Лако-красочные материалы — производство

Active vibration-based monitoring method is a classical SHM technique. The main idea behind the method is that structural dynamic characteristics are functions of the physical properties, such as mass, stiffness and damping [22]. Hence, physical property changes due to damages can cause detectable differences in vibration responses. The dynamic characteristic parameters usually used in the technique include frequency, mode shape, power spectrum, mode curvature, frequency response function (FRF), mode flexibility matrix, energy transfer rate (ETR), etc.

Chiu et al., [23] demonstrated a monitoring system, which provides information about the in-service performance of the repair and the associated structure. The idea was based on the detection of debonding in the adhesive layer between the repair and the metallic parts. They also proposed that piezoceramic sensors could be used in the system for monitoring because of easy application, economical and reliable. Mickens et al., [24] developed a vibration-based method of damage detection system for monitoring ageing aircraft structures. The method was based on the detection of damage during operation of the aircraft before the damage propagation and the catastrophic failure. In this technique, four piezoelectric patches were used alternatively as actuators and sensors in order to send and receive vibration diagnostic signals. White et al., [25] performed experimental investigations on representative adhesively bonded composite scarf structures. Piezoelectric devices were used to excite and measure the response of the repaired structure. The frequency response of the repaired structure with simulated debondings was found to differ significantly from that one with undamaged repaired one, which signified the application of vibration based of a structural health monitoring system for bonded composite repairs and joints. In another work, White et al., [26] described the development of an SHM technique based on frequency responses for the detection of debonding in composite bonded patches. Two commonly applied repair schemes, the external doubler repair and the scarf repair, were investigated. It was verified that damage could be detected through changes in the frequency responses of the repairs with and without defects for both types of bonded repair schemes.