Experimental Study On Thermal Contact Resistance Of Solid-Solid Interface Based On Surface Power Spectral Density

Thermal contact resistance(TCR)is the core parameter for measuring the heat transfer efficiency of solid-solid interfaces in many engineering fields such as microelectronic packaging,photovoltaic systems,aerospace,energy power,etc.However,effective measurement and accuracy forecasting of TCR has always been a bottleneck in the thermal design of cooling systems.The three-dimensional topography of the rough surface determines the actual contact area and interface gap between the contact interfaces,which in turn plays a decisive role in the TCR between the interfaces.Therefore,accurately expressing the topography characteristic of the contact surface is one of the core issues in the study of TCR.Studies have shown that rough surface power spectral density(PSD)contains not only vertical height information,but also information in the horizontal and vertical spatial frequencies when characterizing optical surfaces,which is an international standard parameter for fully characterizing optical surfaces.Therefore,this paper uses PSD to characterize the contact interface to conduct an in-depth study of the solid-solid interface TCR.The main research contents and conclusions are summarized as follows:1.Using PSD to analyze the surface of aluminum and stainless steel materials commonly used in engineering,the results confirm that the slope of the roll-off area of the PSD curve determines the surface fractal dimension,and the size of the roll-off wave vector and cut-off wave vector determine the rms roughness amplitude and average surface slope.Furthermore,according to the actual measured height data,the surface PSD of different magnifications and value areas were calculated,and then the interface spacing of the contact surface was calculated according to the Persson contact theory and PSD,and the TCR was explored.It is found that the magnification has a greater effect on the surface PSD and TCR,while the TCR calculated by PSD at low magnification is relatively close to the experimental value.In addition,PSD calculations show that there is no significant difference in the interface spacing between different areas of the same surface,and the TCR values are almost the same.2.Using PSD to characterize the contact interface spacing,combined with Persson theory and experimental measurements,the effects of surface roughness,contact pressure,material properties,hysteresis effect and interstitial gas film on the contact thermal resistance between interfaces were analyzed: 1)Theoretical calculations show that the surface PSD and interface spacing are significantly different under different roughness surface,which leads to a large difference in interface TCR;2)Affected by material characteristics and contact pressure,when the PSD of the two interfaces has the same roll-off wave vector,the difference in the contact interface distance between different materials makes the TCR significantly different;3)Due to the hysteresis effect,there is a slight difference in the interface spacing at low contact pressures,which results in slightly different TCR,but the TCR is not affected at high pressures;4)The thickness of the gas film at the interface interstitial is different under different gas pressures and the gas thermal conductivity is also different,which in turn has a greater impact on the TCR of the contact interface.