Thermal Wave Detection and Analysis of Adhesion Disbonds and Corrosion in Aircraft Panels

Pulse-echo ultrasonic techniques are widely used for the purpose of nondestructive evaluation (NDE) of materials. Knowledge of the elastic wave velocities in a material permits time-of-flight measurements to be converted into measurements of the subsurface depths of various subsurface defects which are strong elastic wave scatterers. In recent years, the authors and others have utilized an analogous pulse-echo technique to study thermal wave scattering from subsurface defects [1–4]. In this technique, the waves are launched as the result of energy deposited at the sample surface from a suitably pulsed heat source, and the resulting time evolution of the surface temperature is monitored by means of an infrared (IR) camera. Descriptions of the detailed methods for processing the data stream from the camera in real time, so as to effect box-car or lock-in image processing, have been presented elsewhere [1–4]