Thermographic Estimation of the Area and Depth of Buried Heat Sources for Nondestructive Characterization of Horizontal Defects

• Published in: Journal of nondestructive evaluation Vol. 42; no. 4
• Main Authors: Mendioroz, Arantza, Salazar, Agustín, Lasserre, Paul, Oswald-Tranta, Beate, Tuschl, Christoph
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-12-2023; Springer Nature B.V
• Subjects: Aspect ratio; Characterization and Evaluation of Materials; Classical Mechanics; Control; Defects; Dynamical Systems; Engineering; Evolution; Heat; Heat sources; Nondestructive testing; Solid Mechanics; Synthetic data; Thermography; Vibration; Infrared thermography; Nondestructive evaluation; Delaminations; Inductive thermography
• ISSN: 0195-9298; 1573-4862
• DOI: 10.1007/s10921-023-01002-3

We present a methodology to estimate quantitatively the area and depth of horizontal defects that generate heat in non-destructive tests such as burst vibrothermography or inductive thermography, without previous knowledge of the shape of the heat source. The method is based on extracting the temporal evolution of the temperature at the centre of the heated region, together with the thermogram obtained at the end of the excitation. The temperature displayed in this thermogram is averaged in circumferences concentric with the centre of the heated region to obtain an averaged radial profile which is fitted, together with the temporal evolution of the temperature, to a circular heat source model. By fitting synthetic data corresponding to rectangular heat sources with added noise, we analyse the accuracy of the method to retrieve the area and depth of the heat source for different depths and aspect ratios. Experimental results show that the method is able to estimate the area and depth of heat sources with aspect ratios below 1/1.5 with accuracy of about 10%.