Development of a New Method for Measuring Thermal Contact Resistance by Ultrasonic Waves

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In the academic year 1995, a fundamental study was carried out to clarify the relation between the ultrasonic transmission characteristics through a contact interface of two metallic solids and the thermal contact conductance (or its reciprocal, the thermal contact resistance) by using brass soecimens. In the academic year 1996, the dependence of the thermal contact conductance on the heat flow direction, which is often called rectification, and the application ranges of the present method were mostly studied experimentally and theoretically. The main achievements of the project are concluded as follows :1.As a result of studying the dependence of the ultrasonic transmission through the interface on the mean nominal contact pressure for flat rough surfaces, it is clarified that the measurement of transmitted ultrasonic waves is effective for the estimation of the thermal contact conductance.2.In the case of wavy rough surfaces, an averged value over the nominal contact surface area is obtained for the mean thermal contact conductance h_m, while the transmitted sound energy depends on the size of the specific transducers.3.For flat rough surfaces, an empirical correlation expression h<@D2m@>D2, and the transmitted sound energy ratio is proposed. By using the expression, h<@D2m@>D2, can be presicted within an error of about (]SY.+-。[)50%.4.The rectification is confirmed in the present study. It is shown that the conductance h_m, is affected considerably by the temperature at the interface for such larger wavy surfaces as the present experiments.5.In the rectification experiments of the transmitted ultrasonic waves, the opposite dependence is observed, and it is suggested to take the temperature dependence of the transducers into account.