Identification of the location and level of damage in multiple-bolted-joint structures by PZT actuator-sensors

A piezoceramic (PZT) patch can be used simultaneously as an actuator and as a sensor for structural damage detection by utilizing its electromechanical coupling property. In this technique, a PZT actuator-sensor patch is bonded on a structure. Through the measurement of its electrical impedance, which is related to mechanical impedance of the structure being bonded, the change in structure properties due to damage can be detected. This paper presents the use of PZT actuator-sensors in conjunction with numerical model-based methodology in order to identify the location and level of the damage in multiple-bolted-joint structures. Laboratory experiments were performed on a two-joint and a four-joint aluminum beam, where the damage was simulated by loosening the bolts. The impedance was measured at high frequencies so that the wavelength of the excited motion is small and sensitive enough to detect local damage. Numerical models of structures were formulated by using a spectral element method, which has a high capability for high-frequency modeling. By utilizing the models, the location and level of the damage could be quantitatively identified.