A method for detecting rail oblique peeling crack damage based on ultrasonic creeping wave

Abstract

This invention discloses a method for detecting oblique spalling cracks in rails based on ultrasonic creeping waves, belonging to the field of data processing and display technology in rail non-destructive testing. The invention proposes: initializing a one-transmitter-one-receiver mode and sound path conversion parameters based on the first critical angle; performing relative sensitivity calibration and flaw detection sensitivity benchmark compensation calibration; acquiring echo signals on-site using a combination of sawtooth and fixed-point rotation; the instrument converts the echo time difference within the gate according to preset parameters, directly displaying the horizontal distance, depth, and sound path; and determining the damage level based on a depth threshold. This invention deeply integrates the physical mechanism of creeping wave acoustic field with data processing logic, achieving effective separation and display of shallow-depth oblique crack echoes and initial pulses, as well as accurate damage conversion and positioning. It exhibits strong resistance to surface interference and significantly improves the identification and classification capabilities of early-stage micro-cracks.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology for rails, and in particular to a method for detecting oblique peeling cracks in rails based on ultrasonic creeping waves. Background Technology

[0002] Under the action of wheel-rail contact force, the rail head tread of high-speed railway is prone to oblique peeling cracks. This damage has a "V" shape and the depth is mostly within the target depth range. It is characterized by being difficult to detect in the early stage, developing rapidly in the middle stage, and being difficult to eliminate in the later stage. It is highly concealed and poses a great safety hazard.

[0003] Currently, traditional shear wave testing technology has significant limitations in detecting this type of oblique line-shaped peeling crack:

[0004] Shallow damage waves are masked: When the damage depth is shallow (in the early stage of micro-cracks), its reflected echo is close to the starting pulse on the time axis, causing the damage wave to be masked by the starting pulse at the display end, making it impossible to effectively detect and identify early micro-cracks.

[0005] Surface interference leads to complex waveforms: Conventional ultrasonic testing is easily affected by structural interference such as scratches, unevenness, and dents on the surface of the rail, generating a large amount of noise. The waveforms on the display end are complex, making it difficult to accurately extract echo data of crack depth and horizontal position.

[0006] Lack of targeted data processing closed loop: Existing detection methods mostly rely on general parameters and do not build dedicated data processing logic from signal acquisition and time difference conversion to direct reading of results for the physical and acoustic characteristics of oblique cracks, resulting in insufficient positioning accuracy and reliability. Summary of the Invention

[0007] To overcome the shortcomings of existing methods for detecting oblique spalling cracks in rails, such as the easy obscuring of shallow damage waves, poor signal processing anti-interference ability, and difficulty in accurate conversion and positioning, this invention provides a rail oblique spalling crack damage detection method based on ultrasonic climbing waves, which achieves accurate conversion, display, and grade determination of damage.

[0008] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for detecting oblique peeling cracks in rails based on ultrasonic creeping waves, comprising the following data processing and display steps:

[0009] Step S1, parameter initialization settings: Configure the one-transmitter-one-receiver detection mode in the ultrasonic flaw detector, and input the data processing parameters for sound path conversion. The parameters include: full-scale sound path display range covering the detection depth of the oblique crack target, the climbing wave velocity in the rail, the refraction angle set based on the first critical angle, the probe leading edge length, and the probe delay.

[0010] Step S2, Sensitivity reference data calibration:

[0011] Relative sensitivity calibration: Obtain the noise level data when the instrument is not connected to the probe and record it as the first sensitivity value; obtain the vertical echo data of the climbing wave probe at the specified position of the standard test block and record it as the second sensitivity value; calculate the relative sensitivity; and select the benchmark data that meet the preset relative sensitivity threshold.

[0012] Flaw detection sensitivity calibration: Obtain the echo signal of the probe at the predetermined depth of the transverse hole of the standard test block, adjust its amplitude to the reference wave height and record it as the reference value, combine the on-site rail surface condition data and add the compensation amount on the reference value to generate the on-site scanning sensitivity threshold;

[0013] Step S3, On-site signal acquisition and processing: Place the climbing wave probe on the rail head and acquire ultrasonic reflected echo signals by combining sawtooth scanning with fixed-point rotating probe.

[0014] Step S4, Damage Data Processing and Display: The collected echo signal is extracted by the gate. The instrument internally calculates the time difference of the echo signal inside the gate according to the climbing wave velocity, refraction angle and probe delay parameters preset in step S1, and directly displays the horizontal distance from the damage to the probe tip, damage depth and sound path data on the display screen.

[0015] Step S5, Damage Level Determination: Determine the damage level based on the preset grading range of the damage depth data output by the display screen; wherein, when the damage depth is greater than or equal to the first preset depth threshold, it is determined to be a minor injury, and when the damage depth is greater than the second preset depth threshold, it is determined to be a minor injury with potential for development.

[0016] In some specific embodiments, in step S2, the relative sensitivity calibration specifically involves: adjusting the instrument so that the noise level when the probe is not connected is lower than the preset ratio of the full screen width, placing the probe on the vertical surface of the standard test block to adjust the echo to the reference wave height, and ensuring that the signal-to-noise ratio of the extracted echo signal meets the preset signal-to-noise ratio threshold.

[0017] In some specific embodiments, step S2, after the flaw detection sensitivity calibration is completed, also includes a detection performance verification step: the highest echo signal is extracted using a deep transverse hole test block and covered with a gate, and the horizontal distance and depth data displayed by the instrument are compared with the actual values ​​of the test block. When the displayed data is consistent with the actual values, the verification is completed.

[0018] In some specific embodiments, step S1 further includes setting auxiliary signal processing parameters: damping, repetition frequency, transmission voltage, square wave width, narrow bandwidth, and full-wave detection mode, in order to optimize the signal-to-noise ratio of shallow-depth oblique crack echoes.

[0019] In some specific embodiments, the method can detect damage depths ranging from early microcrack depths to the maximum target depth of oblique cracks, and the damage wave and initial pulse are displayed separately in the shallow depth range.

[0020] In some specific embodiments, step S5, the damage level determination also includes a graded determination based on the size data of the damaged piece: when the size of the piece is less than or equal to a third preset size threshold, it is determined to be level I; when the size of the piece is greater than the third preset size threshold and less than or equal to a fourth preset size threshold, it is determined to be level II; and when the size of the piece is greater than the fourth preset size threshold, it is determined to be level III.

[0021] The beneficial effects of this invention are as follows: It eliminates the problem of initial pulse masking from the mechanism: By configuring the refraction angle based on the first critical angle and the corresponding sound velocity and delay parameters, a special sound path conversion logic for oblique cracks is constructed, so that the echo time difference of shallow cracks can be accurately converted by the instrument and effectively separated from the initial pulse at the display end, breaking through the blind zone of traditional shear wave shallow depth detection.

[0022] Strong resistance to surface interference and intuitive waveform display: The creeping wave is less affected by scratches and dents on the rail surface. Combined with the signal processing settings of narrow bandwidth and full-wave detection, the extracted echo signal has a high signal-to-noise ratio and the displayed waveform is simple and free of noise.

[0023] Closed-loop data processing ensures precise positioning and judgment: Seamless integration of parameter initialization, multi-level sensitivity benchmark calibration, and gate direct-reading conversion of depth and horizontal distance display logic enables full-process quantitative processing from signal acquisition to level determination, avoiding human reading errors and ensuring convenient and efficient on-site operation. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram illustrating the performance verification of the present invention.

[0026] Figure 2 This is a schematic diagram of the on-site sawtooth scanning and rotating scanning methods;

[0027] Figure 3 This is a schematic diagram of the on-site scanning trajectory and damage detection;

[0028] Figure 4 This is a flowchart of a method for detecting oblique peeling cracks in rails based on ultrasonic creeping waves, according to the present invention.

[0029] 1-Ultrasonic probe; 2-Test block; 3-Rule; 4-Railway tread; 5-Oblique crack on rail tread; 6-Probe scanning trajectory; 7-Ultrasonic probe. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0033] Reference Figures 1-4 This is one embodiment of the present invention, which provides a method for detecting oblique peeling cracks in rails based on ultrasonic creep waves, including the following data processing and display steps:

[0034] Step S1, parameter initialization settings: Configure the ultrasonic flaw detector in a one-transmitter-one-receiver detection mode and input the data processing parameters for sound path conversion. The parameters include: full-scale sound path display range covering the detection depth of the oblique crack target, the climbing wave velocity in the rail, the refraction angle set based on the first critical angle, the probe leading edge length, and the probe delay.

[0035] The specific steps are as follows: Select a general-purpose ultrasonic flaw detector or a rail weld flaw detector, paired with a dual-chip, one-transmitter, one-receiver climbing wave probe, connect the equipment and turn it on. Call the one-transmitter, one-receiver detection mode in the instrument (such as dual K1 channels or a dedicated climbing wave channel). Input the data processing parameters for sound path conversion. These parameters serve as the conversion benchmark for the instrument to convert the electrical signal time difference into spatial distance: Set the full-scale sound path display range covering the detection depth of the oblique crack target; in this embodiment, it is set to 50mm, which corresponds to a maximum detection depth covering 12mm, perfectly matching the distribution characteristics of oblique cracks, which are mostly within 10mm; Set the climbing wave velocity in the rail; in this embodiment, it is set to 5850m / s; Set the refraction angle based on the first critical angle; in this embodiment, it is set to 76° to excite climbing waves in the rail that are less affected by surface interference and sensitive to near-surface vertical cracks; Set the probe leading edge length; in this embodiment, it is 10mm; Set the probe delay; in this embodiment, it is 4.5μs. Meanwhile, auxiliary signal processing parameters were configured to optimize the signal-to-noise ratio of shallow-depth oblique crack echoes: damping was set to 400Ω, repetition frequency to 400Hz, transmission voltage to 200V, square wave width to 120ns, and narrow bandwidth and full-wave detection mode were selected to effectively suppress noise interference caused by scratches on the rail surface.

[0036] Step S2, Sensitivity reference data calibration:

[0037] Relative sensitivity calibration: Obtain the noise level data when the instrument is not connected to the probe and record it as the first sensitivity value; obtain the vertical echo data of the climbing wave probe at the specified position of the standard test block and record it as the second sensitivity value; calculate the relative sensitivity; and select the benchmark data that meet the preset relative sensitivity threshold.

[0038] Flaw detection sensitivity calibration: Obtain the echo signal of the probe at the predetermined depth of the transverse hole of the standard test block, adjust its amplitude to the reference wave height and record it as the reference value, and combine the on-site rail surface condition data to add a compensation amount on the reference value to generate the on-site scanning sensitivity threshold.

[0039] (1) Relative sensitivity calibration: With the instrument disconnected from the probe, adjust the sensitivity to the maximum, set the suppression to zero / off, and adjust it until the noise level is lower than the preset ratio of the full screen (10% in this embodiment). Record the sensitivity value S0 at this time. Place the climbing wave probe 10mm away from the H6 facade of the CSK-IA test block, and adjust the facade echo to the reference wave height (80% of the full screen in this embodiment). Ensure that the signal-to-noise ratio of the extracted echo signal meets the preset signal-to-noise ratio threshold (≥24dB in this embodiment). Record the sensitivity value S1. Calculate the relative sensitivity (attenuation type S=S1-S0, gain type S=S0-S1), and select the data that meets the preset relative sensitivity threshold (≥30dB in this embodiment) as the benchmark to ensure that the instrument has the hardware foundation to capture the weak signal of early micro cracks.

[0040] (2) Calibrating the flaw detection sensitivity: Place the probe on the WGT-3 test block and probe the 10mm deep Φ3 transverse hole. Adjust the echo to 80% of the reference wave height and record the sensitivity as the reference value. Combine the on-site rail surface condition data and add the compensation amount (0~6dB in this embodiment) on the basis of the reference value to generate the on-site scanning sensitivity threshold to offset the on-site surface coupling attenuation.

[0041] (3) Detection performance verification: combined with Figure 1 As shown, the CSK-ⅡA-1 test block 2 was used for verification. A 5mm deep Φ3 horizontal hole was probed. The ultrasonic probe 1 was moved to find the highest echo and covered with a gate. The position was determined with the help of a ruler 3. The horizontal distance and depth data displayed by the instrument based on the parameter conversion in step S1 were verified to be consistent with the actual values ​​of the test block, thus proving the accuracy of the sound path conversion logic.

[0042] Step S3, On-site signal acquisition and processing: Place the climbing wave probe on the rail head and acquire ultrasonic reflected echo signals by combining sawtooth scanning with fixed-point rotating probe.

[0043] This step specifically involves: combining Figure 2 and Figure 3 As shown, at the location of the oblique crack in the smooth band area of ​​the rail head tread, the ultrasonic probe 7 is placed on the rail tread 4, and a sawtooth scan is used for large-area coverage search. When abnormal echoes of damage are detected, a fixed-point rotating probe scan method (i.e., moving and rotating along the probe scan trajectory 6) is used to find the deepest highest echo signal of the oblique linear crack 5 on the rail tread. This composite scanning method, combined with the directivity of the climbing wave acoustic field, can maximize the reception of reflected signals from the "V"-shaped crack that is oblique to the tread.

[0044] Step S4, Damage Data Processing and Display: The collected echo signal is extracted by the gate. The instrument internally calculates the time difference of the echo signal inside the gate according to the climbing wave velocity, refraction angle and probe delay parameters preset in step S1, and directly displays the horizontal distance from the damage to the front end of the probe, damage depth and sound path data on the display screen.

[0045] This step is specifically as follows: Cover the highest echo of the damage with a gate. According to the conversion parameters such as the creeping wave sound velocity (5850 m / s), refraction angle (76°), and probe delay (4.5 μs) preset in step S1 inside the instrument, geometric conversion processing is performed on the time difference between the echo signal inside the gate and the initial pulse, and the horizontal distance L from the damage to the front end of the probe, the damage depth H, and the acoustic path are directly displayed on the display screen. Since the conversion system set in this invention is based on the characteristics of the creeping wave sound field, after the time difference of the damage echo at a shallow depth (such as ≤ 6 mm) is converted, effective spatial separation from the initial pulse is achieved at the display end, completely solving the problem of the display blind area where the traditional K2.5 transverse wave damage wave cannot be distinguished within the initial pulse.

[0046] Step S5, damage level determination: Determine the damage level according to the preset grading interval where the damage depth data output on the display screen is located; among them, when the damage depth is greater than or equal to the first preset depth threshold, it is determined as a minor injury, and when the damage depth is greater than the second preset depth threshold, it is determined that the minor injury has developed.

[0047] Determine according to the preset grading interval where the damage depth data H output on the display screen is located:

[0048] Grade by depth: When H is less than the first preset depth threshold (3 mm in this embodiment), it is determined as grade I; when H is greater than or equal to the first preset depth threshold and less than or equal to the second preset depth threshold (6 mm in this embodiment), it is determined as grade II; when H is greater than the second preset depth threshold, it is determined as grade III.

[0049] Damage determination criteria: When H ≥ 3 mm, it is determined as a minor injury, and when H > 6 mm, it is determined that the minor injury has developed.

[0050] At the same time, combined with the damage chipping size data d for comprehensive grading determination: When d ≤ 0.3 mm or 3 mm ≤ h ≤ 6 mm, it is grade I; when 0.3 mm < d ≤ 1 mm or h > 6 mm, it is grade II; when d > 1 mm, it is grade III. By directly connecting the determination rules with the instrument's directly read parameters, the on-site operation is convenient and suitable for large-scale promotion.

[0051] In some specific embodiments, in step S2, the relative sensitivity calibration is specifically as follows: Adjust the instrument to make the noise level when no probe is connected lower than a preset ratio of the full screen amplitude. Place the probe at the vertical surface of the standard test block and adjust the echo to the reference wave height, and the signal-to-noise ratio of the extracted echo signal meets the preset signal-to-noise ratio threshold.

[0052] In some specific embodiments, after the flaw detection sensitivity calibration in step S2, it further includes a detection performance verification step: Use a deep transverse hole test block to extract the highest echo signal and cover it with a gate. Compare the horizontal distance and depth data displayed by the instrument with the actual values of the test block. When the displayed data is consistent with the actual values, the verification is completed.

[0053] In some specific embodiments, step S1 further includes setting auxiliary signal processing parameters: damping, repetition frequency, transmission voltage, square wave width, narrow bandwidth, and full-wave detection mode, in order to optimize the signal-to-noise ratio of shallow-depth oblique crack echoes.

[0054] In some specific embodiments, the method can detect damage depths ranging from early microcrack depths to the maximum target depth of oblique cracks, and the damage wave and initial pulse are displayed separately in the shallow depth range.

[0055] In some specific embodiments, step S5, the damage level determination also includes a graded determination based on the size data of the damaged piece: when the size of the piece is less than or equal to a third preset size threshold, it is determined to be level I; when the size of the piece is greater than the third preset size threshold and less than or equal to a fourth preset size threshold, it is determined to be level II; and when the size of the piece is greater than the fourth preset size threshold, it is determined to be level III.

[0056] In summary, the beneficial effects are:

[0057] 1. High detection accuracy: Minimum detection depth ≤0.3mm, covering the core depth range of 1mm~10mm oblique cracks, significantly improving the ability to identify early cracks;

[0058] 2. Strong anti-interference capability: The creeping wave is less affected by scratches, dents, unevenness, etc. on the rail surface, the waveform is simple and free of noise, and the test results are intuitive;

[0059] 3. Strong adaptability: Perfectly matches the depth distribution of oblique stripping cracks, making up for the blind spot of shallow depth detection by K2.5 shear wave; when using a K2.5 shear wave probe to detect oblique cracks, the waveform is close to the starting pulse. If the depth of the oblique crack is within 3mm, the damage wave will be indistinguishable within the starting pulse when using a K2.5 shear wave probe.

[0060] 4. Easy to operate: The damage level can be directly determined by reading parameters through the gate, and it can be implemented quickly on site, making it suitable for large-scale promotion.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for detecting oblique peeling cracks in steel rails based on ultrasonic creeping waves, characterized in that, The following data processing and display steps are included: Step S1, parameter initialization settings: Configure the one-transmitter-one-receiver detection mode in the ultrasonic flaw detector, and input the data processing parameters for sound path conversion. The parameters include: full-scale sound path display range covering the detection depth of the oblique crack target, the climbing wave velocity in the rail, the refraction angle set based on the first critical angle, the probe leading edge length, and the probe delay. Step S2, Sensitivity reference data calibration: Relative sensitivity calibration: Obtain the noise level data when the instrument is not connected to the probe and record it as the first sensitivity value; obtain the vertical echo data of the climbing wave probe at the specified position of the standard test block and record it as the second sensitivity value; calculate the relative sensitivity; and select the benchmark data that meet the preset relative sensitivity threshold. Flaw detection sensitivity calibration: Obtain the echo signal of the probe at the predetermined depth of the transverse hole of the standard test block, adjust its amplitude to the reference wave height and record it as the reference value, combine the on-site rail surface condition data and add the compensation amount on the reference value to generate the on-site scanning sensitivity threshold; Step S3, On-site signal acquisition and processing: Place the climbing wave probe on the rail head and acquire ultrasonic reflected echo signals by combining sawtooth scanning with fixed-point rotating probe. Step S4, Damage Data Processing and Display: The collected echo signal is extracted by the gate. The instrument internally calculates the time difference of the echo signal inside the gate according to the climbing wave velocity, refraction angle and probe delay parameters preset in step S1, and directly displays the horizontal distance from the damage to the probe tip, damage depth and sound path data on the display screen. Step S5, Damage Level Determination: Determine the damage level based on the preset grading range of the damage depth data output by the display screen; wherein, when the damage depth is greater than or equal to the first preset depth threshold, it is determined to be a minor injury, and when the damage depth is greater than the second preset depth threshold, it is determined to be a minor injury with potential for development.

2. The detection method according to claim 1, characterized in that, In step S2, the relative sensitivity calibration is specifically as follows: the instrument is adjusted so that the noise level when the probe is not connected is lower than the preset ratio of the full screen, the probe is placed on the vertical surface of the standard test block and the echo is adjusted to the reference wave height, and the signal-to-noise ratio of the extracted echo signal meets the preset signal-to-noise ratio threshold.

3. The detection method according to claim 1, characterized in that, In step S2, after the flaw detection sensitivity calibration is completed, the detection performance verification step is also included: the highest echo signal is extracted using a deep transverse hole test block and covered with a gate, and the horizontal distance and depth data displayed by the instrument are compared with the actual values ​​of the test block. When the displayed data is consistent with the actual values, the verification is completed.

4. The detection method according to claim 1, characterized in that, Step S1 further includes setting auxiliary signal processing parameters: damping, repetition frequency, transmission voltage, square wave width, narrow bandwidth, and full-wave detection mode, in order to optimize the signal-to-noise ratio of shallow-depth oblique crack echoes.

5. The detection method according to claim 1, characterized in that, The method can detect damage depths ranging from early microcrack depths to the maximum target depth of oblique cracks, and the damage wave and initial pulse are displayed separately in the shallow depth range.

6. The detection method according to claim 1, characterized in that, In step S5, the damage level determination also includes a graded determination based on the size data of the damaged piece: when the size of the piece is less than or equal to the third preset size threshold, it is determined to be level I; when the size of the piece is greater than the third preset size threshold and less than or equal to the fourth preset size threshold, it is determined to be level II; and when the size of the piece is greater than the fourth preset size threshold, it is determined to be level III.

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