ULTRASONIC TRANSDUCER ASSEMBLY AND SYSTEM FOR MONITORING STRUCTURAL INTEGRITY

• US 20140182382A1
• Filed: 11/07/2011
• Published: 07/03/2014
• Est. Priority Date: 11/05/2010
• Status: Active Grant

• Current Assignee: National Research Council Canada
• Original Assignee: National Research Council Canada
• Inventors: Kruger, Silvio E.
• Granted Patent: US 9,618,481 B2
• Time in Patent Office: Days
• US Class Current: 73/632
• CPC Class Codes: B01B 1/06 Preventing bumping
• CPC Class Codes: B06B 1/0603 using a piezoelectric bender, e.g. bimorph
• CPC Class Codes: B23P 11/00 Connecting or disconnecting metal parts or objects by metal-working techniques not otherwise provided for connecting sheet metal or metal tubes, rods or profiles B21D39/00; riveting B21J; soldering, unsoldering, welding B23K; hand tools for connecting wire or strip B25B25/00; connecting metal parts by adhesives F16B11/00
• CPC Class Codes: G01N 17/04 Corrosion probes
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/2634 cylindrical from outside
• CPC Class Codes: G01N 2291/265 Spherical objects
• CPC Class Codes: G01N 29/228 related to high temperature conditions
• CPC Class Codes: G01N 29/24 Probes transducers for acoustic waves B06B, G10K; for measuring G01H
• CPC Class Codes: G01N 29/245 Ceramic probes, e.g. lead zirconate titanate [PZT] probes
• CPC Class Codes: G01N 29/28 providing acoustic coupling , e.g. water impedance matching G10K11/02
• CPC Class Codes: Y10T 29/49966 with supplemental joining

Abstract

In an ultrasonic transducer assembly, a conformable ultrasonic transducer has a piezoelectric layer and electrodes able to conform to curved surfaces, and a clamp for pressing the transducer into ultrasonic contact with a curved surface. Conformability is ensured with a thin, porous piezoelectric layer and suitable electrical conductors and insulators. The ultrasonic transducer may operate without further thermal shielding under harsh environments and/or at high temperatures.

Claims

1. An ultrasonic transducer assembly, comprising:

a piezoelectric film able to conform to curved surfaces;

an electrode adjacent to a top surface of the piezoelectric film to make the piezoelectric film able to act as an ultrasonic transducer;

a flexible insulating layer covering the top electrode and at least part of a first electrical connector extending from the top electrode to an electronic control, the insulating layer having a shape and size to substantially surround a section of a component to be monitored; and

a permanent or semi-permanent clamp adapted to apply at least a 0.2 MPa compressive stress on a region of the component aligned with the top electrode.

2. The transducer assembly of claim 1 wherein:

the transducer assembly is flexible, and the clamp comprises a band that, when tensioned, causes the assembly to conform to a convex surface of the section of the component such as a cross-section of a pipe or pipe fitting;

or

a tube clamp, comprising a deformable band for surrounding the section, formed of metal or a fibreglass textile;

or

a tensioning mechanism, having a spring or spring washer to maintain a constant tension under different thermal conditions.

3. The transducer assembly of claim 1 further comprising the component, which has the form of a pipe or a pipe fitting.

4. The transducer assembly of claim 1 wherein all materials used to fabricate the assembly retain sufficient structural, electrical, and chemical integrity to operate at high temperatures.

5. The transducer assembly of claim 4 wherein the piezoelectric film has a composition consistent with fabrication using one or more layers of a mixture of a piezoelectric powder and organic precursors of dielectric and/or piezoelectric material, wherein the after heat treatment the piezoelectric film has a level of porosity that improves flexibility, resistance to thermal shock and ultrasonic bandwidth.

6. The transducer assembly of claim 1 further comprising an ultrasonic coupling layer composed of an ultrasonic transmitting material making intimate physical contact with the transducer assembly at a top surface, and for making intimate physical contact with the component at a bottom surface.

7. The transducer assembly of claim 6 wherein the ultrasonic transmitting material comprises:

a high temperature paste or liquid, or a soft metal, such as aluminum, gold, tin, zinc or other alloys known to the art of soldering and brazing.

8. The transducer assembly of claim 6 wherein the coupling layer comprises a metal foil, and wherein:

the clamp is adapted to apply at least 1 MPa compressive stress;

the clamp is adapted to apply at least 10 MPa compressive stress;

the clamp is adapted to apply an initial compressive stress greater than 1 MPa to plastically deform the metal foil, and a far lower compressive stress thereafter; and

the metal foil was strained by a much greater compressive stress than the clamp, which serves only to maintain intimate physical contact between the assembly and component.

9. The transducer assembly of claim 1 further comprising a bottom electrode, wherein:

electrically coupled to the component, which is sufficiently conductive to serve as a ground for the flexible ultrasonic transducer;

or

electrically coupled to the electronic control by a second electrical connector that is insulated from the first electrical connector;

or

a surface of the component serves as a bottom electrode of the flexible ultrasonic transducer, and has an electrical connection to the electrical control;

or

a surface of the component serves as a bottom electrode of the flexible ultrasonic transducer, and has an electrical connection to the electrical control, and the piezoelectric layer is bonded to the component to be monitored by a ceramic binder made from organic precursors of a piezoelectric and/or dielectric ceramic.

11. The transducer assembly of claim 1 wherein the insulating layer comprises:

a conductive path between top and bottom insulations, with a via through the bottom insulation for providing electrical contact between the conductive path and the top electrode;

or

a layer of mica or polyimide.

15. The transducer assembly of claim 1 wherein the clamp comprises:

band that also serves as a bottom electrode for the flexible ultrasonic transducer and the flexible ultrasonic transducer is deposited directly on the clamp;

or

a band that also serves as a bottom electrode for the flexible ultrasonic transducer and the flexible ultrasonic transducer is deposited directly on the clamp, wherein the transducer assembly further comprises a protective layer surrounding the insulating layer;

or

a band that also serves as a protective cover for the flexible ultrasonic transducer, surrounding the insulating layer.

18. The transducer assembly of claim 1:

wherein a plurality of similar separate piezoelectric films are spaced along the insulating layer to provide a transducer array;

or

wherein a plurality of similar separate piezoelectric films are spaced along the insulating layer to provide a transducer array; and

the separate films are independently electronically addressable by the electronic control;

or

wherein a plurality of similar separate piezoelectric films are spaced along the insulating layer to provide a transducer array; and

the separate films are commonly electronically controlled.

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22. A method for producing a transducer assembly, the method comprising:

providing a flexible ultrasonic transducer, including at least a top electrode adjacent to a flexible piezoelectric film;

bonding said top electrode to an insulating layer, the insulating layer having a shape and size to substantially surround a section of a component to be monitored,

providing insulated electrical connection from the top electrode to an electronic control, and

providing a permanent or semi-permanent clamp adapted to apply at least a 0.2 MPa compressive pressure on a region of the component aligned with the top electrode.

23. The method of claim 22 further comprising:

preparing a part of a surface of the section of the component;

applying a couplant to the part of the surface to provide intimate physical contact between the couplant and the surface; and

mounting the previously assembled layers to the couplant to provide intimate physical contact between the couplant and the flexible ultrasonic transducer.

24. The method of claim 23 wherein applying the couplant comprises applying a foil of mounting the previously assembled layers comprises applying a soft metal, such as aluminum, gold, tin, zinc or other alloys known to the art of soldering and brazing as a foil, and wherein mounting the previously assembled layers comprises apply an initial compressive stress greater than 1 MPa to plastically deform the soft metal foil.

25. The method of claim 23 wherein one of the couplant and the component is not electrically conductive, and providing the flexible ultrasonic transducer comprises applying a bottom electrode and an insulated conductor from the bottom electrode to the electrical control.

26. The method of claim 25 wherein the bottom electrode is provided with a metal foil such as titanium or stainless steel foil.

27. The method of claim 23 wherein applying the couplant comprises applying an adhesive material, such as a polymer based glue, silver paste, ceramic cement, glass known in the art of adhesive bonding.

28. The method of claim 22 wherein providing the flexible ultrasonic transducer comprises applying one or more layers of a mixture of a piezoelectric powder and organic precursors of dielectric and/or piezoelectric material;

heat treating the applied layers; and

poling the applied layers to produce the piezoelectric film.

29. The method of claim 28 wherein providing the flexible ultrasonic transducer comprises applying the top electrode as a silver or gold paste or by thin film deposition of a conductive metal, such as gold, silver, platinum or aluminum.