Study On Damage Detecting Technique Of Mechanical Structural Monitoring Using Piezoelectric Impedance Measurement

This paper presents a study on development of Piazoceramic Embedded Impedance system for truss type structures. We developed a simple impedance measuring system for measuring impedance and structural monitoring which consists of piezoelectric element, an impedance analyzer and computer.At first, the conception of piezoelectric impedance measuring method was presented. The result of experiment and analysis indicates that the impedance response is easy to obtained, the position of PZT and the monitoring frequency range can be determined by the length of PZT patches and the beam.Then, a structure consisting of aluminum beam and L-plate joints was used for investigation of the looseness of bolts at the joint, as the sample of damage. In the experiment, the bolts were fastened at 2 Nm as healthy condition, and then were loosened by the torque wrench in a step of 0.25 Nm until 1 Nm as damage. The impedance response of PZT patches were measured and recorded at each step. The change of torque and the impedance response can be ascertained by comparing with healthy condition. Furthermore, in order to increase the measuring precision of system, we develop the effect of system parameters, the peak frequency shift ?F, the peak amplitude ratioδand the change rate of Qγ.At last, it is confirmed that the piezoelectric impedance measuring method and the three parameters is efficacious by testing other bolts in the truss structure. It can be used for measuring impedance structural damage monitoring by compeered the impedance experimental result on the truss structure in various torques.