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.
Keywords: structural health monitoring, truss structure, PZT patches, piezoelectric impedance spectrum, joint fastening condition, health estimation indices, healthy factor
