Measuring thermal contact resistances between metallic rods using laser spot heating and infrared thermography. Part 1

TL;DR

This paper presents a method to measure thermal contact resistances between metallic cylinders using laser spot heating and IR thermography, with a simplified analytical model suitable for complex media analysis.

Contribution

It introduces a simplified thermal model and analytical approach for estimating contact resistances, enabling application to complex media like granular materials.

Findings

Validated method for two or three cylinders

Potential for analyzing complex media

Analytical model reduces computational complexity

Abstract

Estimation of thermal contact resistances between cylinders can be achieved using heating on the cross sections by a laser spot and measurement of the temperature response by IR thermography. This type of measurement makes it possible to characterise contacts in clusters of cylinders to simulate clusters of grains, or the properties of fibrous media in the transverse direction or, under certain conditions, to detect emerging thermal resistances (cracks perpendicular to the observation plane) by IR thermography. Here, the thermal model is simplified because the temperature field in relaxation on either side of the resistance can be considered isothermal with a separation of transfers in the plane and along the thickness. The mathematical model is then analytical (relaxation of a linear system), and the processing of the temperature field can be inversed thanks to the consideration of the logarithm of matrices, useful when studying the propagation of measurement noise. The method proposed in the case of two or three cylinders is a first step and a validation for applications to the study of more complex media (large number of cylinders, granular media).