Method for positioning steel rail defect based on ultrasonic sound path distance change

Abstract

The invention provides a steel rail defect positioning method based on ultrasonic sound path distance change, which comprises the following steps of: S1, filtering echoes received on two adjacent detection points, acquiring sound path distances Fi and Fi + 1 of the defect echoes of the two detection points when judging that the defect echoes are received on the two detection points, and acquiring mileages Li and Li + 1 of the two detection points; and S2, according to a formula # imgabs0 #, calculating an upward inclination angle beta of the defect, and according to a formula # imgabs1 # # imgabs2 #, calculating to obtain mileage and depth corresponding to a defect echo reflection position, and displaying the mileage and depth in a B scanning image. According to the method, through a two-point positioning method, the actual trend of the defect can be more accurately determined, a more accurate defect B scanning image is obtained, and a more accurate data basis is provided for subsequent steel rail maintenance.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing, and in particular to a method for locating rail defects based on ultrasonic sound path changes. Background Art

[0002] The B-scan image in rail flaw detection is a two-dimensional image obtained by the ultrasonic flaw detector when detecting the rail, which can reflect the shape and depth of the internal defects of the rail. In the B-scan image, the horizontal axis is the mileage, which is used to record the corresponding relationship between the defect location and the rail mileage, and the vertical axis is the depth, which is used to record the distance between the defect location and the rail detection surface (usually the top surface of the rail). The mileage is obtained by the encoder on the ultrasonic flaw detector and the horizontal distance between the defect and the probe is obtained, and the depth of the defect is calculated based on the corresponding probe angle and the acoustic path of the echo. At present, the ultrasonic flaw detector moves on the top surface of the optical rail during inspection. When a defect is detected, it is first assumed that the defect is perpendicular to the central sound beam of the ultrasonic wave emitted by the probe, that is, after the ultrasonic wave is emitted, its central sound beam touches the defect and is reflected, and returns to the original path to be received by the ultrasonic flaw detector. The vertical deflection angle of the central sound beam of the ultrasonic wave is the same as the angle of the sound wave emitted by the probe, which is known. The sound path of the central sound beam of the ultrasonic wave can be obtained by calculating the sound speed and the time difference between the ultrasonic wave emission and reception. Then, through trigonometric calculation, the depth of the detected defect and the horizontal distance from the probe can be obtained. According to the horizontal distance, the mileage position of the defect corresponding to the optical rail is calculated, and points are drawn in the B-scan diagram at the corresponding mileage and depth value positions. As the ultrasonic flaw detector moves, the second point, the third point... are drawn in the same way. Several points form a two-dimensional image of the shape and depth of the defect, and finally a B-scan diagram of the rail inspection is obtained.

[0003] However, in actual flaw detection operations, the angle of natural defects is random, and sometimes it is not perpendicular to the angle of the sound wave generated by the probe, and there is a certain range of error. If the defect depth is still calculated based on the current calculation method of the assumed defect angle, then the defect B scan image drawn will have errors, and it is difficult to accurately judge the size and position of the defect.

[0004] In addition, in the process of obtaining the B-scan image, there are many types of interference waves in the received sound waves, such as noise waves from equipment, which result in a lot of interference data appearing on the B-scan image, often causing misjudgment by data analysts, and even defect echoes are hidden by interference waves, resulting in missed defects and posing a major safety hazard.

[0005] Currently, the commonly used filtering algorithms are mostly based on continuity judgment. If a certain sound wave channel is a continuous wave, it will be displayed; if it is a discontinuous wave, it will be filtered out. The algorithm is relatively simple, but it cannot filter out the interference waves of continuous waves, which still affects the accuracy of obtaining the B-scan image. Summary of the invention

[0006] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method for locating rail defects based on changes in ultrasonic sound path.

[0007] The technical solution of the present invention is as follows:

[0008] A method for locating rail defects based on ultrasonic sound path changes comprises the following steps:

[0009] S1. Filter the echoes received at two adjacent detection points. When it is determined that defect echoes are received at both detection points, obtain the acoustic path F of the defect echoes at the two detection points. i and F i+1 , and obtain the mileage L of the two detection points i and L i+1 , where i represents the i-th detection point;

[0010] S2, according to the formula Calculate the upward inclination angle β of the defect and use the formula The mileage and depth corresponding to the defect echo reflection position are calculated and displayed in the B-scan image.

[0011] Among them, β is the inclination angle of the defect in the interval corresponding to the i-th and i+1-th detection points,

[0012] Y i and X i is the mileage and depth corresponding to the defect echo reflection position of the i-th detection point,

[0013] Y i+1 and X i+1 is the mileage and defect depth corresponding to the defect echo reflection position of the i+1th detection point.

[0014] Furthermore, in S1, the echoes received at two adjacent detection points are filtered, including the following steps:

[0015] a. Determine whether the same channel in the corresponding channel of each echo receives echoes at two adjacent detection points. If so, execute step b. Otherwise, filter out the corresponding echo;

[0016] b. Obtain the acoustic path F of the echo received at two adjacent detection points on the same channel i ' and F i ' +1 , and obtain the mileage L of the two detection points i and L i+1 , and according to the formula and The height difference Δh' of the echo reflection positions at the two detection points is calculated;

[0017] c. Compare Δh' with the theoretical threshold range. If it falls within the theoretical threshold range, the corresponding two echoes are determined to be defect echoes. Otherwise, they are filtered out.

[0018] Further, step a specifically includes, in the same channel,

[0019] If the current detection point receives an echo, but the previous detection point does not receive an echo, the echo received by the current detection point is temporarily retained and the detection result of the next detection point is awaited. If the next detection point receives an echo, step b is executed; otherwise, the echo corresponding to the current detection point is filtered out.

[0020] Furthermore, the setting of the theoretical threshold range includes:

[0021] If θ+ɑ≤45° or θ-ɑ≥45°, the theoretical threshold range is (L i+1 -L i )*sin(θ-α)*cos(θ-α) to (L i+1 -L i )*sin(θ+α)*cos(θ+α);

[0022] On the contrary, the theoretical threshold range is (L i+1 -L i )*sin(θ-α)*cos(θ-α) and (L i+1 -L i )*sin(θ+α)*cos(θ+α) to the minimum value (L i+1 -L i )*sin45°*cos45°;

[0023] Among them, θ is the inclination angle of the central sound beam emitted by the probe relative to the vertical direction, and α is the angle at which the ultrasound waves spread outward.

[0024] In the above scheme, when the probe receives the echo, it calculates and records the acoustic path of the echo, and also records the mileage of the current detection point.

[0025] In the above scheme, the mileage of the detection point is obtained through the encoder.

[0026] In the above scheme, the acoustic path of the echo is obtained by multiplying the known sound velocity of the ultrasonic wave by the time difference between emitting the ultrasonic wave and receiving the echo.

[0027] Furthermore, during detection, the probe emits ultrasonic waves in sequence at evenly spaced distances during movement.

[0028] Preferably, the interval distance at which the probe emits ultrasonic waves is 3-5 mm.

[0029] The present invention provides a method for locating rail defects based on ultrasonic sound path changes. Through a two-point positioning method, the actual trend of the defect can be determined more accurately, and a more accurate defect B scan can be obtained, thereby providing a more accurate data basis for subsequent rail maintenance.

[0030] In addition, through the two-point measurement method, the interference waves in the continuous wave can be further filtered out, and the actual useful echo data can be obtained, thereby improving the accuracy of defect positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the attached picture:

[0032] Figure 1 Schematic diagram of rail defect location. DETAILED DESCRIPTION

[0033] like Figure 1 As shown, an embodiment of the present invention provides a method for locating rail defects based on ultrasonic sound path changes, which is applied to ultrasonic flaw detectors in track inspection. As is well known, ultrasonic flaw detectors usually have multiple probes such as 0 degrees, 37-45 degrees, and 70 degrees, where the degree is the angle at which the central sound beam of the ultrasonic wave deflects upward relative to the vertical direction when the probe emits the ultrasonic wave, which is represented by the symbol θ in this application. The vertical direction described here is based on the assumption that the rail is placed horizontally, and is also for the convenience of subsequent description and understanding of the assumptions made in the technical solution of this application. If the rail is not placed horizontally, the normal to the top surface of the rail is used as a reference reference for the angle θ.

[0034] The method for locating rail defects of the present application comprises the following steps:

[0035] S1. Filter the echoes received at two adjacent detection points. When it is determined that defect echoes are received at both detection points, obtain the acoustic path F of the defect echoes at the two detection points. i and F i+1 , and obtain the mileage L of the two detection points i and L i+1 , where i represents the i-th detection point, and corresponds to Figure 1 In , the i-th and i+1-th detection points correspond to position A and position B respectively.

[0036] S2, according to the formula Calculate the upward inclination angle β of the defect and use the formula The mileage and depth corresponding to the defect echo reflection position are calculated and displayed in the B-scan image.

[0037] Among them, β is the inclination angle of the defect in the interval corresponding to the i-th and i+1-th detection points,

[0038] Yi and X i is the mileage and depth corresponding to the defect echo reflection position of the i-th detection point,

[0039] Y i+1 and X i+1 is the mileage and defect depth corresponding to the defect echo reflection position of the i+1th detection point.

[0040] Here, first, each time the probe receives an echo, it calculates and records the acoustic path of the echo, and also records the mileage of the current detection point.

[0041] The acoustic path of the echo is obtained by multiplying the known sound velocity of the ultrasonic wave by the time difference between emitting the ultrasonic wave and receiving the echo.

[0042] The mileage of the inspection point is directly obtained through an encoder. The ultrasonic flaw detector is provided with an encoder, such as an incremental encoder or a linear encoder.

[0043] Secondly, during the detection, the probe emits ultrasonic waves at uniform intervals in sequence, that is, the mileage difference between two adjacent detection points is fixed, which is L. i+1 -L i . The mileage difference, i.e., the interval distance at which the probe emits ultrasonic waves, is preferably 3-5 mm. Since the interval distance is very short, if there is a defect within the distance interval, the defect can usually be measured simultaneously by two adjacent detection points, and since the distance is short, theoretically, the trend of the defect within the distance interval generally does not change, while in fact, the trend of the defect will change with a certain probability, but 1) the probability of change is low, and 2) the change in the defect trend is small and can be ignored. Therefore, in the technical solution of the present application, the trend of the defect is deemed to be unchanged, that is, the inclination angle of the defect remains unchanged.

[0044] Since the angle of the probe emitting ultrasonic waves remains unchanged, the inclination angle of the defect changes between adjacent detection points, so the sound beams corresponding to the echoes received at the two detection points are two parallel lines, such as Figure 1 As shown, the inclination angle β of the defect can be calculated according to the trigonometric function formula in step S2, and the value range of β is between -90° and 90°.

[0045] Since the sound beam corresponding to the echo is perpendicular to the defect, the inclination angle of the echo sound beam relative to the vertical direction is equal to the inclination angle β of the defect. Then, according to the trigonometric function formula in step S2, the mileage and depth values ​​corresponding to the two reflection points on the defect can be calculated. According to the calculated values, the position of the defect on the rail is displayed in the B-scan image. Similarly, the measurement is performed to obtain the B-scan image corresponding to the defect on the entire rail to be inspected.

[0046] When using an ultrasonic flaw detector for testing, since there are interference waves in the echo received by the probe, the received echo needs to be filtered first.

[0047] As mentioned above, the inclination angle of the central sound beam of the ultrasonic wave emitted by the probe relative to the vertical direction is θ, and it is well known that the ultrasonic wave will propagate in a diffuse manner. In the vertical plane of the rail detection (i.e., the vertical plane along the extension direction of the rail), the ultrasonic wave spreads in a fan-shaped manner with its central sound beam as the center. In the present application, the angle of the ultrasonic wave spreading outward is represented by α, which can be set by the probe when it leaves the factory and is a known value. Therefore, the defect echo is generated by the sound beam within the angle range of θ-ɑ to θ+ɑ, and when any sound beam within this angle range generates an echo at two corresponding adjacent detection points, since the sound beam angle does not change and the defect angle does not change, the height difference between the two reflection positions of the sound beam on the defect will be within a range of values. If the height difference of the echo reflection points corresponding to the two adjacent detection points calculated by continuous wave output is not within this range, the wave is considered to be an interference wave. Based on this, in S1, the echoes received at two adjacent detection points are filtered, including the following steps:

[0048] a. Determine whether the same channel in the channels corresponding to each echo receives echoes at two adjacent detection points. If so, execute step b. Otherwise, filter out the corresponding echo.

[0049] This step specifically includes, in the same channel, if the current detection point receives an echo, but the previous detection point does not receive an echo, then the echo received by the current detection point is temporarily retained, waiting for the detection result of the next detection point. If the next detection point receives an echo, step b is executed, otherwise the echo corresponding to the current detection point is filtered out.

[0050] This step aims to filter out non-continuous interference waves, that is, if no echo is received in the two adjacent detection points before and after the detection point where the echo is received, the current echo is a non-continuous interference wave and is filtered out. Otherwise, it is processed as a continuous wave and step b is executed.

[0051] b. Obtain the acoustic path F of the echo received at two adjacent detection points on the same channel i ' and F i ' +1 , and obtain the mileage L of the two detection points i and L i+1 , and according to the formula and The height difference Δh' between the echo reflection positions at the two detection points is calculated.

[0052] c. Compare Δh' with the theoretical threshold range. If it falls within the theoretical threshold range, the corresponding two echoes are determined to be defect echoes. Otherwise, they are filtered out.

[0053] Among them, the setting of the theoretical threshold range includes:

[0054] If θ+ɑ≤45° or θ-ɑ≥45°, the theoretical threshold range is (L i+1 -L i )*sin(θ-α)*cos(θ-α) to (L i+1 -L i )*sin(θ+α)*cos(θ+α);

[0055] On the contrary, the theoretical threshold range is (L i+1 -L i )*sin(θ-α)*cos(θ-α) and (L i+1 -L i )*sin(θ+α)*cos(θ+α) to the minimum value (L i+1 -L i )*sin45°*cos45°.

[0056] The present invention provides a method for locating rail defects based on ultrasonic sound path changes. Through a two-point positioning method, the actual trend of the defect can be determined more accurately, and a more accurate defect B scan can be obtained, thereby providing a more accurate data basis for subsequent rail maintenance.

[0057] In addition, through the two-point measurement method, while filtering out the interference waves of non-continuous waves, the interference waves in the continuous waves can be further filtered out to obtain more accurate and practically useful echo data, thereby improving the accuracy of defect positioning.

Claims

1. A method for locating rail defects based on ultrasonic sound path changes, characterized in that: The steps include: S1. Filter the echoes received at two adjacent detection points. When it is determined that defect echoes are received at both detection points, obtain the acoustic path F of the defect echoes at the two detection points. i and F i+1 , and obtain the mileage L of the two detection points i and L i+1 , where i represents the i-th detection point; S2, according to the formula Calculate the upward inclination angle β of the defect and use the formula The mileage and depth corresponding to the defect echo reflection position are calculated and displayed in the B-scan image. Among them, β is the inclination angle of the defect in the interval corresponding to the i-th and i+1-th detection points, Y i and X i is the mileage and depth corresponding to the defect echo reflection position of the i-th detection point, Y i+1 and X i+1 is the mileage and defect depth corresponding to the defect echo reflection position of the i+1th detection point.

2. A method for locating rail defects based on ultrasonic sound path changes as claimed in claim 1, characterized in that: In S1, the echoes received at two adjacent detection points are filtered, including the following steps: a. Determine whether the same channel in the corresponding channel of each echo receives echoes at two adjacent detection points. If so, execute step b. Otherwise, filter out the corresponding echo; b. Obtain the acoustic path F of the echo received at two adjacent detection points on the same channel i ' and F i ' +1 , and obtain the mileage L of the two detection points i and L i+1 , and according to the formula and The height difference Δh' of the echo reflection positions at the two detection points is calculated; c. Compare Δh' with the theoretical threshold range. If it falls within the theoretical threshold range, the corresponding two echoes are determined to be defect echoes. Otherwise, they are filtered out.

3. A method for locating rail defects based on ultrasonic sound path changes as claimed in claim 2, characterized in that: Step a specifically includes, in the same channel, If the current detection point receives an echo, but the previous detection point does not receive an echo, the echo received by the current detection point is temporarily retained and the detection result of the next detection point is awaited. If the next detection point receives an echo, step b is executed; otherwise, the echo corresponding to the current detection point is filtered out.

4. A method for locating rail defects based on ultrasonic sound path change as claimed in claim 3, characterized in that: Theoretical threshold range settings include: If θ+ɑ≤45° or θ-ɑ≥45°, the theoretical threshold range is (L i+1 -L i )*sin(θ-α)*cos(θ-α) to (L i+1 -L i )*sin(θ+α)*cos(θ+α); On the contrary, the theoretical threshold range is (L i+1 -L i )*sin(θ-α)*cos(θ-α) and (L i+1 -L i )*sin(θ+α)*cos(θ+α) to the minimum value (L i+1 -L i )*sin45°*cos45°; Among them, θ is the inclination angle of the central sound beam emitted by the probe relative to the vertical direction, and α is the angle at which the ultrasound waves spread outward.

5. The method for locating rail defects based on ultrasonic sound path change according to claim 2, characterized in that: When the probe receives the echo, it calculates and records the acoustic path of the echo, and also records the mileage of the current detection point.

6. A method for locating rail defects based on ultrasonic sound path change as claimed in claim 5, characterized in that: The mileage of the detection point is obtained through the encoder.

7. A method for locating rail defects based on ultrasonic sound path change according to claim 6, characterized in that: The acoustic path of the echo is obtained by multiplying the known sound velocity of the ultrasound with the time difference between emitting the ultrasound and receiving the echo.

8. The method for locating rail defects based on ultrasonic sound path change according to claim 1, characterized in that: During detection, the probe emits ultrasonic waves in sequence at evenly spaced distances while moving.

9. A method for locating rail defects based on ultrasonic sound path change as claimed in claim 8, characterized in that: The probe emits ultrasonic waves at a distance of 3-5mm.

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