Ultrasonic nondestructive evaluation of solid-solid bonds

The solid-state bonding of metals, e.g. diffusion bonding, friction welding, and inertial welding, is finding increasing use in the fabrication of structural components. A summary is presented of recent progress toward the development of nondestructive techniques to monitor the quality of such bonds. Emphasis is placed on the characterization of a particular microstructural origin of bond weakness, a distributed array of microcracks in the bond plane. Included is a discussion of theories for the interaction of ultrasound with such distributed defects, results of model experiments designed to validate the theories, and applications of techniques based on the resulting understanding to fracture studies of bonded surfaces and to inspection of aircraft engine turbine rotors