Cleavage Crack Propagation and Arrest Prediction in French PWR Vessel Steel

Abstract

The integrity assessment of Reactor Pressure Vessels is mainly based on crack initiation. Nevertheless, in the frame of component life extension, crack arrest conception is investigated. This paper presents a local non-linear dynamic model to predict the propagation and arrest of cleavage crack in French PWR vessel steel (16MND5). The propagation criterion used in this model is a Ritchie Knott and Rice (RKR) fracture stress criterion: the crack propagates when the maximum stress ahead of crack tip reaches a critical level, which has been shown to depend on temperature and plastic strain rate. In the first step, the criterion has been identified from crack growth and arrest analysis on CT specimens at different temperatures. Then it was applied to predict the propagation and arrest of cleavage cracks on pre-cracked rings under mixed mode loading, at three different temperatures: −150°C, −125°C and −100°C. 2D modeling was performed by using extended element method (XFEM) in CAST3M software. The propagation direction on pre-crack rings under mixed mode loading was determined from maximum hoop stress criterion. Numerical computation showed a good agreement with experiments, for both curved crack paths and crack arrest locations. Furthermore it showed that crack paths and crack arrest also depend on the level of the crack loading at initiation.