Simulation of cracking patterns in sprayed coating under equi-biaxial tension

In order to characterize the "Repeating-division type" and the "Island-delamination type" cracking patterns which are often observed in a brittle coating on a ductile substrate under increasing biaxial tensile stress, computer simulations of the cracking processes were performed for the cermet or the ceramic coating which was thermally sprayed on the substrate of a low carbon steel. The simulation was carried out using the Monte Carlo method and the analytical equations which express the relationships among crack size, tensile stress, strain, thickness and material constants of the coating and substrate. In the simulation, many cracks which have been nucleated randomly on the coating grow to either of the above cracking patterns depending on the relative strength of the coating and interface. The simulated cracking patterns agree well with those observed in bulge experiments.