One-Level, Two-Point Method for Estimation of Thermal Diffusivity by the Converging Thermal-Wave Technique

The thermal diffusivity of several kinds of metal sheets was measured by the converging thermal-wave technique. This is a typical technique which can obtain the in-plane thermal diffusivity by measurement of the temperature evolution at the ceInter of the pulsed annular laser beam when the laser beam irradiates the surface of the samples. However, the rapid temperature increase and nonlinearity of the infrared detector in the earlier part, and convection heat loss from the sample surface in the later part, of the temperature evolution can be sources of errors. In this study, when the temperature of the ceInter reached half of the maximum, the times t1 and t2 , in the ascending and descending parts of the temperature evolution curve, respectively, were determined and other points, t$1 and t$2 , were determined by increasing the temperature to 900 of the maximum in successive increments of 100 of the maximum. By using these determined times, the variation of thermal diffusivity was investigated and com- pared with results from existing methods and with reference values.