Probes and methods for detecting defects in metallic structures
First Claim
1. An eddy current probe for detecting defects in an electrically conductive specimen under test (SUT), the eddy current probe comprising:
- a. at least one excitation coil having a cross-section disposed within a common plane, the at least one excitation coil having a symmetry axis within the common plane, wherein the at least one excitation coil creates a magnetic field and eddy currents into SUT; and
b. at least one magnetic senor operable to be positioned on the symmetry axis of the at least one excitation coil and having a sensitive axis operable to be disposed within the common plane perpendicular to the symmetry axis of the at least one excitation coil.
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Abstract
The present invention is directed to configurations of eddy current probes and methods for using these probes to detect cracks initiating at the edge of holes in single-layered or multi-layered metallic structures. The new devices and methods are suitable to detect buried cracks around fastener holes located in layers of multi-layered structures, for example in airplane wing splices, containing fasteners disposed in rows. The probes include excitations coils and one or more magnetic sensors. The magnetic sensors can be arranged in absolute, differential or array configurations. The probe is scanned linearly along the fastener row. The invention also contains an apparatus or system for monitoring cracks around holes, including signal processing circuits, driving circuits, data acquisition and display, and scanning systems.
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Citations
51 Claims
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1. An eddy current probe for detecting defects in an electrically conductive specimen under test (SUT), the eddy current probe comprising:
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a. at least one excitation coil having a cross-section disposed within a common plane, the at least one excitation coil having a symmetry axis within the common plane, wherein the at least one excitation coil creates a magnetic field and eddy currents into SUT; and
b. at least one magnetic senor operable to be positioned on the symmetry axis of the at least one excitation coil and having a sensitive axis operable to be disposed within the common plane perpendicular to the symmetry axis of the at least one excitation coil. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29)
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27. An eddy current probe for detecting defects within a specimen under test (SUT) comprising:
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a. a flat excitation coil of rectangular cross-section having an axis of symmetry within a plane of the cross-section; and
b. a linear array of magnetoresistive sensors disposed at the axis of symmetry of the flat excitation coil, each magnetoresistive sensor in the array having a sensitive axis operable to be disposed perpendicular to the axis of symmetry of the excitation coil.
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30. An eddy current probe comprising:
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a. a flat excitation coil having a substantially rectangular cross-section and having an axis of symmetry within the plane of the cross-section;
b. two magnetoresistive sensors operable to be disposed at the axis of symmetry of the excitation coil, each magnetoresistive sensor having a sensitive axis operable to be disposed perpendicular to the axis of symmetry of the excitation coil, wherein the two magnetoresistive sensors are operable to be connected in a gradiometer configuration. - View Dependent Claims (31)
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32. An eddy current probe for detecting defects in an electrically conductive specimen under test (SUT), the eddy current probe comprising:
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a. a pair of substantially identical excitation coils having substantially rectangular cross-sections operable to be disposed within a common plane, the pair of excitation coils having a first symmetry axis and a second symmetry axis orthogonal to the first symmetry axis within the common plane, wherein the pair of excitation coils are interconnected such that they create magnetic field and eddy currents into SUT in opposite directions if an electric current is passed through the pair of excitation coils; and
b. at least one magnetic sensor operable to be positioned on the second symmetry axis of the pair of excitation coils and having a sensitive axis operable to be disposed within the common plane perpendicular to the second symmetry axis of the pair of excitation coils. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 50, 51)
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48. An eddy current probe for detecting defects within a specimen under test (SUT) comprising:
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a. a pair of flat excitation coils having a rectangular cross-section and having a first symmetry axis and a second symmetry axis orthogonal to the first symmetry axis within the plane of the cross-section; and
b. a linear array of magnetoresistive sensors disposed at the second symmetry axis of the pair of excitation coils, each magnetoresistive sensor in the array having a sensitive axis disposed within the plane of the cross-section, wherein the sensitive axis is perpendicular to the second symmetry axis of the pair of excitation coils.
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49. An eddy current probe for detecting cracks in a specimen under testing (SUT) having a row of fastener holes, wherein the row of fastener holes has a symmetry axis that intersects the centers of all holes in the row, wherein the eddy current probe comprises:
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a. a pair of flat excitation coils having rectangular cross-sections and having a first symmetry axis and a second symmetry axis orthogonal to the first symmetry axis within the plane of the cross-section;
b. a magnetoresistive sensor disposed at the intersection of the first symmetry axis and the second symmetry axis of the pair of excitation coils, the magnetoresistive sensor having a sensitive axis disposed within the plane of the cross-section, wherein the sensitive axis of the magnetoresisitve sensor is perpendicular to the second symmetry axis of the excitation coil.
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Specification