One-level two points method for estimation of thermal diffusivity by the converging thermal wave method

The thermal diffusivity of several kinds of metal sheet was measured by the converging thermal wave method. This is a typical method which can obtain the in-plane thermal diffusivity by measurement of the temperature evolution at the center of a pulsed annular laser beam when the laser beam irradiated the surface of the samples. However, the rapid temperature increase, nonlinearity of the infrared detector, and convection heat loss from the sample surface in the latter part of the temperature evolution can sources of error. In this study, when the temperature of the center reached half of the maximum, the times t₁ and t₂ which were the ascending and descending parts of the temperature evolution curve, respectively, were determined and other points t₁´ and t₂´ were determined by increasing the temperature to 90% of the maximum with each 10% successively. By using the determined times, the variation of thermal diffusivity was investigated and compared with results from existing methods and reference values, and analyzed in terms of the reduction of errors