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. 2022 Mar 16;22(6):2296.
doi: 10.3390/s22062296.

Structural Damage Detection through EMI and Wave Propagation Techniques Using Embedded PZT Smart Sensing Units

Himanshi Gayakwad  1 , Jothi Saravanan Thiyagarajan  1
Affiliations

Structural Damage Detection through EMI and Wave Propagation Techniques Using Embedded PZT Smart Sensing Units

Himanshi Gayakwad et al. Sensors (Basel). .

Abstract

Lead Zirconate Titanate (PZT) sensors have become popular in structural health monitoring (SHM) using the electromechanical impedance (EMI) technique for damage identification. The vibrations generated during the casting process in concrete structures substantially impact the conductance signature's (real part of admittance) magnitude and sensitivity. The concept of smart sensing units (SSU) is presented, composed of a PZT patch, an adhesive layer, and a steel plate. It is embedded in the concrete structure to study the impact of damage since it has high sensitivity to detect any structural changes, resulting in a high electrical conductance signature. The conductance signatures are obtained from the EMI technique at the damage state in the 10-500 kHz high-frequency range. The wave propagation technique proposes implementing the novel embedded SSUs to detect damage in the host structure. The numerical simulation is carried out with COMSOL multiphysics, and the received voltage signal is compared between the damaged and undamaged concrete beam with the applied actuation signal. A five-cycle sine burst modulated by a Hanning window is employed as the transient excitation signal. For numerical investigation, six cases are explored to better understand how the wave travels when a structural discontinuity is accounted for. The changes in the received signal during actuator-receiver mode in the damage state of the host structure are quantified using time of flight (TOF). Furthermore, the numerical studies are carried out by combining the EMI-WP technique, which implies synchronous activation of EMI-based measurements and wave stimulation. The fundamental idea is to implement EMI-WP to improve the effectiveness of SSU patches in detecting both near-field and far-field damage in structures. One SSU is used as an EMI admittance sensor for local damage identification. Meanwhile, the same EMI admittance sensor is used to acquire elastic waves generated by another SSU to monitor damages outside the EMI admittance sensor's sensing area. Finally, the experimental validation is carried out to verify the proposed methodology. The results show that combining both techniques is an effective SHM method for detecting damage in concrete structures.

Keywords: COMSOL multiphysics; concrete; conductance; damage detection; embedded sensor; impedance; piezoelectric sensor.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic diagram: (a) PZT patch; (b) Concrete cube with embedded PZT transducer.
Figure 2
Figure 2
Interactive model of PZT patch and concrete structure.
Figure 3
Figure 3
Surface displacement contours of beam for longitudinal mode shapes: (a) First mode; (b) Second mode.
Figure 4
Figure 4
Surface displacement contours of beam for flexural mode shapes: (a) First mode; (b) Second mode.
Figure 5
Figure 5
Surface displacement contours of beam for torsional mode shapes: (a) First mode; (b) Second mode.
Figure 6
Figure 6
Representation of two-axis symmetry 3D model of (a) free-free PZT patch; (b) PZT patch with epoxy layer; (c) conductance and (d) susceptance plot based on the EMI measurement.
Figure 6
Figure 6
Representation of two-axis symmetry 3D model of (a) free-free PZT patch; (b) PZT patch with epoxy layer; (c) conductance and (d) susceptance plot based on the EMI measurement.
Figure 7
Figure 7
Concrete cube with embedded PZT sensor: (a) The schematic one-fourth model; (b) Two-axis symmetry 3D model.
Figure 8
Figure 8
Conductance response obtained for embedded PZT patch in concrete.
Figure 9
Figure 9
Schematic diagram concrete cube with embedded SSU.
Figure 10
Figure 10
EMI response of SSU: (a) Schematic two-sided symmetry model of SSU; (b) Conductance and susceptance signatures obtained in a free–free mode of PZT sensors (without steel plate) and free–free mode SSU (with steel plate).
Figure 11
Figure 11
EMI measurement of SSU embedded in concrete: (a) One-fourth symmetry model; (b) Conductance response obtained.
Figure 12
Figure 12
Schematic diagram of wave propagation with PZT transducer.
Figure 13
Figure 13
Concrete beam with two PZT sensors attached to the surface of the beam: (a) Schematic 3D model; (b) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode.
Figure 14
Figure 14
Damaged concrete beam with surface mounted PZT sensors: (a) Schematic 3D model; (b) FE model; (c) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode; (d) Comparison of received signal between the damaged and undamaged concrete beam with the applied actuation signal.
Figure 14
Figure 14
Damaged concrete beam with surface mounted PZT sensors: (a) Schematic 3D model; (b) FE model; (c) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode; (d) Comparison of received signal between the damaged and undamaged concrete beam with the applied actuation signal.
Figure 15
Figure 15
Concrete beam with surface-mounted SSU sensors: (a) Schematic 3D model; (b) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode.
Figure 15
Figure 15
Concrete beam with surface-mounted SSU sensors: (a) Schematic 3D model; (b) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode.
Figure 16
Figure 16
Damaged concrete beam with surface mounted SSUs: (a) Schematic 3D model; (b) FE model; (c) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode; (d) Comparison of received signal between the damaged and no damaged concrete beam with the applied actuation signal.
Figure 16
Figure 16
Damaged concrete beam with surface mounted SSUs: (a) Schematic 3D model; (b) FE model; (c) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode; (d) Comparison of received signal between the damaged and no damaged concrete beam with the applied actuation signal.
Figure 17
Figure 17
Concrete beam with embedded SSU: (a) Schematic 3-D model; (b) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode.
Figure 17
Figure 17
Concrete beam with embedded SSU: (a) Schematic 3-D model; (b) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode.
Figure 18
Figure 18
Damaged concrete beam with embedded SSU: (a) Schematic 3D model; (b) FE model; (c) Response spectrum obtained from wave propagation measurements in the actuator–receiver mode; (d) Comparison of received signal between the damaged and no damaged concrete beam with the applied actuation signal.
Figure 19
Figure 19
RMSD comparison plot for a damaged concrete beam with: (a) surface-mounted PZT patches (case-2) and SSUs (case-4); (b) surface-mounted SSUs (case-4) and embedded SSUs (case-6).
Figure 20
Figure 20
Schematic representation of the combined EMI-WP technique for damage detection in concrete structure utilizing two SSUs.
Figure 21
Figure 21
Combined EMI-WP measurement: (a) 3D model; (b) FE model of a damaged concrete beam with surface-mounted SSUs.
Figure 22
Figure 22
FFT Admittance spectrums for an undamaged and damaged concrete beam with: (a) Active wave propagation; (b) When EMI admittance sensor is activated simultaneously with wave propagation.
Figure 23
Figure 23
RMSD plot for a concrete beam under different structural conditions.
Figure 24
Figure 24
Experimental specimen with crack and hole [48].
Figure 25
Figure 25
Three-dimensional model geometry: (a) Type-B specimen as crack damage; (b) Type-C specimen as hole damage; (c) Type-B specimen as crack damage with embedded SSUs; (d) Type-C specimen as hole damage with embedded SSUs.
Figure 26
Figure 26
RMSD comparison plot between numerical simulation of existing smart aggregate, experimental results, and numerical simulation with SSU: (a) for a beam with crack; (b) for a beam with hole.
Figure 27
Figure 27
FFT Admittance spectrums for an undamaged and damaged concrete beam with: (a,c) active wave propagation; (b,d) when an EMI admittance sensor is activated simultaneously with wave propagation.
Figure 28
Figure 28
RMSD plot for a concrete beam under different structural conditions.
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