Waves causing undesired heat pattern detected via ultrasound-excited active thermography

Abstract

Undesired heat patterns detected via ultrasound-excited active thermography are observed and their origin is determined based on ultrasound propagation. Waves generated during the inspection of strip- and hollow cylindrical-shaped objects are investigated via experiments and numerical studies. The results show that the dominant waves propagating in the strip- and cylindrical-shaped objects are A₀-mode Lamb waves and flexural-mode guided waves, respectively, and that the heat patterns are caused by standing waves generated by the propagation of the guided waves. The findings of this study should be fundamental knowledge to distinguish the temperature abnormalities caused by defects from undesired heat patterns and to improve the defect detection capability of ultrasound-excited thermography.