The computational micromechanics of materials with porous ceramic coatings

Plastic strain localization and fracture in materials with porous coatings are investigated. A dynamic boundary-value problem is solved using a plane strain approximation. A microstructure-based numerical simulation is performed by the finite difference method. The microstructure of the coated material corresponds to that found experimentally and is assigned explicitly in the calculations. An initial finite difference mesh generation procedure for an explicit account of curvilinear pore-coating and coating-substrate interfaces is developed. Constitutive relations incorporate an elastoplastic model for the isotropic strain hardening of the steel substrate and a model for the brittle fracture of the coating. The specific character of the deformation and fracture is shown to be due to the local tension regions developing near pores and along the coating-substrate interface. Notably, the regions are formed both under tension and in compression of the coated material. The interrelation between inhomogeneous plastic flow in the steel substrate and crack propagation in the coating is examined.