Mesomechanics of multiple cracking of nanostructured gradient coatings under loading

The paper reports on theoretical and experimental investigations on deformation and fracture patterns of surface hardened materials. Simulation results on modeling processes of energy distribution and transformation at coating-substrate interface of a solid under loading by means of Stochastic Excitable Cellular Automata (SECA)-method are described. In doing so, deformable solid is considered as a multilevel system. The method allows taking into account self-organization of configuration perturbations for different levels of the system. An important role of stochastic modulation of an inelastic deformation at the interface in origin of inelastic deformation is discussed. It is shown experimentally that formation of toothed interface between nanostructured coating and substrate also results in formation of chessboard pattern of stress distribution there. This is manifested by multiple cracking of the coating with preferential crack orientation toward direction of maximum tangential stresses. This phenomenon could give rise to increase both strength and ductility of the surface hardened materials.