On-line damage detection on a wing panel using transmission of multisine ultrasonic waves

Fatigue damage of materials is an important problem that causes a lot of failures in mechanical systems. It is very important to detect this fatigue as early as possible. Nowadays, most of the nondestructive testing methods are off-line: the inspection is carried out periodically and in some cases the device has to be dismounted. So we risk to exceed, for example, the critical length of a crack. In this article, an on-line method based on the variation in transmission of a multisine ultrasonic wave during opening and closing of a surface crack is developed. As a validation experiment, a propagation fatigue crack in a sinusoidally loaded wing panel is considered. It will be shown that the on-line method is very sensitive to crack propagation.