FEM-DBEM approach to simulate crack propagation in a turbine vane segment undergoing a fatigue load spectrum

Abstract

In this work a thermo-mechanical fatigue application, related to a crack propagation in an aircraft turbine vane undergoing a complex load spectrum, is simulated. A computationally efficient FEM-DBEM submodelling approach, whose implementation leverages on the principle of linear superposition, is adopted.When tackling a crack propagation problem with a FEM-DBEM combined approach, the global analysis is generally worked out by FEM whereas the fracture problem is solved in a DBEM environment. In particular, a DBEM submodel is extracted from the global uncracked FEM model and, generally, is loaded on the boundaries with temperatures and either displacements or tractions; then the crack propagation is simulated by repeated thermal-stress DBEM analyses. Differently from that, the proposed equivalent approach solves the crack propagation problem by adopting a simpler pure stress DBEM analyses in which the boundary conditions, in terms of tractions, are just needed on the DBEM crack faces. Such tractions are evaluated by the FEM global analysis along a virtual surface traced by the advancing crack (the FEM model is uncracked). Such an approach provides accuracy enhancement and computational advantages.