Thermo-mechanical analysis of an inhomogeneous double-layer coating system under hertz pressure and tangential traction

The surface temperature distribution and thermo-elastic stress fields of an inhomogeneous coating system subjected to mixed Hertz pressure, tangential traction, and frictional heating are studied in this paper. The coating system consists of a surface coating and an intermediate functionally graded layer perfectly bonded to a substrate. The surface coating and the substrate are homogeneous materials with distinct physical properties while the intermediate layer is inhomogeneous with material properties changing exponentially along the thickness direction. It is assumed that the friction is of Coulomb type. Solutions for the temperature field and interfacial stresses are obtained using Fourier transform technique. The effects of total thickness, the graded layer thickness, Peclet number, and friction coefficient on the surface temperature field and interfacial stresses are investigated in detail. Direct comparisons with the results of a homogeneous single-layer coating system show that the use of the double-layer coating system can significantly reduce the surface temperature and interfacial normal stress.