This paper deals with the problem of an asperity-excited thermo-mechanical field in a medium with a thin surface layer and a near surface void defect. The solutions for the temperature distribution and stress state in the vicinity of the void are obtained. Numerical results are obtained using the material properties of Stellite III for both the coating and the substrate. The parametric effects of material properties in the coating and the substrate are considered by varying the corresponding property in the coating or the substrate. The stress field solutions of the coated medium with a cavity are compared with the solutions for a single material with a cavity. In the case of the single material with a cavity, while the thermal stress is much larger than the thermal stress of the no cavity case, the principal directions of the thermal stress are not significantly changed. However, for the case of a coated medium with a cavity, not only is the thermal stress much larger than that of the no cavity case, but also the principal directions of the thermal stress are changed. The principal directions of the thermal stress field depend on both the material properties and the ligament thickness (thickness between the wear surface and the top edge of the cavity). When the angle of the principal directions becomes larger, shear delamination will initiate at the coating/substrate interface.

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