Ultrasound wave excitation in thermal NDE for defect detection

Sonic Infrared Imaging is a novel non-destructive evaluation method that has received attention in the NDE community. It uses ultrasound excitation and infrared imaging to detect defects in different materials, including metals, metal alloys, and composites. When a high-frequency ultrasonic pulse injects into the test object, the sound wave will cause the opposing surfaces of the crack to rub each other resulting in a noticeable temperature change. This thermal signal can be captured by an IR camera and used to locate the defect within the target. The probability of detection is significantly improved when nonlinearity is observed. Nonlinearity in the coupling between the ultrasound transducer and the target need to be studied to enhance the repeatability and reliability of this technology. In this paper, we present our study including the experimental as well as the FEA modelling of a sonic IR system with an emphasis on the vibration characteristics in the crack vicinity.