Hybrid wound/etched winding constructs for scanning and monitoring

• US 7,518,360 B2
• Filed: 06/01/2007
• Issued: 04/14/2009
• Est. Priority Date: 05/23/2003
• Status: Active Grant

• Current Assignee: Jentek Sensors, Inc.
• Original Assignee: Jentek Sensors, Inc.
• Inventors: Shav, Ian C., Root, Christopher, Goldfine, Neil J., Grundy, David C., Schlicker, Darrell E., Washabaugh, Andrew P., Zilberstein, Vladimir A., Tsukernik, Vladimir, Windoloski, Mark D.
• Primary Examiner(s): WHITTINGTON, KENNETH
• Application Number:
  US11/809,555
• Publication Number:
  US 20080258720A1
• Time in Patent Office: 683 Days
• Field of Search: 324/209, 324/227, 324/228, 324/232, 324/239, 324/240, 324/241, 324/242, 324/243, 324/252
• US Class Current: 324/240
• CPC Class Codes: G01N 27/82 for investigating the presence of flaws
• CPC Class Codes: G01N 27/9046 by analysing electrical signals

Abstract

Combined wound and micro-fabricated winding constructs are described for the inspection of materials and the detection and characterization of hidden features or flaws. These constructs can be configured as sensors or sensor arrays that are surface mounted or scanned over conducting and/or magnetizable test materials. The well-defined geometry obtained micro-fabricated windings and from carefully wound coils with known winding positions permits the use of model based inversions of sensed responses into material properties. In a preferred embodiment, the primary winding is a wound coil and the sense elements are etched or printed. The drive or sense windings can also be mounted under fasteners to improve sensitivity to hidden flaws. Ferrites and other means may be used to guide the magnetic flux and enhance the magnetic field in the test material.

Claims

1. A method for monitoring damage at a fastener comprising:

mounting a drive coil having at least two conducting wire windings with a support material shaped in the form of a washer, the windings being wrapped around a sleeve along a length of the fastener;

placing the washer on a test substrate under the fastener;

placing at least one microfabricated sense element proximate to the drive coil; and

measuring a response from each sense element as a magnetic field is imposed in the test substrate by an electric current driven through the drive coil.

2. The method as claimed in claim 1 wherein the at least one sense element is an inductive coil.

3. The method as claimed in claim 1 wherein the at least one sense element is a giant magnetoresistive sensor.

4. The method as claimed in claim 1 wherein the at least one sense element responds to a different component of the magnetic field than another sense element.

5. The method as claimed in claim 1 wherein the at least one sense element is at a different radial distance from the drive coil than another sense element.

6. The method as claimed in claim 1 wherein the support material has a lower electrical conductivity than the electrical conductivity of the test substrate.

7. The method as claimed in claim 6 wherein the support material is a composite.

8. The method as claimed in claim 1 wherein the support material is split to reduce induced eddy currents in the support material.

9. The method as claimed in claim 1 wherein the drive coil is enclosed by the support material.

10. The method as claimed in claim 1 wherein the support material includes a magnetizable material.

11. The method as claimed in claim 10 wherein the magnetizable material is a ferrite.

12. The method as claimed in claim 1 wherein the shaft of the fastener is coated with a magnetizable material.

13. The method as claimed in claim 1 wherein the fastener has a hollow shaft filled with a magnetizable material.

14. The method as claimed in claim 1 further comprising scanning a sense element around the fastener.

15. A method for monitoring damage at a fastener comprising:

placing a drive coil having at least one conducting wire winding wrapped around a sleeve along a length of the fastener;

mounting at least one microfabricated sense element to a test substrate under the fastener; and

measuring a response from each sense element as a magnetic field is imposed in the test substrate by an electric current driven through the drive coil.

16. The method as claimed in claim 15 wherein the at least one sense element is an inductive coil.

17. The method as claimed in claim 15 wherein the at least one sense element is at a different radial distance from the drive coil than another sense element.

18. The method as claimed in claim 15 wherein the at least one sense element is mounted into a support material formed into a washer.

19. The method as claimed in claim 15 wherein the support material has a lower electrical conductivity than the electrical conductivity of the test substrate.

20. The method as claimed in claim 19 wherein the support material is a composite.

21. The method as claimed in claim 18 wherein the support material is split to reduce induced eddy currents in the support material.

22. The method as claimed in claim 18 wherein the support material includes a ferrite.

23. The method as claimed in claim 15 wherein the shaft of the fastener is coated with a magnetizable material.

24. The method as claimed in claim 15 wherein the fastener has a hollow shaft filled with a magnetizable material.

25. The method as claimed in claim 15 wherein the fastener further comprises a nut and the nut has an electrical conductivity lower than the electrical conductivity of the test substrate.

26. The method as claimed in claim 15 further comprising:

scanning the drive coil around the fastener.

27. The method as claimed in claim 15 further comprising:

measuring the response at multiple proximities to the test material surface.

28. A test circuit comprising:

at least one conducting winding wrapped around a sleeve along a length of a fastener; and

at least one microfabricated sense element mounted on a test substrate under the fastener, the at least one sense element being configured to provide a response as a magnetic field is imposed in the test substrate by an electric current driven through the at least on conducting winding.

29. The test circuit as claimed in claim 28 wherein the at least one sense element is mounted into a support material formed into a washer.

30. The test circuit as claimed in claim 28 wherein the support material is split to reduce induced eddy currents in the support material.