Enhanced FEM-DBEM approach for fatigue crack-growth simulation

Abstract

To comply with fatigue life requirements, it is often necessary to carry out fracture mechanics assessments of structural components undergoing cyclic loadings. Fatigue growth analyses of cracks is one of the most important aspects of the structural integrity prediction for components (bars, wires, bolts, shafts, etc.) in presence of initial or accumulated in‐service damage. Stresses and strains due to mechanical as well as thermal, electromagnetical, etc., loading conditions are typical for the components of engineering structures. The problem of residual fatigue life prediction of such type of structural elements is complex, and a closed form solution is usually not available because the applied loads not rarely lead to mixed-mode conditions. Frequently, engineering structures are modelled by using the Finite Element Method (FEM) due to the availability of many well‐known commercial packages, a widespread use of the method and its well-known flexibility when dealing with complex structures. However, modelling crack-growth with FEM involves complex remeshing processes as the crack propagates, especially when mixed‐mode conditions occur. Hence, extended FEMs (XFEMs) and meshless methods have been widely and successfully applied to crack propagation analyses in the last years. These techniques allow a mesh‐independent crack representation, and remeshing is not even required to model the crack growth. The drawbacks of such mesh independency consist of high complexity of the finite elements, of material law formulation and solver algorithm. On the other hand, the Dual Boundary Element Method (DBEM) both simplifies the meshing processes and accurately characterizes the singular stress fields at the crack tips (linear assumption must be verified). Furthermore, it can be easily used in combination with FEM and, such a combination between DBEM and FEM, allows to simulate fracture problems leveraging on the high accuracy of DBEM when working on fracture, and on the versatility of FEM when working on complex structural problems... [edited by Author]