Nondestructive Testing System to Assess Lack-Of-Bond in Brazed Generator Coils by Ultrasonic Retro-Reflection

Margetan et al. investigated the problem of assessing the integrity of diffusion bonds using reflected ultrasound at oblique incidence [1,2]. They presented a quasi-static distributed spring model to derive the ultrasonic reflectivity of an imperfectly-bonded interface as a function of frequency and angle of incidence. The results were then incorporated in a model for the corner reflection from a diffusion-bonded joint between two butting plates. Rose also studied the ultrasonic reflectivity of diffusion bonds and utilized it for quantitatively characterizing defective joints [3, 4]. Angel and Achenbach investigated the reflection of ultrasonic waves by an array of microcracks [5]