A structural integrity assessment framework using SAFT and XFEM

Abstract

The study presents a basic framework for structural integrity assessment using synthetic aperture focusing technique and the extended finite element method. Synthetic aperture focusing technique (SAFT) is used to acquire detailed descriptions of three-dimensional flaws in engineering structures. Flaws extracted from SAFT can readily be represented as a surface mesh or a volume mesh. The mesh is integrated into a normal structural finite element model (FEM) via level set method to formulate an XFEM problem. Applying the cyclic fatigue load and solving the problem provides essential quantities for evaluation of the stress intensity factor (SIF), serving as a driven force of crack growth. The crack front is updated using crack growth equations, such as Paris' equation and its variants under cyclic loading condition. The result is considered to be accurate due to the fact that, for one thing it can minimize the uncertainty in quantification of three-dimensional flaws, and for another it provides a highly reliable solution to SIF for any point in the crack front under mixed mode loading conditions. Combination of the two components allows for removal of approximations and over conservativeness in conventional ultrasound based structural integrity assessment.