The flash method proposed by Parker is characterized by creativity and has become a classic for laser-flash experiments. However, there are contexts in which the determination of thermal diffusion properties cannot follow this classical approach. The paper proposes one of these cases, in which the layer of material to be studied is completely hidden between two layers of identical material whose properties are known. In addition to the inhomogeneity of the sample in the direction of thermal propagation, what suggests not to adopt the traditional approach are the expected heat losses, due both to the high thickness of the samples and to the duration of the transient (even 10 s). Since the heat losses, which are decidedly limited at room temperature, increase significantly as the temperature increases (the tests were carried out up to 600 °C), it was decided to limit the analysis to the first part of the transient. Therefore, the maximum temperature reached at the end of the transient, necessary to apply the classical method, has not been determined experimentally. For this reason, the analysis of the thermal response to the laser pulse has been carried out without normalizing the temperature values with respect to this maximum value, which probably makes the proposed approach unconventional. Using the described methodology and applying the quadrupole method, the quality of the results obtained was consistent with the experimental uncertainties. The comparison of the estimated thermal diffusion properties with the few data available in the literature showed a fair agreement. • Laser-flash method for the estimation of both thermal conductivity and diffusivity. • Quadrupole method combined with numerical inverse Laplace transform. • Finite duration of the laser pulse and sample heat losses are considered. • The analysis is performed using the non-normalized temperature response. • Thermal properties of Ti 6 Al 4 V sintered powder from room temperature up to 600 °C.
Campagnoli et al. (2026) studied this question.