Eddy current detection probe and method capable of identifying any crack around hole and direction

Abstract

An eddy current detection probe and method capable of identifying any crack and direction around a hole, the probe comprising a cake-type detection coil with a central magnetic core, the magnetic core not only ensures accurate positioning, but also enhances magnetic fields inside and on the back of the hole by enhancing coil inductance to utilize a magnetic collection effect. The probe is further provided with three layers of exciting coils, the first layer of coil and the second layer of coil are arranged in an orthogonal mode, the included angle between the third layer of coil and the first layer of coil is 135 degrees, and efficient detection of cracks in any direction and recognition of any crack defect direction are achieved. The flexible support of the probe enables the probe to adapt to a curved surface structure, and the application range is widened. According to the detection method, an orthogonal difference technology is adopted, and the hole periphery defects are identified by using the symmetry of the hole structure, so that the detection sensitivity of the back and internal defects around the hole structure is remarkably improved. Compared with a traditional surface and near-surface defect eddy current detection technology, a more effective solution is provided for high-precision detection of the hole periphery structure through an innovative coil configuration and defect identification method.

Description

Technical Field

[0001] The present invention relates to an eddy current detection probe and a use method, and in particular to an eddy current detection probe and a method capable of identifying any cracks and directions around a hole. Background Art

[0002] Gas turbines are highly efficient internal combustion power machines that use a continuously flowing gas as a working fluid to drive the high-speed rotation of their impellers, converting fuel energy into useful work. They are widely used in power generation, oil and gas transportation, shipbuilding, heavy-duty locomotives, and other fields. Film hole technology plays a crucial role in this process. By forming a protective film layer on the surface of turbine blades, it effectively reduces blade temperature, improves blade heat resistance, and increases service life, thereby enhancing the blade's thermal protection. Furthermore, the use of film holes supports the gas turbine's high-efficiency energy conversion, ensures equipment reliability and safety, and adapts to changing operating conditions. These holes are typically manufactured using precision machining techniques such as electro-spark drilling and laser drilling to ensure that the hole shape, size, and distribution meet design requirements. However, this machining process can produce defects such as rough hole walls, inconsistent hole diameters, and cracks. These defects can affect the uniformity of the film and cooling efficiency, and even lead to premature blade failure. Summary of the Invention

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

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] An eddy current detection probe that can identify any crack and direction around a hole, the probe includes an excitation unit, a detection unit and a flexible support; the detection unit 1 consists of a pancake detection coil 2 and a cylindrical soft magnetic material 3 with one end inserted into the pancake detection coil 2; the flexible support 4 is an insulating soft material, and a wire groove 5 is arranged on the flexible support to lead out the wire of the pancake detection coil for extraction of the detection signal; the excitation unit consists of a first layer of excitation coil 6, a second layer of excitation coil 7 and a third layer of excitation coil 8. The excitation coils are printed on a flexible PCB circuit board, and adjacent layers of excitation coils are added between them. Polyimide film is used to reduce the mutual crosstalk between the excitation coils. Each layer of excitation coils is arranged in parallel to ensure that the excitation current of the circuit in the same direction is consistent. The second layer of excitation coil 7 is arranged 90° apart from the first layer of excitation coil 6, and the third layer of excitation coil 8 is arranged 135° apart from the first layer of excitation coil 6; the detection unit is embedded in the flexible support, and the upper surface of the pancake-shaped detection coil in the detection unit is coplanar with the upper surface of the flexible support, and the lower surface of the pancake-shaped detection coil in the detection unit is coplanar with the lower surface of the flexible support, and the lower surface is close to the test piece 10 to be detected, and 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 pancake-shaped detection coil 2 is consistent with the aperture 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 detection requirements.

[0007] The flexible support 4 enables the detection unit 1 to fit the surface of the curved test piece to the greatest extent; while ensuring that the detection unit 1 is fixed, the flexible support has a wire groove 5 arranged on the upper surface to reduce the lifting effect of the welding structure on the excitation coil and the effect of the welding part on the excitation eddy current field.

[0008] Sinusoidal excitation voltage signals are respectively passed through the first layer excitation coil 6 and the second layer excitation coil 7. The second layer excitation coil 7 excites an eddy current field around the hole, which is 90° to the direction of the eddy current field excited by the first layer excitation coil 6. At this time, 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 layer excitation coil 8 around the hole is perpendicular to the 45° crack direction, which meets the requirements of high-precision detection of cracks in any direction around the hole and effectively identifies the direction of the crack defect.

[0009] The soft magnetic material used in the cylindrical soft magnetic material 3 is a type of magnetic material with low coercive force and high magnetic permeability characteristics. During the detection process, this material can significantly enhance the magnetic field inside and on the back of the hole through the magnetic collection effect, so that the magnetic flux lines penetrate the hole structure more deeply, and introduce the eddy current field into the inner wall of the hole, so that the pancake-shaped detection coil 2 can capture the eddy current field changes on the back of the hole, thereby realizing accurate detection of defects.

[0010] The detection method of the eddy current detection probe capable of identifying any crack and direction around the hole can effectively detect defects in any direction. Since the detection unit has an inserted cylindrical soft magnetic material, the signal-to-noise ratio is effectively increased, and effective detection of internal and back cracks in any direction is achieved; the details are as follows:

[0011] Arrange the detection probes as required, insert the cylindrical soft magnetic material 3 in the detection unit 1 into the hole of the test piece to be tested, 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 applied to the first layer of excitation coil 6. At this time, the detection signal in the pancake-shaped detection coil 2 is V1. Then, a sinusoidal AC voltage signal is applied to the second layer of excitation coil 7. At this time, the detection signal in the pancake-shaped detection coil 2 is V2. Finally, a sinusoidal AC voltage signal is applied to the third layer of excitation coil 8. At this time, the detection signal in the pancake-shaped detection coil 2 is V3.

[0012] Since the hole structure of the test piece to be inspected is a completely symmetrical structure, the eddy current field is also completely symmetrical. When there is no defect, the detection signal should be equal, that is, V1=V2=V3. When there is a crack defect around the hole, the detection signal is not equal, that is, V1≠V2≠V3. The detection signals corresponding to the three layers of excitation coils are integrated and the detection signal is set to 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 detection, the average value of the detection signal is set to V0, that is, V0=(|V1+V2+V3|) / 3, and 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 layer of excitation coil 6 and the second layer of excitation coil 7 on the surface of the test piece are perpendicular to each other. The hole structure without circumferential crack defects is set as a control. The above detection process is repeated. The detection signals corresponding to the first layer of excitation coil 6 and the second layer of excitation coil 7 are taken as V n1 With V n2 At this time, the detection signal of the hole crack with the horizontal direction of θ in the eddy current field of the two layers of excitation coils satisfies tanθ=(V1-V n1 ) / (V2-V n2 ), which means 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 technology, can sensitively detect cracks and other defects that may exist around the air film holes, and is of great significance to ensuring the integrity of the blades and the long-term stable operation of the gas turbine. By performing eddy current testing on the air film holes of gas turbine blades, crack defects can be identified and repaired in a timely manner, thereby improving the operating efficiency and reliability of the gas turbine and extending the service life of the blades. The eddy current detection technology of the present invention effectively solves the problem of low sensitivity to cracks parallel to the eddy current field in traditional eddy current testing through innovative probe design. The present invention adopts three groups of excitation coils, supplemented by arranging coils in a 145° direction, which significantly improves the detection sensitivity of cracks in any direction around the hole. This design not only avoids the possibility of missed detection in traditional methods, but also identifies the direction of the crack, ensuring comprehensive and accurate detection of cracks in any direction, thereby greatly improving the accuracy and reliability of the detection. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0016] Figure 2 Schematic diagram of the detection unit structure of the present invention.

[0017] Figure 3 Schematic diagram of the flexible support of the present invention.

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

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

[0020] Figure 6 This is a schematic diagram of the wiring circuit of 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 of the three-layer excitation coil arranged at 145 degrees in parallel in the present invention.

[0022] Figure 8 This is a schematic diagram of the structural position of the hole to be tested during detection by the probe of the present invention. DETAILED DESCRIPTION

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

[0024] like Figure 1As shown, an eddy current detection probe that can identify any crack and direction around a hole includes an excitation unit, a detection unit and a flexible support. The detection unit is embedded in the flexible support. The upper surface of the pancake-shaped detection coil in the detection unit is coplanar with the upper surface of the flexible support. The lower surface of the pancake-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 to be detected. The excitation unit vertically covers the upper part of the detection unit.

[0025] like Figure 2 As shown, the detection unit 1 consists of a pancake-shaped detection coil 2 and a cylindrical soft magnetic material 3 with one end inserted into the pancake-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 the best match. Soft magnetic material is a type of magnetic material with low coercive force and high magnetic permeability. During the detection process, this material can significantly enhance the magnetic field inside and on the back of the hole through the magnetic collection effect. This design allows the magnetic flux lines to penetrate the hole structure more deeply, introducing the eddy current field into the inner wall of the hole, so that the pancake-shaped detection coil 2 can capture the eddy current field changes on the back of the hole and achieve accurate detection of defects. The inner diameter of the pancake-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, and a wire groove 5 is arranged on the flexible support to lead out the wires of the pancake-shaped detection coil for extraction of the detection signal. The flexible support can make the detection unit 1 fit the surface of the curved test piece to the greatest extent, and ensure that the first layer of excitation coil 6, the second layer of excitation coil 7 and the third layer of excitation coil 8 are lifted off the surface of the test piece in the curved structure working condition, so that the eddy current field generated by each excitation coil is uniform, reducing the impact of the curved surface structure on the detection. While ensuring that the pancake-shaped detection coil is fixed, the flexible support is provided with a wire groove 5 on the upper surface to reduce the lifting effect of the welding structure on the excitation coil and the impact of the welding part on the excitation eddy current field. The flexible support of the probe enables 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 horizontal parallel arrangement, and the second-layer excitation coil 7 and the first-layer excitation coil 6 are arranged in parallel at an angle of 90°. This arrangement effectively overcomes the problem that traditional single-direction coils are insensitive to parallel crack detection; the third-layer excitation coil 8 makes the angle between the wire and the first-layer excitation coil 6 be 135°. The application of the third-layer excitation coil effectively overcomes the situation that the eddy current field excited by the double-layer orthogonal excitation coil is insensitive to oblique 45° cracks, thereby realizing efficient detection of cracks in any direction and identification of any crack defect direction.

[0028] like Figure 5 As shown, the first layer of excitation coils 6 has the conductors arranged in parallel horizontally. When a sinusoidal AC signal is passed through the coils, 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 of excitation coils 7 has the wires arranged in vertical parallel. When a sinusoidal AC signal is passed through the coils, 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 of excitation coils 8 has the conductors arranged in parallel at 145°. When a sinusoidal AC signal is passed through the coils, a uniformly changing eddy current field at 145° is formed on the surface of the curved test piece.

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

[0032] The working principle of the present invention is as follows: The present invention is to achieve high-sensitivity detection of back cracks in any direction around the hole, and 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 detected, and the flexible support and excitation coil flexible PCB circuit board completely fit the surface of the test piece 10 to be detected.

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

[0035] Step 3: Since the hole structure of the test piece to be inspected 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 signal should be equal, that is, V1=V2=V3. When there is a crack defect around the hole, the detection signal is not equal, that is, V1≠V2≠V3. The detection signals corresponding to the three-layer excitation coil are integrated and the detection signal is set to V, V=|V1-V2|+|V1-V3|+|V2-V3|, to determine whether there is a defect. However, since the detection conditions cannot be perfectly met during actual detection, the average value of the detection signal is set to V0, that is, V0=(|V1+V2+V3|) / 3, and 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 by the first layer of excitation coil 6 and the second layer of excitation coil on the surface of the test piece are perpendicular to each other. The hole structure without circumferential crack defects is set as the control. The above detection process is repeated. The detection signals corresponding to the first layer of excitation coil 6 and the second layer of excitation coil 7 are taken as V n1 With V n2 At this time, the detection signal of the hole crack with the horizontal direction of θ in the eddy current field of the two layers of excitation coils satisfies tanθ=(V1-V n1 ) / (V2-V n2 ), we can get θ=arctan[(V1-V n1 ) / (V2-V n2 )], that is, the angle between the crack and the horizontal direction.

[0037] The detection method of this invention uses orthogonal differential technology, leveraging the symmetry of the hole structure to identify perimeter defects. This significantly improves the detection sensitivity for defects on the backside and within the perimeter of the hole structure. Compared with traditional eddy current detection technology for surface and near-surface defects, this invention, through its innovative coil configuration and defect identification method, provides a more effective solution for high-precision perimeter inspection of hole structures.

Claims

1. An eddy current detection probe capable of identifying any crack and direction around a hole, characterized in that: The probe comprises an excitation unit, a detection unit and a flexible support. The detection unit (1) is composed of a pancake-shaped detection coil (2) and a cylindrical soft magnetic material (3) with one end inserted into the pancake-shaped detection coil (2). The flexible support (4) is made of an insulating soft material. A wire groove (5) is arranged on the flexible support to lead out the wire of the pancake-shaped detection coil for extracting the detection signal. The excitation unit is composed of a first layer of excitation coils (6), a second layer of excitation coils (7) and a third layer of excitation coils (8). The excitation coils are printed on a flexible PCB circuit board. A polyimide film is added between adjacent layers of excitation coils. In order to reduce the mutual crosstalk between the excitation coils, each layer of excitation coils is arranged in parallel to ensure that the excitation current of the circuit in the same direction is consistent. The second layer of excitation coils (7) are arranged 90 degrees apart from the first layer of excitation coils (6), and the third layer of excitation coils (8) are arranged 135 degrees apart from the first layer of excitation coils (6). The detection unit is embedded in the flexible support, the upper surface of the pancake-shaped detection coil in the detection unit is coplanar with the upper surface of the flexible support, the lower surface of the pancake-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 detected, and the excitation unit vertically covers the upper part of the detection unit.

2. The eddy current detection probe capable of identifying any crack and direction around a hole 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 the best match. The inner diameter of the pancake-shaped detection coil (2) is consistent with the aperture 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 any crack and direction around a hole according to claim 1, characterized in that: The flexible support (4) enables the detection unit (1) to fit the surface of the curved test piece to the greatest extent; while the flexible support ensures that the detection unit (1) is fixed, a wire groove (5) is arranged on the upper surface to reduce the lifting effect of the welding structure on the excitation coil and the effect of the welding part on the generation of the excitation eddy current field.

4. The eddy current detection probe capable of identifying any crack and direction around a hole according to claim 1, characterized in that: Sinusoidal excitation voltage signals are respectively introduced into 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° from the direction of the eddy current field excited by the first excitation coil (6). At this time, 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, thereby meeting the requirements for high-precision detection of cracks in any direction around the hole and effectively identifying the direction of the crack defect.

5. The eddy current detection probe capable of identifying any crack and direction around a hole according to claim 1, characterized in that: The soft magnetic material used in the cylindrical soft magnetic material (3) is a type of magnetic material with low coercive force and high magnetic permeability. During the detection process, the material can significantly enhance the magnetic field inside and on the back of the hole through the magnetic collection effect, so that the magnetic flux lines penetrate the hole structure more deeply and introduce the eddy current field into the inner wall of the hole, so that the pancake-shaped detection coil (2) can capture the eddy current field changes on the back of the hole, thereby realizing accurate detection of defects.

6. A detection method for an eddy current detection probe capable of identifying any crack and direction around a hole according to any one of claims 1 to 5, characterized in that: This detection method can effectively detect defects in any direction. Since the detection unit has an inserted cylindrical soft magnetic material, the signal-to-noise ratio is effectively increased, and effective detection of internal and back cracks in any direction is achieved; the details are as follows: Arrange the detection probe as required, insert the cylindrical soft magnetic material (3) in the detection unit (1) into the hole of the test piece to be detected, and make the flexible support and the flexible PCB circuit board where the excitation coil is located completely fit the curved surface. First, a sinusoidal AC voltage signal is passed through the first layer of excitation coil (6), and the detection signal in the pancake-shaped detection coil (2) is V1. Then, a sinusoidal AC voltage signal is passed through the second layer of excitation coil (7), and the detection signal in the pancake-shaped detection coil (2) is V2. Finally, a sinusoidal AC voltage signal is passed through the third layer of excitation coil (8), and the detection signal in the pancake-shaped detection coil (2) is V3. Since the hole structure of the test piece to be inspected is a completely symmetrical structure, the eddy current field is also completely symmetrical. When there is no defect, the detection signal should be equal, that is, V1 = V2 = V3. When there is a crack defect around the hole, the detection signal is not equal, that is, V1≠V2≠V3. The detection signal corresponding to the three layers of excitation coils is integrated and the detection signal is set to 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 detection, the average value of the detection signal is set to V0, that is, V0=(|V1+V2+V3|) / 3, and 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 layer of excitation coil (6) and the second layer of excitation coil (7) on the surface of the test piece to be tested are perpendicular to each other. A hole structure without a hole crack defect is set as a control, and the above-mentioned detection process is repeated. The detection signal corresponding to the first layer of excitation coil (6) and the second layer of excitation coil (7) is taken as V n1 With V n2 At this time, the detection signal of the hole crack with a horizontal direction of θ in the eddy current field of the two layers of 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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