Eddy-current flaw detector probe

• US 6,501,267 B1
• Filed: 02/29/2000
• Issued: 12/31/2002
• Est. Priority Date: 08/06/1998
• Status: Expired due to Term

• Current Assignee: Mitsubishi Heavy Industries, Ltd.
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Matsumoto, Mitsuyoshi, Kurokawa, Masaaki
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US09/486,637
• Time in Patent Office: 1,036 Days
• Field of Search: 324/242, 324/238, 324/239, 324/240, 324/241, 324/243, 324/262, 336/232
• US Class Current: 324/242
• CPC Class Codes: G01N 27/904 with two or more sensors

Abstract

The present invention relates to an eddy current testing probe, which is suitable for used in a nondestructive test. The eddy current testing probe is provided with an excitation coil (2, 2a, 2b) which generates an alternating magnetic field to generate an eddy current (12) in a specimen (10), and a pair of detection coils (1a, 1b) differentially connected and arranged in phase. A central portion (C1) of the pair of detection coils and a central portion (C2) of the excitation coil (2, 2a, 2b) are arranged to be located at an identical or an almost identical position in a plan view taken in the direction toward the specimen (10), and a flaw (11) on the specimen (10) is detected based on a difference between voltages generated in the pair of detection coils (1a, 1b) due to the eddy current (12).

Claims

1. An eddy current flaw detector comprising:

a pair of excitation coils which generates an alternating magnetic filed to generate an eddy current in a specimen; and

a pair of detection coils differentially connection and arranged in phase;

wherein a central portion of the pair of detection coils and a central portion of the pair of excitation coils are arranged to be located at an identical or an almost identical position in a plan view taken in a direction toward the specimen, and a flaw on the specimen is detected based on a difference between voltages generated in the pair of detection coils due to the eddy current.

2. An eddy current flaw detector according to claim 1, wherein the excitation coil generates the eddy current in a slanting direction with respect to a direction of the flaw on the specimen.

3. An eddy current flaw detector according to claim 1, wherein the detection coils in the pair are arranged on a plane, side by side, and symmetrically with respect to a line.

4. An eddy current flaw detector according to claim 1, further comprising a bridge circuit which is connected to the pair of detection coils for obtaining as a flaw signal the difference between voltages generated in the pair of detection coils due to the eddy current.

5. An eddy current flaw detector according to claim 2, wherein the detection coils in the pair are arranged on a plane, side by side, and symmetrically with respect to a line.

6. An eddy current flaw detector according to claim 2, further comprising a bridge circuit which is connected to the pair of detection coils for obtaining as a flaw signal the difference between voltages generated in the pair of detection coils due to the eddy current.

23. An eddy current flaw detector according to claim 1,

wherein the pair of detection coils and the pair of excitation coils are arranged so that a centerline of symmetry of the detection coils is perpendicular to a centerline of symmetry of the excitation coils in the plan view of the specimen.

7. An eddy current flaw detector for detecting a flaw on a specimen comprising:

a plurality of excitation coils for generating an alternating magnetic field to generate an eddy current in the specimen while the specimen is moved relatively with respect to said detector; and

a plurality of thin-film detection coil rows, said each thin-film detection coil row comprises a plurality of thin-film detection coils which are arranged in a row along the specimen, for detecting a flaw on the specimen based on said eddy current generated by said plural excitation coils;

said plural thin-film detection coil rows arranged one over another,

and a centerline of each of said plural thin-film detection coil rows extending in an alignment with the centerline of any of the remaining thin-film detection coil rows in the plan view.

8. An eddy current flaw detector according to claim 7, wherein said individual thin-film detection coils of one of the rows are relatively shifted by about a half pitch from the other row if the number of said thin-film detection coil rows is two.

9. An eddy current flaw detector according to claim 7, wherein a thin-film insulating layer is inserted between adjacent ones of said thin-film detection coil rows.

10. An eddy current flaw detector according to claim 7, wherein each of the excitation coils is realized by a circular coil having a small length in an axis direction and being arranged to stand almost perpendicularly to a surface of the specimen, and the plurality of excitation coils are arranged in one or more rows above the plurality of thin-film detection coils.

11. An eddy current flaw detector according to claim 7, wherein voltages are not applied concurrently to adjacent ones of the plurality of excitation coils.

12. An eddy current flaw detector according to claim 7, being moved along a surface of the specimen in a direction perpendicular to a direction of extending of said plural thin-film detection coil rows, to detect a flaw at the surface of the specimen.

13. An eddy current flaw detector according to claim 8, wherein a thin-film insulating layer is inserted between adjacent ones of said thin-film detection coil rows.

14. An eddy current flaw detector according to claim 8, wherein each of the excitation coils is realized by a circular coil having a small length in an axis direction and being arranged to stand almost perpendicularly to a surface of the specimen, and the plurality of excitation coils are arranged in one or more rows above the plurality of thin-film detection coils.

15. An eddy current flaw detector according to claim 8, wherein voltages are not applied concurrently to adjacent ones of the plurality of excitation coils.

16. An eddy current flaw detector according to claim 8, being moved along a surface of the specimen in a direction perpendicular to a direction of extending of said plural thin-film detection coil rows, to detect a flaw at the surface of the specimen.

17. An eddy current flaw detector according to claim 9, wherein said insulation layer has a through hole for leading out a signal wire of each detection coil in the lower thin-film detection coil row.

18. An eddy current flaw detector according to claim 10, wherein said each of the excitation coils is oriented in a slanting direction with respect to a direction of extending of the layers of the plurality of excitation coils.

19. An eddy current flaw detector according to claim 11, wherein said voltages are applied to the excitation coils in a pulsed mode.

20. An eddy current flaw detector according to claim 13, wherein said insulation layer has a through hole for leading out a signal wire of each detection coil in the lower thin-film detection coil row.

21. An eddy current flaw detector according to claim 14, wherein said each of the excitation coils is oriented in a slanting direction with respect to a direction of extending of the layers of the plurality of excitation coils.

22. An eddy current flaw detector according to claim 15, wherein said voltages are applied to the excitation coils in a pulsed mode.

24. An eddy current flaw detector for detecting a flaw on a specimen comprising:

means for generating an alternating magnetic field to generate an eddy current in the specimen while the specimen is moved relatively with respect to said detector; and

a plurality of thin-film detection coil rows, said each thin-film detection coil row comprises a plurality of thin-film detection coils which are arranged in a row along the specimen, for detecting a flaw on the specimen based on said eddy current generated by said generating means;

said plural thin-film detection coil rows arranged one over another,

and a centerline of each of said plural thin-film detection coil rows extending in alignment with the centerline of those of any of the remaining thin-film detection coil rows in the plan view.