Determination of Thermal Diffusivity of Two-Layer Composites by Flash Method(Physics, Process, Instrument & Measurement)

概要

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A laser flash method of determining the thermal diffusivity of one layer of two-layer composites with the thermal contact resistance at the interlayer surfaces is described. A flash pulse is absorbed in the front surface of a thermally insulated specimen, and the resulting temperature history of the rear face is measured by a radiation thermometer and recorded with a transient memory and a pen-recorder. The time required for the temperature to rise 30 and 70 percents, for example, of the maximum temperature increase is read from the temperature versus time curve. These results are used for the numerical computation based on the theoretical equation of the normalized temperature increase on the rear face and the method of bisection, and the thermal contact resistance can be obtained easily as well as the thermal diffusivity. The fundamental equation of the temperature increase on the rear face in the present one-dimensional heat conduction problem is derived by Laplace transformation. The present method is applied to some joining specimens whose themophysical properties have been all measured in advance by the laser flash half-time method, and the effectiveness of this method is confirmed. The thermal contact resistance is also measured in addition by another method alredy proposed by the authors, and these obtained results are in fairly good agreement each other.
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