Thermal Constriction Resistance of Sphere/Layered Flat Contacts: Theory and Experiment

Abstract

The effect of surface layers on the thermal constriction resistance of contacts is of interest to the thermal analyst. This paper investigates analytically and experimentally the thermomechanical problem of a sphere in elastic contact with a flat coated with a layer. An approximate solution is developed that utilizes the solution to the thermal portion of the problem and the Hertzian limits of the mechanical portion. The approximation shows good agreement with the full solution for two examples that represent extremes in elastic properties for common metallics. Thermal constriction resistance measurements for a steel sphere contacting a nickel flat coated with a silver layer are compared to theoretical predictions. Resistance predictions from both full and approximate solutions show good agreement with measurements for light loads within the elastic load range. For heavy loads, the resistance is over-predicted due to plastic yielding of the nickel substrate.