A method to compensate non-damage-related influences on Damage Indices used for pitch-catch scheme of piezoelectric transducer based Structural Health Monitoring

Abstract

The risk of false calls of structural health monitoring systems is as much important for their application as their damage detection capabilities. Structural health monitoring based on guided waves propagation is particularly vulnerable to false calls. Signals acquired for piezoelectric transducer networks can be changed by many factors other than damage, for example, environmental factors or those related to the transducers’ aging or degradation of the transducers’ bonding with the monitored structure. A lot of studies were devoted to examine non-damage-related influences on structural health monitoring systems based on Lamb waves and to compensate the undesired effects. Most of compensation methods act on the level of the signal, that is, for a given factor influencing performance of piezoelectric transducers, signals are transformed to match the corresponding baselines. After such compensation procedure, the Damage Indices are calculated for the purpose of damage detection. In order to compensate the impact of all of non-damage-related factors, all of them need to be, at least, recognized. In this article, a different technique to compensate changes of Damage Indices values caused by factors other than damage is proposed. The method does not involve any operation on signals, but on the Damage Indices themselves. The factors causing Damage Indices’ changes neither have to be measured nor are even known. The capabilities of the method have been evaluated on the example of fatigue cracks detection in laboratory specimen tests and using results obtained during Full-Scale Fatigue Test of an aircraft.

Structural Health Monitoring of a Composite Panel Based on PZT Sensors and a Transfer Impedance Framework

“…Due to those properties, PZT transducers have found a variety of applications in SHM. They can be applied to: fatigue crack and corrosion detection [ 9 , 10 , 11 , 12 , 13 , 14 ]; bolt and bolted joint monitoring [ 15 , 16 ]; adhesive and welded joint monitoring [ 17 , 18 , 19 , 20 , 21 ]; detection of impact damage of composite materials [ 22 , 23 , 24 ]; civil structure monitoring [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]; transducers’ self-diagnosis [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. …”

“…Waves reflected from a damage of a finite size decay with the distance from it [ 4 ], therefore whether they can be detected by a PZT transducer depends on the distance of the damage from it. Also, pairs of PZT transducers can be used for structure monitoring—one of the transducers is exciting elastic waves, i.e., it is a PZT actuator, whereas the second one is receiving them, i.e., it is a PZT sensor [ 5 , 12 , 13 , 15 , 16 , 17 , 18 , 38 ]. If pairs of PZT transducers are used, the so called transmission mode of elastic wave interaction with a damage can be utilized in addition to the reflection mode [ 8 ].…”

“…The actuator can be sourced with a short pulsed or steady state sinusoidal voltage. In the first case [ 5 , 13 , 14 , 15 , 16 , 23 , 24 , 38 ], the voltage on the PZT sensor is acquired over a certain period. For the pulse-echo wave propagation approach, i.e., a single PZT transducer excited with a short pulsed voltage, the acquired signal is due to waves reflected from structure discontinuities surrounding the transducer.…”

Application of PZT Ceramic Sensors for Composite Structure Monitoring Using Harmonic Excitation Signals and Bayesian Classification Approach

“…Then probability density π j (µ, σ) on parameter space in Equation ( 7) can be written in the following form: (15) and integration limits in Equation ( 7) can be adopted as in Equations ( 11) and (12).…”

“…Elastic waves can interact with structure discontinuities caused by different kinds of damage enabling successful PZT use for Structural Health Monitoring. There exists a vast literature on the subject, providing numerous examples of PZT application [ 11 ], in particular to: cracks detection and their growth monitoring [ 12 , 13 , 14 ]; bolt and rivet joints monitoring [ 15 , 16 , 17 , 18 , 19 ]; corrosion detection [ 20 , 21 , 22 ]; concrete structures and soil properties monitoring [ 23 , 24 , 25 , 26 ]; pipeline damage detection [ 27 , 28 ]; large structure monitoring [ 29 , 30 , 31 , 32 ]; malignant tumor detection [ 33 ]; other applications [ 34 , 35 ]. …”