaction between the cell elements forming the fracture process zone and the crack including a single cavity-crack tip interaction and (ii) interaction between the fracture process and the plastic dissipation in the background material. The full three-dimensional computational model is applied to two crack geometries known to give rise to significantly different crack tip constraints and crack growth resistance behavior. Details of the load, displacement and crack growth histories in these specimens including the measured three-dimensional crack profiles are accurately predicted by the computational model. The comparison of model predictions and test data of surface cracked plates loaded by different combinations of tension and bending is reported in the third paper (Gao et al., 1998a) in this series.