Microscale mapping of thermal contact resistance using lock-in thermography
International Journal of Thermal Sciences(2023)
Abstract
This paper proposes a new thermal contact resistance distribution measurement method using lock-in thermography. This method was used to evaluate a two-dimensional local thermal contact resistance distribution. To be able to measure the distribution, a uniform intensity laser heating system was developed. The developed system has a top-hat intensity distribution with a diameter of 30 mm. By combining this heat source and the lockin thermography, a new measurement instrument was developed, which can evaluate local temperature behavior in the frequency domain, including the information of the contact interface in high spatial resolution of about 70 mu m. Additionally, a new thermal contact resistance measurement principle was constructed based on a onedimensional heat transfer equation that considers the reflected and transmitted temperature waves at the boundary and contact interface. The thermal contact resistance was acquired as a solution to the inverse problem of the temperature response done by fitting analyses. The validation of this method was performed quantitatively with two samples made of two bonded isotropic graphite plates. The one sample has an intentional defect area that has a slightly higher thermal resistance. The other sample has the known thermal contact resistance value measured with a validated method. Based on the results, the measurement value agreed with the referenced value. Also, the defect area was quantitatively detected clearly as a high thermal resistance region. Furthermore, as a practical example, the measurement method was applied for two different contact interface roughness samples consisting of aluminum alloys and thermal grease. Consequently, it was revealed and visualized that the contact interface with a rough surface has a high thermal resistance spot.
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Key words
Lock -in thermography,Mapping,Measurement method,Periodic heating method,Thermal contact resistance
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