A periodic array of cracks in a functionally graded coating bonded to a homogeneous substrate is considered. The medium is subjected to transient or static mechanical loads. 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 stresses and stress intensity factors 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 is the influence of the material gradient (material nonhomogeneity) on the crack tip intensity factors and stresses. Solutions for a single graded layer and a graded coating bonded to an infinite substrate are given.

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