FEM-DBEM approach for crack propagation in a low pressure aeroengine turbine vane segment

Abstract

In this work a realistic thermo-mechanical fatigue application, related to a fracture process simulation in a turbine vane, is implemented to highlight the advantages, in terms of accuracy and runtimes, of a peculiar submodelling approach based on the superposition principle. When tackling a crack propagation problem with a FEM-DBEM combined approach, the global analysis is generally demanded to FEM whereas the cracked subvolume is solved in a DBEM environment. In particular, a DBEM submodel is extracted from a global uncracked FE model and, in the “classical” approach, is loaded on the boundaries with displacements/tractions and temperatures; then the crack propagation is simulated by repeated thermal-stress analyses. Differently from that, the proposed equivalent approach solves the crack propagation problem by resorting to simpler pure stress analyses, with boundary conditions just applied on crack faces and consisting in tractions evaluated by an FEM global analysis along a virtual surface traced by the advancing crack (the FEM model is uncracked). The computational advantages of such alternative approach are highlighted and, in addition, a fatigue assessment is provided for a turbine vane in presence of a defect like that experimentally detected and numerically analyzed in this paper.