The CAFE model of fracture - application to a TMCR steel

CAFE, a combination of Cellular Automata (CA) to describe the material microstructural properties, and Finite Elements to represent the macroscopic strain, allows the evolving states of microstructural change to be analysed in a deforming body. The paper explores the potential of the technique for the assessment of the ductile-to-brittle transition behaviour of ferritic steels. The most important features are due to the microstructural control of cleavage. The model was applied to the Charpy test on a TMCR (Thermo-Mechanically Controlled Rolled) steel. The results include simulations of the full Charpy energy transition curve, the varying amount of scatter in the data, and, in distinction to most other models in the literature, a full description of the state of the fracture surface on each specimen. The results agree reasonably well with the experimental data. The model follows the development of both ductile and cleavage micro-mechanisms throughout the deformation of the structure or component. As a consequence, it allows cleavage to develop as a progressive point-to-point process. The model can, and does, predict the arrest of cleavage cracks by ductile processes. It can be easily generalized to include more sophisticated aspects of a material microstructure.