Abstract
“Logarithmic method” is a novel method for determining thermal diffusivity in the laser-flash technique. The advantages of logarithmic method over the conventional “t1/2 method” are discussed in this paper.
By solving the one-dimentional thermal diffusion equation using Laplace transformation and term-by-term inversion, we obtain a solution which is useful for early stage of elapsed time. In the logarithmic method, one term approximation of this solution is utilized to determine the thermal diffusivity from the experimental rear-surface temperature history of a sample after being flashed by a laser-pulse. The sensitivity analysis showed the following advantages of this method: The effects of heat leak from the sample and of non-uniform heating by a pulse to the determined thermla diffusivity values are much less in this method than those in case of t1/2 method. This is associated with the fact that the deviation of the maximum temperature rise of a sample from the ideal case affects very little in the determination of thermal diffusivity in this method.
It is concluded that the logarithmic method is much superior to t1/2 method and we propose this method to be used as the standard one for determining thermal diffusivity in the laser-flash technique.
