Multiple surface cracking of elastic coatings subjected to dynamic load

A periodic array of surface cracks in an elastic coating bonded to a homogeneous substrate is investigated in this paper. The medium is subjected to mechanical loads, either at transient state or at steady state. The problem is formulated in terms of a singular integral equation with the crack face displacement as the unknown variable. In addition to the time-varied stress intensity factors and stresses for various parameters of the problem, the effect of periodic cracking on the relaxation of the transient stress on the coating surface is discussed. Also included in this paper is the influence of the stiffness difference between the coating and the substrate on the crack tip intensity factors and stresses. Solutions for a single elastic layer and an elastic coating bonded to an infinite substrate are given. It is found that effect of the mass density of the substrate on the transient stresses and stress intensity factors is relatively small. The stiffness of the substrate has little influence on the stress and stress intensities for small values of crack length.