Probabilistic evaluation on fatigue crack growth behavior in nickel based GH4169 superalloy through experimental data

The present paper developed a stochastic model to evaluate the scatter in fatigue crack growth (FCG) behavior of turbine disc GH4169 superalloy. Model parameters were calculated based on systematic experiments on compact tension (CT) specimens cut from the rim and installation flange locations of a turbine disk at corresponding service temperatures with stress ratios of 0.1 and 0.5. Based on the experimental data, piecewise FASTRAN model combined with Dugdale strip-yield model that includes the crack closure effect in GH4169 superalloy were proposed to formulate the deterministic FCG model. The probabilistic distribution of FCG rate was represented by a life distribution factor (LDF), combined with the deterministic model. Modeling results revealed that the variance of FCG rate followed a decrease-to-increase trend as crack propagates, which was consistent with the microstructural dependence of FCG revealed in typical polycrystalline materials. Proposed probabilistic model effectively reflected the stochastic property of FCG, offering a promising tool for probabilistic damage tolerance assessment (DTA).