Piezoelectric-based structural health monitoring of flexible beam connection damage

Abstract

Structural health monitoring is an emerging technology addressing major concerns in the operation of in-service structures, i.e. the reliability of the structures and the cost associated with maintaining reliability. In this thesis, the motivation of structural health monitoring has been discussed within the framework of non-destructive evaluation. To be a common failure mode, connection damage or lap joint damage is chosen as damage signature in a structure, consisting of a flexible aluminum beam jointed on a frame by bolts. To simulate connection damage, the stress relaxing on the bolt is achieved by the action of bolt looseness quantified by rotation angle. The dynamic response of flexible beam system is monitored with a piezoelectric transducer. To produce exciting signal, an electro-mechanical system processes the voltage signal. Response interpretation is carried out on PC or on an embedded DSP chip in real time. The two analysis methods, frequency response method and wavelet analysis method, were explored to identify early "changes" of beam connection so as to reach the goal of structural health monitoring.