APPLICATIONS OF THROUGH-AIR ULTRASOUND FOR RAPID NDE SCANNING IN THE AEROSPACE INDUSTRY

This work describes two separate applications of air-coupled ultrasoni c nondestructive evaluation (NDE) for rapid inspection of aerospace co mponents, First, air-coupled transducer arrays are used for through tr ansmission scanning of relatively large preproduction test samples, In this case a focused array system was designed to facilitate faster in spection rates and at the same time match the resolution and performan ce of available water jet apparatus. The second approach is geared tow ard in situ inspection and involves single-sided scanning using a dual transducer configuration for generation of surface, shear, and Lamb w aves within the test specimen. In both cases, the difficulties of prac tical air-coupled inspection are discussed and the design solutions pr esented for each application. Piezocomposite transducer technology, in conjunction with narrow-band low-noise electronics, constitutes the b asis for achieving the required signal to noise ratio (SNR) to ensure robust operation within the industrial environment. A number of scan i mages, performed on realistic samples, are shown and the results compa red with those obtained using alternative methods, Excellent image qua lity is demonstrated from real time scanning and without recourse to a ny off-line data processing.