Abstract
This study presents the detection and localization method of contact-type failure based on the reflectivity modulation which is the reflectivity fluctuation caused by nonlinear wave modulation. When the structure including contact-type failure, such as fatigue crack, delamination of composite material and bolt loosening, is vibrating at low-frequency, the contact interfaces are breathing due to low-frequency vibration. Then, the scatter characteristics of high-frequency waves, such as wave transmisivirity and reflectivity, in the vicinity of the contact-type failure are fluctuated in synchronization with low-frequency vibration. The fluctuation of the reflection intensity of high- frequency waves which expresses the reflectivity in the specific location is given at the location of the contact-type failure. So, the time-spatial map of the reflection intensity can figure out the location of contact-type failure as the reflectivity fluctuation point. Especially, in this paper, the theory of some contact-type failures detection based on the reflection intensity fluctuation caused by nonlinear wave modulation is proposed, and investigated for a beam specimen which has some simulated contact-type failures experimentally.
