A unified cohesive zone approach to model the ductile to brittle transition of fracture toughness in reactor pressure vessel steels

In this study, a unified cohesive zone model is proposed to predict the ductile to brittle transition of fracture toughness in reactor pressure vessel steels. A general procedure is described to obtain the temperature and failure probability dependent cohesive zone model parameters. In order to establish the full master-curve, the procedure requires calibration at two different temperatures with one at the upper shelf for ductile fracture and one near the lower shelf for cleavage failure. In the present study, these calibrations are performed using the experimental fracture toughness values and the flow curves. Subsequently, fracture simulations are performed on one-inch thick compact tension and 3-point bend specimens at different temperatures and the resulting fracture toughness values are compared with experiments. A satisfactory agreement is observed which indicates the viability of such a unified modeling approach.