Ultrasonic Techniques for hidden corrosion detection

ABSTRACT

Detection of corrosion damage in aircraft wing skin structures is an ongoing NDT challenge. Ultrasonic methods are known and well-accepted techniques, which are relatively simple to carry out in terms of setup, probes and instrumentation and operator training. However, with conventional inspection from the top surface using a transducer at normal incidence (0o to the normal to the surface) producing a visual picture in the form of a C-scan, it is very time consuming to point-by-point inspects large aircraft wing skin areas. In addition it is too difficult to detect disbonds in thin multilayered and fatigue cracks in the shadow region at fastener holes in airframe structures where water and humidity then are infiltrated to create corrosion and exfoliation around and under the rivets. Ultrasonic guided waves demonstrate potential as promising, global and fast inspection method. It can be used to compliment and in some cases, be an alternative to conventional ultrasonic C-scan inspection method.