The accuracy of laser flash analysis explored by finite element method and numerical fitting

Abstract

Laser flash analysis (LFA) has become over the last decades a widely used standard technique to measure the thermal diffusivity of bulk materials under various conditions like different gases, atmospheric pressures, and temperatures. A curve fitting procedure forms the heart of LFA. This procedure bases on a mathematical model that should ideally account for inherent shortcomings of the experimental realization such as: duration of the heating pulse, heat losses to the environment and sample holder, non-opaque samples, and radiative heat transfer. The accuracy of the mathematical model and curve fitting algorithm underlying LFA defines an upper bound of the accuracy of LFA in general. Unfortunately, not much is known about the range of parameters and conditions for which this accuracy is acceptable. In this paper, we examine the limits of accuracy of LFA resulting from its underlying computational framework. To this end, we developed a particularly accurate and comprehensive computational framework and applied it to data from simulated experiments. We quantify the impact of different (simulated) experimental conditions on the accuracy of the results by comparing the fit results of our computational framework to the known simulation input parameters. This way we demonstrate that a state-of-the-art computational framework for LFA admits determining thermal conductivities of materials in a broad range from at least 0.16 W/mK to 238 W/mK with relative errors typically well below 4% even in the presence of common undesired experimental side effects.