Ultrasonic microscopy of contact joints

Ultrasonic techniques allow examination of internal structure and the detection of discontinuities at the interface of various joints. Contact joints obtained via diffusion welding, sintering, and other adhesive methods are investigated using impulse acoustic microscopy. It is shown that short probing pulses of focused ultrasound with frequencies of 50–100 MHz reveal areas with different adhesion strengths, areas of partial contact, peeling or air bubbles, and buffer layer thicknesses. Mechanisms of acoustic contrast at such interfaces are discussed. The results are of interest to specialists in the field of high-resolution ultrasonic nondestructive testing. They are needed to predict the failure mechanisms of composite products, from carbon fiber–reinforced plastics for the aviation industry to high-density ceramics used in medical prosthetics.