Flexible electromagnetic acoustic transducer sensor

• US 7,165,453 B2
• Filed: 07/20/2005
• Issued: 01/23/2007
• Est. Priority Date: 07/23/2004
• Status: Expired due to Fees

• Current Assignee: Electric Power Research Institute
• Original Assignee: Electric Power Research Institute
• Inventors: Flora, John, Powers, Grady, Ali, Muhammad
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/185,143
• Publication Number:
  US 20060027022A1
• Time in Patent Office: 552 Days
• Field of Search: 736/43, 736/44, 736/42, 736/27, 736/22, 736/35, 736/36, 736/37, 736/38, 736/39, 367/140, 367/168
• US Class Current: 73/643
• CPC Class Codes: B06B 1/04 operating with electromagnetism dynamo-electric motors with vibrating magnet, armature or coil system H02K33/00
• CPC Class Codes: G01N 2291/0234 Metals, e.g. steel
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/106 one or more transducer arrays
• CPC Class Codes: G01N 2291/2638 Complex surfaces
• CPC Class Codes: G01N 29/041 on the surface of the material, e.g. using Lamb, Rayleigh or shear waves
• CPC Class Codes: G01N 29/221 Arrangements for directing or focusing the acoustical waves electronic orientation or focusing G01N29/262; sound directing or focusing G10K11/26; mechanical steering of sound transducers or their beams G10K11/35
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• CPC Class Codes: G01N 29/2487 Directing probes, e.g. angle probes directing arrangements G01N29/221
• CPC Class Codes: G01N 29/26 Arrangements for orientation or scanning by relative movement of the head and the sensor mechanical steering of sound transducers or their beams G10K11/35
• CPC Class Codes: G10K 11/32 characterised by the shape of the source

Abstract

An array of magnets designed of flexible components and materials can be easily shaped to fit to the contour of various curved surfaces and structures. EMATs that incorporate these magnets, in addition to being flexible, may be smaller in volume than the conventional EMAT magnets and therefore easier to apply to complex structures where access may be restricted. Also, flexible multiple-pole magnet arrays can be easily and economically fabricated in various shapes and configurations, thereby increasing versatility, utility and cost effectiveness in comparison to the rigid, conventional magnet designs.

Claims

1. An electromagnetic acoustic transducer adapted to conform to the surface of a non-planar test substrate;

wherein the electromagnetic acoustic transducer is adapted for generation and detection of ultrasonic acoustic waves and comprises an array of flexible multiple-pole magnets conformable to the non-planar test substrate surface, wherein the magnets contain magnetic poles and interconnecting segments; and

wherein the magnetic poles are disposed in a plurality of rows.

2. The electromagnetic acoustic transducer of claim 1 wherein the flexible multiple-pole magnet array comprises a flexible compound containing particles of ferromagnetic material, wherein at least one electrical conductor is disposed between the magnetic poles capable of generating magnetic fields perpendicular to the faces of each magnetic pole when conducting current.

3. The electromagnetic acoustic transducer of claim 2 wherein at least one layer of electrical conductor is disposed between the magnetic poles to provide magnetization in a direction that has a predominant magnetic field vector component perpendicular to the magnetic pole face and the surface of the test substrate.

4. The electromagnetic acoustic transducer of claim 3 wherein the electrical conductor is disposed between the magnetic poles in a pattern to produce opposite polarity in adjacent magnetic poles when the electrical conductor is conducting current.

5. The electromagnetic acoustic transducer of claim 3 wherein a layer of a second electrical conductor at least in part overlays the at least one electrical conductor layer and is connected electrically thereto, wherein the magnetic poles interior to the electrical conductor and the second electrical conductor are effectively encircled by two electrical conductors that carry electrical current in the same direction when conducting current.

6. The electromagnetic acoustic transducer of claim 5 wherein at least one additional pair of electrical conductor layers is disposed over the at least one electrical conductor layer and second electrical conductor layer and is connected in series or in parallel with said at least one electrical conductor layer and said second electrical conductor layer.

7. The electromagnetic acoustic transducer of claim 1 wherein the flexible multiple-pole magnet array comprises a flexible compound containing particles of permanent magnet material, wherein the magnetic poles are optionally magnetized to provide static magnetic fields perpendicular to the face of each magnetic pole.

8. The electromagnetic acoustic transducer of claim 1 wherein each row has a radius of curvature about at least one focal point capable of focusing a generated sound wave in the test substrate.

9. The electromagnetic acoustic transducer of claim 8 wherein the distance between adjacent magnetic poles varies as a function of the radial distance from the focal point.

10. The electromagnetic acoustic transducer of claim 8 comprising at least two flexible multiple-pole magnet arrays in tandem wherein each array has a different radial distance between magnetic poles but approximately the same focal point, and wherein the at least two arrays are capable of effecting approximately the same sound wave angle.

11. The electromagnetic acoustic transducer of claim 8 wherein the flexible multiple-pole magnet array has RF conductors embedded in grooves which lie across the magnetic pole faces and are collinear with radial projections from the focal point.

12. The electromagnetic acoustic transducer of claim 1 wherein the magnets comprise iron.

13. The electromagnetic acoustic transducer of claim 7 wherein the magnets comprise neodymium iron boron.

14. The electromagnetic acoustic transducer of claim 2 wherein the flexible compound is an elastomer.

15. The electromagnetic acoustic transducer of claim 14 wherein the elastomer comprises silicone rubber.

16. The electromagnetic acoustic transducer of claim 7 wherein the flexible compound is an elastomer.

17. The electromagnetic acoustic transducer of claim 16 wherein the elastomer comprises silicone rubber.

18. A method of interrogating a test substrate having a non-planar surface using the electromagnetic acoustic transducer of claim 1 comprising:

conforming the electromagnetic acoustic transducer to the surface of the test substrate in monitoring proximity to the surface,

generating a sound wave by interaction of fields from the electromagnetic acoustic transducer magnets and an electrical conductor, and,

detecting at least one characteristic of the sound wave reflected by the test substrate.