阅读说明：本技术 一种钢轨表面裂纹的涡流探伤方法及装置 (Eddy current flaw detection method and device for surface cracks of steel rail ) 是由 胡乾午 赵文芳 曾晓雁 侯康乐 王邓志 吴细水 杨国涛 徐其瑞 于 2020-05-19 设计创作，主要内容包括：本发明属于无损检测相关技术领域,其公开了一种钢轨表面裂纹的涡流探伤方法及装置,方法包括以下步骤：(1)提供涡流探伤装置,并确定所述涡流探伤装置的探头前平面线与待检测裂纹之间的夹角；(2)判断该夹角是否为零,若是则转至步骤(4),否则转至步骤(3)；(3)调整探头的位姿直至夹角的角度为零；(4)依据相邻的待检测裂纹之间的间距及待检测信号的波高与信号曲线的半波宽度的比值来判断待检测裂纹的类型,并相应地计算待测裂纹的深度或者数量；其中裂纹类型分别为单个裂纹、等深度密集裂纹及不同深度密集裂纹。本发明提高了检测准确性,适用性较强,且装置结构紧凑,体积较小,便于携带。(The invention belongs to the technical field related to nondestructive testing, and discloses an eddy current flaw detection method and device for surface cracks of a steel rail, wherein the method comprises the following steps: (1) providing an eddy current flaw detection device, and determining an included angle between a front plane line of a probe of the eddy current flaw detection device and a crack to be detected; (2) judging whether the included angle is zero, if so, turning to the step (4), otherwise, turning to the step (3); (3) adjusting the pose of the probe until the included angle is zero; (4) judging the type of the cracks to be detected according to the distance between the adjacent cracks to be detected and the ratio of the wave height of the signals to be detected to the half-wave width of the signal curve, and correspondingly calculating the depth or the number of the cracks to be detected; wherein the crack types are single cracks, equal-depth dense cracks and different-depth dense cracks respectively. The invention improves the detection accuracy, has stronger applicability, compact structure, smaller volume and convenient carrying.)

1. An eddy current flaw detection method for a steel rail surface crack is characterized by comprising the following steps:

(1) providing an eddy current flaw detection device, and determining an included angle between a front plane line of a probe of the eddy current flaw detection device and a crack to be detected;

(2) judging whether the angle of the included angle is zero, if so, turning to the step (4), otherwise, turning to the step (3);

(3) adjusting the pose of the probe by the eddy current flaw detection device until the angle of the included angle is zero;

(4) judging whether the distance between the adjacent cracks to be detected is larger than or equal to 4mm, if so, judging that the cracks to be detected are single cracks, calculating the depth of the cracks to be detected, and finishing the detection; otherwise, turning to the step (5);

(5) judging whether the distance between adjacent cracks to be detected is smaller than 4mm and the ratio of the wave height of a signal to be detected to the half-wave width of a signal curve is smaller than 0.9, if so, judging that the cracks to be detected are dense cracks with equal depth, calculating the number of the cracks to be detected, and finishing the detection; otherwise, turning to the step (6);

(6) judging whether the distance between adjacent cracks to be detected is smaller than 4mm and the ratio of the wave height of a signal to be detected to the half-wave width of a signal curve is larger than or equal to 0.9, if so, judging that the cracks to be detected are dense cracks with different depths, calculating the depth of the deepest crack, and finishing the detection; otherwise, the detection is also finished.

2. An eddy current testing method for surface cracks of a steel rail according to claim 1, wherein: in the step (4), the calculation formula of the depth of the crack to be detected is as follows:

wherein the variable of the crack depth to be detected is z, and the variable of the crack signal wave height is A (z).

3. An eddy current testing method for surface cracks of a steel rail according to claim 1, wherein: in the step (5), the calculation formula of the number of the cracks to be detected is as follows:

in the formula, the variable of the crack signal wave height is A (n).

4. The utility model provides an eddy current inspection device of rail surface crack which characterized in that: the eddy current inspection device is used for inspecting the steel rail by adopting the eddy current inspection method for the surface cracks of the steel rail according to any one of claims 1 to 3.

5. An eddy current flaw detector for detecting a flaw on a steel rail surface according to claim 4, wherein: the eddy current flaw detection device comprises a flaw detection executing mechanism (1), a flaw detector (2), a control system (3) and a software analysis system (4), wherein the flaw detection executing mechanism (1) and the software analysis system (4) are respectively connected to the control system (3), and the flaw detector (2) is connected with the flaw detection executing mechanism (1) and the software analysis system (4); the software analysis system (4) is used for classifying the cracks to be detected through a logic judgment and calculation formula according to the received data and calculating the depth or the number of the cracks to be detected.

6. An eddy current flaw detector for detecting a flaw on a steel rail surface according to claim 5, wherein: the flaw detection executing mechanism (1) comprises a main support frame part (11), a counterweight part (12), a front support plate part (13), a working track (14) and a base (15), wherein the working track (14) is arranged on the base (15), and the main support frame part (11) is connected to the working track (14) in a sliding mode and can move horizontally along the working track (14); the front support plate part (13) is connected to the main support frame part (11), and the counterweight part (12) is connected to the front support plate part (13).

7. An eddy current flaw detector for detecting a flaw on a steel rail surface according to claim 6, wherein: the working rail (14) and the main support frame part (11) form a meshing connection.

8. An eddy current flaw detector for detecting a flaw on a steel rail surface according to claim 6, wherein: the main support frame part (11) comprises a main support plate (111), a double-pulley assembly (118) and a connecting rope (119), the double-pulley assembly (118) is arranged on the main support plate (111), the connecting rope (119) is movably arranged on the double-pulley assembly (118), and two ends of the connecting rope are respectively connected to the counterweight part (12) and the front support plate part (13).

9. An eddy current flaw detector for detecting a flaw on a steel rail surface according to claim 8, wherein: the mass of the front support plate component (13) is larger than that of the counterweight component (12), so that the bottom of a pen test probe (132-1) of the front support plate component (13) is automatically contacted with the surface of a steel rail.

10. An eddy current flaw detector for detecting a flaw on a steel rail surface according to claim 6, wherein: the front support plate part (13) is slidably connected to the main support frame part (11) and can move up and down along the main support frame part (11).

Technical Field

The invention belongs to the technical field related to nondestructive testing, and particularly relates to an eddy current flaw detection method and device for surface cracks of a steel rail.

Background

With the development of railway transportation and the increase of transportation capacity, the fatigue damage of the steel rail is increasingly serious, wherein the surface crack has a great influence on the service life of the steel rail. According to the current railway maintenance regulations, for cracks with the depth of more than 3mm, grinding or abandonment treatment of the steel rail on the way needs to be carried out. Obviously, the nondestructive detection method is adopted to detect and quantitatively evaluate the depth of the surface crack of the steel rail, so that the method has important significance, and the transportation capacity of the line is improved on the premise of ensuring safety.

At present, the nondestructive detection method for the small cracks on the surface of the steel rail has the phenomenon of low accuracy, and the main problems are that: the difference between the defect signal of a dense crack and the defect signal of a single crack is difficult to distinguish, which is particularly serious for ultrasonic flaw detection and ultrasonic thickness measurement; in principle, ultrasonic flaw detection methods have difficulty solving similar problems. For example, patent CN201310269247.9 discloses an eddy current video comprehensive detection and evaluation method for in-service steel rail tread scale cracks, which detects steel rail tread scale cracks by using a semi-wrapped array eddy current probe and an array video sensor for the outline of the steel rail, and the patent corresponds the height of the eddy current signal acquired by the array probe to the depth of the crack, and further converts the eddy current amplitude signal into a two-dimensional gray scale imaging map, where the depth of the color represents the depth of the crack, and the depth range is set according to the range of 0% -100%. That is, the patent determines whether the crack belongs to the shape of the fish scale crack according to the two-dimensional video imaging diagram, and determines the depth of the crack according to the gray scale diagram (the height of the eddy current signal), however, the influence of the number of dense cracks on the height of the eddy current signal is not considered, and the false determination of the crack depth is easily caused. Accordingly, there is a need in the art to develop an eddy current testing method and apparatus for detecting surface cracks of steel rails with high accuracy.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides an eddy current flaw detection method and device for surface cracks of a steel rail, which are provided on the basis of researching the high influence of crack orientation and the number of cracks on eddy current signals.

In order to achieve the above object, according to one aspect of the present invention, there is provided an eddy current testing method for a crack on a surface of a steel rail, the method mainly comprising the steps of:

(1) providing an eddy current flaw detection device, and determining an included angle between a front plane line of a probe of the eddy current flaw detection device and a crack to be detected;

(2) judging whether the angle of the included angle is zero, if so, turning to the step (4), otherwise, turning to the step (3);

(3) adjusting the pose of the probe by the eddy current flaw detection device until the angle of the included angle is zero;

(4) judging whether the distance between the adjacent cracks to be detected is larger than or equal to 4mm, if so, judging that the cracks to be detected are single cracks, calculating the depth of the cracks to be detected, and finishing the detection; otherwise, turning to the step (5);

(5) judging whether the distance between adjacent cracks to be detected is smaller than 4mm and the ratio of the wave height of a signal to be detected to the half-wave width of a signal curve is smaller than 0.9, if so, judging that the cracks to be detected are dense cracks with equal depth, calculating the number of the cracks to be detected, and finishing the detection; otherwise, turning to the step (6);

(6) judging whether the distance between adjacent cracks to be detected is smaller than 4mm and the ratio of the wave height of a signal to be detected to the half-wave width of a signal curve is larger than or equal to 0.9, if so, judging that the cracks to be detected are dense cracks with different depths, calculating the depth of the deepest crack, and finishing the detection; otherwise, the detection is also finished.

Further, in the step (4), the calculation formula of the depth of the crack to be detected is as follows:

wherein the variable of the crack depth to be detected is z, and the variable of the crack signal wave height is A (z).

Further, in the step (5), the calculation formula of the number of cracks to be detected is as follows:

in the formula, the variable of the crack signal wave height is A (n).

According to another aspect of the present invention, there is provided an eddy current flaw detection apparatus for detecting a flaw on a surface of a steel rail, the eddy current flaw detection apparatus being configured to detect a steel rail by using the eddy current flaw detection method for a flaw on a surface of a steel rail as described above.

Further, the eddy current flaw detection device comprises a flaw detection execution mechanism, a flaw detector, a control system and a software analysis system, wherein the flaw detection execution mechanism and the software analysis system are respectively connected with the control system, and the flaw detector is connected with the flaw detection execution mechanism and the software analysis system; the software analysis system is used for classifying the cracks to be detected through a logic judgment and calculation formula according to the received data and calculating the depth or the number of the cracks to be detected.

Further, the flaw detection executing mechanism comprises a main support frame part, a counterweight part, a front support plate part, a working track and a base, wherein the working track is arranged on the base, and the main support frame part is connected to the working track in a sliding manner and can move horizontally along the working track; the front support plate member is connected to the main support frame member and the counterweight member is connected to the front support plate member.

Further, a meshing connection is formed between the work rails and the main support frame part.

Furthermore, the main support frame part comprises a main support plate, a double pulley assembly and a connecting cable, the double pulley assembly is arranged on the main support plate, the connecting cable is movably arranged on the double pulley assembly, and two ends of the connecting cable are respectively connected to the counterweight part and the front support plate part.

Further, the mass of the front support plate component is larger than that of the counterweight component, so that the bottom of the pen test probe of the front support plate component is automatically contacted with the surface of the steel rail.

Further, the front support plate member is slidably connected to the main support frame member, which is movable up and down the main support frame member.

Generally, compared with the prior art, the eddy current flaw detection method and device for the surface cracks of the steel rail provided by the invention have the following beneficial effects:

1. the eddy current flaw detection method is used for classifying and detecting single cracks, dense cracks with equal depth and dense cracks with different depths, correspondingly calculating the depth or the number of the cracks to be detected, considering the influence of the number of the dense cracks on the height of an eddy current signal, improving the detection accuracy and efficiency and having strong applicability.

2. The connecting cable is movably arranged on the double-pulley assembly, two ends of the connecting cable are respectively connected with the counterweight component and the front supporting plate component, and the mass of the front supporting plate component is larger than that of the counterweight component, so that the bottom of a pen test probe of the front supporting plate component is automatically contacted with the surface of the steel rail and can follow up along with the fluctuation change of the surface of the steel rail, the detection stability and accuracy are improved, and the flexibility is better.

3. The eddy current flaw detection method is simple, easy to implement and beneficial to popularization and application.

4. The eddy current flaw detection device is compact in structure, small in size, light in weight and convenient to carry.

Drawings

FIG. 1 is a schematic flow chart of an eddy current testing method for surface cracks of a steel rail provided by the invention;

FIG. 2 shows L of the eddy current flaw detection method for a surface crack of the steel rail in FIG. 1_xAnd L₀A schematic illustration of the calculation of the included angle β therebetween;

FIG. 3 is a partial schematic view of a flaw detection actuator of the eddy current flaw detection apparatus for detecting flaws on the surface of a steel rail according to the present invention;

FIG. 4 is a schematic view of a base of the inspection actuator of FIG. 3;

FIG. 5 is a schematic view of the inspection actuator of FIG. 3 at an angle;

FIG. 6 is a schematic view of the main support member and the working rail of the flaw detection actuator of FIG. 3;

FIG. 7 is a schematic view of the primary support member of FIG. 6 at an angle;

FIG. 8 is a schematic view of the inspection actuator of FIG. 3 at another angle;

FIG. 9 is a system block diagram of an eddy current testing apparatus for detecting flaws in the surface of the steel rail in FIG. 3;

fig. 10 is a schematic diagram showing the relationship between the signal wave heights of the a-type flaw, the B-type flaw and the C-type flaw according to the eddy current flaw detection method for a rail surface flaw in fig. 1 and a time base line.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-flaw detection actuating mechanism, 11-main support frame component, 111-main support plate, 112-first gear shaft, 113-main motor, 114-walking slider, 115-lifting guide rail, 116-lifting slider, 118-double pulley component, 119-connecting cable, 12-counterweight component, 13-front support plate component, 132-pen test probe component, 132-1-pen test probe, 132-2-probe support frame, 132-3-second gear shaft, 133-rotating shaft component, 133-1-third gear shaft, 133-2-synchronous belt, 133-3-angle adjusting motor, 134-CCD component, 134-1-CCD camera, 134-2-camera support frame and 14-working track, 141-a walking guide rail, 142-a rack, 143-a widening strip, 15-a base, 151-a rotating magnet, 152-a switch, 153-a pressing block, 154-a locking nut, 2-a flaw detector, 3-a control system and 4-a software analysis system.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1, the eddy current flaw detection method for the surface cracks of the steel rail provided by the invention, wherein an included angle β between a front plane of a probe and the cracks in eddy current flaw detection has a large influence on a flaw detection result, when β is 45 degrees, a detection blind area is formed, and the height of a detection signal is 0; when the beta is 0 degrees or 90 degrees, the detection signal is strongest, and when the flaw is detected actually, the probe needs to be kept parallel or perpendicular to the flaw as much as possible. In addition, the hardening depth of the quenched and strengthened steel rail is 0.8mm-1mm, fine fatigue cracks sometimes appear in a quenching area, the depth of the cracks is about 1mm, the depth of the dense small cracks is quantitatively detected, the expansion condition of the small cracks is mastered, and the rail is very necessary for normal maintenance of a railway.

In the embodiment, a single crack and an intensive crack are distinguished through a CCD screen, and the category of the intensive crack is comprehensively judged through the ratio of the wave height of a detection signal to the half-wave width of a signal curve; after accurately classifying the cracks, calculating the depth of the small cracks, the number of the dense cracks or the maximum depth of the dense cracks according to a corresponding formula; the cracks with the spacing larger than 4mm are defined as single cracks, the eddy current detection signal amplitude corresponding to the cracks with the spacing larger than the single cracks is not influenced by the adjacent cracks, the dense cracks are the cracks with the spacing smaller than 4mm, and the influence of the adjacent cracks on the eddy current detection signal amplitude is larger; of course, the number level of cracks can be judged according to the image detected by the CCD during flaw detection so as to distinguish single cracks from dense cracks.

In the embodiment, the eddy current flaw detection method further needs a special test block, the material of the special test block is the same as that of the steel rail, the gap of a single crack is about 0.2mm, and the distance between cracks is 50 mm; the gap of each crack in the dense cracks is about 0.2mm, and the distance between the cracks is 1 mm.

The eddy current flaw detection method mainly comprises the following steps:

providing an eddy current flaw detection device, and determining an included angle between a probe front plane line of the eddy current flaw detection device and a crack to be detected.

Specifically, referring to fig. 2, the intersection points of the cracks at the edge of the CCD display frame are defined as a and B, the line connecting a and B is defined as a linear crack to be detected, and is denoted by Lx, and the center of the rotation circle of the pen probe is D. Wherein, if A type is a single crack, use A_1×zDenotes, for example, A_1×5mmRepresenting a single crack with a depth of 5 mm; if B type is equal depth dense crack, use B_n×1Is represented by, for example, B_2×1mmTwo 1mm deep dense cracks are shown, C type is set as the dense crack with different depth, C is used_2×1+1×zRepresents, for example, C_{2×1mm+1×5mm}Indicating a 5mm deep crack in the middle of two 1mm deep cracks; meanwhile, the front plane line of the probe in the CCD display screen is set to be L₀And L is₀The crack to be detected at the position 5mm away is L_xDefinition of L_xAnd L₀The included angle between the eddy current detection and the eddy current detection is β, the eddy current detection frequency is 500kHz, the gain is 19dB, and the flaw detection speed V is 1 m/min.

In addition, the serial number of the cracks to be detected displayed in the CCD display frame is set as q, and the distance between the q-th crack to be detected and the q + 1-th crack to be detected is set as x; the variable of the depth of the cracks to be detected is z, the variable of the number of the dense cracks to be detected is n, and the variable of the wave height of the detected crack signal is A (z) or A (n).

Referring to fig. 9, the eddy current flaw detection apparatus includes a flaw detection execution mechanism 1, a flaw detector 2, a control system 3, and a software analysis system 4, wherein the flaw detection execution mechanism 1 and the software analysis system 4 are respectively connected to the control system 3, and the flaw detector 2 is connected to the flaw detection execution mechanism 1 and the software analysis system 4. The control system 3 is used for controlling the movement of the flaw detection actuating mechanism 1, wherein the front plane line L of the probe₀To be detected crack L_xThe included angle β between the two crack detectors is subjected to feedback control through inspection of a CCD display screen and the software analysis system 4, the flaw detector 2 is used for collecting parameters such as signal wave height, half wave width and the like and transmitting collected data to the software analysis system 4, and the software analysis system 4 classifies cracks to be detected through logic judgment and a calculation formula in the software analysis system according to the received data and calculates the depths or the number of the cracks.

Referring to fig. 3, 4, 5, 6, 7 and 8, the flaw detection actuator 1 includes a main support frame member 11, a counterweight member 12, a front support plate member 13, a working rail 14 and a base 15, wherein the working rail 14 is disposed on the base 15, the main support frame member 11 is slidably connected to the working rail 14, the front support plate member 13 is connected to the main support frame member 11, and the counterweight member 12 is connected to the front support plate member 13.

The working track 14 includes a traveling rail 141, a rack 142, and a widening bar 143, and the widening bar 143 is disposed at an end of the traveling rail 141 facing the steel rail, and forms an L-shaped support with the traveling rail 141. The rack 142 is connected to the widening bar 143 and the traveling rail 141, and is disposed along the longitudinal direction of the traveling rail 141. In the present embodiment, the working rail 14 is connected to the main support frame part 11 by means of the toothed rack 142 in a meshing manner.

The base 15 includes a first body, a rotary magnet 151, a switch 152, a pressing block 153 and a lock nut 154, the rotary magnet 151 and the switch 152 are disposed at one side of the body, and the pressing block 153 is connected to the body through the lock nut 154 and a bolt. During operation, one end of the working rail 14 is arranged between the pressing block 153 and the first body, and the pressing block 153 presses the working rail 14 on the first body by tightening the locking nut 154; the rotary magnet 151 can be turned on by the switch 152 to fix the base 15 to the rail.

The main support frame part 11 comprises a main support plate 111, a first gear shaft 112, a main motor 113, a traveling slider 114, a lifting guide rail 115, a lifting slider 116, a double-pulley assembly 118 and a connecting cable 119, wherein the main motor 113 is arranged on the main support plate 111, the first gear shaft 112 is connected to the main motor 113, and the main motor 113 and the first gear shaft 112 are respectively located on two opposite sides of the main support plate 111. In this embodiment, the main support frame member 11 is engaged with the rack 142 via the first gear shaft 112, the main motor 113 drives the first gear shaft 112 to rotate, and the first gear shaft 112 moves along the length direction of the rack 142, which in turn drives the front support member 13 to move.

The walking slider 114 is connected to the main supporting plate 111 and disposed opposite to the first gear shaft 112, the working rail 14 is located between the main supporting plate 111 and the first gear shaft 112, and the walking slider 114 is slidably connected to the working rail 14. The lifting guide rail 115 is disposed on the traveling block 114, and is disposed in a vertical direction. The lifting slider 116 is slidably connected to the lifting rail 115. The main support frame member 11 is connected to the front support plate member 13 via the lifting slide 116 to move the front support plate member 13 up and down.

The double pulley assembly 118 is disposed on the main support plate 111, which is disposed opposite to the main motor 113. The connecting cable 119 is movably disposed on the double pulley assembly 118, and both ends thereof are connected to the weight member 12 and the front support plate member 13, respectively. The mass of the front support plate member 13 is greater than that of the weight member 12, so that the bottom of the pen probe 132-1 of the front support plate member 13 can automatically contact with the surface of the rail and follow up the undulation of the rail surface.

Preceding backup pad part 13 includes the second body, the probe subassembly 132 of trying on a brush, axis of rotation subassembly 133 and CCD subassembly 134 of L type, the second body connect in lift slider 116, axis of rotation subassembly 133 sets up on the body, it is used for driving probe subassembly 132 of trying on a brush rotates. The pen test probe assembly 132 and the CCD assembly 134 are respectively disposed on the second body.

The pen test probe assembly 132 comprises a pen test probe 132-1, a probe support frame 132-2 and a second gear shaft 132-3, the probe support frame 132-2 is disposed on the second body, the pen test probe 132-1 is disposed on the probe support frame 132-2, and the second gear shaft 132-3 is connected to the probe support frame 132-2 and is connected to the rotating shaft assembly 133.

The rotating shaft assembly 133 comprises a third gear shaft 133-1, a synchronous belt 133-2 and an angle adjusting motor 133-3, the angle adjusting motor 133-3 is arranged on the second body, the third gear shaft 133-1 is connected to an output shaft of the angle adjusting motor 133-3, the synchronous belt 133-2 is sleeved on the third gear shaft 133-1 and the second gear shaft 132-3, and the angle adjusting motor 133-3 drives the pen test probe 132-1 to rotate sequentially through the third gear shaft 133-1, the synchronous belt 133-2, the second gear shaft 132-3 and the probe bracket 132-2.

And step two, judging whether the angle of the included angle is zero, if so, turning to step four, and otherwise, turning to step three.

And step three, adjusting the pose of the probe by the eddy current flaw detection device until the angle of the included angle is zero.

Step four, judging whether the distance between the adjacent cracks to be detected is larger than or equal to 4mm, if so, judging the cracks to be detected to be single cracks, calculating the depth of the cracks to be detected, and finishing the detection; otherwise, go to step five. Specifically, the depth of the crack to be measured is calculated by the following formula:

judging whether the distance between adjacent cracks to be detected is smaller than 4mm and the ratio of the wave height of a signal to be detected to the half-wave width of a signal curve is smaller than 0.9, if so, judging that the cracks to be detected are dense cracks with equal depth, calculating the number of the cracks to be detected, and finishing the detection; otherwise, go to step six. Specifically, the number of cracks to be measured is calculated by the following formula:

eta is a scale factor defined as the ratio of the wave height of the detection signal to the half-wave width of the signal curve; the half-wave width refers to the width of the signal curve at half-wave height.

Judging whether the distance between adjacent cracks to be detected is smaller than 4mm and the ratio of the wave height of a signal to be detected to the half-wave width of a signal curve is larger than or equal to 0.9, if so, judging that the cracks to be detected are dense cracks with different depths, calculating the depth of the deepest crack, and finishing the detection; otherwise, the detection is also finished. Specifically, if the distance between adjacent to-be-detected cracks is smaller than 4mm and the ratio of the wave height of the to-be-detected signal to the half-wave width of the signal curve is not smaller than 0.9, the detection is finished.

Specifically, the depth of the deepest crack is calculated using the following formula:

the invention also provides an eddy current flaw detection device for the surface cracks of the steel rail, which is used for detecting the cracks by adopting the eddy current flaw detection method for the surface cracks of the steel rail.