Damage detection with self-powered wireless smart coating sensor

Patent metadata

Field	Value
Publication number	US-10830665-B2
Application number	US-201716318547-A
Country	US
Kind code	B2
Filing date	Aug 8, 2017
Priority date	Aug 15, 2016
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

A low cost and efficient damage detection method is developed by introducing a new piezoelectric composite coating combined with a self-powered wireless signal transmission module. The new piezoelectric composite coating composed with a piezoelectric layer, an electrical conductive layer and an insulator, is designed as the sensor and to be easily applied on rough surfaces of engineering structures, such as concrete and the welded joint area. An energy harvesting circuit and an automatic electronic switch controlled by the piezoelectric coating sensor are designed to power and control the wireless signal transmitter sending warning signals of the damage occurrence. Methodology is explained in detail, and successful detection of the occurrence of crack propagation on a beam structure has been realized through experimental testing.

First claim

The invention claimed is:

1. A composite coating for use in detecting damage to a structure that is subject to vibrations, said coating comprising:
a piezoelectric layer applied to an electrically conductive surface on the structure at a first area thereof;
an electrically conductive layer overlapping an outer surface of said piezoelectric layer and spanning to a discrete second area of the electrically conductive surface where said electrically conductive layer contacts said second area of the electrically conductive surface; and
an isolating layer of electrically insulative material disposed between the electrically conductive surface and the electrically conductive layer at an intermediate area residing between said first and second areas to electrically isolate the electrically conductive layer from the electrically conductive surface over said intermediate area.

2. The coating of claim 1 in combination with a detection circuit connected between the outer surface of the piezoelectric layer and the second area of the electrically conductive surface, said detection circuit normally having a zero voltage measurement thereacross due to an electrical short defined between the outer surface of the piezoelectric layers and the second area of the electrically conductive surface by the conductive layer, until damage to the structure at the intermediate area causes a break in the electrically conductive layer, at which point excitation of the piezoelectric layer by vibration of the structure creates a non-zero voltage in the detection circuit, thereby confirming the presence of said damage.

3. The combination of claim 2 wherein detection circuit comprises a transmitter arranged to wirelessly transmit a damage warning signal in response to said non-zero voltage.

4. The combination of claim 3 wherein the detection circuit is configured to trigger closing of a switch between the transmitter and a power source in response to said non-zero voltage.

5. The combination of claim 3 wherein the transmitter is powered by a power source comprising a piezoelectric voltage source that is separate from the piezoelectric layer of the coating.

6. The combination of claim 5 wherein the piezoelectric voltage source is a piezoelectric element installed on the same structure as the coating.

7. The combination of claim 6 wherein the piezoelectric voltage source is a second piezoelectric layer residing at a separate area located discretely of the first, second and intermediate areas.

8. The combination of claim 5 wherein the power source further comprises a storage device from which the transmitter is powered and which is charged by the piezoelectric voltage source.

9. The combination of claim 8 wherein the storage device is a capacitor.

10. The combination of claim 9 wherein the detection circuit comprises a second capacitor arranged to be charged by the non-zero voltage created in the detection circuit by said damage to the structure, and to trigger activation of the transmitter once fully charged.

11. The combination of claim 4 comprising an electronic switch connected between the transmitter and the power source to establish connection therebetween in response to said non-zero voltage, and the detection circuit comprises a voltage stabilizer connected between the piezoelectric layer and the electronic switch to ensure sufficient voltage to trigger closure of said electronic switch in response to said non-zero voltage.

12. The combination of claim 11 wherein the voltage stabilizer is a capacitor.

13. The coating of claim 1 wherein the isolating layer comprises a non-conductive epoxy.

14. The coating of claim 1 wherein the structure is made of non-conductive material and the electrically conductive surface is a conductive surface coating applied over the non-conductive material of the structure.

15. The coating of claim 14 wherein the conductive surface coating comprises a conductive epoxy.

16. The coating of claim 1 wherein the structure comprises first and second metal members attached together at a welded joint therebetween, the first and second areas of the conductive surface being respectively defined on the first and second metal members with the welded joint residing at the intermediate area between said first and second areas, and the conductive layer spanning across said welded joint to detect damage thereto.

17. The coating of claim 1 wherein the electrically conductive layer comprises a conductive epoxy.

18. The coating of claim 1 wherein each piezoelectric layer comprises a piezoelectric patch.

19. A system for use in detecting damage to a structure that is subject to vibrations, said system comprising:
a composite coating comprising:
a piezoelectric element for application over an electrically conductive surface on said structure at a first area thereof; and
an electrically insulative material for application over said electrically conductive surface in a position adjacent said piezoelectric element to define an isolating layer;
a spreadable electrically conductive material for application to the structure along a path reaching from a position overlapping the piezoelectric element and bridging over the isolating layer to a second discrete area on the electrically conductive structure, thereby defining an electrical short spanning between the first and second areas of the electrically conductive surface and bridging over an intermediate area between said first and second areas; and

a detection circuit connectable between an outer surface of the piezoelectric layer and the second area of the electrically conductive surface to detect occurrence of damage to the structure at the intermediate area via a change in relative voltage between the outer surface of the piezoelectric layer and the second area of the conductive surface when said damage to the structure causes a break in the electrical short between the piezoelectric layer and the second area of the electrically conductive surface, whereby a zero-voltage normally exists in the detection circuit, even during excitation of the piezoelectric element by vibration of the structure, due to the electrical short between the piezoelectric element and the second area of the electrically conductive surface, but breakage of the conductive layer by said damage to the structure generates a non-zero voltage in the detection circuit during excitation of the piezoelectric element by vibration of the structure.

20. The system of claim 19 wherein the electrically insulative material is a spreadable material.

Assignees

• Univ Manitoba

Inventors

• Wu Nan
• Faisal Farjana
• Osho Samuel

Classifications

• G01M5/0066

  by exciting or detecting vibration or acceleration (vibration testing of structures G01M7/00) · CPC title

• G01M5/0083 Primary

  by measuring variation of impedance, e.g. resistance, capacitance, induction · CPC title

• G01M5/0033

  by determining damage, crack or wear · CPC title

• G01M7/00

  Vibration-testing of structures; Shock-testing of structures (G01M9/00 takes precedence) · CPC title

• G01H11/08

  using piezoelectric devices · CPC title