Nonlinear ultrasonic imaging of imperfectly bonded interfaces

A nonlinear ultrasonic imaging system is developed for detecting and imaging damages and defects with nm order gaps in industrial materials, which were undetectable by conventional ultrasonic imaging systems. A high power pulser generating large amplitude incident waves and high gain receiver with high- pass or band- pass filters extracting the second harmonic signals are combined with a conventional C- scan imaging system. The system is applied to visualize fiber/ matrix debondings or matrix crackings in CFRP plates. It also visualizes anomalous substructures in amorphous diffusion- bonded interfaces, spot- welded nuggets, and projection- welded interfaces. This system would be also useful to detect semi- closed cracks whose opening is in nm order. (c) 2006 Elsevier B. V. All rights reserved.