Failure Assessment of Piezoelectric Actuators and Sensors for Increased Reliability of SHM Systems

Abstract

In the chain from sensing to information extraction, there are many traps where errors can occur, which might lead to false alarms and therefore leave us with the impression of an unreliable system. In this chapter, we deal with the important first element of the chain, the sensor, which can undergo various faults and defects during its lifetime. Especially for the use of acousto-ultrasonic (AU)-based methods or the electro-mechanical impedance (EMI) method, piezoelectric transducers are frequently used. Subsequent steps within the chain of SHM rely on the quality and reliability of these measurements. An overview is given on the usage of piezoelectric transducers within SHM systems, their electromechanical coupling and its modeling as well as frequent faults of these devices and methods on how to inspect them and diagnose defects. The authors show the effects of different transducer faults on the excited wave field, used for AU. It is shown how a sensor fault can be detected before the SHM system indicates a (false) alarm. With the help of application scenarios-including temperature variations-the advantages and disadvantages of the introduced methods of transducer inspection are presented, enabling an increased reliability of SHM systems.

Durability Assessment of Bonded Piezoelectric Wafer Active Sensors for Aircraft Health Monitoring Applications

“…Moreover, due to debonding, the generated wave field was no longer concentric to the PWAS’s position, and the amplitude was significantly reduced with increasing debonding area. These results are consistent with previous studies that used LDV scans to examine the health of PWASs bonded to metallic and composite plates [ 28 , 45 ].…”

“…Moreover, due to debonding, the generated wave field was no longer concentric to the PWAS's position, and the amplitude was significantly reduced with increasing debonding area. These results are consistent with previous studies that used LDV scans to examine the health of PWASs bonded to metallic and composite plates[28,45].The experimental LDV scans were binarized and thresholded to estimate the debonded area, as detailed in Section 2.2.2. Figure6displays the RMS amplitude scans, illustrating the applied filtering process to these scans (note the difference in RMS amplitude representation compared to Figure5).…”

“…Moreover, the physical degradation of the PWAS was likewise discernible in the EMI spectra. In practical terms, various error metrics (e.g., root-mean-square deviation) related to the initial (pristine) EMI measurement have been employed to identify faulty sensors [ 13 , 28 , 29 ]. However, such metrics may not consistently exhibit a monotonically increasing trend with sensor degradation.…”

“…In the latter case, any break of the reciprocity principle may be informative of sensor health [ 44 ]. In other instances, specifically in laboratory condition measurements, laser Doppler vibrometry (LDV) scans were used to assess the generated wave field [ 11 , 21 , 27 , 28 , 45 ]. This method allows for comprehensive imaging of the generated wave field, enabling the discernment of waves trapped within the PWAS due to local debonding.…”

Fault Assessment in Piezoelectric-Based Smart Strand Using 1D Convolutional Neural Network

“…Debonding at the adhesive region between the transducer and its host structure can lead to a degradation in their electromechanical coupling, as seen in Figure 3b. Insufficient bonding quality and debonding defects might happen right from the beginning due to a contaminated surface during the bonding process, as reported in [30]. While embedded in a post-tensioned structure, the smart strand could be forced to vibrate with the structure under an external load.…”