Application of RC delay time for thermal non-destructive characterization

Abstract

The electro-thermal analogy approach has been extensively used to solve different kinds of direct heat conduction problems. However, this analogy approach has not been explored much to solve inverse heat conduction problems. Quantification of defect characteristics (like thickness, area, location) which is an important aspect of thermal non-destructive characterization, is an inverse heat conduction problem. In this paper, an analytical method of thickness estimation of the interfacial defect (a commonly observed defect in multi-layered structure) in a bi-layer structure (a multi-layered structure with two layers) using the electro-thermal analogy approach has been presented. An analytical expression of the defect thickness is derived by analyzing the RC delay time of the equivalent electrical model of heat conduction in a bi-layer structure with an interfacial defect. The proposed method is fast, simple and devoid of extensive data handling. This method has been verified by simulations and experiments performed on bi-layer structures with constituent materials belonging to varied conductivity ranges. The implementation of the methodology can be instrumental in quality control, in situ defect characterization, interfacial resistance estimation etc.