An investigation of short crack propagation in a single crystal Ni-based superalloy using crystal plasticity and the extended finite element method

Abstract

Short cracks propagating under fatigue conditions are major concerns for the structural integrity of safety-critical applications. These defects tend to grow at high and irregular rates compared to long cracks under similar load, making the prediction of their evolution a challenging task. In this study, a computational approach comprising a crystal plasticity constitutive model and the Extended Finite Element Method (XFEM) is developed to investigate the slip-controlled short crack growth in a single crystal Ni-based superalloy. The onset of fracture is controlled by the cumulative shear strain of individual slip systems and crack develops along crystallographic directions. The model is calibrated from low-cycle fatigue experiments and used to evaluate short crack growth paths and rates in [111] and [001] orientations at 24 °C and 650 °C. Furthermore, the slip behaviour around cracks is investigated. The obtained results show that this modelling approach can capture the tortuous short crack paths and predict the fluctuating propagation rates.