An eddy current testing probe and method capable of identifying any crack and direction around a hole

Abstract

A kind of eddy current testing probe and method for identifying any crack and direction around hole, the probe includes a pie-shaped detection coil with middle magnetic core, the magnetic core not only ensures accurate positioning, but also uses magnetic collection effect by enhancing coil inductance, to strengthen the magnetic field inside and back of hole.The probe is also equipped with three layers of excitation coil, one layer and two layers of coil are arranged orthogonally, three layers and one layer of coil are at an angle of 135 °, realize the efficient detection of any direction crack and identify the direction of any crack defect.The flexible support of probe enables it to adapt to curved surface structure, widen the application range.The detection method uses orthogonal differential technology, uses the symmetry of hole structure to identify defects around hole, significantly improve the detection sensitivity of defects on the back and inside of hole structure.Compared with traditional surface and near-surface defect eddy current testing technology, the present application provides a more effective solution for high-precision detection of hole structure through innovative coil configuration and defect identification method.

Description

Technical Field

[0001] This invention relates to an eddy current detection probe and its usage method, specifically to an eddy current detection probe and method capable of identifying eddy current cracks around holes of arbitrary direction. Background Technology

[0002] Gas turbines, as highly efficient internal combustion power machines, use continuously flowing gas as the working fluid to drive a high-speed rotating impeller, converting fuel energy into useful work. They are widely used in power generation, oil and gas transportation, shipbuilding, and heavy-duty locomotives. Film cooling perforation technology plays a crucial role in this process. By forming a protective film layer on the turbine blade surface, it effectively reduces blade temperature, improves blade temperature resistance and service life, and thus enhances the blade's thermal protection capabilities. Furthermore, the application of film cooling perforations supports the high-efficiency energy conversion of gas turbines, ensuring equipment reliability and safety, and adapting to varying operating conditions. These perforations are typically manufactured using precision machining techniques such as EDM and laser drilling to ensure that the shape, size, and distribution of the perforations meet design requirements. However, defects such as rough hole walls, inconsistent hole diameters, and cracks may occur during the machining process. These defects can affect the uniformity of the film cooling and cooling efficiency, and even lead to premature blade failure. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the purpose of this invention is to provide an eddy current detection probe and method that can identify cracks around holes in any direction, so as to achieve high-precision and blind-zone-free detection of back crack defects in any direction around holes.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] An eddy current detection probe capable of identifying cracks around holes of arbitrary direction comprises three parts: an excitation unit, a detection unit, and a flexible support. The detection unit 1 consists of a disc-shaped detection coil 2 and a cylindrical soft magnetic material 3 with one end inserted into the disc-shaped detection coil 2. The flexible support 4 is made of insulating soft material, and wire grooves 5 are arranged on the flexible support to lead out the wires of the disc-shaped detection coil for signal extraction. The excitation unit consists of a first-layer excitation coil 6, a second-layer excitation coil 7, and a third-layer excitation coil 8. The excitation coils are printed on a flexible PCB circuit board, and additional layers are added between adjacent excitation coils. A polyimide film is used to reduce crosstalk between the excitation coils. Each layer of excitation coils is arranged in parallel to ensure that the excitation current in the same direction is consistent. The second layer of excitation coil 7 is arranged at a 90° angle to the first layer of excitation coil 6, and the third layer of excitation coil 8 is arranged at a 135° angle to the first layer of excitation coil 6. The detection unit is embedded in the flexible support. The upper surface of the disc-shaped detection coil in the detection unit is coplanar with the upper surface of the flexible support, and the lower surface of the disc-shaped detection coil in the detection unit is coplanar with the lower surface of the flexible support. The lower surface is in close contact with the test piece 10 to be tested. The excitation unit vertically covers the upper part of the detection unit.

[0006] The core component of the probe is the detection unit 1. The diameter of the cylindrical soft magnetic material 3 is equal to or smaller than the diameter of the hole to be tested to ensure optimal matching. The inner diameter of the disc-shaped detection coil 2 is consistent with the diameter of the hole to be tested, while its outer diameter and thickness are comprehensively designed according to the specific size of the test piece and the required number of coil turns to meet the testing requirements.

[0007] The flexible support 4 enables the detection unit 1 to fit the curved surface of the test piece to the maximum extent. While ensuring the detection unit 1 is fixed, the flexible support has wire grooves 5 arranged on its upper surface to reduce the impact of the welding structure on the lifting of the excitation coil and the impact of the welding part on the excitation eddy current field.

[0008] Sinusoidal excitation voltage signals are applied to the first excitation coil 6 and the second excitation coil 7 respectively. The second excitation coil 7 excites an eddy current field around the hole, which is at an angle of 90° to the direction of the eddy current field excited by the first excitation coil 6. If the direction of the crack around the hole is 45°, it cannot be detected. At this time, the direction of the eddy current field excited by the third excitation coil 8 around the hole is perpendicular to the 45° crack direction, which satisfies the high-precision detection of cracks in any direction around the hole and effectively identifies the direction of crack defects.

[0009] The cylindrical soft magnetic material 3 is a type of magnetic material with low coercivity and high permeability. During the detection process, this material can significantly enhance the magnetic field inside and on the back of the hole through the magnetic field collection effect, so that the magnetic field lines penetrate the hole structure more deeply and introduce the eddy current field into the inner wall of the hole. This allows the disc detection coil 2 to capture the changes in the eddy current field on the back of the hole, thereby achieving accurate detection of defects.

[0010] The method for detecting eddy current detectors with arbitrarily oriented cracks around holes is described above. This method can effectively detect defects in any direction. Because the detection unit has an inserted cylindrical soft magnetic material, the signal-to-noise ratio is effectively increased, enabling effective detection of internal and back-side cracks in any direction. Details are as follows:

[0011] Set up the detection probe as required, insert the cylindrical soft magnetic material 3 in detection unit 1 into the hole of the test piece, and ensure that the flexible support and the flexible PCB circuit board where the excitation coil is located are completely in contact with the curved surface. First, a sinusoidal AC voltage signal is passed through the first layer excitation coil 6, and the detection signal in the disc detection coil 2 is V1. Then, a sinusoidal AC voltage signal is passed through the second layer excitation coil 7, and the detection signal in the disc detection coil 2 is V2. Finally, a sinusoidal AC voltage signal is passed through the third layer excitation coil 8, and the detection signal in the disc detection coil 2 is V3.

[0012] Since the hole structure of the test piece is a completely symmetrical structure, the eddy current field is also completely symmetrical. When there is no defect, the detection signals should be equal, i.e., V1 = V2 = V3. When there is a crack defect around the hole, the detection signals are not equal, i.e., V1 ≠ V2 ≠ V3. Combining the detection signals corresponding to the three layers of excitation coils, the detection signal is set as V, V = |V1-V2| + |V1-V3| + |V2-V3|, which can determine whether there is a defect. However, since the detection conditions are not perfect in actual testing, the average value of the detection signal is taken as V0, i.e., V0 = (|V1+V2+V3|) / 3. The relative error Δ = |V / V0| × 100% is used as the judgment standard. When Δ ≤ 3%, it is judged that there is no crack defect around the hole; when Δ ≥ 3%, it is judged that there is a crack defect around the hole.

[0013] The two eddy current fields formed by the first excitation coil 6 and the second excitation coil 7 on the surface of the test piece are perpendicular to each other. A hole structure without peripore crack defects is taken as a control. The above detection process is repeated, and the detection signals corresponding to the first excitation coil 6 and the second excitation coil 7 are taken as V. n1 With V n2 At this time, the detected signal of the hole periapical crack with horizontal direction θ in the eddy current field of the two excitation coils satisfies tanθ=(V1-V n1 ) / (V2-V n2 ), that is, θ=arctan[(V1-V n1 ) / (V2-V n2 )], that is, the angle between the crack and the horizontal direction.

[0014] Eddy current testing, as a non-destructive testing technique, can sensitively detect cracks and other defects that may exist around film cooling holes, which is of great significance for ensuring the integrity of blades and the long-term stable operation of gas turbines. By performing eddy current testing on the film cooling holes of gas turbine blades, crack defects can be identified and repaired in a timely manner, thereby improving the operating efficiency and reliability of gas turbines and extending the service life of blades. The eddy current testing technology of this invention effectively solves the problem of low sensitivity to cracks parallel to the eddy current field direction in traditional eddy current testing through an innovative probe design. This invention uses three sets of excitation coils, supplemented by coils arranged at a 135° angle, which significantly improves the detection sensitivity to cracks in any direction around the hole. This design not only avoids the missed detection that may occur in traditional methods, but also identifies the crack direction, ensuring comprehensive and accurate detection of cracks in any direction, thereby greatly improving the accuracy and reliability of the detection. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the eddy current detection probe for back cracks in any direction around a hole, according to the present invention.

[0016] Figure 2 This is a schematic diagram of the detection unit structure of the present invention.

[0017] Figure 3 This is a schematic diagram of the flexible support of the present invention.

[0018] Figure 4 This is a schematic diagram of the multilayer excitation coil structure of the present invention.

[0019] Figure 5 This is a schematic diagram of the horizontally arranged parallel circuit of the excitation coil of the present invention.

[0020] Figure 6 This is a schematic diagram of the wiring circuit for the vertically arranged parallel circuit of the two-layer excitation coils of the present invention.

[0021] Figure 7 This is a schematic diagram of the wiring circuit for the parallel circuit of the three-layer excitation coils arranged at 135° according to the present invention.

[0022] Figure 8 This is a schematic diagram showing the position of the probe relative to the structure of the hole to be tested during the detection process of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1As shown, an eddy current detection probe capable of identifying any cracks and directions around a hole is disclosed. The probe comprises three parts: an excitation unit, a detection unit, and a flexible support. The detection unit is embedded within the flexible support. The upper surface of the disc-shaped detection coil in the detection unit is coplanar with the upper surface of the flexible support, and the lower surface of the disc-shaped detection coil in the detection unit is coplanar with the lower surface of the flexible support, with the lower surface closely attached to the test piece. The excitation unit vertically covers the upper part of the detection unit.

[0025] like Figure 2 As shown, the detection unit 1 consists of two parts: a disc-shaped detection coil 2 and a cylindrical soft magnetic material 3 with one end inserted into the disc-shaped detection coil 2. The diameter of the cylindrical soft magnetic material 3 is designed to be the same as or slightly smaller than the diameter of the hole to be detected to ensure optimal matching. Soft magnetic materials are a type of magnetic material with low coercivity and high permeability. During the detection process, this material can significantly enhance the magnetic field inside and on the back of the hole through the magnetic focusing effect. This design allows magnetic field lines to penetrate deeper into the hole structure, introducing the eddy current field into the inner wall of the hole, enabling the disc-shaped detection coil 2 to capture the changes in the eddy current field on the back of the hole, thus achieving accurate detection of defects. The inner diameter of the disc-shaped detection coil 2 is consistent with the hole diameter, while its outer diameter and thickness are comprehensively designed according to the specific size of the test piece and the required number of coil turns to meet the detection requirements.

[0026] like Figure 3 As shown, the flexible support 4 is made of insulating soft material. Wire grooves 5 are arranged on the flexible support to lead out the wires of the disc-shaped detection coil for signal extraction. The flexible support allows the detection unit 1 to fit the curved test specimen surface to the greatest extent possible. Under curved surface conditions, it ensures that the lifting of the first-layer excitation coil 6, the second-layer excitation coil 7, and the third-layer excitation coil 8 onto the specimen surface remains consistent, thereby generating a uniform eddy current field in each excitation coil and reducing the impact of the curved surface structure on the detection. While ensuring the disc-shaped detection coil is fixed, the flexible support also has wire grooves 5 on its upper surface to reduce the impact of the welding structure on the lifting of the excitation coil and the influence of the welding area on the excitation eddy current field. The flexible support of the probe allows it to adapt to curved surface structures, broadening its application range.

[0027] like Figure 4 As shown, the excitation unit consists of three parts: a first-layer excitation coil 6, a second-layer excitation coil 7, and a third-layer excitation coil 8. The first-layer excitation coil arranges the wires in a horizontal parallel configuration. The second-layer excitation coil 7 is arranged in parallel with the first-layer excitation coil 6 at a 90° angle. This arrangement effectively overcomes the problem that traditional single-direction coils are insensitive to parallel crack detection. The third-layer excitation coil 8 arranges the wires at a 135° angle with the first-layer excitation coil 6. Applying the third-layer excitation coil effectively overcomes the insensitivity of the eddy current field excited by the double-layer orthogonal excitation coil to oblique 45° cracks, thus achieving efficient detection of cracks in any direction and identification of any crack defect direction.

[0028] like Figure 5 As shown, the first-layer excitation coil 6 arranges the wires in horizontal parallel connection. When a sinusoidal AC signal is passed through the coil, a uniformly changing eddy current field in the horizontal direction is formed on the surface of the curved test piece.

[0029] like Figure 6 As shown, the second-layer excitation coil 7 arranges the wires in a vertical parallel arrangement. When a sinusoidal AC signal is passed through the coil, a uniformly changing eddy current field in the vertical direction is formed on the surface of the curved test piece.

[0030] like Figure 7 As shown, the third-layer excitation coil 8 arranges the wires in parallel at a 135° angle. When a sinusoidal AC signal is passed through the coil, a uniformly changing eddy current field at a 135° angle is formed on the surface of the curved test piece.

[0031] like Figure 8 As shown, when setting up the probe, the cylindrical soft magnetic material 3 in the detection unit is inserted into the hole to be tested, and the flexible support and the flexible PCB circuit board of the excitation coil are completely attached to the surface of the test piece.

[0032] The working principle of this invention is as follows: This invention aims to achieve highly sensitive detection of back cracks in any direction around a hole. The specific implementation steps are as follows:

[0033] Step 1: Insert the cylindrical soft magnetic material 3 in the detection unit 1 into the hole to be tested, and make the flexible support and the flexible PCB circuit board of the excitation coil completely fit the surface of the test piece 10 to be tested.

[0034] Step 2: A sinusoidal AC voltage signal is passed through the first excitation coil 6. At this time, the detected signal in the disc detection coil 2 is V1. Then, a sinusoidal AC voltage signal is passed through the second excitation coil 7. At this time, the detected signal in the disc detection coil 2 is V2. Finally, a sinusoidal AC voltage signal is passed through the third excitation coil 8. At this time, the detected signal in the disc detection coil 2 is V3.

[0035] Step 3: Since the hole structure of the test piece is a completely symmetrical structure, the eddy current field excited by the three-layer excitation coil is also completely symmetrical. When there is no defect, the detection signals should be equal, i.e., V1 = V2 = V3. When there is a crack defect around the hole, the detection signals are not equal, i.e., V1 ≠ V2 ≠ V3. Combining the detection signals corresponding to the three-layer excitation coil, the detection signal is set as V, V = |V1-V2| + |V1-V3| + |V2-V3|, which can be used to determine whether there is a defect. However, since the detection conditions cannot be perfectly met in actual testing, the average value of the detection signal is taken as V0, i.e., V0 = (|V1+V2+V3|) / 3. The relative error Δ = |V / V0| × 100% is used as the judgment standard. When Δ ≤ 3%, it is judged that there is no crack defect around the hole. When Δ ≥ 3%, it is judged that there is a crack defect around the hole.

[0036] The two eddy current fields formed on the surface of the test piece by the first excitation coil 6 and the second excitation coil are perpendicular to each other. A hole structure without peripore crack defects is taken as a control. The above detection process is repeated, and the detection signal corresponding to the first excitation coil 6 and the second excitation coil 7 is taken as V. n1 With V n2 At this time, the detected signal of the hole periapical crack with horizontal direction θ in the eddy current field of the two excitation coils satisfies tanθ=(V1-V n1 ) / (V2-V n2 ), from which we can obtain θ=arctan[(V1-V n1 ) / (V2-V n2 )], that is, the angle between the crack and the horizontal direction.

[0037] This invention employs orthogonal differential technology, utilizing the symmetry of the hole structure to identify defects around the hole, significantly improving the detection sensitivity for defects on the back side and inside the hole structure. Compared with traditional eddy current detection techniques for surface and near-surface defects, this invention provides a more effective solution for high-precision detection of hole structures through innovative coil configuration and defect identification methods.

Claims

1. An eddy current detection probe capable of identifying cracks around holes of arbitrary direction, characterized in that: The probe comprises three parts: an excitation unit, a detection unit, and a flexible support. The detection unit (1) consists of a disc-shaped detection coil (2) and a cylindrical soft magnetic material (3) with one end inserted into the disc-shaped detection coil (2). The flexible support (4) is made of insulating soft material, and wire grooves (5) are arranged on the flexible support to lead out the wires of the disc-shaped detection coil for signal extraction. The excitation unit consists of a first-layer excitation coil (6), a second-layer excitation coil (7), and a third-layer excitation coil (8). The excitation coils are printed on a flexible PCB circuit board, and a polyimide film is added between adjacent excitation coil layers. To reduce crosstalk between the excitation coils, each layer of excitation coils is arranged in parallel to ensure that the excitation current in the same direction is consistent. The second layer of excitation coil (7) is arranged at a 90° angle to the first layer of excitation coil (6), and the third layer of excitation coil (8) is arranged at a 135° angle to the first layer of excitation coil (6). The detection unit is embedded in the flexible support. The upper surface of the disc-shaped detection coil in the detection unit is coplanar with the upper surface of the flexible support. The lower surface of the disc-shaped detection coil in the detection unit is coplanar with the lower surface of the flexible support, and the lower surface is in close contact with the test piece (10) to be tested. The excitation unit vertically covers the upper part of the detection unit.

2. The eddy current detection probe capable of identifying cracks and their directions around holes according to claim 1, characterized in that: The core component of the probe is the detection unit (1). The diameter of the cylindrical soft magnetic material (3) is equal to or smaller than the diameter of the hole to be detected to ensure optimal matching. The inner diameter of the disc-shaped detection coil (2) is consistent with the diameter of the hole to be detected, while its outer diameter and thickness are comprehensively designed according to the specific size of the test piece and the required number of coil turns to meet the detection requirements.

3. The eddy current detection probe capable of identifying cracks and their directions around holes according to claim 1, characterized in that: The flexible support (4) enables the detection unit (1) to fit against the surface of the curved test piece. While ensuring the detection unit (1) is fixed, the flexible support has wire grooves (5) arranged on its upper surface to reduce the influence of the welding structure on the lifting of the excitation coil and the influence of the welding part on the excitation eddy current field.

4. The eddy current detection probe capable of identifying cracks of arbitrary direction around a hole according to claim 1, characterized in that: Sinusoidal excitation voltage signals are respectively passed through the first excitation coil (6) and the second excitation coil (7). The second excitation coil (7) excites an eddy current field around the hole, which is 90° away from the direction of the eddy current field excited by the first excitation coil (6). If the direction of the crack around the hole is 45°, it cannot be detected. At this time, the direction of the eddy current field excited by the third excitation coil (8) around the hole is perpendicular to the 45° crack direction, which satisfies the high-precision detection of cracks in any direction around the hole and effectively identifies the direction of crack defects.

5. The eddy current detection probe capable of identifying cracks and their directions around holes according to claim 1, characterized in that: The cylindrical soft magnetic material (3) uses a type of magnetic material with low coercivity and high permeability. During the detection process, this material can significantly enhance the magnetic field inside and on the back of the hole through the magnetic field collection effect, so that the magnetic field lines penetrate the hole structure more deeply and introduce the eddy current field into the inner wall of the hole, so that the disc detection coil (2) can capture the change of the eddy current field on the back of the hole and realize the accurate detection of defects.

6. A detection method for an eddy current detection probe capable of identifying cracks of arbitrary direction around a hole, as described in any one of claims 1 to 5, characterized in that: This detection method can effectively detect defects in any direction. Because the detection unit has inserted cylindrical soft magnetic material, the signal-to-noise ratio is effectively increased, enabling effective detection of internal and back-side cracks in any direction. Details are as follows: After setting up the detection probe, insert the cylindrical soft magnetic material (3) in the detection unit (1) into the hole of the test piece. The flexible support and the flexible PCB circuit board where the excitation coil is located are completely in contact with the curved surface. First, a sinusoidal AC voltage signal is passed into the first layer excitation coil (6). At this time, the detection signal in the pancake detection coil (2) is V1. Then, a sinusoidal AC voltage signal is passed into the second layer excitation coil (7). At this time, the detection signal in the pancake detection coil (2) is V2. Finally, a sinusoidal AC voltage signal is passed into the third layer excitation coil (8). At this time, the detection signal in the pancake detection coil (2) is V3. Since the hole structure of the test piece is a completely symmetrical structure, the eddy current field is also completely symmetrical. When there is no defect, the detection signals should be equal, i.e., V1 = V2 = V3. When there is a crack defect around the hole, the detection signals are not equal, i.e., V1 ≠ V2 ≠ V3. Combining the detection signals corresponding to the three layers of excitation coils, the detection signal is set as V, V = |V1-V2| + |V1-V3| + |V2-V3|, which can determine whether there is a defect. However, since the detection conditions are not perfect in actual testing, the average value of the detection signal is taken as V0, i.e., V0 = (|V1+V2+V3|) / 3. The relative error Δ = |V / V0| × 100% is used as the judgment standard. When Δ < 3%, it is judged that there is no crack defect around the hole. When Δ ≥ 3%, it is judged that there is a crack defect around the hole. The two eddy current fields formed by the first excitation coil (6) and the second excitation coil (7) on the surface of the test piece are perpendicular to each other. A hole structure without peripore crack defects is taken as a control. The above detection process is repeated, and the detection signals corresponding to the first excitation coil (6) and the second excitation coil (7) are taken as V. n1 With V n2 At this time, the detected signal of the hole periapical crack with horizontal direction θ in the eddy current field of the two excitation coils satisfies tanθ=(V1-V n1 ) / (V2-V n2 ), that is, θ=arctan[(V1-V n1 ) / (V2-V n2 )], that is, the angle between the crack and the horizontal direction.

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