The constriction resistance of a coated asperity is considered in this work through numerical analysis. Unlike plane contacts of a semi-infinite cylinder considered earlier, the contact spots in this work terminate in the shape of the frustum of a cone. In previous work by the authors, the gap between the cone and contact surface was considered to be evacuated or filled with gas, and the temperature jump phenomenon was included in the gas-gap model. The present analysis includes the effects of radiation in the gas-filled model. The results indicate that an optimum coating thickness for minimizing constriction resistance exists in all cases. The effect of radiation on the model is shown to be highly dependent on the joint temperature, substrate and coating thermal conductivities, and constriction ratio. Contrary to current assumptions, radiation is shown not to be negligible for temperatures below 300°C when either the substrate conductivity or the constriction ratio is very low.
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