JP2014102197A - Magnetic induction rail flow detection method, and magnetic induction rail flow detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect in an early stage a surface flaw and an internal lateral laceration so as to take measures for repairing and replacement of a rail, ensuring a safe travelling.SOLUTION: An exciting coil and two detection coils arranged apart in a longitudinal direction of an inspection rail by sandwiching the exciting coil are arranged above a head part of the inspection rail by a liftoff. Both of the detection coils are reversely wound and connected in series, and an AC magnetic flux generated from the exiting coil is applied to the inspection rail so as to generate an eddy current in the inspection rail. An amplitude of the induced voltage generated based on the eddy current is detected by the two detection coils regardless of whether the flaw exists or not, and an amplitude difference between the detected amplitude in the case that no flaw exists and the amplitude of the fluctuating induced voltage based on the eddy current fluctuated by receiving the influence of the flaw in the case that the flaw exists is subtracted and detected by the reversely wound detection coils, and the presence or absence of the flaw is detected from this amplitude difference, and the surface flaw and the lateral laceration of the inspection rail is detected.

Description

  The present invention relates to a magnetic induction rail flaw detection method capable of detecting both surface flaws of rails for railroads and other vehicle rails (hereinafter referred to as “rails”), internal flaws of the head, cracks, and the like, and a magnetic induction type used therein. The present invention relates to a rail flaw detector.

  The rail may be scratched and cracked inside the rail after long-term use. One of the surface scratches is shelling. Internal cracks (lateral fissures or lateral fissures) are thought to be caused by rainwater penetrating the inside of the rail from the shelling and the flaw growing toward the lateral width of the rail or toward the bottom.

  Rail scratches, particularly lateral tears, tend to lead to rail breakage and are extremely dangerous for safe driving of the train. In order to ensure the safe traveling of the train, it is necessary to prevent the rail from breaking. For this purpose, it is important to detect not only the surface flaws on the rails but also the internal lateral fissures as early as possible.

  There are a magnetic induction type flaw detection method, an ultrasonic flaw detection method, etc. as a method for flawlessly detecting a metal flaw. The magnetic induction type flaw detection method is a method in which a magnetic field is generated in the vicinity of an inspection object, an eddy current is generated in the inspection object by a magnetic induction action, and a change in the output level of the eddy current is detected to detect a flaw. The ultrasonic flaw detection method is a method in which a reflected wave is detected by irradiating an object to be inspected with ultrasonic waves, and flaw detection is performed from the time difference between the reflected wave when it is affected and when it is not affected.

  Patent Documents 1 and 2 are examples of magnetic induction type flaw detection methods. These are used to detect surface defects such as metal pipes and metal plates, metal parts embedded in buildings, for example, inspection objects such as steel frames, etc. However, the conventional rail flaw detection methods are mainly ultrasonic flaw detection methods.

JP-A-10-288605 JP 2007-127600 A

  The rail flaw detection method conventionally used is an ultrasonic flaw detection method. In this method, an ultrasonic flaw detector is mounted on a self-propelled flaw detection vehicle or a hand-held flaw detection vehicle that runs on the rail, and while the flaw detection vehicle is moving, water is sprayed from the flaw detection vehicle onto the rail surface. In this method, the surface of the rail 1 is irradiated with ultrasonic waves, and ultrasonic waves reflected from the rails (if there are flaws, are affected by the flaws) are detected for flaw detection. In this case, as shown in FIG. 11, the ultrasonic wave generated from the ultrasonic generator 2 is irradiated on the upper surface of the rail (detection rail) 1 for flaw detection at various angles such as perpendicular (0 degree), 40 degrees, and 70 degrees. Then, the reflected wave is detected and flaw detection is performed.

The ultrasonic flaw detection method has the following difficulties.
1. If there is a surface flaw on the rail, the ultrasonic wave will bounce off the flaw, the internal flaw below the surface flaw cannot be detected, and a lateral fissure that leads to rail breakage may be missed.
2. Since the probe of the ultrasonic rail flaw detector is fixed, the angle with respect to the rail cannot be changed, the swinging operation and the reciprocating operation cannot be performed, and detection may be lost.
3. Rail flaw detectors are expensive (one billion yen) and cannot be easily installed.
4). Since a large amount of water is supplied between the probe and the rail, a large amount of water is required to perform rail flaw detection over a long distance, and a large-sized water storage tank is required. However, since there is a limit even if a large-sized water storage tank is mounted on a rail flaw detection vehicle, there is a limit to continuous flaw detection over a long distance while replenishing water. In cold regions such as Hokkaido, water may freeze and not be used.

  Currently, secondary flaw detection (re-flaw detection) is performed to detect internal transverse lacerations under surface flaws that could not be detected by rail flaw detection vehicles. As one of the secondary flaw detection methods, an operator manually performs two inspections on the side surface of the head 1a where a horizontal flaw is detected in the first flaw detection (a portion where a transverse flaw is likely) as shown in FIG. A method of applying flaws 3, irradiating ultrasonic waves from one probe 3 to the side surface of the head 1 a, detecting the ultrasonic waves transmitted through the head 1 a with the other probe 3, and performing flaw detection (transmission method) : Bipolar flaw detection method: manual inspection). However, this transmission method has the following difficulties.

1. If the side surface of the head 1a is worn or missing as shown in FIG. 12, the probe 3 cannot be brought into close surface contact with the missing portion 4 on the side surface of the head 1a. There is a space between the side surface of the probe and the probe 3 so that air is interposed, and the ultrasonic wave output from the probe 3 is difficult to propagate through the head, and there are places where flaws cannot be detected.
2. In order to improve the contact between the side surface of the head 1a and the probe 3, a cleaning operation for removing oil and dirt on the side surface of the head 1a is necessary, and the previous operation is troublesome.
3. In order to reduce the gap, oil is applied or grease is applied to the side surface of the head 1a, and these operations are also troublesome.
4). The inspection speed is slow due to manual work by the workers, and workability is poor.
5. When there are many or many surface flaws in the primary flaw detection, the secondary flaw detection range in the manual inspection becomes long and the workability is poor in order to reliably find the transverse laceration by the second flaw detection.
6). Since it is necessary to sandwich the side surface of the head 1a with a probe, it is impossible to perform inspections at places such as before and after level crossings and gaps.
7). Skilled workers are required to detect transverse lacerations.

  There is a phased array ultrasonic method as another method of the secondary flaw detection method. As shown in FIG. 13, a probe 3a on the transmitting side is arranged on the back side of the head 1a where a surface flaw is detected by primary flaw detection (a place where a transverse laceration is likely to occur). The transmission timing of ultrasonic waves from a plurality of arranged transducers is controlled to irradiate the rail 1 with an ultrasonic beam and to be reflected from the rail 1 (if there is a flaw, it is affected by the flaw. ) Is received by the probe 3b on the receiving side arranged on the back side of the head and the flaw is detected. According to this flaw detection method, flaw detection can be performed over a wide range of the inspection rail 1, but there are the same problems as the transmission method.

  The problem to be solved by the present invention is to detect an internal flaw under a surface flaw, and at a shallow stage of the surface flaw, it is possible to correct the rail surface and extend the life of the rail, and to easily break the rail. It is intended to be able to ensure safe driving by detecting the internal lateral laceration at an early stage and taking measures such as rail life estimation, repair, and replacement.

  In order to solve the above-mentioned problems, the present invention can perform surface flaw detection in a non-contact and non-destructive manner, and a lateral laceration (about 1/2 the depth from the rail head: about a half from the rail head surface) exists under the shelling. An object of the present invention is to provide a rail flaw detection method capable of flawing lateral cracks that are difficult to visually observe up to a depth of 20 mm, and a rail flaw detection device that can be used therefor.

(Flaw detection method 1)
The magnetic induction rail flaw detection method of the present invention is a rail flaw detection method for detecting surface flaws and lateral fissures (hereinafter referred to as “flaws”) of a rail to be flawed (inspection rail) by electromagnetic induction. The two detection coils that are spaced apart in the longitudinal direction of the test rail across the excitation coil are placed with a lift-off above the head of the test rail, and both detection coils are wound in reverse and connected in series. In addition, the AC magnetic flux generated from the exciting coil is added to the measurement rail to generate an eddy current in the measurement rail, and the change in the magnetic flux of the measurement rail caused by the eddy current may not be damaged. The amplitude difference (level difference) between the detection amplitude when there is no flaw detected by the two detection coils and the amplitude of the fluctuation induced voltage based on the eddy current that fluctuates due to the flaw when there is a flaw, The reverse winding detection coil Detecting a method of detecting the presence or absence of scratches gage rails from the amplitude difference. In this case, the excitation coil and the two detection coils may be arranged as one sensor unit in the arrangement, and the sensor unit may be arranged with a lift-off above the head of the measurement rail.

(Flaw detection method 2)
In the magnetic induction type rail flaw detection method of the present invention, one sensor coil of a sensor unit having two sensor coils in which an excitation coil and a detection coil are coaxially wound and both detection coils are wound in reverse is connected to the top of the head of the measurement rail. The other sensor coil is placed above the head of the intact reference rail with the lift-off, and the AC magnetic flux generated from the excitation coil above the inspection rail is added to the inspection rail. The AC magnetic flux generated from the upper excitation coil is applied to the reference rail to generate eddy currents in the measurement rail and the reference rail, and the amplitude of the induced voltage generated based on each eddy current is detected by the two sensor coils. If the inspection rail has a flaw, the amplitude of the fluctuation induced voltage based on the eddy current that fluctuates due to the flaw and the amplitude of the induced voltage of the reference rail (constant) The amplitude difference, detected and subtracted in the reverse winding detection coil, can also be adapted to detect the presence or absence of scratches gage rails from the amplitude difference. The driving voltage for exciting the two exciting coils is the same common driving signal.

(Flaw detection method 3)
In the magnetic induction type rail flaw detection method of the present invention, the excitation coil and the detection coil are coaxially wound, and the two sensor coils having both detection coils wound in reverse are separated in the longitudinal direction of the measurement rail and above the head of the measurement rail. Are arranged with lift-off, the detection coils of the respective sensor coils are opposed to two different locations in the longitudinal direction of the measurement rail, the detection coils of the two sensor coils are reversely wound and connected in series, and from the excitation coil The generated AC magnetic flux is applied to the inspection rail to generate an eddy current in the inspection rail, and the amplitude of the induced voltage at the two locations of the inspection rail generated based on the eddy current may not be damaged. The difference between the amplitude when there is no flaw and the fluctuation induced voltage based on the eddy current that fluctuates under the influence of the flaw when there is a flaw is detected by the detection coils of the two sensor coils. Detected by subtracting the detection coils, it is also possible to detect the presence or absence of scratches gage rails from the amplitude difference. In this case, it is also possible to arrange the coaxially wound excitation coils as one sensor unit in the arrangement, and arrange the sensor unit above the head of the measurement rail with a lift-off.

  According to the experiments by the present inventors, in any of the flaw detection methods, when there is a flaw on the inspection rail, the amplitude difference of the induced voltage is detected, and the amplitude difference depends on the size and depth of the flaw. It was found that it fluctuated (FIGS. 6A and 6B). Therefore, not only the presence or absence of a flaw but also the size and depth of the flaw can be detected (flaw detection is possible) by detecting the amplitude difference of the induced voltage. According to the experiments by the present inventors, in the present invention, it was possible to detect a flaw at the same location as the flaw detected by the ultrasonic flaw detection method. Furthermore, it was possible to detect scratches that could not be detected by the ultrasonic flaw detection method. Moreover, when the location detected by this invention was cut | disconnected, the damage | wound was actually confirmed.

(Flaw detection method 1 combined with phase difference detection)
Any of the above magnetic induction type rail flaw detection methods is a method for detecting the presence or absence of a flaw from the amplitude difference of the induced voltage. In the present invention, in order to detect the presence or absence of a flaw more reliably, the phase and detection of the excitation voltage are detected. A method of detecting a difference from the phase of the induced voltage detected by the coil (phase difference detection method) can also be used in combination. In the magnetic induction rail flaw detection method of the present invention, if the inspection rail has a flaw, the phase of the induced voltage is also affected and shifted. Therefore, before flaw detection of the inspection rail, the phase of the excitation voltage and the phase of the induced voltage when the flawless rail is flawed are adjusted to make the phase difference zero, and this phase difference zero is set as the reference phase. The difference between the reference phase and the phase of the induced voltage when a flaw on the inspection rail is detected can be obtained. According to the experiments by the present inventors, it has been found that when the inspection rail has a flaw (when flaw detection is performed), a phase difference is detected, and at the same time, an amplitude difference of the induced voltage is also detected (see FIG. 6 (a), (b)). Therefore, by detecting both the amplitude difference and the phase difference at the same time, the presence or absence of a flaw can be detected more reliably. Also in this case, the same detection as described above could be performed, and the presence of scratches could be confirmed.

(Mobile flaw detection method 1)
In any of the magnetic induction type rail flaw detection methods, in addition to the sensor unit, a magnetic induction type flaw detection device necessary for flaw detection is mounted on a mobile vehicle such as a self-propelled vehicle or a truck, and the mobile vehicle is mounted on the inspection rail. The inspection rail can be flawed while moving.

(Detection of flaws and flaw position)
In any of the magnetic induction type rail flaw detection methods, it is also possible to detect where the detected flaw is in the longitudinal direction of the rail (existing location). For this purpose, it is necessary to set a reference point for distance measurement and measure the distance from the reference point to the inspection point. Various methods are conceivable as the distance measuring method. In the present invention, for example, a laser Doppler type measuring method or a rotary encoder method can be used. In this case, in addition to the magnetic induction type flaw detection device, a laser Doppler type measurement device or a rotary encoder as a moving distance measurement device is mounted on a moving vehicle that can travel on the inspection rail, and the flaw detection device detects the flaw. The moving distance of the moving vehicle is also measured by the measuring device, and the flaw detection position (scratch location) of the inspection rail can be detected from the moving distance.

(Quantification)
In the electromagnetic induction rail flaw detection method of the present invention, the phase difference between the subtraction output of the two detection coils and the drive voltage for driving the excitation coil is also measured at the same time, and the quantification of the flaw is determined from the phase difference and the amplitude difference of the detection signal. Can be made. Quantification can be performed in contrast to the amount of flaw detection when a rail (a test piece with a flaw) with a predetermined shape and a predetermined position is damaged.

(Flaw detection device 1)
The electromagnetic induction type rail flaw detector of the present invention detects a rail flaw by an electromagnetic induction type, and can be arranged with a lift-off above the head of the measurement rail during rail flaw detection, and the sensor unit An excitation voltage supply unit that supplies an excitation voltage to the excitation coil and a signal processing unit that processes the detection signal detected by the sensor unit are arranged on both outer sides in the longitudinal direction of the rail across the excitation coil. Two detection coils, the excitation coil can apply an alternating magnetic flux to the measurement rail to generate an eddy current in the measurement rail, the two detection coils are reversely wound with each other and connected in series, and the vortex An amplitude difference of the induced voltage generated based on the current can be detected, and the signal processing unit processes the amplitude difference detected by the detection coil of the sensor unit. It is also available outputs an amplitude signal to the outside.

(Flaw detection device 2)
The magnetic induction type rail flaw detector of the present invention includes a sensor coil that can be placed opposite to the inspection rail with a lift-off above the head of the inspection rail, and a sensor coil that can be placed opposite to the head of an intact reference rail with a lift-off. Each sensor coil includes an excitation coil and a detection coil wound around a common core (coaxially wound), and the excitation coil of one sensor coil applies an alternating magnetic flux to the measurement rail to generate an eddy current in the rail. The excitation coil of the other sensor coil is driven with a voltage in phase with the excitation coil of the previous sensor coil, and an eddy current can be generated in the rail by applying an alternating magnetic flux to the reference rail. Both detection coils are reversely wound and connected in series, and the detection coil placed above the detection rail detects the amplitude of the excitation voltage generated by the eddy current in the detection rail The detection coil placed above the reference rail can detect the amplitude of the excitation voltage generated by the eddy current of the reference rail. When the measurement rail has a flaw, it is based on the eddy current that fluctuates due to the flaw. The difference in amplitude between the amplitude of the induced voltage that changes and the amplitude of the induced voltage detected by the detection coil above the reference rail (constant) may be subtracted and detected by the two reverse-wound detection coils. it can.

(Flaw detection device 3)
The magnetic induction type rail flaw detector according to the present invention includes at least two sensor units arranged laterally so as to be opposed to each other in two positions in the longitudinal direction of the measurement rail, and each sensor unit is coaxially wound. An excitation coil and a detection coil are provided, and both the detection coils are reversely wound with each other and connected in series to detect the induced voltage at the two positions of the measurement rail caused by the influence of the eddy current, and the measurement rail is damaged. To detect the amplitude difference between the amplitude of the induced voltage caused by the eddy current that fluctuates under the influence of the flaw and the amplitude of the induced voltage caused by the eddy current when there is no flaw You can also.

(Scratch detection, size inspection)
According to the experiments by the inventors of the present application, even if any of the flaw detection devices is used, the amplitude difference is detected when the inspection rail has a flaw, and the amplitude difference increases depending on the size or depth of the flaw. (FIGS. 6A and 6B). Therefore, the magnetic induction type rail flaw detector can detect not only the presence / absence of a flaw but also the size of the flaw by detecting the amplitude difference.

(Flaw detection combined with phase difference detection)
Any of the magnetic induction type rail flaw detectors can detect the presence or absence of a flaw from the amplitude difference of the induced voltage, but the signal processing unit compares the excitation voltage with the phase of the induced voltage detected by the detection coil. Thus, it is possible to detect the phase difference and output the phase difference to the outside. If a magnetic induction rail flaw detector equipped with this signal processing unit is used, when the inspection rail has a flaw, not only the amplitude difference but also the phase difference can be detected at the same time. It can detect more reliably.

(Identification of scratch position on inspection rail)
By mounting any of the magnetic induction type rail flaw detectors on a moving vehicle, the inspection rail can be detected while moving the moving vehicle on the inspection rail. In any of the above magnetic induction type rail flaw detectors, the position where the detected flaw is located on the measurement rail in the longitudinal direction by using the position measuring device using the laser Doppler type or the rotary encoder (where the flaw is present) Can also be detected. When the moving distance measuring device is used in combination, the moving distance measuring device is mounted on the moving vehicle together with the magnetic induction type rail flaw detecting device, and the moving vehicle is moved on the measurement rail to detect the flaw. At this time, by measuring the moving distance of the moving vehicle by the moving distance measuring device, it is also possible to detect a flaw location on the inspection rail from the moving distance. In this case, the signal processing unit processes a signal from the moving distance measuring device and outputs the moving distance (flaw detection position) to the outside.

(Display device)
Any of the magnetic induction type rail flaw detectors can be provided with a display device capable of displaying the output from the signal processing unit, and the waveform diagrams of the amplitude wave and the phase wave can be simultaneously displayed on the same screen of the display device. In this case, the presence / absence, size, and depth of a flaw can be visually observed by setting the horizontal axis to the measurement position and the vertical axis to the amplitude difference and phase difference. On the screen, the waveform diagram of the amplitude wave and phase wave of the left and right rails can be displayed simultaneously.

The present invention has the following effects.
1. Internal scratches close to the surface existing under the shelling can be detected as well as slight shelling and other surface scratches that cannot be detected by the ultrasonic flaw detection method. An internal transverse laceration at a depth of about 1/2 from the rail head (about 20 mm from the surface of the rail head) can be detected almost certainly without overlooking.
2. Not only the presence or absence of scratches, but also the location of the scratch in the longitudinal direction of the rail (distance from the base point to the location of the scratch), the depth are almost known, and the range of shelling is also known, so there is almost no need for secondary flaw detection. Even if necessary, since the surface flaw detection is reliable and the secondary flaw detection location is specified, the secondary flaw detection distance can be shortened and the flaw detection time can be greatly shortened.
3. Since it can be mounted on a truck or the like for flaw detection, rail flaw detection can be easily performed in each track maintenance section.
4). It is easy to operate and can detect flaws without being a skilled worker.
5. Non-destructive and non-destructive flaw detection with rails.
6). The flaw detection can be performed at a high speed of several km / h to 10 km / h.
7). The right and left rails can be detected at the same time.
8). It can be mounted on a self-propelled vehicle for flaw detection, as well as flaw detection while attached to a trolley and pushed by hand.
9. No water or grease is required.
10. A small, lightweight and low cost flaw detector.

The block explanatory view of the rail flaw detector of the present invention. FIG. 2 is a detailed diagram of the block explanatory diagram of FIG. The relationship between the sensor unit A and the rail in the present invention is shown, (a) is a plan view, (b) is an explanatory diagram showing the relationship between the excitation voltage of the sensor unit A and the induced voltage due to magnetic coupling of the detection coil, (C) is a side view of (a). (A) is connection explanatory drawing which shows the relationship between the excitation coil of the sensor unit B in this invention, and a detection coil, (b) is the relationship between the induced voltage by the magnetic coupling of the excitation coil of the sensor unit B coaxially wound, and a detection coil. Explanatory drawing which shows, (c) is a top view of the state which has arrange | positioned two sensor units of (b) with the lift-off above the measurement rail. The relationship between the excitation coil and detection coil of the sensor unit B and the rail in the present invention is shown, (a) is a plan view, (b) is a side view, and (c) is a sensor unit B arranged above the reference rail. Plan explanatory drawing of the state fixed, (d) is a side view of (c). (A), (b) is an example of the waveform chart of the flaw detection data of the left and right rails by the electromagnetic induction type rail flaw detection method of the present invention, and in either case, the amplitude fluctuation and the phase difference fluctuation when there is a flaw correspond. Explanatory drawing which shows having done. Explanatory drawing of the flaw detection position detection method by a laser Doppler system. It is principle explanatory drawing of electromagnetic induction, (a) is a schematic diagram which shows the relationship between a conductor, a sensor unit, and a magnetic field, (b) is explanatory drawing which shows the relationship between the eddy current which arises in a rail, and a damage | wound. (A) is explanatory drawing in the conductor surface of the magnetic flux in electromagnetic induction, (b) is explanatory drawing of a magnetic flux line and leakage flux in case a conductor surface has a damage | wound. The principle explanatory drawing of the electromagnetic induction type rail flaw detection method. Explanatory drawing of the bevel flaw detection method which is an example of the rail flaw detection method by an ultrasonic wave. Explanatory drawing of the two probe method which is an example of the rail flaw detection method by an ultrasonic wave. Explanatory drawing of the phased array method which is an example of the rail flaw detection method by an ultrasonic wave.

Example 1
The magnetic induction rail flaw detection method of the present invention (hereinafter referred to as “rail flaw detection method”) uses the principle of electromagnetic induction. As shown in FIG. 9A, when a magnetic field is applied to a conductor without a flaw, the magnetic flux lines pass through the conductor without being disturbed, but the conductor has a flaw. As shown in FIG. 9 (b), the magnetic flux lines pass through the conductor as a leakage magnetic flux in a damaged part. By detecting the magnitude of the change in the induced voltage that accompanies the change in the magnetic flux lines, it is possible to detect the presence or absence of the conductor and the size of the damage. When an AC magnetic field is applied to the conductor, an eddy current is generated in the conductor. Eddy currents are generated on the surface of the conductor as the magnetic permeability and electrical conductivity of the conductor and the frequency of the AC power supply increase (skin effect). For this reason, eddy currents are easily affected by flaws on the conductor surface (variation due to flaws), but flaws deeper in the conductor are less likely to be affected (fluctuation due to flaws is small). For this reason, the fluctuation of the induced voltage induced based on the eddy current is large when there is a shallow flaw, but is small when there is a deep flaw. When a flaw is detected by detecting a change in the induced voltage (flaw detection by electromagnetic induction), a surface flaw on the conductor is easy to detect, but a deeper internal flaw is harder to detect.
Therefore, as shown in FIG. 10, when the sensor coil is brought close to the damaged rail 1, a predetermined induced voltage can be obtained at a position where there is no damage on the rail, but the magnetic flux is affected by the damage at the position where there is a damage. In response, the induced voltage fluctuates. The present invention is a flaw detection method in which this difference is detected to detect the presence or absence of a flaw. The embodiment will be described below with reference to FIGS.

(Example of rail flaw detection method 1: using sensor unit A)
This rail flaw detection method is an example when the sensor unit A shown in FIGS. 1 and 2 is used. In these sensor units A, as shown in FIGS. 3A and 3B, two detection coils 7 a and 7 b are arranged apart from each other in the longitudinal direction of the measurement rail 1 with the excitation coil 6 as the center. The two detection coils 7a and 7b are reversely wound the same number of times on a core different from the core around which the exciting coil 6 is wound, and are connected in series.

  In the present invention, as shown in FIGS. 3A and 3C, the sensor unit A is disposed above the heads 1a of the left and right inspection rails 1 at a desired distance (about 10 to 30 mm) from the head 1a. ) Separated (with lift-off), the two detection coils 7a, 7b are arranged opposite to each other at two positions separated in the longitudinal direction of the measurement rail 1. In this state, an excitation voltage is supplied to the excitation coil 6 from the excitation voltage supply unit 11 (FIG. 2) of the flaw detection signal processor 10 shown in FIGS. 1 and 2, and the magnetic field generated from the excitation coil 6 is measured. In addition to 1, an eddy current is generated in the inspection rail 1. This eddy current changes when the inspection rail 1 has a surface flaw or an internal lateral fissure (hereinafter referred to as “flaw”). With this change, the magnetic field returning to the detection coils 7a and 7b changes, and the induced voltage induced in the detection coils 7a and 7b changes (FIGS. 8A and 8B). In the present invention, the amplitude change (level change) of the induced voltage is detected by the two detection coils 7a and 7b. In this case, the amplitude detected by the detection coils 7a and 7b is a subtracted difference because the winding directions of the coils 7a and 7b are opposite.

  A high-frequency component (mainly noise) is removed from the differential signal through a low-pass filter (LPF) of the output processing unit 12 (FIG. 2) of the flaw detection signal processor 10 shown in FIGS. 1 and 2, and an amplifier (AMP) 12a The amplitude signal is output to a display (for example, LCD: liquid crystal display) 13 outside the flaw detection signal processor 10 and displayed on the screen of the display 13 as shown in FIG. Displayed as (a), (b).

  In the present invention, not only the amplitude but also the phase difference between the excitation voltage and the detection signal detected by the detection coils 7a and 7b can be detected. If the inspection rail 1 is damaged, the phase of the induced voltage is also affected and the phase is shifted. Therefore, in this embodiment, before starting the flaw detection of the inspection rail, the phase difference between the excitation voltage and the induced voltage when the flawless rail (reference rail) is flawed is adjusted to zero (zero phase difference), This zero phase difference is set as a reference phase. A phase difference is detected by obtaining a difference between this reference phase and the phase of the induced voltage when a flaw on the measuring rail 1 is detected. The phase difference detection is performed by the arithmetic unit 12b (FIG. 2), which is output as a phase output to the display unit 13 of FIGS. 1 and 2, and displayed on the display unit 13 as shown in FIGS. 6 (a) and 6 (b). To display. 6A and 6B, the horizontal axis represents the moving distance (the distance traveled by the flaw detector from the reference point), and the vertical axis represents the amplitude and the phase difference. FIG. 6A shows the flaw detection waveform diagram of the right rail, and FIG. 6B shows the amplitude difference and phase difference of the flaw detection waveform diagram of the left rail.

  According to the experiments by the present inventors, in any of the flaw detection methods described above, when the inspection rail 1 has a flaw, the amplitude difference of the induced voltage is detected, and the induced voltage difference depends on the size or depth of the flaw. It was found to fluctuate. 6 (a) and 6 (b) are greatly changed in the amplitude waveform and the phase waveform, and only by looking at the waveform diagrams of FIGS. 6 (a) and 6 (b), the induced voltage difference, that is, the presence of a flaw is observed. In addition, it is possible to detect the size of the scratch from the magnitude of the waveform change. It was also confirmed that the flaw detection results did not overlook flaws as compared to flaw detection results obtained by the ultrasonic flaw detection method.

  According to the experiments by the present inventors, it was found that when the inspection rail 1 is flawed (when flaw detection is performed), a phase difference is detected, and at the same time, the induced voltage difference is also detected (FIG. 6). (A), (b)). Therefore, it is possible to more clearly detect the presence / absence and size of a flaw by simply looking at the waveforms in FIGS. 6 (a) and 6 (b).

(Example 2 of rail flaw detection method: when sensor unit B is used)
In the magnetic induction type rail flaw detection method of the present invention, rail flaw detection can also be performed using a sensor unit B (FIGS. 4A and 4B) different from the sensor unit A. In this sensor unit B, as shown in these drawings, the excitation coils 6a and 6b and the detection coils 7a and 7b are wound around one core (coaxially wound), and the detection coils 7a and 7b are wound around each other in a reverse direction (see FIG. An inspection rail) 8a and a sensor coil (reference rail) 8b are connected in series. The flaw detection using this sensor unit B can be performed as follows.

  One sensor coil (sensor coil for inspection rail) 8a of the sensor unit B is arranged with a lift-off above the head 1a of the inspection rail 1 as shown in FIG. The other sensor coil (reference rail sensor coil) 8b is fixed to a scratch-free reference rail (about several tens of centimeters) 15 as shown in FIGS. 6 (FIGS. 4A and 4B), an excitation voltage is supplied from the excitation voltage supply unit 11 (FIG. 2) of the flaw detection signal processor 10 shown in FIG. In addition to the head 1a of the inspection rail 1 and the head 15a of the reference rail 15, an eddy current is generated in the inspection rail 1 and the reference rail 15. Even if the inspection rail 1 is damaged, there is no damage. However, it does not occur in the two detection coils 7a and 7b according to the eddy current. When there is no flaw in the measuring rail 1, the amplitude difference between the induced voltages detected by the two detection coils 7a and 7b is zero, but when there is a flaw, the eddy current changes, The induced voltage changes with the change, resulting in an amplitude difference, which varies depending on the size and depth of the scratch, etc. The detected amplitude is also the reverse of the winding direction of the coils 7a and 7b. 2 is passed through a low-pass filter (LPF) of the output processing unit 12 of the flaw detection signal processor 10 shown in Fig. 2, amplified by an amplifier (AMP) 12a, and calculated by an arithmetic unit 12b. An arithmetic process is performed to output the amplitude signal to the external display 13 and display the flaw detection waveform on the screen, in which case the phase difference is detected and the phase difference is simultaneously displayed on the same screen as in the first embodiment. Can be displayed. It is possible to detect the flaws of gage rails 1 from reduction.

(Example 3 of rail flaw detection method: other usage example of sensor unit B)
In the third embodiment, the sensor unit B is used, but unlike the second embodiment, the two sensor coils 8a and 8b are both lifted off above the inspection rail 1 as shown in FIG. 4C. The eddy current is generated in the measurement rail 1 by the alternating magnetic flux generated from the excitation coils 6 of the sensor coils 8a and 8b. Induced voltages generated under the influence of the respective eddy currents are separately detected by the detection coils 7a and 7b of both sensor coils 8a and 8b. When a flaw is detected by one detection coil (7a or 7b) and no flaw is detected by the other detection coil (7b or 7a), an amplitude difference between the induced voltages is detected by both detection coils 7a and 7b. The differential signal is passed through the low-pass filter (LPF) of FIG. 2, amplified by the amplifier (AMP) 12 a, processed by the calculator 12 b, and the amplitude signal is output to the display device 13 outside the flaw detection signal processor 10. The flaw detection waveform can also be displayed on the screen. In this case, the phase difference can also be detected and the phase difference can be simultaneously displayed on the same screen as in the second embodiment. A flaw on the inspection rail 1 can be detected from the change in these waveforms.

(Quantification)
In the rail flaw detection method of any of the above-described embodiments, the amplitude difference and phase difference (subtraction output) of the excitation voltage detected by the two detection coils 7a and 7b, and a rail with a scratch of a predetermined shape at a predetermined position (scratched The scratch can be quantified by comparing the amplitude difference and the phase difference of the excitation voltage detected when the test piece is detected. However, in the flaw detection methods of the first and third embodiments, when both the detection coils 7a and 7b straddle one large flaw, or when the detection coils 7a and 7b reach different flaws at the same time, the quantification of the flaws is performed. It becomes difficult to make accurate flaw detection. In this case, the sensor unit B can be quantified by fixing it to the intact reference rail 15 as shown in FIGS. 5C and 5D as in the second embodiment.

(Detection of flaws and flaw position)
In any of the magnetic induction type rail flaw detection methods, in addition to the sensor unit A or B, a flaw detection signal processor and other devices necessary for flaw detection are mounted on a mobile vehicle such as a self-propelled vehicle or a truck. The inspection rail 1 can be flawed while moving on the inspection rail 1. In this case, if a point where the moving vehicle starts moving is set as a reference point for moving distance measurement, and the distance from the reference point to the flaw detection point is measured, the flaw detection position (flaw existing point on the measurement rail) is detected. You can also.

  Various methods are conceivable as a method for measuring the flaw detection position. As an example, the Doppler signal processor 14 (FIG. 2) can be employed. This Doppler signal processor 14 is mounted on a moving vehicle together with the sensor units A, B, etc., and the moving distance of the moving vehicle is measured simultaneously with the flaw detection. ) Can be specified. Instead of the Doppler signal processor 14, a rotary encoder or other distance measuring device can be used.

(Principle of laser Doppler sensor)
As shown in FIG. 7, the Doppler signal processor 14 divides the laser light from the laser light source LD into two by a beam splitter, one laser light goes straight as it is, and the other laser light is driven by a shift signal fm. When the frequency of irradiation light is shifted by an element (Acousto Optical Modulator) AOM and irradiation light with different frequencies is irradiated onto the moving measurement object at an intersection angle φ from two directions, scattered light from the measurement object is received by the light receiving lens. The light is received by a photoelectric conversion element (for example, APD: Avalanche Photo Diode) via an optical system such as heterodyne detection. At this time, the frequency Fd of the Doppler signal obtained from the photoelectric conversion element APD is expressed by the following equation.
Fd = fm ± (2V / λ) · sin (φ / 2) · cos (Δθ)
V: Surface speed of the object to be measured
λ: Laser wavelength
φ: beam crossing angle Δθ: angle of deviation between the beam normal and the object to be measured from the right angle As shown in the above formula, the Doppler frequency Fd is a frequency proportional to the surface velocity V of the object to be measured that moves. For this reason, if the wave number (number of pulses p) of the Doppler frequency Fd at a certain time is integrated, the length of the object to be measured at that time can be obtained. The pulse interval is determined by the beam crossing angle φ and the laser wavelength λ. As described above, the distance and moving speed of the object to be measured can be accurately measured by shifting the frequency of the irradiation light with the AOM.

(Mobile vehicle position detection)
In order to detect the position of a moving vehicle by means of a laser Doppler sensor (hereinafter referred to as “Doppler sensor”) mounted on the moving vehicle, laser light is irradiated on the inspection rail laying side, and scattered light (reflected from the laying side). Light) is received by the Doppler sensor, the reflected light is electrically converted and a Doppler signal is output, and the Doppler signal is processed to detect the position of the moving vehicle on the measurement rail (position position). In this train position detection method, a distance reference is installed on the inspection rail laying side in advance, and the laser beam emitted from the Doppler sensor is also applied to the distance reference, and the reflected light from this distance reference The Doppler sensor receives reflected light from the rail laying side including and outputs a Doppler pitch signal based on the Doppler signal. The travel distance of the train can be calculated by integrating the Doppler pitch signals. Here, the rail laying side is a track laying surface (usually gravel road surface) side provided with rails, sleepers, railroad crossings, the distance reference, etc., and the reflected light includes these rails, railroad crossings, track discriminators, etc. Various signals based on the reflected light from are also included.

(Example of rail flaw detector)
An example of the magnetic induction rail flaw detector according to the present invention will be described with reference to FIGS. As shown in FIG. 1, the rail flaw detector includes two sensor units A, a flaw detection signal processor 10, a Doppler signal processor 14, and a display 13. The magnetic induction type rail flaw detector of the present invention may be other than this, and the illustrated one is only an example, and other than this, as long as the problem to be solved of the present invention can be solved and the object can be achieved. May be.

  The two sensor units A in FIG. 1 are provided with an exciting coil 6 and two detection coils 7a and 7b as shown in FIG. The exciting coil 6 and the two detection coils 7a and 7b are wound around different cores. The two detection coils 7a and 7b have the same number of turns but are reversely wound so that the amplitude values detected by both the detection coils 7a and 7b are output as a subtraction value (amplitude difference).

  The phenomenon acting on the detection coils 7a and 7b is a result of a combination of three types of principles of eddy current, leakage magnetic flux, and air electromagnetic coupling. Any phenomenon reacts to the presence / absence, size, depth, etc. of the inspection rail 1 and is output to the detection coils 7a, 7b although it is a minute amount. The detection coil output (subtraction output) when the inspection rail 1 has neither a surface flaw nor a lateral fissure theoretically becomes zero, and when either one of the detection coils reaches a flawed position, both detection coils 7a, 7b The balance is lost and output is generated. This is amplified and used as an amplitude output, and the phase of the drive voltage of the excitation coil and the differential output of the detection coil is measured to obtain the phase output.

  The flaw detection signal processor 10 of FIG. 1 includes an excitation voltage supply unit 11, an output processing unit 12, and a phase shifter 17 as shown in FIG. 1 and 2, a display device (monitor) 13 such as a liquid crystal display for displaying flaw detection information is also provided.

As shown in FIG. 2, the excitation voltage supply unit 11 includes an oscillator 11a that oscillates a reference signal, a frequency divider (DIV), a write-only memory element (ROM), a digital / analog converter (D / A), and a sine wave converter. A section 11b, a variable resistor VR ₁ , and an amplifier 11c are provided.

The output processing unit 12 is a detection signal detected by the detection coil 7a, 7b (amplitude, phase) low-pass filter for removing high frequency noise components from (LPF), a variable resistor VR _2, amplifiers 12a, calculator 12b, a central A processing device (CPU) is provided.

  The arithmetic unit 12b can process the detection signals detected by the detection coils 7a and 7b and the signal from the Doppler signal processor 14, and output an amplitude output signal, a phase output signal, and a movement distance output signal.

  The CPU controls the computing unit 12b. The CPU may be integrated with the calculator 12b.

  In FIG. 2, an operation panel 16 is provided. The operation panel 16 operates the CPU to set various conditions, change conditions, and delete.

  The phase shifter 17 determines the phase of the excitation voltage supplied from the excitation voltage supply unit 11 (FIG. 2) and the level of the induced voltage when the intact rail (reference rail) is detected before the inspection rail 1 starts flaw detection. The phase difference is adjusted to zero, and this zero phase is set as a reference phase.

  In FIG. 2, a power source 18 is provided. The power source 18 is a power source for driving the flaw detection signal processor 10 and can supply various voltages necessary for driving the flaw detection signal processor 10. A power stabilization device or other power-related equipment can also be provided.

  The Doppler signal processor 14 is an application of the principle of a laser Doppler sensor, and the above-described configuration and function can be used. By using the Doppler signal processor 14, when a flaw on the inspection rail 1 is detected, the position in the longitudinal direction of the inspection rail 1 (how many kilometers away from the reference position) is measured. Can do.

  FIG. 4 shows an example of the sensor unit B. In this sensor unit B, one detection coil 7a and a reference rail detection coil 7b are arranged centering on the excitation coil 6 apart from each other in the longitudinal direction of the inspection rail 1. The detection coil 7b of the reference coil is for detecting an induced current from the reference rail 15 (FIGS. 5C and 5D). The reference rail 15 is an intact rail with no surface scratches or lateral lacerations, has a desired length, for example, a length of about several tens of centimeters, and has the same material and magnetic characteristics as those of the inspection rail 1.

  When the sensor unit B is used, the sensor unit B is fixed to the reference rail 15, the positional relationship among the reference rail 15, the exciting coil 6, and the reference coil detection coil 7b is kept constant, and the reference coil detection coil is used. 7b should not reach the inspection rail 1 scratch. In this case, scratches can be quantified and accurate flaw detection can be performed.

  When the sensor unit B is used, the excitation coil 6 and the detection coil 7a can be coaxially wound around the same core to reduce the leakage magnetic flux, increase the flux linkage rate, and increase the detection sensitivity.

  Both the sensor unit A and the sensor unit B can be mounted on a moving vehicle together with the flaw detection signal processor, the display unit 13, the Doppler signal processor 14, and other necessary devices shown in FIG. . Both the sensor unit A and the sensor unit B can be mounted on one moving vehicle, and the two sensor units A and B can be switched and used according to the measurement environment and conditions.

  The flaw detection method of the present invention can also be used for flaw detection of conductors other than rails.

DESCRIPTION OF SYMBOLS 1 Inspection rail 1a Inspection rail head 2 Ultrasonic generator 3 Probe 3a Transmission side probe 3b Reception side probe 4 Rail head missing part 6 Excitation coil 6a, 6b Excitation coil 7a 7b, detection coil 8a, sensor coil for inspection rail, 8b, sensor coil for reference rail, 10 flaw detection signal processor, 11 excitation voltage supply unit, 11a oscillator, 11b, sine wave conversion unit, 11c amplifier, 12 output processing unit (detection coil output signal processing unit)
12a amplifier 12b arithmetic unit 13 display unit 14 Doppler signal processor 15 reference rail 15a head of reference rail 16 operation panel 17 phase shifter 18 power supply AMP amplifier DIV frequency divider LPF low pass filter ROM write-only storage element D / A , Digital / analog converter VR ₁ , VR ₂ variable resistor CPU central processing unit

Claims (14)

In the rail flaw detection method for detecting surface flaws and lateral fissures (hereinafter referred to as “scratches”) of the inspection rail by electromagnetic induction,
An excitation coil and two detection coils that are arranged apart from each other in the longitudinal direction of the measurement rail across the excitation coil are arranged with a lift-off above the head of the measurement rail,
Both detection coils are wound in reverse and connected in series.
Add AC magnetic flux generated from the exciting coil to the inspection rail to generate eddy current in the inspection rail,
The amplitude of the induced voltage generated based on the eddy current may be detected by the two detection coils even when there is no scratch,
Detects the presence or absence of flaws on the measurement rail from the amplitude difference between the detection amplitude when there is no flaw and the fluctuation induced voltage based on the eddy current that fluctuates due to the flaw when there is a flaw,
A magnetic induction rail flaw detection method characterized by the above. The magnetic induction rail flaw detection method according to claim 1,
The excitation coil and the two detection coils form one sensor unit in the arrangement, and the sensor unit is arranged with a lift-off above the head of the measurement rail.
A magnetic induction rail flaw detection method characterized by the above. In the rail flaw detection method that detects flaws on the inspection rail by electromagnetic induction,
Place one sensor coil of the sensor unit with two sensor coils with the excitation coil and the detection coil reversely wound coaxially with a lift-off above the head of the measurement rail, and the other sensor coil with an intact reference rail Is placed with a lift-off above the head, and the AC magnetic flux generated from the excitation coil above the measurement rail is added to the measurement rail, and the AC magnetic flux generated from the excitation coil above the reference rail is added to the reference rail, Generate eddy currents on the inspection and reference rails,
The two sensor coils detect the amplitude of the induced voltage generated by the influence of each eddy current,
If there is a flaw on the inspection rail, the difference between the amplitude of the fluctuation induced voltage based on the eddy current that fluctuates due to the flaw and the amplitude of the induced voltage of the reference rail is subtracted by the reverse winding detection coil and detected. And
Detecting the presence or absence of scratches on the inspection rail from this amplitude difference,
A magnetic induction rail flaw detection method characterized by the above. In the rail flaw detection method that detects flaws on the inspection rail by electromagnetic induction,
Two sensor coils, in which the excitation coil and the detection coil are coaxially wound in reverse, are placed apart from each other in the longitudinal direction of the measurement rail and with a lift-off above the head of the measurement rail, and the detection coil of each sensor coil is detected. Opposing to two different places in the longitudinal direction of the measuring rail,
The detection coils of the two sensor coils are connected in series,
Add AC magnetic flux generated from the exciting coil to the inspection rail to generate an eddy current in the inspection rail,
Detecting the amplitude of the induced voltage at the two positions of the measurement rail generated according to the eddy current may be detected by the detection coils of the two sensor coils in some cases.
A detection amplitude when there is no flaw and a difference between amplitudes of fluctuation-induced voltages based on eddy currents fluctuated under the influence of the flaw when there is a flaw is detected by subtracting with the reverse winding detection coil,
Detecting the presence or absence of scratches on the inspection rail from this amplitude difference,
A magnetic induction rail flaw detection method characterized by the above. In the magnetic induction type rail flaw detection method according to any one of claims 1 to 4,
Before the inspection rail flaw detection, the phase of the excitation voltage and the phase of the induced voltage when the flawless rail is flawed are adjusted to make the phase difference zero, and this phase difference is set as the reference phase. And the difference between the phase of the induced voltage when a flaw on the inspection rail is detected,
A magnetic induction rail flaw detection method characterized by the above. In the magnetic induction type rail flaw detection method according to any one of claims 1 to 5,
The equipment necessary for flaw detection of inspection rails is mounted on moving vehicles,
Detecting the inspection rail while moving the moving vehicle on the inspection rail,
A magnetic induction rail flaw detection method characterized by the above. The magnetic induction rail flaw detection method according to claim 6,
A moving distance measuring device is installed in a moving vehicle,
With the movement distance measuring device, measure the movement distance of the moving vehicle at the time of flaw detection,
Detects the position of the flaw detection location,
A magnetic induction rail flaw detection method characterized by the above. In the magnetic induction type rail flaw detection method according to any one of claims 1 to 7,
Measure the phase difference between the subtraction output of both detection coils and the drive voltage that drives the excitation coil,
The detected phase difference and amplitude difference are compared with the amount of flaw detection when a flawed test piece with a flaw in a predetermined position is detected, and the flaw is quantified.
A magnetic induction rail flaw detection method characterized by the above. In rail flaw detectors that detect flaws in inspection rails using electromagnetic induction,
A sensor unit that can be placed with a lift-off above the head of the measurement rail during rail flaw detection, an excitation voltage supply unit that supplies an excitation voltage to the excitation coil of the sensor unit, and a detection signal detected by the sensor unit A signal processing unit,
The sensor unit includes an excitation coil and two detection coils arranged in the longitudinal direction of the rail across the excitation coil,
The excitation coil can generate an eddy current in the inspection rail by applying an alternating magnetic flux to the inspection rail.
The two detection coils are reversely wound with each other and are connected in series to detect an amplitude difference between induced voltages based on the eddy current,
The signal processing unit is configured to process an amplitude difference detected by a detection coil of the sensor unit and output an amplitude signal to the outside.
An electromagnetic induction rail flaw detector characterized by the above. In rail flaw detectors that detect flaws in inspection rails using electromagnetic induction,
It has a sensor coil that can be placed opposite to the head of the inspection rail with a lift-off, and a sensor coil that can be placed opposite to the head of an intact reference rail with a lift-off,
Each sensor coil includes an excitation coil and a detection coil that are coaxially wound around a common core, and the excitation coil of one sensor coil can generate an eddy current in the rail by applying AC magnetic flux to the measurement rail, The excitation coil of the other sensor coil can apply an alternating magnetic flux to the reference rail to generate an eddy current in the rail,
Both detection coils are reversely wound and connected in series;
The detection coil arranged above the detection rail can detect the amplitude of the excitation voltage caused by the eddy current of the measurement rail, and the detection coil arranged above the reference rail can detect the amplitude of the excitation voltage caused by the eddy current of the reference rail. Can be detected,
When there is a flaw on the inspection rail, the amplitude difference between the amplitude of the induced voltage that changes based on the eddy current that fluctuates due to the flaw and the amplitude of the induced voltage detected by the detection coil above the reference rail , Subtracted by both detection coils that were wound in reverse, so that it can be detected,
An electromagnetic induction rail flaw detector characterized by the above. In rail flaw detectors that detect flaws in inspection rails using electromagnetic induction,
At least two sensor units arranged apart from each other in the longitudinal direction so that they can be opposed to each other in two places in the longitudinal direction of the inspection rail,
Each sensor unit includes an excitation coil and a detection coil that are coaxially wound around a common core.
These two detection coils are wound in reverse and connected in series to detect the induced voltage at the two points of the test rail that is generated by the influence of the eddy current. The difference between the amplitude of the induced voltage caused by the eddy current that fluctuates in response to the amplitude of the induced voltage caused by the eddy current when there is no flaw can be detected.
An electromagnetic induction rail flaw detector characterized by the above. In the electromagnetic induction type rail flaw detector according to any one of claims 9 to 11,
The signal processing unit can output the phase difference between the excitation voltage phase and the induced voltage detected by the detection coil to the outside so that the presence or absence of a flaw can be detected by both the amplitude difference and the phase difference.
An electromagnetic induction rail flaw detector characterized by the above. In the electromagnetic induction type rail flaw detector according to any one of claims 9 to 12,
The electromagnetic induction rail flaw detector is mounted on a moving vehicle,
While detecting the inspection rail while moving the moving vehicle on the inspection rail, the moving position of the moving vehicle can be detected,
The signal processing unit is also equipped with a function that processes the signal from the moving distance measuring device and outputs the moving distance (flaw detection position) to the outside to check the position of the detected flaw on the measurement rail.
An electromagnetic induction rail flaw detector characterized by the above. In the electromagnetic induction type rail flaw detector according to any one of claims 9 to 13,
Provided with a display device that can display the output from the signal processing unit, so that the waveform diagram of the amplitude wave and the phase wave can be displayed simultaneously on the same screen of the display device,
The display screen can display the waveform diagram with the horizontal axis as the measurement position, the vertical axis as the amplitude, and the phase difference.
An electromagnetic induction rail flaw detector characterized by the above.

Images