DEM model for simulation of crack propagation in plasma-sprayed alumina coatings

Abstract

In this work, a Discrete Element Method (DEM)-based numerical model has been developed in C++ program, which enables to simulate the crack propagation of plasma-sprayed Al2O3 coatings thus enabling to predict their failure. DEM-based approach is combined with the image analysis procedure applied on two-dimensional (2D) cross-section images of as-sprayed coatings. This procedure allows to build up the model of the coating microstructure taking into account defects which can be regarded as pores and cracks. Pores are then discriminated from cracks and these latter are in turn categorized into two types intra- and inter-splat cracks which have been considered in the simulations of crack propagation. Results indicate that the Young's modulus of as-sprayed coatings depends strongly on the geometric features of the porosity, namely the shape and the distribution. The simulation results on crack propagation exhibit that the generation of cracks which begin inside the splat due to the intra-splat cracks yield large cracks which propagate vertically until to reach the surface of the coating, while inter-splat cracks located at the interface between splats evolve by creating a bifurcation through an interlinking mechanism with other cracks.