Three-dimensional crack growth modelling of a Ni-based superalloy at elevated temperature and sustained loading

•Three-dimensional crack growth modelling under sustained load.•Crack front evolution of surface cracks of Inconel 718 at high temperature.•History dependent material damage with crack growth rate control in 3D.•Finite Element simulations of crack growth.

High temperature materials subjected to elevated temperature have been shown to be sensitive to dwell times, giving an increased crack growth rate. The interaction between these dwell times and rapid cyclic loads have been shown to constitute a complex problem. Many models have been developed for 1D conditions, but the application to general 3D conditions has seldom been seen, although this is the most common case in most structures. In this paper a model for taking care of the interaction between these load modes in general 3D crack growth has been developed. The model uses 1D results for extension to general 3D, thus providing for local crack front evolution with a minimum of numerical simulations. Consequently, a history dependent crack growth law in 3D is given in this paper, which is capable of tracking the damage from the sustained load, and the interaction with rapid cyclic loading. The model has been implemented for usage with finite element calculations and several different tests are simulated and compared with experimental results for the nickel based superalloy Inconel 718 at 550 °C. The simulation results show crack shapes in agreement with experimental fracture surfaces and time to failure.