The use of Flash Laser Method in the analysis of thermal diffusivity of metallic materials

The method effectiveness for thermal analysis of metallic materials named Flash Laser was analyzed and proved from studies concerning duplex stainless steel. This method is based on the analytical solution of the unidimensional thermal diffusivity equation, and its importance comes from the fact that material thermophysical properties are the key to determine its application and performance in the face of thermal conditions imposed. Flash Laser method consists in the use of a cylindrical sample, in adiabatic conditions, which receives an initial pulse of laser in one of the faces. On the opposite side, the range of temperature profile is measured, and an experimental curve is obtained. From then on, it’s possible to determine time required to increase the temperature of the opposite side to the half of its maximum. With this information in hands, and knowing the thickness of the sample, these data are applied to Parker equations to determine the thermal diffusivity of the studied material. A sample of stainless steel UNS S32304 was analyzed in the condition as received from the supplier, and the value obtained with the method in focus was compared to the one exposed on the material technical specifications. This baseline ensured the effectiveness of the Flash Laser method. Once qualified, Flash Laser method will be employed in the analysis of possible modifications on the thermal diffusivity of metals due to welding process.


Abstract
The method effectiveness for thermal analysis of metallic materials named Flash Laser was analyzed and proved from studies concerning duplex stainless steel. This method is based on the analytical solution of the unidimensional thermal diffusivity equation, and its importance comes from the fact that material thermophysical properties are the key to determine its application and performance in the face of thermal conditions imposed. Flash Laser method consists in the use of a cylindrical sample, in adiabatic conditions, which receives an initial pulse of laser in one of the faces. On the opposite side, the range of temperature profile is measured, and an experimental curve is obtained. From then on, it's possible to determine time required to increase the temperature of the opposite side to the half of its maximum. With this information in hands, and knowing the thickness of the sample, these data are applied to Parker equations to determine the thermal diffusivity of the studied material. A sample of stainless steel UNS S32304 was analyzed in the condition as received from the supplier, and the value obtained with the method in focus was compared to the one exposed on the material technical specifications. This baseline ensured the effectiveness of the Flash Laser method. Once qualified, Flash Laser method will be employed in the analysis of possible modifications on the thermal diffusivity of metals due to welding process.

Introduction
Precision on engineering projects is closely related to the knowledge of materials thermophysical properties. Where α is the thermal diffusivity.
(8) The bench scheme is shown on

Results from the supplier data
Based on data shown at the Table   1, and considering that the thermal diffusivity of a material is the ratio between its capacity to conduct heat and its capacity to storage it, it's obtained that: Where: is thermal diffusivity; is thermal conductivity; is the materials specific mass; is the specific heat.
Replacing the literature values to the analyzed steel: . Analyzing the graphic, it's possible to notice that and

Conclusion
The equivalency between the value of thermal diffusivity resulted from calculation using the data from the supplier and the one obtained by