PRIMARY WINDINGS HAVING MULTIPLE PARALLEL EXTENDED PORTIONS

• US 20090315540A1
• Filed: 08/03/2009
• Published: 12/24/2009
• Est. Priority Date: 09/20/1999
• Status: Active Grant

• Current Assignee: Jentek Sensors, Inc.
• Original Assignee: Jentek Sensors, Inc.
• Inventors: Goldfine, Neil J., Schlicker, Darrell E., Washabaugh, Andrew P., Walrath, Karen E.
• Granted Patent: US 7,994,781 B2
• Time in Patent Office: Days
• US Class Current: 324/202
• CPC Class Codes: B24B 21/06 involving members with limited contact area pressing the belt against the work, e.g. shoes sweeping across the whole area to be ground B24B21/12 takes precedence
• CPC Class Codes: B24B 37/005 Control means for lapping machines or devices

Abstract

Reference standards or articles having prescribed levels of damage are fabricated by monitoring an electrical property of the article material, mechanically loading the article, and removing the load when a change in electrical properties indicates a prescribed level of damage. The electrical property is measured with an electromagnetic sensor, such as a flexible eddy current sensor, attached to a material surface, which may be between layers of the article material. The damage may be in the form of a fatigue crack or a change in the mechanical stress underneath the sensor. The shape of the article material may be adjusted to concentrate the stress so that the damage initiates under the sensor. Examples adjustments to the article shape include the use of dogbone geometries with thin center sections, reinforcement ribs on the edges of the article, and radius cut-outs in the vicinity of the thin section.

Claims

1. A test circuit comprising:

a meandering primary winding having concentric substantially closed winding segments for imposing a spatially periodic magnetic field in the radial direction of at least two spatial wavelengths in a test substrate; and

at least one sensing element for sensing the response of the test substrate to the imposed magnetic field.

2. The test circuit of claim 1 wherein the closed winding segments are circular.

3. The test circuit of claim 1 wherein the closed winding segments follow a shape in the material under test.

4. The test circuit of claim 1 further including at least one sensing element positioned between the concentric circular segments of a half wavelength of the primary winding and located every other half wavelength of the primary winding, and with extended portions of the individual sensing elements concentric with the concentric circular segments of the primary winding.

5. The test circuit of claim 4 wherein a single sensing element is placed within in each half wavelength of the primary winding.

6. The test circuit of claim 5 wherein separate output connections are made to the sensing element in each half wavelength.

7. The test circuit of claim 6 wherein at least two of the sensing elements are connected together to provide a common output.

8. The test circuit of claim 7 wherein all of the sensing elements are connected together to provide single output.

9. The test circuit of claim 8 wherein the sensing elements are in a different plane than the primary windings.

10. The test circuit of claim 4 wherein the circumference of at least two half wavelengths of the primary winding is spanned by more than one sensing element and the sensing elements spanning the same angular dimensions in every other half-wavelength of the primary winding are connected together, and separate output connections are made to each group of sensing elements spanning the circumference of the primary winding.

11. The test circuit of claim 10 wherein the sensing elements are connected together with a series connection.

12. The test circuit of claim 11 wherein the series connections are in a different plane than the primary winding.

13. The test circuit of claim 10 wherein the individual sensing elements are located in at least two adjacent half wavelengths of the primary winding.

14. The test circuit of claim 13 wherein the individual sensing elements in adjacent half wavelengths are rotationally offset from one another.

15. The test circuit of claim 14 wherein the rotational offset is one half the angle spanned by an individual sensing element.

16. The test circuit of claim 15 further comprising extensions of the inner-most rotationally offset sensing elements between the sensing elements in the inner adjacent half wavelength.

17. The test circuit of claim 4 wherein the sensing elements are in a different plane than the primary windings.

18. The test circuit of claim 1 that is conformable to inspect curved parts.

19. The test circuit of claim 1 placed on a curved and compliant substrate to inspect a curved part.

20. The test circuit of claim 1 that is mounted against a surface of a part for the detection of flaws.

21. The test circuit of claim 4 where the part under test temperature is varied to vary the part conductivity for calibration.

22. The test circuit of claim 4 where the part under test temperature is varied to vary the part conductivity for measurements.

23. The test circuit of claim 4 where measurements grids with one or more dimensions are generated in advance and used as databases to look up and interpolate the electrical and geometric properties of interest at the location measured by each individual sensing element.

24. The test circuit of claim 23 where the electrical and geometric properties at each sensing element location are correlated with dependent properties of interest.

25. The test circuit of claim 23 where the array is scanned to build images of electrical properties across the surface of a part.

26. The test circuit of claim 24 where multiple frequencies are used to measure property variations with depth at each sensing element.

27. The test circuit of claim 25 where multiple frequencies are used to create three-dimensional images of properties.

28. The test circuit of claim 4 wherein the sensing windings link flux over regions of incremental area along the length of a drive winding segment, the sensing windings are located in a second plane with each sensing winding linking magnetic flux every other half period, and the leads to the sensing elements exit the sensor footprint radially, perpendicular to the direction of the drive winding segments.

29. The test circuit of claim 4 further comprising a hollow center region for placement around a fastener shaft.

30. A test apparatus comprising:

concentric substantially closed winding segments that impose a radial spatially periodic magnetic field, with at least two periods in a single plane, in a test substrate when driven by electric current; and

one or more sensing windings that link flux over each region bordered by the drive winding segments and concentric with the drive winding segments.