Eddy current device for inspecting a component having a flexible support with a plural sensor array

• US 5,315,234 A
• Filed: 04/03/1992
• Issued: 05/24/1994
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Kornrumpf, William P., Sutton, George H. Jr., Little, Francis H., Charles, Richard J., Hedengren, Kristina H. V., Hurley, Donna C.
• Primary Examiner(s): Strecker, Gerard R.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US07/862,950
• Time in Patent Office: 781 Days
• Field of Search: 324/234, 324/236, 324/237-243, 324/260-262, 324/219-221, 336/20, 336/200
• US Class Current: 324/242
• CPC Class Codes: G01N 27/902 by moving the sensors
• CPC Class Codes: G01N 27/904 with two or more sensors

Abstract

An eddy current device for inspecting a component includes an eddy current array circuit having respective pluralities of drive and sense elements and having an active face for positioning on a surface of the component during the inspection operation. A backing is disposed on a face of the eddy current array circuit opposite to the active face for concentrating an electromagnetic flux from the eddy current array circuit into the component when each of the plurality of drive elements is being energized. A mechanical arrangement is provided for supporting and deploying the backing and the array circuit to substantially conform with the surface portion under inspection and to cause each of the pluralities of drive and sense elements to be maintained at their respective substantially constant distances from the inspection surface during scanning, preferably at a controlled rate of scan.

Claims

1. A device for inspecting a component, comprising:

an eddy current array circuit having respective pluralities of drive and sense elements disposed on at least one flexible substrate and having an active face for positioning on a surface portion of the component during an inspection operation;

a flexible backing layer disposed on a face of said eddy current array circuit opposite to said active face for applying a uniform pressure behind said array circuit to maintain the array circuit against the surface portion during the inspection operation;

means for supporting and deploying said backing layer and said array circuit to conform to the surface portion of the component and to cause each of said respective pluralities of drive and sense elements to remain at a respective substantially constant distance from the component surface portion during the inspection operation; and

means for electrically connecting said eddy current array circuit to an eddy current instrument.

2. The device of claim 1, wherein said backing layer is a flexible composite material comprising a particulate soft ferrite and a bonding organic elastomer to concentrate an electromagnetic flux from said eddy current array circuit into the component, when each of said plurality of drive elements is being energized and for shielding said eddy current array circuit from any extraneous electromagnetic energy.

3. The device of claim 2, wherein said ferrite material has a relative magnetic permeability of at least about 4.

4. The device of claim 2, wherein said ferrite material comprises about 50% to about 60% by volume particulate soft ferrite and the remaining volume including an elastomer, said particulate ferrite comprising:

about 37% by molar composition MnO;

about 9% by molar composition ZnO; and

about 54% by molar composition Fe₂ O₃.

5. The device of claim 1, wherein said supporting and deploying means is a core of material shaped to substantially conform with the surface of the component under inspection.

6. The device of claim 5, wherein said core material is compressible to provide a close uniform fit between said eddy current array circuit and the surface of the component under inspection.

7. The device of claim 1, further comprising means for registering said eddy current array circuit relative to said supporting and deploying means to provide accurate location and size information of any detected defect during an inspection operation.

8. The device of claim 1, wherein said supporting and deploying means comprises:

location means for orienting said eddy current array circuit at substantially a same location relative to the component surface portion under inspection to provide repeatable and comparable inspection results for the same component surface portion, a different but similarly shaped surface portion of the same component and between similarly shaped surface portions of different components; and

means for conforming said eddy current array circuit to a shape of the component surface portion under inspection and for maintaining each of said respective pluralities of drive and sensing elements at their respective substantially constant distances from the component surface while sliding said array circuit along the component surface portion to detect defects therein during an inspection operation.

9. The device of claim 8, wherein said locating means and said conforming means are a forming bar having an operating face shaped to cause said eddy current array circuit to conform to the shape of the component surface under inspection, said eddy current array circuit and said backing layer being disposed over said operating face with said array circuit active face being closest to the component surface portion.

10. The device of claim 9, wherein said layer has a plurality of longitudinal ridges formed therein in a face thereof adjacent to said forming bar to facilitate disposition of said backing means and said array circuit over said operating face and to prevent liftoff of said array circuit while sliding said array circuit along the component surface.

11. The device of claim 1, further comprising a sacrificial layer of material disposed over said array circuit active face to prevent wear of said active face and to facilitate sliding of said active face along the component surface portion during an inspection operation.

12. A device for inspecting a dovetail slot of a gas turbine engine component, comprising;

an eddy current array circuit having respective pluralities of drive and sense elements disposed on at least one flexible substrate and having an active face for positioning on a surface of the dovetail slot during an inspection operation;

a flexible backing layer disposed on a face of said eddy current array circuit opposite to said active face for applying a uniform pressure behind said array circuit to maintain the array circuit against the dovetail slot surface during the inspection operation;

means for supporting and deploying said backing layer and said array circuit to conform to the surface of the dovetail slot and to cause each of said respective pluralities of drive and sense elements to each remain at a respective substantially constant distance from the dovetail slot surface during the inspection operation; and

means for electrically connecting said eddy current array circuit to an eddy current instrument.

13. The device of claim 12, wherein said backing layer is a soft magnetic ferrite material having a relative magnetic permeability of at least 4.

14. The device of claim 12, wherein the supporting and deploying means is a core of material shaped to substantially conform with the dovetail slot surface under inspection.

15. The device of claim 14, wherein said core material is compressible to provide a close uniform fit between said eddy current array circuit and the dovetail slot surface under inspection.

16. The device of claim 12, wherein said supporting and deploying means comprises:

a guide body having a guide body base and a guide body extension member extending from said base;

a forming bar positioned at an end of said extension member opposite to said base and movable between a retracted position against said extension member and an inspection position at a spacing from said extension member end, said forming bar having an operating face and said array circuit and said backing layer being disposed over said operating face, said operating face being shaped to cause said eddy current array circuit to conform to a shape of the dovetail slot surface under inspection when said forming bar is in said inspection position within a dovetail slot; and

means for moving said forming bar between said retracted position and said inspection position to position said array circuit at substantially a same location relative to the dovetail slot surface under inspection when said forming bar is in said inspection position to provide repeatable and comparable inspection results for different dovetail slots, and to cause said array circuit to conform to the shape of the dovetail slot surface and to maintain each of said pluralities of drive and sense elements at their respective substantially constant distances from the dovetail slot surface during the inspection operation.

17. The device of claim 16, wherein said forming bar moving means comprises:

a plurality of forming pins each extending through a respective one of a plurality of channels formed through said guide body and each coupled to said forming bar; and

actuator means for extending and retracting each of said plurality of forming pins to cause said forming bar to move between said retracted position and said inspection position.

18. The device of claim 17, wherein said actuator means comprises:

a housing;

an elongated forming gib slidably mounted within said housing and having a pair of substantially saw-tooth shaped surfaces on opposite sides thereof to form a plurality of paired, inclined surface portions along the elongated extent of said gib;

a plurality of substantially C-shaped forming pin operating members each disposed about one of said paired, inclined surface portions and each coupled to one of said plurality of forming pins to cause each of said forming pins to extend and retract when said forming gib is respectively slid in one direction corresponding to its elongated extent and in an opposite direction; and

means for sliding said gib between said one direction and said opposite direction.

19. The device of claim 18, further comprising means for readily attaching and detaching said actuator means and said supporting and deploying means to permit attachment of a different supporting and deploying means.

20. The device of claim 18, wherein said sliding means is a pneumatically operated cylinder coupled to an end portion of said forming gib.

21. The device of claim 18, further comprising:

a locating bar movable between a retracted position adjacent to said forming bar operating face and a locating position extending from said operating face; and

means for moving said locating bar between said retracted position and said locating position to position said array circuit at substantially a same location relative to the dovetail slot surface under inspection when said locating bar is in said locating position, to provide repeatable and comparable inspection results for different dovetail slots.

22. The device of claim 21, wherein said locating bar moving means comprises:

a plurality of locating pins each extending through a respective one of a second plurality of channels formed through said guide body and said forming bar and each coupled to said locating bar; and

said actuator means extends and retracts each of said plurality of locating pins to cause said locating bar to move between said retracted position and said locating position.

23. The device of claim 22, wherein said actuator means further comprises:

an elongated locating gib slidably mounted within said housing and having a pair of substantially saw-tooth shaped surfaces on opposite sides thereof to form a plurality of paired, inclined surface portions along the elongated extent of said locating gib;

a plurality of substantially C-shaped locating pin operating members each disposed about one of said paired, inclined surface portions and each coupled to one of said plurality of locating pins to cause each of said locating pins to extend and retract when said locating gib is respectively slid in one direction corresponding to its elongated extent and in an opposite direction; and

means for sliding said gib between said one direction and said opposite direction.

24. The device of claim 23, wherein said sliding means is a pneumatically operated cylinder coupled to an end portion of said forming gib.

25. The device of claim 16, further comprising:

a locating bar movable between a retracted position adjacent to said forming bar operating face and a locating position extending from said operating face; and

means for moving said locating bar between said retracted position and said locating position to position said array circuit at substantially a same location relative to the dovetail slot surface under inspection when said locating bar is in said locating position, to provide repeatable and comparable inspection results for different dovetail slots.

26. The device of claim 12, wherein said eddy current array circuit is formed in a pair of array circuits and said backing layer is formed in a pair of backing means;

said supporting and deploying means, comprising;

a pair of array circuit support members each shaped to matingly fit the surface under inspection, one of said pair of backing layer being disposed over each of said support members and one of said pair of array circuits being disposed over each of said backing layer and over each of said support members;

a base member, each of said pair of support members being pivotably mounted for movement to said base member in opposed spaced relation;

biasing means for urging each of said support members and said array circuit associated with each support member into close uniform contact with the surface under inspection to cause each of said respective pluralities of drive and sense elements to remain at their respective substantially constant distances from the surface under inspection during a scanning operation.

27. The device of claim 26, wherein said biasing means urges said support members away from each other.

28. The device of claim 26, wherein said biasing means urges said support members toward each other.

29. The device of claim 26, further comprising registration means for properly orienting said array circuit relative to said support member to provide repeatable and comparable results between inspections of different surfaces.

30. The device of claim 26, wherein at least a portion of each of said pair of backing means behind each of said pair of array circuits is a magnetic ferrite containing material.

31. A device for inspecting a component, comprising:

an eddy current array circuit having respective pluralities of drive and sense elements disposed on at least one substrate and having an active face for positioning on a surface of the component during an inspection operation;

outer backing means disposed on a face of said eddy current array circuit opposite to said active face for supporting said eddy current array circuit, said outer backing means being premoldable to conform substantially to a near net shape of the surface to be inspected to cause said array circuit to conform to the near net shape of the inspection surface;

inner backing means disposed on a face of said outer backing means opposite to said eddy current array circuit, said inner backing being a pliable, compressible material for providing uniform pressure behind said array circuit when in contact with the inspection surface; and

means for supporting and deploying said inner and outer backing means and said array circuit against the inspection surface during the inspection operation; and

means for electrically connecting said eddy current array circuit to an eddy current instrument.

32. The device of claim 31, wherein said supporting and deploying means comprises:

a guide body having a guide body base and a guide body extension member extending from said base;

a primary forming bar positioned at an end of said extension member opposite to said base and movable between a retracted position against said extension member and an inspection position at a spacing from said extension member end to properly position said array circuit and said inner and outer backing means relative to the inspection surface;

a secondary forming bar positioned at an end of said primary forming bar opposite to said extension member and movable between a retracted position against said primary forming bar and an inspection position at a spacing from said primary forming bar to cause said array circuit to contact and conform to the inspection surface; and

means for moving said primary and secondary forming bars between their respective retracted and inspection positions.

33. A device for inspecting a component, comprising:

an eddy current array circuit having respective pluralities of drive and sense elements and having an active face for positioning on a surface portion of the component during an inspection operation;

backing means disposed on a face of said eddy current array circuit opposite to said active face for applying a uniform pressure behind said array circuit to maintain the array circuit against the surface portion during the inspection operation; and

means for supporting and deploying said backing means and said array circuit to conform to the surface portion of the component and to cause each of said respective pluralities of drive and sense elements to remain at a respective substantially constant distance from the component surface portion during the inspection operation, said supporting and deploying means including a support member having an operating face and a groove formed in said operating face for receipt and retention of said backing means; and

means for electrically connecting said eddy current array circuit to an eddy current instrument.

34. The device of claim 33, wherein said backing means is a resilient, compressible material and extends slightly above said support member operating face to cause the array circuit to remain in contact with the surface portion during an inspection operation.

35. The device of claim 34, wherein at least a portion of said backing means immediately behind said array circuit is a magnetic ferrite containing material.