An eddy current testing system and method for electrically conductive spherical structures

Abstract

The application provides a kind of eddy current detection system and method for conductive spherical surface structure, the system includes detection probe and detection radius auxiliary adjusting device.Detection probe is an absolute coil in Fermat spiral appearance, which can realize the surface detection of detection area, and the detection radius auxiliary adjusting device is used to set the protruding distance of the center of the detection coil.In actual detection, the protruding distance of the center of the detection coil is calculated by the radius of the spherical surface to be detected and the outer diameter of the coil, which improves the induced eddy current intensity near the coil center and the parallelism between the coil and the spherical surface to be detected, so that the difference signal between the detection signal and the detection signal of the defect-free place can be calculated to reduce the environmental noise interference, especially the lift-off noise signal.The probe has the advantages of being able to detect defects of conductive spherical surfaces with arbitrary curvature radius, fast detection speed and high adhesion to the spherical surface to be detected.

Description

TECHNICAL FIELD

[0001] The present application relates to an eddy current testing system and method for a conductive spherical structure, and belongs to the field of electromagnetic nondestructive testing. BACKGROUND

[0002] The conductive spherical structure is widely used in various industrial fields such as aerospace and machinery, such as solid rocket engine shell head, nozzle plug, pressure vessel wall, etc. The nozzle plug must ensure the airtightness of the engine during service. Therefore, in order to avoid internal gas leakage and ensure the normal work of each part, nondestructive testing is required during the manufacturing process.

[0003] The eddy current testing method is a nondestructive testing method based on the principle of electromagnetic induction, which has the advantages of non-contact, high detection sensitivity for the surface and near-surface of the conductive test object, high detection speed, no need for coupling agent, etc. It is suitable for defect detection of small thickness test objects and conductive test object surface and near-surface. The current eddy current testing probe in industry is mainly designed and developed for conductive flat plate structure and conductive pipe structure. For conductive spherical structure, small size conventional probe or flexible probe is often used. The small size conventional probe has low efficiency for detecting large size conductive spherical surface, and the parallelism between the coil bottom surface and the test spherical surface is low, resulting in large lift-off noise. The coil in the flexible probe can only be arranged in one layer, which limits the number of turns of the detection coil and the signal-to-noise ratio of the defect signal. Therefore, for defect detection of conductive spherical structure, it has good application prospect to develop a detection probe structure or detection system with high parallelism to the test spherical surface and low lift-off noise. SUMMARY

[0004] The technical problem of the present application is to overcome the shortcomings of the prior art and provide an eddy current testing system and method for a conductive spherical structure. The present application ensures stable lift-off in the detection area, increases the induced eddy current intensity below the center of the detection coil, and further improves the signal-to-noise ratio of the defect signal.

[0005] To achieve the above purpose, the present application adopts the following technical scheme:

[0006] The application discloses a kind of eddy current detection systems for conductive spherical surface structure, comprising: solenoid, fixing device, auxiliary positioning rod and top cover;Wherein, the outer side of the solenoid is connected with fixing device, for fixing solenoid outer side position invariable;The center of the solenoid is connected with top cover;Auxiliary positioning rod end is provided with protrusion, and the inside of top cover is cavity structure, the protrusion is movably connected with cavity structure, realize the axial location of auxiliary positioning rod and top cover, annular direction can be rotated;The fixing device is connected with auxiliary positioning rod, by rotating auxiliary positioning rod push or drag top cover, then adjust the axial length of solenoid, reach the purpose that solenoid and the high parallelism of the spherical surface to be measured, guarantee the consistency of detection area lift, improve signal-to-noise ratio;Eddy current detection method is used to detect conductive spherical surface structure.

[0007] In the above detection system, the solenoid as a whole presents Fermat solenoid appearance, the radius corresponding to the point with angle θ on the solenoid is r, Wherein, a is a constant.

[0008] In the above detection system, the protruding depth z of the solenoid center relative to the outer ring is adjusted by the auxiliary positioning rod, Wherein, R is the radius of the spherical surface to be measured, R s Is the outer radius of the solenoid.

[0009] In the above detection system, the positioning rod connecting groove is provided with internal threads, the auxiliary positioning rod is provided with external threads, and a scale value is provided on the auxiliary positioning rod, for displaying the value of the adjusted protruding depth z, when the solenoid is a planar structure, the protruding depth z is 0; when the solenoid is a downward convex structure, the protruding depth z is greater than 0; when the solenoid is an upward convex structure, the protruding depth z is less than 0.

[0010] In the above detection system, the number of turns N of the solenoid is greater than 1, which is determined according to the physical characteristic parameters of the detection object.

[0011] In the above detection system, a coil center connecting groove is provided on one end surface of the top cover, and the center coil of the solenoid is wrapped around the coil center connecting groove, for connecting the solenoid and the top cover.

[0012] In the above detection system, the fixing device is a symmetrical structure, and the two ends of the fixing device are connected with the two ends of the solenoid, respectively, and a positioning rod linking groove is provided in the middle; the auxiliary positioning rod passes through the positioning rod linking groove to realize the connection with the fixing device.

[0013] In the above detection system, the center of the solenoid is connected with the top cover through the coil center connecting groove.

[0014] In the above detection system, the eddy current detection method specifically includes:

[0015] Step S11, according to the radius R of the to-be-tested spherical surface 5 and the outer radius R of the solenoid 1 s The protruding depth z of the center of the solenoid 1 relative to the outer ring is calculated.

[0016] Step S12, the auxiliary positioning rod 3 is rotated to move the auxiliary positioning rod 3 relative to the positioning rod connecting groove 6 in the axial direction, to push the top cover 4 to move in the axial direction by a movement distance of the protruding depth z, and to further push the center of the solenoid 1 to move in the axial direction by the protruding depth z.

[0017] Step S13, the excitation signal 8 is first input into the solenoid 1, eddy currents are induced on the surface and the near surface of the to-be-tested spherical surface 5, the eddy currents are distributed in the form of Fermat solenoids, defects in the to-be-tested spherical surface 5 disturb the eddy currents, and further disturb the detection signals at the two ends of the solenoid 1.

[0018] Step S14, the detection signals collected by the solenoid 1 are differentiated from the detection signals when there is no defect, to obtain a defect signal.

[0019] Step S15, the defect signal is analyzed, defect characteristic quantities are extracted, a defect criterion is obtained, and the detection of the spherical surface structure is completed.

[0020] The application discloses a kind of eddy current detection methods for conductive spherical surface structure, comprising:

[0021] Step S1, according to the radius R of the to-be-tested spherical surface 5 and the outer radius R of the solenoid 1 s The protruding depth z of the center of the solenoid 1 relative to the outer ring is calculated.

[0022] Step S2, the auxiliary positioning rod 3 is rotated to move the auxiliary positioning rod 3 relative to the positioning rod connecting groove 6 in the axial direction, to push the top cover 4 to move in the axial direction by a movement distance of the protruding depth z, and to further push the center of the solenoid 1 to move in the axial direction by the protruding depth z.

[0023] Step S3, the excitation signal 8 is first input into the solenoid 1, eddy currents are induced on the surface and the near surface of the to-be-tested spherical surface 5, the eddy currents are distributed in the form of Fermat solenoids, defects in the to-be-tested spherical surface 5 disturb the eddy currents, and further disturb the detection signals at the two ends of the solenoid 1.

[0024] Step S4, the detection signals collected by the solenoid 1 are differentiated from the detection signals when there is no defect, to obtain a defect signal.

[0025] Step S5, the defect signal is analyzed, defect characteristic quantities are extracted, a defect criterion is obtained, and the detection of the spherical surface structure is completed.

[0026] Compared with the prior art, the application has the following advantages:

[0027] (1) The present invention mainly includes a Fermat spiral detection coil and related auxiliary adjustment device. Through the auxiliary adjustment device, the center of the detection coil can be pushed out by a certain distance. Compared with the existing traditional small-size planar coil or pen-type coil, the system of the present invention can improve the parallelism between the detection coil and the spherical surface to be tested, ensure the stability of the lifting in the detection area, and increase the intensity of induced eddy current below the center of the detection coil, thereby improving the signal-to-noise ratio of the defect signal, so as to realize eddy current detection of conductive concave spherical surface, conductive convex spherical surface and conductive planar surface and near surface.

[0028] (2) The detection coil of the Fermat spiral of the present invention is composed of a wire bundle, not a single-turn wire. That is, the number of turns N of the spiral coil of the present invention can be set to multiple turns, so the signal-to-noise ratio of the detected signal is higher than that of the flexible coil of the same size.

[0029] (3) This invention retains the advantages of traditional absolute coil detection, such as fast detection speed and high detection efficiency. Since there is only one coil, the required detection equipment is simple. The auxiliary positioning rod is engraved with scale values, making the detection process efficient and fast. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the position of the probe of the present invention relative to the spherical surface under test during service.

[0031] Figure 2 This is an exploded view of the components of the probe of the present invention;

[0032] Figure 3 This is a diagram showing the relative positions of the probe's helical coil and the concave spherical surface.

[0033] Figure 4 This is a diagram showing the relative positions of the probe's solenoid coil and the flat plate.

[0034] Figure 5 This is a diagram showing the relative positions of the probe's helical coil and the convex spherical surface. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] This invention discloses an eddy current detection system for conductive spherical structures, comprising: a solenoid coil 1, a fixing device 2, an auxiliary positioning rod 3, and a top cover 4; wherein, the outer side of the solenoid coil 1 is connected to the fixing device 2 to fix the outer side of the solenoid coil 1 in a fixed position; the center of the solenoid coil 1 is connected to the top cover 4; a protrusion is provided at the end of the auxiliary positioning rod 3, and the top cover 4 has a hollow structure inside, with the protrusion and the hollow structure being movably connected, realizing axial limiting of the auxiliary positioning rod 3 and the top cover 4, and allowing circumferential rotation; the fixing device 2 is connected to the auxiliary positioning rod 3, and by rotating the auxiliary positioning rod 3 to push or pull the top cover 4, the axial length of the solenoid coil 1 is adjusted to achieve high parallelism between the solenoid coil 1 and the spherical surface 5 to be tested, ensuring the consistency of lifting within the detection area and improving the signal-to-noise ratio; the conductive spherical structure is detected using an eddy current detection method.

[0037] The solenoid coil 1 exhibits a Fermat spiral shape overall, and its geometric governing equation is: The radius r is described as the radius corresponding to the point with angle θ on the helix, where a is a constant used to adjust the size of the coil. The protrusion depth z of the center of the helix coil 1 relative to the outer ring is adjusted by the auxiliary positioning rod 3. The value of the protrusion depth z is determined by the radius R of the spherical surface 5 to be measured and the outer radius R of the helix coil 1. s The calculation is as follows:

[0038] The positioning rod connecting groove 6 is provided with an internal thread, and the auxiliary positioning rod 3 is provided with an external thread. The auxiliary positioning rod 3 is provided with a scale value to display the value of the protrusion depth z. When the helical coil 1 is a planar structure, the protrusion depth z is 0; when the helical coil 1 is a downward convex structure, the protrusion depth z is greater than 0; when the helical coil 1 is an upward convex structure, the protrusion depth z is less than 0.

[0039] The number of turns N of the solenoid coil 1 is greater than 1, and is determined based on the physical characteristics of the object being tested. A raised coil center connecting groove 7 is provided on one end face of the top cover 4. The center coil of the solenoid coil 1 is wound around the coil center connecting groove 7 to connect the solenoid coil 1 to the top cover 4. The fixing device 2 has a symmetrical structure, with both ends connected to the two ends of the solenoid coil 1, and a positioning rod connecting groove 6 in the middle. The auxiliary positioning rod 3 passes through the positioning rod connecting groove 6 to connect with the fixing device 2. The center of the solenoid coil 1 is connected to the top cover 4 through the coil center connecting groove 7.

[0040] The eddy current testing method is as follows:

[0041] Step S11: Based on the radius R of the sphere 5 to be measured and the outer radius R of the solenoid 1 s The protrusion depth z of the center of solenoid coil 1 relative to the outer coil is calculated;

[0042] Step S12: Rotate the auxiliary positioning rod 3 to move the auxiliary positioning rod 3 axially relative to the positioning rod connecting groove 6, push the top cover 4 to move a protrusion depth z in the axial direction, and then push the center of the solenoid coil 1 to move a protrusion depth z in the axial direction.

[0043] Step S13: First, an excitation signal 8 is passed into the solenoid coil 1. Eddy currents are induced on the surface and near the surface of the spherical surface 5 to be tested. The eddy currents are distributed in the shape of a Fermat spiral. The defects in the spherical surface 5 to be tested disturb the eddy currents, thereby disturbing the detection signals at both ends of the solenoid coil 1.

[0044] Step S14: Differentiate the detection signal acquired by the solenoid coil 1 with the detection signal when there is no defect to obtain the defect signal;

[0045] Step S15: Analyze the defect signal, extract defect feature quantities, obtain defect criteria, and complete the detection of the spherical structure.

[0046] This invention discloses an eddy current detection method for conductive spherical structures, comprising:

[0047] Step S1: Based on the radius R of the sphere 5 to be measured and the outer radius R of the solenoid 1 s The protrusion depth z of the center of solenoid coil 1 relative to the outer coil is calculated;

[0048] Step S2: Rotate the auxiliary positioning rod 3 so that the auxiliary positioning rod 3 moves axially relative to the positioning rod connecting groove 6, pushing the top cover 4 to move a protrusion depth z in the axial direction, thereby pushing the center of the solenoid coil 1 to move a protrusion depth z in the axial direction.

[0049] Step S3: First, an excitation signal 8 is passed into the solenoid coil 1. Eddy currents are induced on the surface and near the surface of the spherical surface 5 to be tested. The eddy currents are distributed in the shape of a Fermat spiral. The defects in the spherical surface 5 to be tested disturb the eddy currents, thereby disturbing the detection signals at both ends of the solenoid coil 1.

[0050] Step S4: Differentiate the detection signal acquired by the solenoid coil 1 with the detection signal when there is no defect to obtain the defect signal;

[0051] Step S5: Analyze the defect signal, extract defect feature quantities, obtain defect criteria, and complete the detection of the spherical structure.

[0052] Example

[0053] like Figure 1 As shown in the figure, this embodiment discloses an eddy current detection system for a conductive spherical structure. The detection system includes a solenoid coil 1, a fixing device 2, an auxiliary positioning rod 3, and a top cover 4. The spherical surface to be measured 5 has a radius R = 500 mm. The solenoid coil 1 is made of wire wound according to the Fermat spiral shape path. The geometric control equation of the solenoid coil is: Macroscopically, it consists of a multi-turn wire bundle with a Fermat spiral shape. The solenoid coil 1 has a relatively high degree of parallelism with the spherical surface 5 to be measured. The outer side of the solenoid coil 1 is connected to the fixing device 2 to fix the position of the wire bundle on the outer side of the solenoid coil 1.

[0054] like Figure 2 As shown in the figure, this embodiment provides an eddy current detection system for a conductive spherical structure. The outer side of the solenoid coil 1 is connected to the fixing device 2 to fix the position of the wire bundle on the outer side of the solenoid coil 1. The center of the solenoid coil 1 is connected to the top cover 4 through the coil center connecting groove 7. The top cover 4 is a hollowed-out cylindrical shape and is connected to the bottom protrusion of the auxiliary positioning rod 3, realizing the axial limitation of the auxiliary positioning rod 3 and the top cover 4, and allowing circumferential rotation. The fixing device 2 and the auxiliary positioning rod 3 are threadedly connected to the positioning rod connecting groove 6. The positioning rod connecting groove 6 is provided with internal threads, and the auxiliary positioning rod 3 is provided with external cracks. The auxiliary positioning rod 3 is provided with a scale value to display the value of adjusting the protrusion depth z. By rotating the auxiliary positioning rod 3, the top cover 4 can be pushed or pulled, thereby adjusting the axial length of the solenoid coil 1, achieving a high parallelism between the solenoid coil 1 and the spherical surface 5 to be tested, ensuring the consistency of the lifting within the detection area, and improving the signal-to-noise ratio.

[0055] like Figure 3 As shown, when the detection spherical surface 5 is a concave spherical surface, the auxiliary positioning rod 3 is rotated, and the auxiliary positioning rod 3 moves axially downward relative to the positioning rod connecting groove 6, pushing the top cover 4 to generate a downward protrusion depth z in the axial direction, thereby pushing the center of the helical coil 1 to move the protrusion depth z on the axis, and the helical coil 1 presents a downward convex shape as a whole.

[0056] like Figure 4 As shown, when the detection sphere 5 is a flat plate, there is no need to rotate the auxiliary positioning rod 3, and the spiral coil 1 is a planar coil as a whole.

[0057] like Figure 5 As shown, when the detection spherical surface 5 is a convex spherical surface, the auxiliary positioning rod 3 is rotated, and the auxiliary positioning rod 3 moves axially upward relative to the positioning rod connecting groove 6, pulling the top cover 4 to generate an upward protrusion depth z in the axial direction, thereby pulling the center of the helical coil 1 to move the protrusion depth z on the axis, and the helical coil 1 presents an upward convex shape as a whole.

[0058] The working principle of this invention is as follows: This invention aims to detect and evaluate defects in the spherical surface under test.

[0059] exist Figure 1 In the embodiment shown, before detection, the radius R of the spherical surface 5 to be tested and the outer radius R of the solenoid coil 1 are determined. s The depth of the protrusion of the center of solenoid coil 1 relative to the outer coil was calculated. Rotate the auxiliary positioning rod 3 so that it moves axially relative to the positioning rod connecting groove 6, pushing the top cover 4 to move axially downward by 0.94mm, which in turn pushes the center of the solenoid coil 1 to move axially downward by 0.94mm.

[0060] During the detection process, an excitation signal 8 is first applied to the solenoid coil 1. Eddy currents are induced on the surface and near the surface of the spherical surface 5 under test, exhibiting a Fermat spiral shape. Defects in the spherical surface 5 disturb these eddy currents, thereby affecting the detection signals at both ends of the solenoid coil 1. Secondly, during the detection process, the detection signal acquired by the solenoid coil 1 is differentiated from the detection signal when there are no defects, yielding the final defect signal. This defect signal is then analyzed to extract defect feature quantities, and defect criteria are summarized. Because the solenoid coil 1 has a high degree of parallelism with the spherical surface 5 under test, the signal-to-noise ratio is improved.

[0061] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0062] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. An eddy current detection system for conductive spherical structures, characterized in that, include: The system comprises a solenoid coil (1), a fixing device (2), an auxiliary positioning rod (3), and a top cover (4). The outer side of the solenoid coil (1) is connected to the fixing device (2) to fix the outer side of the solenoid coil (1) in a fixed position. The center of the solenoid coil (1) is connected to the top cover (4). The auxiliary positioning rod (3) has a protrusion at its end, and the top cover (4) has a hollow structure inside. The protrusion is movably connected to the hollow structure, thereby achieving axial positioning of the auxiliary positioning rod (3) and the top cover (4) and circumferential rotation. The fixing device (2) is connected to the auxiliary positioning rod (3). By rotating the auxiliary positioning rod (3), the top cover (4) is pushed or pulled, thereby adjusting the axial length of the solenoid coil (1) to achieve high parallelism between the solenoid coil (1) and the spherical surface (5) to be tested, ensuring the consistency of the lifting within the detection area and improving the signal-to-noise ratio. The conductive spherical structure is tested using an eddy current detection method. The solenoid coil (1) generally exhibits a Fermat spiral morphology, with an angle of [missing information]. θ The radius corresponding to the point is r , ,in, a It is a constant; Adjust the protrusion depth of the center of the solenoid coil (1) relative to the outer ring by means of the auxiliary positioning rod (3). z , Where R is the radius of the sphere (5) to be measured. Let be the outer radius of the solenoid coil (1); The positioning rod connecting groove (6) is provided with an internal thread, the auxiliary positioning rod (3) is provided with an external thread, and a scale value is provided on the auxiliary positioning rod (3) to display the adjustment protrusion depth. z Value, when the solenoid (1) is a planar structure, the protrusion depth z The depth is 0; when the solenoid coil (1) has a convex structure, the protrusion depth is 0. z Greater than 0; when the solenoid coil (1) has an upward convex structure, the protrusion depth is greater than 0. z Less than 0; Number of turns of the solenoid coil (1) N A value greater than 1 is determined based on the physical characteristic parameters of the object being detected. The top cover (4) is provided with a coil center connection groove (7) on one end face, and the center coil of the solenoid (1) is wrapped around the coil center connection groove (7) to connect the solenoid (1) to the top cover (4); The fixing device (2) has a symmetrical structure. The two ends of the fixing device (2) are respectively connected to the two ends of the spiral coil (1), and a positioning rod connecting groove (6) is set in the middle. The auxiliary positioning rod (3) passes through the positioning rod connecting groove (6) to achieve connection with the fixing device (2). The center of the solenoid coil (1) is connected to the top cover (4) through the coil center connecting groove (7).

2. The eddy current detection system for a conductive spherical structure according to claim 1, characterized in that: The eddy current detection method is specifically as follows: Based on the radius of the sphere (5) to be measured R outer radius of the solenoid coil (1) The depth of the protrusion of the center of the solenoid coil (1) relative to the outer coil was calculated. z ; Rotate the auxiliary positioning rod (3) to move it axially relative to the positioning rod connecting groove (6), thereby pushing the top cover (4) to protrude axially. z The distance of movement, thereby driving the center of the solenoid (1) to move axially and protrude to a greater depth. z ; First, an excitation signal (8) is passed into the solenoid (1). Eddy currents are induced on the surface and near the surface of the spherical surface (5) to be tested. The eddy currents are distributed in the shape of Fermat spirals. Defects in the spherical surface (5) to be tested disturb the eddy currents, which in turn disturb the detection signals at both ends of the solenoid (1). The defect signal is obtained by differentiating the detection signal collected by the solenoid (1) with the detection signal when there is no defect. The defect signal is analyzed, defect feature quantities are extracted, defect criteria are obtained, and the detection of the spherical structure is completed.

3. A method for eddy current detection of conductive spherical structures, employing the eddy current detection system for conductive spherical structures as described in claim 1, characterized in that... include: Based on the radius of the sphere (5) to be measured R outer radius of the solenoid coil (1) The depth of the protrusion of the center of the solenoid coil (1) relative to the outer coil was calculated. z ; Rotate the auxiliary positioning rod (3) to move it axially relative to the positioning rod connecting groove (6), thereby pushing the top cover (4) to protrude axially. z The distance of movement, thereby driving the center of the solenoid (1) to move axially and protrude to a greater depth. z ; First, an excitation signal (8) is passed into the solenoid (1). Eddy currents are induced on the surface and near the surface of the spherical surface (5) to be tested. The eddy currents are distributed in the shape of Fermat spirals. Defects in the spherical surface (5) to be tested disturb the eddy currents, which in turn disturb the detection signals at both ends of the solenoid (1). The defect signal is obtained by differentiating the detection signal collected by the solenoid (1) with the detection signal when there is no defect. The defect signal is analyzed, defect feature quantities are extracted, defect criteria are obtained, and the detection of the spherical structure is completed.

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