A detection probe for oblique cracks on rail surface and performance testing method thereof

Abstract

The present invention discloses a detection probe for oblique cracks on the surface of a rail and a performance testing method thereof. The detection probe for oblique cracks on the surface of a rail comprises: an excitation coil T arranged on a flexible printed circuit board; X and the receiving coil R X The excitation coil T X It includes a square coil arranged at the four corners of the flexible printed circuit board, the receiving coil R X It includes two "8" shaped coils R arranged orthogonally and connected end to end. x1 and R x2 , and four square coils surround two orthogonally arranged "8" shaped coils R x1 and R x2 The present invention innovatively designs a new type of detection probe, which is suitable for the complex morphology of rails. Through three-dimensional simulation and experimental tests, it is shown that it has high sensitivity and strong immunity to lift-off effect. It can solve the detection sensitivity and lift-off problems of crack direction detection on complex curved surfaces, and can provide guidance for the development of application-oriented equipment for real-time online monitoring and evaluation of rails based on eddy current detection.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing, in particular to a detection probe for oblique cracks on the surface of a rail and a performance testing method thereof. Background Art

[0002] Rolling contact fatigue (RCF) is a defect caused by repeated loading during the rolling contact of rails, which appears on the rail surface in the form of shelling and cracks. RCF cracks are directional cracks formed along the rail surface at an angle of 15° to 40°. These cracks will expand into the inside of the rail at 10° to 30°, which is one of the important reasons for rail breakage. This directional oblique crack is a potential challenge to train operation safety and reducing railway maintenance costs. Therefore, a sufficiently reliable detection method is needed to ensure the safe operation of trains.

[0003] So far, the application of non-destructive testing methods to the study of rail damage has a history of nearly 150 years. Among them, eddy current testing has a better detection effect on defects such as RCF than other methods. However, the detection sensitivity of eddy current testing is affected by factors such as lift-off, crack direction and permeability, which is a challenge for eddy current testing. Because when eddy current detects RCF cracks, due to the influence of vibration, the distance between the eddy current sensor and the rail is constantly changing, resulting in a decrease in the sensitivity of detecting oblique cracks on the complex shape surface of the rail head, which in turn leads to low detection accuracy and quality of oblique cracks on the complex shape surface of the rail head. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the existing rail detection, the present invention is proposed.

[0006] Therefore, the object of the present invention is to provide a detection probe for oblique cracks on the surface of a rail and a performance testing method thereof, which can improve the detection sensitivity and anti-lift-off effect of oblique cracks on the complex shape surface of the rail head.

[0007] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0008] A detection probe for oblique cracks on the surface of a rail, comprising: an excitation coil T arranged on a flexible printed circuit board X and the receiving coil R X ;

[0009] The excitation coil T X It includes a square coil arranged at the four corners of the flexible printed circuit board, the receiving coil R X It includes two "8" shaped coils R arranged orthogonally and connected end to end. x1 and R x2 , and four square coils surround two orthogonally arranged "8" shaped coils R x1 and R x2 .

[0010] As a preferred solution of the detection probe for oblique cracks on the rail surface described in the present invention, the square coil is double-layered.

[0011] As a preferred solution of the detection probe for oblique cracks on the surface of a rail described in the present invention, the flexible printed circuit board is made of multiple layers of flexible films.

[0012] A performance testing method for a detection probe for oblique cracks on a rail surface, the specific steps are as follows:

[0013] S1. Establish a three-dimensional simulation model of the detection probe, and test the detection sensitivity of the simulated detection probe at different excitation frequencies, the influence of different oblique crack directions and different lift-off distances on the detection sensitivity;

[0014] S2. Build an experimental platform to test the high sensitivity and high resistance to lift-off detection of oblique cracks on the rail surface in different directions through the experimental platform.

[0015] As a preferred solution of the performance testing method of a detection probe for oblique cracks on the rail surface described in the present invention, in step S1, the specific steps of testing the influence of the detection sensitivity of the simulated detection probe at different excitation frequencies on the detection sensitivity are as follows:

[0016] The excitation frequency is 2kHz-20kHz, the step is 2kHz, the simulation of different frequencies uses the same scanning parameters, the input current is 1A, and the amplitude response of the test simulated detection probe is between 2kHz and 2kHz.

[0017] As a preferred embodiment of the performance test method of a detection probe for oblique cracks on the surface of a rail according to the present invention, in step S1, the specific steps of testing the influence of the detection probe of the simulation on the detection sensitivity in different oblique crack directions are as follows: 6 oblique crack defects of different angles are established, with a length and depth of 15 mm and 4 mm, and angles of 15°, 30°, 45°, 60°, 75°, and 90°, respectively, and a unidirectional eddy current is generated by exciting a coil in the detection area;

[0018] The normalized amplitude responses of the simulated detection probe corresponding to oblique cracks in different directions are plotted, and the changing pattern of the response signal is analyzed.

[0019] As a preferred embodiment of the performance testing method of a detection probe for oblique cracks on the surface of a rail described in the present invention, in step S1, when testing the influence of different lifting distances of the simulated detection probe on the detection sensitivity, the simulated detection probe gradually changes the lifting distance from 0 mm to 0.8 mm, with a step size of 0.2 mm, and the excitation frequency is set to 17 kHz.

[0020] As a preferred embodiment of the performance testing method of a detection probe for oblique cracks on the rail surface of the present invention, in step S2, the specific steps of testing the high sensitivity of the detection probe to oblique cracks on the rail surface in different directions through an experimental platform are as follows:

[0021] The response signals of the detection probe to oblique cracks of different angles are collected through the adjustment circuit of the experimental platform;

[0022] The response signals of oblique cracks at different angles are normalized.

[0023] As a preferred embodiment of the performance test method of the detection probe for oblique cracks on the rail surface described in the present invention, in step S2, the specific steps of testing the detection probe for high resistance to lift-off through the experimental platform are as follows:

[0024] Extract the data of 30° oblique crack of the detection probe at different lift-off distances, the lift-off distance changes from 0mm to 2mm, and the step distance is 0.5mm;

[0025] The response signals of 30° inclined cracks at different lifting distances were normalized.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention innovatively designs a new type of detection probe, which is suitable for the complex morphology of rails, and through three-dimensional simulation and experimental tests, it is shown that the probe has high sensitivity and strong immunity to lift-off effect, and can solve the detection sensitivity and lift-off problems of crack direction detection on complex curved surfaces, and can provide guidance for the development of application-oriented equipment for real-time online monitoring and evaluation of rails based on eddy current detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in combination with the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0028] Figure 1 This is a schematic diagram of the structure of a detection probe for oblique cracks on the surface of a rail according to the present invention;

[0029] Figure 2 The excitation-receiving ECT probe model (a) and the ECT probe equivalent circuit diagram (b) of the detection probe for oblique cracks on the rail surface based on the TR model of the present invention;

[0030] Figure 3 The invention is a probe for detecting oblique cracks on the surface of a rail. X Schematic diagram of the simulation model of the coil in the x direction (a) and R X Schematic diagram of the simulation model of the coil in the y direction (b);

[0031] Figure 4 The invention is a probe for detecting oblique cracks on the surface of a rail. X Coil model of the coil in the x and y directions (a), the response of the coil in the x direction and the response of the coil in the y direction (b), and the final response after the difference between the two parts of the simulation results (c);

[0032] Figure 5 The normalized amplitude response (a) of a detection probe for oblique cracks on the rail surface under different excitation frequencies and the detection sensitivity (b) of the probe under different excitation frequencies of the present invention;

[0033] Figure 6 It is a schematic diagram of eddy current disturbance of cracks in different directions of a detection probe for oblique cracks on the surface of a rail according to the present invention;

[0034] Figure 7 The normalized amplitude response (a) of a detection probe for oblique cracks on the rail surface under different excitation frequencies and the detection sensitivity to oblique cracks in different directions (b) of the present invention;

[0035] Figure 8 The normalized amplitude response (a) of a detection probe for oblique cracks on the surface of a rail according to the present invention at different lift-off heights and the sensitivity (b) of the probe response amplitude at different lift-off heights;

[0036] Fig. 9 This is a PCB diagram of an excitation coil and a receiving coil of a detection probe for oblique cracks on a rail surface according to the present invention;

[0037] Fig.10 The signal conditioning circuit diagram of the present invention based on AD698;

[0038] Fig.11 Schematic diagram of the experimental platform of the present invention;

[0039] Fig.12Schematic diagram of defects detected by the experimental platform of the present invention;

[0040] Fig.13 It is a schematic diagram of the detection results of oblique cracks at different angles by a detection probe for oblique cracks on the surface of a rail according to the present invention;

[0041] Fig.14 The present invention is a schematic diagram of detection results of a detection probe for oblique cracks on the surface of a rail at different lifting distances. DETAILED DESCRIPTION

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0043] Secondly, the present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0045] The present invention provides a detection probe for oblique cracks on the surface of a rail and a performance testing method thereof, which can improve the accuracy and quality of detecting cracks on the surface of a rail head with complex shapes.

[0046] Example 1

[0047] See also Figure 1 The detection probe for oblique cracks on the rail surface comprises an excitation coil T arranged on a flexible printed circuit board. X and the receiving coil R X , the excitation coil T X It includes a square coil arranged at the four corners of the flexible printed circuit board, the receiving coil R X It includes two "8" shaped coils R arranged orthogonally and connected end to end. x1 and R x2 , and four square coils surround two orthogonally arranged 8" shaped coils R x1 and R x2 , when a sine wave signal is applied to the excitation coil T X When the probe is close to the sample with oblique cracks, the "8" shaped coil R X1 With R X2 The magnetic field changes in the opposite direction, causing the "8" shaped coil R X1 With R X2A reverse induced voltage is generated. Mainly, the mutual inductance change between Tx and one of the "8"-shaped Rx coils is positive, while the mutual inductance change between Tx and the other "8"-shaped Rx coil is negative. That is, the angle crack makes the change of eddy current in the x direction opposite to the change in the y direction, one increases and the other decreases, resulting in the change of indirect mutual inductance in the x direction opposite to the change in the y direction. The two "8"-shaped coils can sense the change of indirect mutual inductance in the x and y directions, respectively. Therefore, this structure can improve the detection sensitivity of oblique cracks. Preferably, in this embodiment, the square coil is double-layered, and the flexible printed circuit board is made of multiple layers of flexible film.

[0048] Among them, the detection principle of the new eddy current detection probe is as follows:

[0049] (1) To understand how the TR-based probe works, it can be equivalent to Figure 2 (b) Transformer model shown. The time-varying voltage generates a magnetic field (magnetic flux) in the excitation coil, and the excitation coil is coupled with the receiving coil in a direct and indirect manner through the magnetic flux. In the presence of a test piece, the following equation can be listed:

[0050]

[0051]

[0052]

[0053]

[0054] E1, E2 are the mutual inductance electromotive force of Tx and Rx, V S is the excitation voltage, M0 is the direct mutual inductance of Tx and Rx, M1 is the mutual inductance of Tx and Rx when passing through the test piece, l1, l2 are the self-coupling of Tx and Rx (coil) when passing through the test piece, L1, L2 are the self-inductance of Tx and Rx respectively, r1, r2 are the internal resistance of Tx and Rx, i1, i2 are the currents of Tx and Rx, Δr1, Δr2 are the changes of internal resistance affected by the test piece.

[0055] (2) The output voltage V0 of RX is:

[0056] Vo=R L ×i2=(L2+M1+l2)di2 / dt +(r2+Δr2)i2-M0di1 / dt

[0057] (3) The impedance change Δz caused by the coupling between the specimen and the probe is:

[0058] Δz=M1+l2+Δr2

[0059] (4) The change of eddy current in the x direction is opposite to that in the y direction, one increases and the other decreases. This causes the change of indirect mutual inductance in the x direction to be opposite to that in the y direction, which are expressed as M X , M Y Therefore, the effect of crack on indirect mutual inductance M1, ΔM, can be expressed as:

[0060] ΔM=M X -(-M Y )=M X +M Y

[0061] The self-inductance of the receiving coil and the mutual inductance M0 between the driving coil and the receiving coil are the main sources of background noise that limit the signal-to-noise ratio of the response signal. Therefore, the proposed probe can not only effectively suppress the common-mode components such as the peeling noise in the induced voltage, but also significantly improve the detection sensitivity of oblique cracks.

[0062] Example 2

[0063] In order to verify the performance of the detection probe for oblique cracks on the rail surface designed by the present invention, the present invention provides a performance testing method for the detection probe for oblique cracks on the rail surface, and the specific steps are as follows:

[0064] S1. Establish a three-dimensional simulation model of the detection probe, and test the detection sensitivity of the simulated detection probe at different excitation frequencies, the influence of different oblique crack directions and different lift-off distances on the detection sensitivity;

[0065] S2. Build an experimental platform to test the high sensitivity and high resistance to lift-off detection of oblique cracks on the rail surface in different directions through the experimental platform.

[0066] Specifically, the three-dimensional simulation is as follows: The simulation sets up the AC / DC module to analyze the electromagnetic field, and uses a three-dimensional rail head model, such as Figure 3 To simulate the characteristics of the flexible coil and reduce the influence of the coil thickness on the simulation, the simulation is divided into two simulations of the 8-shaped coil in two different directions (x direction and y direction), as shown in Figure 4 (a) shows the simulation results of the two parts. Figure 4 (b) The difference calculation is the actual response of the double-layer receiving coil, such as Figure 4 (c). Considering the consumption of computer time domain analysis, the AC / DC module uses frequency domain analysis. The detection sensitivity of the new probe at different frequencies and the influence of crack angle and lift-off on the detection sensitivity are analyzed through simulation. The simulation parameters are shown in the following table:

[0067]

[0068]

[0069] In step S1, the specific steps of testing the influence of the detection sensitivity of the simulated detection probe at different excitation frequencies on the detection sensitivity are as follows:

[0070] In order to evaluate the influence of different frequency input current on the probe response signal, the present invention uses 2kHz-20kHz as the excitation frequency, with a step of 2kHz. The simulation of different frequencies uses the same scanning parameters, and the input current is 1A. The defect is an oblique crack with an angle of 45° with the x-direction, a length of 15mm, a width of 0.5mm, and a depth of 4mm. The amplitude response of the test frequency between 2kHz and 2kHz is obtained through simulation, and the response normalization expression is:

[0071]

[0072] Where V defect is the amplitude response of the probe at different frequencies, V max and V min are respectively the maximum and minimum values ​​of the amplitude response of the probe at different frequencies.

[0073] In order to evaluate the response performance of the probe at different frequencies, the sensitivity of the designed probe is used as the evaluation standard. The probe detection sensitivity is expressed as:

[0074]

[0075] v norm_defect =max(V norm )-min(V norm )

[0076] V norm_defect is the normalized value of the probe amplitude response when there is a defect, V norm_non is the normalized value of the probe amplitude response when there is no defect. Figure 5 (a) is the normalized amplitude response of the probe under oblique cracks in different directions. Figure 5 (b) is the detection sensitivity of the probe to oblique cracks in different directions. It can be seen from the figure that when the excitation frequency is 17kHz, the detection sensitivity of the probe to oblique cracks is the highest.

[0077] In step S1, the specific steps of testing the influence of different oblique crack directions on the detection sensitivity of the detection probe of the simulation are as follows: 6 oblique crack defects with different angles are established, with a length and depth of 15 mm and 4 mm, and angles of 15°, 30°, 45°, 60°, 75°, and 90° respectively. The excitation coil in the detection area generates a unidirectional eddy current, such as Figure 6As shown in the figure, the presence of cracks changes the flow path of eddy currents, resulting in a decrease in the eddy current intensity in the y direction and an increase in the eddy current intensity in the x direction, which can be sensed by the 8-shaped coils in both the x and y directions. The probe response contains the eddy current disturbance information in the x and y directions, which can be used to characterize the orientation of the crack. The normalized amplitude response of the probe corresponding to oblique cracks in different directions is plotted to analyze the change pattern of the response signal.

[0078] The numerical simulation results of cracks in different directions are shown in Figure 2. Figure 7 (a) When the defect size is the same, the response of the designed probe in different directions is different. Figure 7 It can be seen from (a) that when the crack angle is between 15° and 75°, the detection signal presents a typical shape. As the crack angle increases, the shape of the detection signal changes, and the normalized amplitude response of the probe decreases. As the crack angle increases, when the unidirectional eddy current interacts with the crack, the eddy current in the x-direction no longer increases in one direction, but increases in both the positive and negative x-directions. Therefore, the induced voltage caused by the change in the eddy current in the x-direction gradually decreases, resulting in a decrease in the probe response. When the crack angle is 90°, the increase in eddy current intensity in the positive and negative x-directions is equal, so the induced voltage caused by the change in eddy current in the x-direction is basically zero. At this time, the response of the probe is mainly caused by the change in eddy current in the y-direction. Therefore, when the crack orientation is 90°, the response of the probe is minimal. From Figure 7 (b) It can be seen that the detection sensitivity of the probe decreases with the increase of the crack angle. As the crack angle increases, the induced voltage caused by the eddy current change in the x direction gradually decreases, while the induced voltage caused by the eddy current change in the y direction becomes the main part of the probe response. Therefore, when the crack angle is 90°, the detection sensitivity of the probe is the lowest.

[0079] In step S1, when testing the effect of different lifting distances on the detection sensitivity of the simulated detection probe, the simulated detection probe gradually changes the lifting distance from 0 mm to 0.8 mm with a step length of 0.2 mm, and the excitation frequency is set to 17 kHz. During the simulation process, the lifting distance changes from 0 mm to 0.8 mm with a step length of 0.2 mm. The excitation frequency is set to 17 kHz. Figure 8 (a) is the normalized amplitude response of the probe at different launch heights. Figure 8 (b) is the sensitivity of the probe response amplitude at different lift-offs. When the lift-off distances are 0.3 mm and 1.8 mm, the detection sensitivity of the designed probe fluctuates slightly, with the sensitivity changing from 1.787 to 2.125. The ideal sensitivity of the probe's response signal to the crack is 5.2 times the sensitivity fluctuation range caused by the lift-off effect, which means that the probe designed in the present invention can improve the effect of suppressing the lift-off effect.

[0080] In step S2, the experimental platform is constructed as follows: The PCB diagram of the excitation coil and the receiving coil is as follows: Fig. 9 As shown in the figure, in order to reduce the power consumption of the detection equipment, a signal conditioning circuit based on AD698 is designed. AD698 combined with an inductive sensor can convert the change of inductance into a DC voltage with high accuracy and high repeatability. Fig.10 As shown in the figure, the AD698 chip has a signal generation module that can generate a 20-20kHz sine wave signal. The sine wave signal is loaded on the excitation coil. Two 8-shaped coils are connected end to end as receiving coils. When the probe approaches a directional crack, R x1 and R x2 The magnetic field changes in the opposite direction, causing R x1 and R x2 The induced voltage is reversed. Considering that the induced voltage generated by the two "8"-shaped coils is weak and mixed with a large amount of power frequency interference and high-frequency interference, the present invention adds a filtering and amplification module. In AD698, the ratio of the detection signal to the excitation signal is output after filtering and amplification. The experimental platform consists of a computer, a regulating circuit, and a data acquisition module. The conditioning circuit of the experimental platform is based on AD698 and OPA1611 operational amplifier chips. AD698 generates a sinusoidal signal with a frequency of 17kHz and a peak-to-peak value of 15V as an excitation signal, which is controlled by a capacitor and a resistor. The excitation signal is used as the driving coil input of the new probe. The induced voltage output by the receiving coil is amplified and sent to AD698. Finally, the output of AD698 is the ratio of the detection signal (after amplification) to the excitation signal. The test piece is six groups of artificial groove defects with different angles on the surface of the rail head, which are cut by wire electrospark machining, and the wire diameter is 0.5mm. The defect length and depth are both 15mm and 4mm, and the angles are 15°, 30°, 45°, 60°, 75°, and 90° respectively. Defect detection and data collection are performed by scanning the rail head surface at a constant speed with the probe. The specific parameters of the probe are shown in the table:

[0081]

[0082]

[0083] In step S2, the high sensitivity of the detection probe to oblique cracks on the rail surface in different directions is tested by the experimental platform. The specific steps are as follows:

[0084] The response signals of oblique cracks at different angles are normalized, such as Fig.12As shown in (a), determine whether the new probe has good detection capabilities for cracks in different directions. The test results show that the probe has good detection capabilities for oblique cracks in different directions, and the shape of the detection signal is basically consistent with the excitation signal. The experimental results show that when the crack direction changes from 15° to 75°, the shape of the detection signal can remain consistent. When the crack direction is 90°, the response of the probe is the smallest. Because when the crack angle is 90°, the response of the probe is mainly contributed by the 8-shaped coil arranged in the x-direction, while the induced voltage change of the 8-shaped coil arranged in the y-direction is almost zero. In order to evaluate the detection sensitivity of the probe to cracks in different orientations, the average value of the amplitude response starting point of cracks in different directions is used as the response of the defect-free probe, and V sensitivity ,like Fig.12 As shown in (b), the detection sensitivity of the probe decreases with the increase of the crack angle. The main reason is that the induced voltage generated by the eddy current disturbance in the x direction gradually decreases. When the crack angle is 90°, the response of the probe only comes from the eddy current change in the y direction, and the detection sensitivity is the lowest.

[0085] The specific steps of testing the high resistance lift-off detection of the detection probe through the experimental platform are as follows: extract the data of the probe used to detect 30° oblique cracks at different lift-off distances, the lift-off distance changes from 0mm to 2mm, and the step distance is 0.5mm. Normalize the response signal, Fig.13 (a) is the detection result at different lift-off distances. The shape of the probe response is basically consistent with the simulation result. Fig.13 (b) It can be seen that the ideal sensitivity of the crack probe response signal is 2.9 times the sensitivity fluctuation range caused by the lift-off effect, which means that the differential configuration adopted by the probe can improve the immunity to the lift-off effect.

[0086] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A probe for detecting oblique cracks on the surface of a rail, characterized in that: include: The excitation coil T is arranged on the flexible printed circuit board X and receiving coil R X ; The excitation coil T X It includes a square coil arranged at the four corners of the flexible printed circuit board, the receiving coil R X It includes two "8" shaped coils R arranged orthogonally and connected end to end. x1 and R x2 , and four square coils surround two orthogonally arranged "8" shaped coils R x1 and R x2 .

2. A detection probe for oblique cracks on the rail surface according to claim 1, characterized in that: The square coil is double-layered.

3. A detection probe for oblique cracks on the rail surface according to claim 1, characterized in that: The flexible printed circuit board is made of multiple layers of flexible films.

4. A performance testing method for a detection probe for oblique cracks on a rail surface as claimed in any one of claims 1 to 3, characterized in that: The specific steps are as follows: S1. Establish a three-dimensional simulation model of the detection probe, and test the detection sensitivity of the simulated detection probe at different excitation frequencies, the influence of different oblique crack directions and different lift-off distances on the detection sensitivity; S2. Build an experimental platform to test the high sensitivity and high resistance to lift-off detection of oblique cracks on the rail surface in different directions through the experimental platform.

5. The performance testing method for a detection probe for oblique cracks on a rail surface according to claim 4, characterized in that: In step S1, the specific steps of testing the influence of the detection sensitivity of the simulated detection probe at different excitation frequencies on the detection sensitivity are as follows: The excitation frequency is 2kHz-20kHz, with a step of 2kHz. The simulations of different frequencies use the same scanning parameters, the input current is 1A, and the amplitude response of the test simulated detection probe at frequencies between 2kHz and 2kHz.

6. The performance testing method for a detection probe for oblique cracks on a rail surface according to claim 4, characterized in that: In the step S1, the specific steps of testing the influence of the detection probe of the simulation on the detection sensitivity in different oblique crack directions are as follows: 6 oblique crack defects with different angles are established, with a length and depth of 15 mm and 4 mm, and angles of 15°, 30°, 45°, 60°, 75°, and 90°, respectively, and the excitation coil in the detection area generates a unidirectional eddy current; The normalized amplitude responses of the simulated detection probe corresponding to oblique cracks in different directions are plotted, and the changing pattern of the response signal is analyzed.

7. The performance testing method for a detection probe for oblique cracks on a rail surface according to claim 4, characterized in that: In the step S1, when testing the effect of different lifting distances of the simulated detection probe on the detection sensitivity, the simulated detection probe gradually changes the lifting distance from 0 mm to 0.8 mm, with a step length of 0.2 mm, and the excitation frequency is set to 17 kHz.

8. The performance testing method for a detection probe for oblique cracks on a rail surface according to claim 4, characterized in that: In step S2, the specific steps of testing the high sensitivity of the detection probe to oblique cracks on the rail surface in different directions through the experimental platform are as follows: The response signals of the detection probe to oblique cracks of different angles are collected through the adjustment circuit of the experimental platform; The response signals of oblique cracks at different angles are normalized.

9. The performance testing method for a detection probe for oblique cracks on a rail surface according to claim 4, characterized in that: In step S2, the specific steps of testing the high resistance to lift-off detection by the test probe on the experimental platform are as follows: Extract the data of 30° oblique crack of the detection probe at different lift-off distances. The lift-off distance changes from 0 mm to 2 mm, and the step distance is 0.5 mm. The response signals of 30° inclined cracks at different lifting distances were normalized.

Images