Abstract
A truss structure consisting of aluminium beams and L-shape joints was used for investigation of the evaluation of the joint connection. Since the fastening state of bolts affects the mechanical impedance in the joint, near which a pair of PZT patches was utilised and embedded on the structure. Therefore, a high accuracy result on the mechanical impedance variation can be obtained by measurement of the electric impedance change in PZT patches. In the experiment, the joint fastening condition is given by tightening and loosening a bolt with a torque wrench. In order to improve the estimation accuracy whether the joint is in safe or not, two new evaluation indices ε, area difference, and Δ S, template shift distance, are proposed by impedance spectrum curve matching method. The experimental results show that damage overlooking can be improved by the indices ε and Δ S with aid of the impedance peak amplitude ratio δ and the peak frequency shift Δ F, which were proposed in our previous work.
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