Measurement of the thermal resistance of through cracks. A simple method based on flying spot instrumentation

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Abstract
The detection of through cracks using thermal methods is crucial in order to replace penetrant testing methods, which are polluting and only qualitative. The flying spot thermal method has been developed, but only as a detection method. Methods for estimating the characteristics of this type of defect (estimation of thermal resistance and depth) have been developed by Salazar et al., but only in periodic mode, requiring long analysis time and inverse methods that need a 3D study of transfers. We propose a simplified method for estimating these characteristics, based on a laser spot operating in pulsed mode, placed near the defect. It allows the temperature fields (measured by IR thermography) to be separated and reduces the estimation problem to a 1D signal inversion. Preliminary results have been obtained with isothermal media in the case of 2D granular media. We will present results obtained under non-isothermal conditions in calibrated conditions. The experiment will consider two metal plates in contact and the dedicated instrumentation (pulse laser spot and IR thermography).