An eddy current testing method and sensor for detecting surface cracks in different bolt hole diameters

Abstract

The present application relates to the field of nondestructive testing, in particular to a kind of eddy current testing method for detecting the surface crack of different bolt aperture, and the bolt aperture of different aperture size is detected using the eddy current testing sensor of conical frustum skeleton, the aperture of conical frustum skeleton gradually decreases from top to bottom, coil winding is radially wound on the conical frustum skeleton, and a plurality of coil windings are equidistantly arranged along the circumference of the conical frustum skeleton;When detecting, the eddy current testing sensor is placed on the bolt hole to be detected, and is slightly rotated, so that the coil winding scans the detection area and obtains the crack condition of the edge of the bolt hole to be detected.The present application solves the problem of frequent replacement of probe and parameter adjustment when detecting different aperture size of the hole to be detected, realizes that the problem of variable diameter can not be considered within a certain range, and the circumferential crack can be detected by slight rotation.The structure is simple, the adaptability is strong, the operation is convenient, the coil arrangement mode of annular array can form a variety of detection modes, and the detection flexibility is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nondestructive testing, in particular to a kind of eddy current testing method and sensor for detecting surface crack of different bolt aperture. BACKGROUND

[0002] In modern industrial equipment, there are a large number of bolt holes, for example, on an aircraft, there are many kinds of bolt holes with different diameters, for safety, they must be periodically or as the case may be for flaw detection, as one of the five conventional nondestructive testing methods, eddy current method is widely used for detecting such workpieces due to no need of coupling agent, no pollution, simple to use and fast. For aircraft, there are multiple specifications of bolt holes, which makes the detection personnel have to replace the corresponding size of the sensor, at the same time, the instrument parameters must also be adjusted, which is very troublesome in field application.

[0003] Based on the above problems, the present application is based on the prior art, and a kind of eddy current testing method and eddy current testing sensor for detecting surface crack of different bolt aperture are researched. SUMMARY

[0004] To solve the above problems, the present application provides an eddy current testing method and eddy current testing sensor for detecting surface crack of different bolt aperture, which is realized as follows:

[0005] An eddy current testing method for detecting surface crack of different bolt aperture is to insert a conical frustum-shaped eddy current testing sensor into the bolt hole to be detected, and at least one group of coil windings is arranged along the conical surface of the eddy current testing sensor, so as to obtain the crack signal of the edge of the bolt hole to be detected by using the corresponding adaptation of the conical surface of the eddy current testing sensor and the bolt hole with different aperture sizes. Further, the eddy current testing sensor used is provided with a plurality of groups of coil windings, which are arrayed along the conical surface to realize small-angle rotation of the eddy current testing sensor.

[0006] Further, the eddy current testing sensor with conical frustum-shaped skeleton is used to detect bolt holes with different aperture sizes, wherein the conical frustum-shaped skeleton gradually decreases from top to bottom, and the coil windings are radially wound on the conical frustum-shaped skeleton, and a plurality of coil windings are equidistantly arranged along the circumference of the conical frustum-shaped skeleton. During detection, the eddy current testing sensor is placed on the bolt hole to be detected, and is rotated by a fixed angle, so that the coil windings scan and cover the detection area to obtain the crack condition of the edge of the bolt hole to be detected.

[0007] Further, the specific steps are as follows:

[0008] S1: Design of eddy current detection sensor: according to the actual working condition, the number of coil windings is set, the coil windings are equidistantly arranged on the conical skeleton, the adjacent coil windings form an arc angle, the coil windings are correspondingly numbered, and each coil winding corresponds to a detection area;

[0009] S2: Placement of eddy current detection sensor: during detection, the eddy current detection sensor with a conical structure is placed with the smaller end of the ring opening downward and vertically inserted into the bolt hole to be detected;

[0010] S3: Actual detection: the eddy current detection sensor is rotated clockwise or counterclockwise, and the rotation angle is the arc angle formed between two coil windings; during rotation, the coil windings are synchronously scanned, and the scanned area covers all the detection areas of the edge of the bolt hole to be detected;

[0011] S4: Data acquisition and analysis: the eddy current detection signals of each coil winding are acquired, the crack conditions of the corresponding detection areas are analyzed, and the crack conditions of the edge of the bolt hole are positioned and quantitatively evaluated.

[0012] Further, in the design of the eddy current detection sensor in the S1 step, the coil windings are all detection coils or the coil windings are detection coils and excitation coils arranged in cross.

[0013] Further, when the coil windings are all detection coils, in the actual detection of the S3 step, a single coil winding detection mode is adopted to form absolute detection.

[0014] Further, when the coil windings are detection coils and excitation coils arranged in cross, in the actual detection of the S3 step, two adjacent groups of coil windings cooperate with each other to form differential detection, and during detection, the rotation angle is two arc angles; or, three adjacent groups of coil windings cooperate with each other to form a structure in which the middle is detected and the two ends are excited or a structure in which the middle is excited and the two ends are detected, to form D-P detection, and during detection, the rotation angle is two arc angles.

[0015] Further, before the actual detection in the S3 step, pre-detection can also be performed to measure the hole diameter of the bolt hole to be detected, determine the ring opening position of the conical structure eddy current detection sensor, and calculate the detection path.

[0016] The application also discloses an eddy current detection sensor for detecting surface cracks of different bolt hole diameters, which adopts the above detection method and comprises a shell, a skeleton and coil windings arranged on the skeleton.

[0017] Further, the middle part of the frustum-shaped framework is hollowed out, and a cylindrical chip accommodating groove is arranged, which is used for placing circuit components.

[0018] Further, a plurality of connecting fins are arranged between the frustum-shaped framework and the chip accommodating groove, which form a plurality of heat dissipation cavities between the frustum-shaped framework and the chip accommodating groove.

[0019] The connecting fins and the coil windings are arranged alternately, and one connecting fin is arranged between two adjacent coil windings.

[0020] Further, a wiring hole is arranged on the side wall of the chip accommodating groove, which is used for connecting the lead of the coil winding to the chip accommodating groove, and the wiring hole is arranged at a position opposite to the coil winding.

[0021] Compared with the prior art, the application can obtain the following technical effects:

[0022] 1. The application adopts a frustum-shaped coil framework, and forms an array eddy current coil like an umbrella by a special winding method, forms a new type of sensor, can adapt to the detection of bolt holes with different diameters, can effectively detect the cracks at the hole end, compared with the conventional detection method, during detection, the detection sensor does not need to be frequently plugged in and out and replaced, and the detection parameters do not need to be repeatedly adjusted, the detection efficiency is improved, and the service life of the matching detection element is improved.

[0023] 2. The coil winding is radially arranged on the frustum-shaped framework, a plurality of coil windings are equidistantly arranged along the circumference of the frustum-shaped framework, for detecting circumferential cracks, only a small rotation angle needs to be rotated, in special and complex working conditions, such as narrow detection space, the detection difficulty is greatly reduced.

[0024] 3. The array eddy current sensor formed by the frustum-shaped coil framework and the reflective winding method can not consider the problem of variable diameter within the range of the coil opening of the frustum-shaped framework, has the advantages of simple structure, strong adaptability and convenient operation, and the annular array coil arrangement mode can form a plurality of detection modes including absolute detection, differential detection and D-P detection, and improve the detection flexibility. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions of the application or the prior art in the prior art description, it is obvious that other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0026] Figure 1is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor.

[0027] Figure 2 is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor.

[0028] Figure 3 is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor.

[0029] Figure 4 is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor.

[0030] Figure 5 is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor. Figure 4 is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor.

[0031] Figure 6 is a schematic diagram of the detection using the conventional bolt hole eddy current testing sensor.

[0032] In the drawings:

[0033] 10 - test block;

[0034] 20 - bolt hole eddy current testing sensor;

[0035] 30 - eddy current testing sensor, 31 - upper shell, 32 - lower shell, 33 - frustoconical skeleton, 34 - chip accommodating groove, 341 - wiring hole, 35 - upper cover, 36 - connecting fin, 37 - heat dissipation cavity, 38 - coil winding, 39 - detection lead. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application.

[0037] In the description of the present application, the terms "first", "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0038] As shown in the drawings, Figure 1is a bolt hole eddy current testing standard block 10 and a special bolt hole eddy current testing sensor 20, because the eddy current method is an equivalent comparison method, so one or several artificial cracks need to be made on the same hole diameter of the general test block, and then compared with the natural crack during detection; and the crack usually appears at the end of the hole, the conventional detection generally needs to replace the probe and adjust the parameters, which affects the detection efficiency, and the traditional eddy current testing sensor needs to be rotated for one circle to complete the detection, which is often difficult to complete under special working conditions. Based on this, the present application improves the prior art and strives to invent a method for efficiently and accurately detecting cracks on the surface of different bolt hole diameters. The method is to insert a conical eddy current testing sensor into the bolt hole to be detected, and the conical eddy current testing sensor is provided with at least one group of coil windings along the conical surface, so as to utilize the corresponding adaptation of the conical surface of the eddy current testing sensor and the bolt hole with different hole diameters, thereby obtaining the crack signal of the edge of the bolt hole to be detected. Further, the eddy current testing sensor is provided with a plurality of groups of coil windings, which are arrayed along the conical surface to realize small-angle rotation of the eddy current testing sensor.

[0039] The specific embodiments of the present application are as follows:

[0040] Referring to the accompanying drawings Figure 2 The present application discloses an eddy current testing method for detecting cracks on the surface of different bolt hole diameters, which uses a conical skeleton 33 eddy current testing sensor 30 to detect bolt holes with different hole diameters, wherein the conical skeleton 33 gradually decreases from top to bottom, and the eddy current testing sensor 30 is provided with coil windings 38 radially wound on the conical skeleton 33, and a plurality of coil windings 38 are equidistantly arranged along the circumference of the conical skeleton 33. During detection, the eddy current testing sensor 30 is placed on the bolt hole to be detected, and is rotated by a fixed angle to enable the coil windings 38 to scan and cover the detection area to obtain the crack condition of the edge of the bolt hole to be detected. Further, the specific steps are as follows:

[0041] S1: Design of the eddy current testing sensor 30: according to the actual working condition, the number of coil windings 38 is appropriately increased, the distance between the coil windings is reduced, and the angle of rotation during detection is reduced, and at the same time, the distance between the coil windings should not be too dense to avoid interference between the coils. The coil windings 38 are radially wound on the skeleton, and a plurality of coil windings 38 are equidistantly arranged on the conical skeleton 33, and the adjacent coil windings form an arc angle, and the coil windings are numbered correspondingly, and each coil winding corresponds to a detection area;

[0042] S2: placement of the eddy current detection sensor 30: when detecting, the smaller end of the annular mouth of the eddy current detection sensor 30 with the frustum-shaped skeleton 33 is placed downward and vertically inserted into the bolt hole to be detected;

[0043] The detection positions of the corresponding frustum-shaped skeletons 33 are different when the hole diameters are different, and when a hole with a larger hole diameter is detected, the corresponding detection point is the end of the frustum-shaped skeleton 33 close to the annular mouth with a larger diameter; when a hole with a smaller hole diameter is detected, the corresponding detection point is the end of the frustum-shaped skeleton 33 close to the annular mouth with a smaller diameter.

[0044] S3: actual detection: rotate the eddy current detection sensor 30 clockwise or counterclockwise, and the rotation angle is the arc angle formed between the two coil windings 38; when rotating, the plurality of coil windings 38 are synchronously scanned, and the scanned area covers all the detection areas of the edge of the bolt hole to be detected;

[0045] S4: data acquisition and analysis: acquire the eddy current detection signals of each coil winding 38, analyze the crack conditions of the corresponding detection area, and through the numbering of the corresponding coil winding 38, the crack conditions of the edge of the bolt hole can be positioned and quantitatively evaluated, and the position and number of cracks can be effectively detected.

[0046] Further, in the design of the eddy current detection sensor of the S1 step, the coil windings 38 are all detection coils, or the coil windings are detection coils and excitation coils arranged in cross.

[0047] Further, when the coil windings 38 are all detection coils, in the actual detection of the S3 step, a single coil winding 38 detection mode is adopted to form absolute detection.

[0048] Further, when the coil windings 38 are detection coils and excitation coils arranged in cross, in the actual detection of the S3 step, two adjacent coil windings 38 cooperate with each other to form differential detection, and the rotation angle is two arc angles during detection; or, three adjacent coil windings 38 cooperate with each other to form a structure of providing excitation signals at both ends and detecting in the middle or a structure of providing excitation signals in the middle and detecting at both ends to form D-P detection, and at least two arc angles are rotated during detection.

[0049] The present application can not consider the variable diameter problem within the range of the annular mouth of the frustum-shaped skeleton, has simple structure, strong adaptability and is convenient to operate; the annular array coil arrangement mode can form various detection modes including absolute detection, differential detection and D-P detection, is suitable for various working conditions and can flexibly select the detection mode.

[0050] Further, before the actual detection of the S3 step, a pre-detection can also be carried out, the hole diameter of the bolt hole to be detected is determined in advance, the simulation of the defect-free and defective conditions is carried out, the parameters of the detection sensor are corrected; the position corresponding to the circle opening of the frustoconical skeleton is determined, the detection arc corresponding to different circle openings is measured through the rotation angle, and the detection path is measured.

[0051] Referring to the drawings Figures 3-5 As shown in the drawings, the application also discloses a vortex detection sensor for detecting surface cracks of different bolt hole diameters, which adopts the detection method and comprises a shell, a skeleton and a coil winding arranged on the skeleton. In the embodiment, the shell comprises an upper shell 31 and a lower shell 32, the upper shell 31 is matched with the frustoconical skeleton 33, and the lower shell 32 is in the form of a cover. In the embodiment, a wear-resistant non-conductive and magnetically conductive material is used to protect the coil winding 38 and improve the service life of the vortex detection sensor 30. In other embodiments, the shell can also be a protective film or other structures that can meet the coil protection requirement.

[0052] The skeleton is a frustoconical skeleton 33, and the coil winding 38 is radially arranged on the frustoconical skeleton 33. A plurality of coil windings 38 are equidistantly arranged along the circumference of the frustoconical skeleton 33. Advanced array coil technology is adopted. During detection, the operator only needs to slightly rotate a small angle to complete the detection process, that is, to realize complete scanning of a coil width through the crack position.

[0053] Further, the middle part of the frustoconical skeleton 33 is hollow, and a cylindrical chip accommodating groove 34 is arranged. In other embodiments, the chip accommodating groove 34 can also have other shapes as long as it can meet the chip placement and containing requirements. In the embodiment, the cylindrical groove makes the overall structure more coordinated and reasonable. The chip accommodating groove is used for placing and protecting circuit components. In the embodiment, an upper cover 35 is further arranged at the opening of the chip accommodating groove 34. The center of the upper cover 35 is provided with a plug-in port corresponding to a detection lead 39, so that the plug-in and plug-out are more convenient.

[0054] Further, a plurality of connecting fins 36 are arranged between the frustoconical skeleton 33 and the chip accommodating groove 34, the connecting fins 36 form a plurality of heat dissipation cavities 37 between the frustoconical skeleton 33 and the chip accommodating groove 34, and the connecting fins 37 and the coil windings 38 are arranged alternately, that is, one connecting fin 37 is arranged between adjacent two coil windings 38. The connecting fins 37 connect the frustoconical skeleton 33 and the chip accommodating groove 34 into an integrated whole and have a shielding and isolating effect, so as to avoid mutual interference of detection signals between adjacent two coil windings 38 or magnetic saturation caused by too dense coil winding connection. In the embodiment, the frustoconical skeleton 33, the connecting fins 36 and the chip accommodating groove 34 are integrally formed by injection molding or 3D printing.

[0055] Further, a wiring hole 341 is formed in the side wall of the chip accommodating groove 34, and is used for connecting the lead of the coil winding 38 into the chip accommodating groove 34. The wiring hole 341 is arranged at a position corresponding to the coil winding 38, i.e. between the two connecting fins 36. In addition, a wear-resistant non-conductive and magnetically conductive material can be used between the coils to improve the service life of the sensor.

[0056] The preferred embodiments of the present application have been described above with the aid of drawings and are not intended to limit the present application. Various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the present application.

Claims

1. An eddy current testing method for detecting surface cracks in different bolt hole diameters, characterized by, A frustum-shaped eddy current sensor is inserted into the bolt hole to be tested. The frustum-shaped eddy current sensor has at least one set of coil windings along the conical surface. By utilizing the corresponding adaptation of the conical surface of the eddy current sensor to bolt holes of different diameters, the crack signal at the edge of the bolt hole to be tested can be obtained. An eddy current sensor with a frustum-shaped frame is used to inspect bolt holes of different sizes. The frustum-shaped frame gradually decreases in size from top to bottom. The eddy current sensor has coil windings radially wound on the frustum-shaped frame, with several coil windings equidistantly spaced along the circumference of the frame. During inspection, the eddy current sensor is placed on the bolt hole to be inspected and rotated at a fixed angle, allowing the coil windings to scan and cover the inspection area to obtain information on cracks at the edge of the bolt hole. The specific steps are as follows: S1: Design of eddy current detection sensor: Set the number of coil windings according to the actual working conditions, and set the coil windings equally at intervals on the frustum-shaped frame. An arc angle is formed between adjacent coil windings. The coil windings are numbered accordingly, and each coil winding corresponds to a detection area. S2: Placement of eddy current detection sensor: During testing, place the eddy current detection sensor with the smaller end of the cone-shaped frame facing down and vertically insert it into the bolt hole to be tested. S3: Actual detection: Rotate the eddy current detection sensor clockwise or counterclockwise. The rotation angle is the arc angle formed between the two coil windings. During rotation, several coil windings are scanned simultaneously, and the scanned area covers the entire inspection area of ​​the edge of the bolt hole to be inspected. S4: Data Acquisition and Analysis: Acquire eddy current detection signals for each coil winding, analyze the crack conditions in the corresponding detection area, and locate and quantitatively evaluate the crack conditions at the bolt hole edges.

2. The method of claim 1, wherein the method is characterized by: The eddy current detection sensor used has multiple sets of coil windings, which are arranged in an array along the conical surface to enable the eddy current detection sensor to rotate at a small angle for inspection.

3. The method of claim 2, wherein the method is a method of detecting surface cracks in different bolt hole diameters. In the design of the eddy current detection sensor in step S1, all the coil windings are detection coils or the coil windings are a combination of detection coils and excitation coils.

4. The method of claim 3, wherein the method is characterized by: When all the coil windings are detection coils, in the actual detection of step S3, a single coil winding detection method is adopted to form an absolute detection.

5. The method of claim 3, wherein the method is characterized by: When the coil windings are configured with a combination of detection and excitation coils, in the actual detection of step S3, adjacent sets of coil windings cooperate to form differential detection. During detection, the rotation angle is two radians; or... The three adjacent sets of coil windings cooperate with each other to form a structure in which excitation signals are generated at both ends and detection is performed in the middle, or a structure in which detection is performed at both ends and excitation signals are generated in the middle, forming a DP-type detection. During detection, the rotation angle is two radian angles.

6. An eddy current testing sensor for detecting surface cracks in different bolt hole diameters comprising a housing, a skeleton and a coil winding wound around the skeleton, characterized in that, The frame is a frustum-shaped frame, and the coil windings are radially wound on the frustum-shaped frame. Several coil windings are equidistantly arranged along the circumference of the frustum-shaped frame. The frustum-shaped frame has a hollow center and is provided with a cylindrical chip receiving slot, which is used to place circuit components. A plurality of connecting fins are arranged between the frustum-shaped skeleton and the chip accommodating groove, and the connecting fins form a plurality of heat dissipation cavities between the frustum-shaped skeleton and the chip accommodating groove. The connecting fins and the coil windings are arranged alternately, and one connecting fin is arranged between two adjacent coil windings.

7. The eddy current testing sensor for detecting surface cracks of different bolt hole diameters according to claim 6, characterized in that, A wire hole is arranged on the side wall of the chip accommodating groove, and the wire hole is used for connecting the lead of the coil winding to the chip accommodating groove. The wire hole is arranged at a position opposite to the coil winding.

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