Laser vibrometer measurements of SAWs for nondestructive testing

A non-destructive testing (NDT) technique should be able to calculate the position and the size of any defects, in order to measure quality and safety of materials. Complexity is an issue for most NDT tests, requiring specialist knowledge of the technique. This generally means using qualified staff, and omits the possibility of any kind of automation. In this article an experimental methodology for crack detection using Surface Acoustic Waves (SAWs) and optical laser vibrometer measurements will be introduced. The materials under test are a damaged slat track of an Airbus A320 and a steel beam (because in the zone where critical crack propagation occurs the slat track has a beam-like shape) with slots of known depth (0.2, 0.4, 0.6, 0.8 mm). The goal of this article is to compare these ultrasonic-laser measurements in order to understand how much they are suitable to detect damages and imperfections present on the material itself. For future applications, this methodology can be used to monitor the slat track during a fatigue test, to detect damages in an early stage, before a rapid crack growth.