EDDY CURRENT PROBE AND A METHOD OF USING THE SAME

Abstract

An eddy current probe comprises a first planar coil, a second planar coil and a flexible substrate. The first coil comprises a first conductor having a spiral geometry, and the second coil comprises a second conductor having a spiral geometry. The first conductor is arranged concentrically with the second conductor, with the first conductor being juxtaposed with the second conductor, and the concentrically arranged first and second conductors are embedded within the flexible substrate.

Claims

1. An eddy current probe comprising: a first planar coil; a second planar coil; and a flexible substrate, wherein the first coil comprises a first conductor having a spiral geometry, the second coil comprises a second conductor having a spiral geometry, the first conductor is arranged concentrically with the second conductor, with the first conductor being juxtaposed with the second conductor, and the concentrically arranged first and second planar coils are embedded within the flexible substrate.

2. The eddy current probe as claimed in claim 1, wherein the spiral geometry is a rectilinear spiral geometry.

3. The eddy current probe as claimed in claim 1, wherein the first and second planar coils are completely embedded within the flexible substrate.

4. The eddy current probe as claimed in claim 1, wherein each of the first conductor and the second conductor has a width of between 30 m and 150 m.

5. The eddy current probe as claimed in claim 1, wherein each of the first conductor and the second conductor has a height of between 30 m and 150 m.

6. The eddy current probe as claimed in claim 1, wherein each of the first planar coil and the second planar coil has a pair of electrical connections connected to opposing ends of the respective first and second conductors, and each respective pair of electrical connections is positioned on opposing sides of the concentrically arranged first and second planar coils.

7. An eddy current system, the system comprising an eddy current probe comprising: a first planar coil; a second planar coil; a flexible substrate, wherein the first coil comprises a first conductor having a spiral geometry, the second coil comprises a second conductor having a spiral geometry, the first conductor is arranged concentrically with the second conductor, with the first conductor being juxtaposed with the second conductor, and the concentrically arranged first and second planar coils are embedded within the flexible substrate; and a control unit, wherein the control unit is electrically connected to each of the first planar coil and the second planar coil, and the control unit is configured to transmit a first alternating current signal to one of the first planar coil and the second planar coil, and to receive a second alternating current signal from the other one of the first planar coil and the second planar coil.

8. The eddy current system as claimed in claim 7, further comprising a component, wherein the first planar coil is an excitation coil and the second planar coil is a pickup coil, the eddy current probe is positioned conformally over a surface of the component, the first alternating current signal being arranged to generate eddy currents in the component, the second alternating current being representative of a residual stress condition within the component, and the control unit being further configured to process the second alternating current to provide a measure of the residual stress condition within the component..

9. The eddy current system as claimed in claim 7, wherein each of the first alternating current signal and the second alternating current signal has a sinusoidal signal profile.

10. A method of inspecting a component, the method comprising the steps of: providing an eddy current probe as claimed in claim 1, positioning the eddy current probe conformally over a surface of the component; generating a first alternating current signal in the first planar coil; receiving a second alternating current signal in the second planar coil; and processing the second alternating current signal to provide an indication of the magnitude and distribution of residual stress in the component.

11. A computer program that, when read by a computer, causes performance of the method as claimed in claim 10.

12. A non-transitory computer readable storage medium comprising computer readable instructions that, when read by a computer, cause performance of the method as claimed in claim 10.

13. A signal comprising computer readable instructions that, when read by a computer, cause performance of the method as claimed in claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] There now follows a description of an embodiment of the disclosure, by way of non-limiting example, with reference being made to the accompanying drawings in which:

[0047] FIG. 1 shows a schematic view of an eddy current technique for measuring residual stress in a component, according to the prior art;

[0048] FIG. 2 shows a schematic view of an eddy current probe according to a first embodiment of the disclosure;

[0049] FIG. 3 shows a schematic view of an eddy current probe according to a second embodiment of the disclosure;

[0050] FIG. 4 shows a schematic cross-sectional view on the eddy current probe of FIG. 2;

[0051] FIG. 5 shows a schematic view of an eddy current system according to a third embodiment of the disclosure; and

[0052] FIG. 6 shows a typical impedance plane display produced by the system of FIG. 5.

[0053] It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

[0054] Eddy currents are electrical currents induced in a conductor by a varying magnetic field. They are circular in nature and their paths are oriented perpendicular to the direction of the magnetic field. The source of the varying magnetic field is the electromagnetic field produced by a coil carrying an alternating electric current (see FIG. 1). When an electrical conductive component is placed near this coil, the varying magnetic field intersects the conductive material inducing eddy currents. Eddy current non-destructive inspection can determine various properties of the component such as residual stress, and may also be used to locate flaws in the component and to measure dimensions of the component.

[0055] The strength of the electromagnetic field at the surface of the conductor depends on coil size and configuration, amount of current through the coil and the distance of the coil from the material surface.

[0056] The basic mode of operation of the eddy current equipment when measuring the residual stress in a component is termed conductivity mode. In this mode, the measured probe coil electrical impedance is transformed to another parameter known as apparent eddy current conductivity (AECC). The detail of this technique is well known and will not be described further.

[0057] The conductivity profile in the component can be predicted from the measured frequency dependent AECC. The conductivity profile is influenced by different factors such as residual stress, microstructure, cold work and surface roughness of the material. A simple schematic representation of the method to obtain eddy current stress depth profile is shown in the flow chart of FIG. 1.

[0058] Referring to FIGS. 2 and 4, an eddy current probe according to a first embodiment of the disclosure is designated generally by the reference numeral 100.

[0059] The eddy current probe 100 comprises a first planar coil 110, a second planar coil 130, and a flexible substrate 150.

[0060] The first coil 110 comprises a first conductor 114 having a spiral circular geometry. The second coil 130 comprises a second conductor 134 also having a spiral circular geometry. The first conductor 114 and the second conductor 134 have corresponding spiral circular geometries.

[0061] The first conductor 114 is arranged concentrically with the second conductor 134, with the first conductor 114 being juxtaposed with the second conductor 134. In other words the first conductor 114 and the second conductor 134 are arranged side by side in a spiral circular configuration.

[0062] The first conductor 114 is formed with a rectilinear cross-sectional profile. In the present embodiment, the cross-sectional profile of the first conductor 114 has a width of 100 m and a depth of 100 m. The second conductor 134 is formed with a rectilinear cross-sectional profile. In the present embodiment, the cross-sectional profile of the second conductor 134 has a width of 100 m and a depth of 100 m.

[0063] In the embodiment shown in FIG. 2, each of the first coil 110 and the second coil 130 is arranged in a circular spiral configuration. The first coil 110 has an outer diameter of 8 mm. The second coil 130 also has an outer diameter of 8 mm.

[0064] The first conductor 114 is provided with a pair of electrical connections 116 at the opposing ends of the first conductor 114.

[0065] The second conductor 134 is provided with a pair of electrical connections 136 at the opposing ends of the second conductor 134.

[0066] As shown in FIG. 4, each of the first conductor 114 and the second conductor 134 is partially embedded in the flexible substrate 150.

[0067] In use, the first coil 110 is designated as an excitation coil, and the second coil 130 is designated as a pickup coil. Since the first coil 110 and the second coil 130 are identical to one another this designation may readily be reversed.

[0068] As shown in FIG. 5, the eddy current probe 100 is connected to a controller 160. The controller 160 may be a computer or may be a sub-system of a further control system (not shown).

[0069] Referring to FIGS. 3 and 4, an eddy current probe according to a second embodiment of the disclosure is designated generally by the reference numeral 200. Features of the eddy current probe 200 which correspond to those of eddy current probe 100 have been given corresponding reference numerals for ease of reference.

[0070] The eddy current probe 200 has a first planar coil 210, a second planar coil 230, and a flexible substrate 250.

[0071] The first coil 210 comprises a first conductor 214 having a spiral rectilinear geometry. The second coil 230 comprises a second conductor 234 also having a spiral rectilinear geometry. The first conductor 214 and the second conductor 234 have corresponding rectilinear spiral geometries.

[0072] The first conductor 214 is arranged concentrically with the second conductor 234, with the first conductor 214 being juxtaposed with the second conductor 234. In other words the first conductor 214 and the second conductor 234 are arranged side by side in a spiral rectilinear configuration.

[0073] The first conductor 214 is formed with a rectilinear cross-sectional profile. In the present embodiment, the cross-sectional profile of the first conductor 214 has a width of 100 m and a depth of 100 m. The second conductor 234 is formed with a rectilinear cross-sectional profile. In the present embodiment, the cross-sectional profile of the second conductor 234 has a width of 100 m and a depth of 100 m.

[0074] In the embodiment shown in FIG. 3, each of the first coil 210 and the second coil 230 is arranged in a rectilinear spiral configuration. The first coil 210 has a length of 8 mm. The second coil 230 also has a length of 8 mm.

[0075] The first conductor 214 is provided with a pair of electrical connections 116 at the opposing ends of the first conductor 214.

[0076] The second conductor 234 is provided with a pair of electrical connections 136 at the opposing ends of the second conductor 234.

[0077] As shown in FIG. 4, each of the first conductor 214 and the second conductor 234 is partially embedded in the flexible substrate 250.

[0078] As described above in relation to the embodiment of FIG. 2, in use, the first coil 210 is designated as an excitation coil, and the second coil 230 is designated as a pickup coil. Since the first coil 210 and the second coil 230 are identical to one another this designation may readily be reversed.

[0079] As shown in FIG. 5, the eddy current probe 200 is connected to a controller 160. The controller 160 may be a computer or may be a sub-system of a further control system (not shown).

[0080] Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

[0081] The foregoing description of various aspects of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the disclosure as defined by the accompanying claims.