Contact Acoustic Nonlinearity Identification via Online Vibro-Acoustic Modulation Technique

Employing nonlinear dynamic signature of the host structure for early damage detection and remaining useful life estimation purposes, is an emerging idea in the area of piezoelectric patches based structural health monitoring. Clamped support loosening is one of the defects that not only may cause disorder in system’s functioning, but also obstruct damage identification process through distorting the signals. In this study, support loosening induced contact acoustic nonlinearity (CAN) behavior was monitored by vibro-acoustic modulation (VAM) technique. Using miniaturized PZT patches with the capability to be installed on the host structure permanently for both pump and probe actuation as well as sensing the modulated signal, enabled online monitoring via VAM technique. An appropriate filter was designed to eliminate the unintentionally excited natural frequencies and to reveal the sidebands. In this study, the sensitivity of modulation strength to the pump excitation frequency was also investigated. According to the results, appearance of sidebands around the central probe frequency is an appropriate indicator for CAN identification. In order to study the mechanism of modulation phenomenon, a coupled field electromechanical finite element (FE) model was developed. Proper matching of the numerical and experimental results indicates sufficient accuracy of the developed FE model and its potential to predict the modulation behavior.