Uncertainty Quantification In Non-planar Crack Growth Analysis

Abstract

Due to the various uncertainties and errors inherent to non-planar fatigue crack growth analysis, uncertainty quantification is required to obtain a robust assessment of component reliability. Computational costs associated with high-fidelity 3-D finite element analyses(FEA) prohibit their recurrent use in further probabilistic life prediction analysis. This paper presents two approaches for the development of surrogate model based non-planar fatigue crack growth analysis that allow for a probabilistic assessment of the component life. The first approach employs a parameterized representation of the non-planar crack for use in crack growth analyses that account for uncertainty in crack growth. The proposed method employs two surrogate models: the first surrogate model uses 3-D fatigue crack growth analyses to capture the relationship between the applied load history and equivalent planar crack orientation, and the second surrogate model calculates the stress intensity factor as a function of crack size, crack orientation, and load magnitude. Individual predictions of the two surrogate models, as well as their combined predictions are verified for accuracy using full 3-D finite element simulations. Uncertainty quantification using the verified two-stage surrogate model is then demonstrated. The second approach employs a Principal Component Analysis based non-parametric crack shape representation that allows for construction of a surrogate model for non-planar crack growth with complex crack shapes. In addition to providing a more realistic representation of non-planar cracks, the proposed approach allows for modeling the effects of spatial and temporal discretization in 3-D FEA based non-planar crack growth analysis. The ability of the surrogate model to accurately predict the evolution of the crack growth over entire load histories is verified. Extension of the proposed surrogate model to account for the effects of spatial and temporal discretization is presented. The proposed approaches are illustrated through non-planar crack growth analysis in a cylindrical component that is similar to a rotorcraft mast.