Optimal frequency range for structural health monitoring using electric impedance technique

Abstract

This paper aims to find the best frequency range for structural health monitoring considering external disturbance effect. The proposed damage-sensitive index can be used to detect and locate minor structural faults in aerospace, civil, or mechanical systems. Electric impedance is directly computed using a non-parametric relationship between electrical signals obtained from patches of piezoceramics (PZT) coupled in flexible structures as sensor/actuator, namely a smart structure. In the experimental application, the external disturbance was generated by another PZT actuator bonded closely of the sensor/actuator. The correlation coefficient deviation was investigated as metric chart using the absolute impedance signals. In order to establish a threshold value to recognize the actual integrity stage of the structure the one-way analysis of variance (ANOVA) is performed bended with the Scheffe's multiple comparison procedure. Comparisons were made in an experimental test-bed using an aluminum plate with two PZTs as sensor/actuator and one PZT as external disturbance bonded on the surface considering several structural conditions. The experimental results demonstrated the efficacy of the approach. Careful attention is necessary to choose correctly the frequency range that may be utilized to characterize the influence of the external disturbance in a further monitoring in a real-world structure using smart structure concepts.