JP4367121B2 - Rail inspection method - Google Patents

Description

  The present invention relates to a rail inspection method, and more particularly, to a rail inspection method for mainly evaluating the presence or absence of a horizontal crack in a constricted portion of a rail.

  The rail of the railway is for supporting the load of the railway vehicle, and a large repetitive load is applied to the rail every time the vehicle passes. For this reason, overlooking defects that have occurred inside the rails during manufacturing, or that have been generated and grown by repeated loads acting during use, can lead to serious accidents.

  Therefore, a non-destructive inspection is performed before shipping the rail and after installation in order to check whether there is a defect inside the rail. As a nondestructive inspection method for rails, various test methods such as radiation transmission test method, ultrasonic flaw detection method, penetrant flaw detection method, eddy current flaw detection test method, etc. can be used depending on the rail shape, material, inspection environment, etc. ing.

  For example, in the case of a carbon steel rail, since ultrasonic attenuation is relatively small, an ultrasonic pulse reflection method is generally used as a nondestructive inspection before shipment and after installation. On the other hand, in the case of casting rails such as manganese crossings, the scattering and attenuation of ultrasonic waves is large, so the radiation transmission test method is used for product inspection before shipment, and the penetrant inspection method and visual inspection are used for on-site inspection after installation. Is commonly used.

  Further, Patent Document 1 discloses a transmission probe and a reception probe on both side surfaces of a rail head in order to detect lateral cracks generated in the rail head due to repeated loads when a vehicle passes. An ultrasonic rail head lateral crack detection method for determining the presence or absence of lateral cracks by arranging a child and detecting transmitted waves is disclosed. In this document, instead of a method in which the transmitting probe and the receiving probe are opposed to each other at a right angle with respect to the longitudinal direction of the rail in the width direction of the rail, the positions of both of them are It is described that a lateral crack can be detected without receiving interference from adjacent horizontal cracks by using a method in which they are shifted in the vertical direction.

  Further, Patent Document 2 discloses a transmission oblique probe and a reception oblique probe respectively disposed on both sides of a rail head, and a transmission oblique probe and a reception oblique probe. An ultrasonic inspection apparatus including an adjustment tool for adjusting at least one of the positions in the longitudinal direction and / or the vertical direction is disclosed. In this document, the transmission oblique angle probe and the reception oblique angle probe are arranged so that the center lines of the ultrasonic beams coincide with each other, thereby determining whether or not there is an internal defect in the rail head. The point which can be detected as a change of is described.

  Furthermore, in Patent Document 3, (a) a short pulse transmission wave is input from a transmitter to a specimen via broadband ultrasonic waves, ultrasonic waves generated in the subject are received and amplified, and the frequency of the received signal After selecting the most significant frequency from the spectrum analysis, (b) a burst transmission wave and a transmission reference wave signal of this frequency were generated in synchronization with each other from the transmitter and the transmission reference wave generator, and propagated in the subject. An ultrasonic flaw detection method is disclosed in which, after filtering an ultrasonic reception signal, (c) a cross-correlation calculation process is performed by taking it into a signal processing calculator simultaneously with a transmission reference wave signal. According to this document, by using such a method, a received signal with high sensitivity and high S / N can be detected even when ultrasonic scattering is large such as in concrete and refractory. Points are listed.

JP 2001-183349 A Japanese Patent Application Laid-Open No. 5-29681 JP 7-248317 A

  As is well known, the rail is composed of a head that contacts the wheels of the railway vehicle, a foot that transmits the vehicle load supported by the head to the sleepers, and an abdomen that connects the head and the foot. Since the rail has a narrower abdominal width than the head width, there is a crack that penetrates horizontally in the width direction of the rail in the vicinity of the boundary between the head and the abdomen (hereinafter referred to as the "constriction"). (Hereinafter, this is referred to as a “horizontal crack”). Since such a horizontal crack leads to a rail breakage accident, it is necessary to reliably detect the presence or absence of the horizontal crack before shipment and after installation.

  Here, in the case of a carbon steel rail, since the attenuation of the ultrasonic wave is small, the presence or absence of a horizontal crack can be detected relatively easily using a conventional pulse reflection method. On the other hand, the cast rail generally has a coarse structure and has many cast holes, so that the attenuation of ultrasonic waves is large. In addition, defects caused by casting (such as a cast hole) generally have an irregular inner surface shape, so that the reflectance of ultrasonic waves is small. Therefore, even if the pulse reflection method is applied to the casting rail, a clear reflection echo from the horizontal crack cannot be obtained.

  In addition, the methods disclosed in Patent Documents 1 and 2 have a transmitting probe and a receiving probe arranged on both sides of the head, so that a defect occurring in the head can be detected, but in the vicinity of the constricted portion. It is difficult to detect horizontal fissures that occur. It is also difficult to arrange the transmitting and receiving oblique probes so that the center lines of the ultrasonic beams coincide with each other in order to detect horizontal cracks in the rail installed at the site. It is. On the other hand, Patent Document 3 does not disclose any inspection method suitable for rails.

  Furthermore, there is also a method for inspecting the presence or absence of a horizontal crack using a penetrating flaw detection method for a cast rail. However, in order to inspect the presence or absence of a horizontal crack in the vicinity of the constricted portion of the rail installed at the site, it is necessary to remove the joint plate of the rail and perform penetration inspection. Therefore, enormous inspection time is required. In addition, the working posture for observing the instruction pattern is unsatisfactory, and it takes a long time to confirm the flaw instruction.

  The problem to be solved by the present invention is to provide a rail inspection method capable of detecting a horizontal crack generated in a constricted portion of the rail regardless of the material of the rail and the work environment. In addition, another problem to be solved by the present invention is to provide a rail inspection method capable of detecting a horizontal crack generated in a constricted portion of a rail in a short time and without overloading an operator. There is. In addition, the rail in this application includes the crossing which comprises the part where a rail crosses.

In order to solve the above-described problems, a rail inspection method according to the present invention includes a transmission probe disposed on either the head side or the foot side of a rail, and ultrasonic waves are transmitted from the transmission probe. A transmitting step for transmitting, and placing the receiving probe at a position that is the other of the head side or the foot side of the rail and does not coincide with the axis of the ultrasonic wave transmitted by the transmitting probe; A receiving step of receiving the ultrasonic wave transmitted from the transmitting probe by the receiving probe; and after the transmitting probe transmits the ultrasonic wave, the receiving probe receives the ultrasonic wave. The time until reception is delayed from the time from when the ultrasonic wave is transmitted from the ultrasonic transmission probe to the rail without a horizontal crack near the constricted portion until the reception probe receives the ultrasonic wave. And a determination step of determining the presence or absence of a defect based on the above.

  When a transmitting probe is arranged on either the head side or the foot side of the rail and a receiving probe is arranged on the other side, when transmitting ultrasonic waves from the transmitting probe, the constricted part When there is no horizontal crack in the vicinity, the transmitted wave is received by the receiving probe after a predetermined time has elapsed. On the other hand, when there is a horizontal crack near the constricted portion, the arrival time of the transmitted wave is delayed or the transmitted wave is not detected. Therefore, the presence or absence of a horizontal crack in the constricted portion can be detected with high accuracy by detecting the intensity of the transmitted wave and the arrival time of the transmitted wave.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The rail inspection method according to the present invention includes a transmission step, a reception step, and a determination step.

  The transmission step is a step of arranging a transmission probe on either the head side or the foot side of the rail and transmitting ultrasonic waves from the transmission probe. In the present invention, the material of the rail is not particularly limited, and can be applied to rails having various materials. Specific examples of the material for the rail include carbon steel and high manganese cast steel. In particular, cast rails made of high manganese cast steel have a large attenuation and / or scattering of ultrasonic waves, so it is difficult to determine the presence or absence of defects using the conventional pulse reflection method. It is possible to determine the presence or absence of a horizontal crack in the portion with high accuracy.

  In the present invention, the structure of the transmission probe is not particularly limited, and probes having various structures can be used. In other words, the transmission probe may be provided with a single piezoelectric element, or an array probe capable of transmitting ultrasonic waves from various small piezoelectric elements arranged at different timings. It may be a tentacle. In particular, when an array probe in which a large number of piezoelectric elements are arranged in the longitudinal direction of the rail is used as the transmitting probe, the step of scanning the transmitting probe in the longitudinal direction of the rail can be simplified or omitted. There is an advantage.

  Further, the output of the ultrasonic wave transmitted from the transmission probe is not particularly limited, but the rail is made of a material with high attenuation and / or scattering of the ultrasonic wave (for example, a cast body made of high manganese cast steel). In the case of comprising, it is preferable to use ultrasonic waves stronger than the ultrasonic waves used in the conventional pulse reflection method.

  There are various methods for transmitting strong ultrasonic waves. The first method is to use a frequency having a predetermined frequency as a frequency used for flaw detection. In general, as the frequency of the ultrasonic wave increases, the resolution improves, but the attenuation of the ultrasonic wave increases and the ultrasonic wave that reaches the receiving probe becomes weaker. Therefore, in order to make a strong ultrasonic wave reach the receiving probe, it is preferable to transmit an ultrasonic wave having a relatively low frequency within a range in which the resolution is not lowered.

  In the present invention, specifically, the frequency of the ultrasonic wave used for flaw detection is preferably from 0.5 MHz to 5 MHz. If the frequency of the ultrasonic wave exceeds 5 MHz, the attenuation of the ultrasonic wave increases, which is not preferable. On the other hand, if the frequency of the ultrasonic wave is less than 0.5 MHz, the ultrasonic wave spreads and the resolution decreases, which is not preferable. The frequency of the ultrasonic wave is more preferably 1 MHz or higher and 2 MHz or lower.

  The second method of transmitting strong ultrasonic waves is to increase the amplitude of the electric signal applied to the vibrator. For this purpose, the voltage applied to the vibrator may be increased. The optimum voltage applied to the vibrator varies depending on the type of vibrator. In the case of a normal pulse reflection method, the applied voltage is about 40 to 80 V, but in the present invention, the applied voltage is preferably 200 V or more, more preferably 300 V or more, and still more preferably 400 V or more.

  A third method for transmitting strong ultrasonic waves is to use a probe having a relatively large transducer. In general, as the size of the vibrator increases, a stronger ultrasonic wave can be transmitted. Specifically, the size of the vibrator is preferably such that the diameter or the length of one side is 10 mm or more, and more preferably 30 mm or more.

  A fourth method for transmitting strong ultrasonic waves is to use a burst wave as an electric signal applied to the vibrator. When a burst wave is used, the frequency band is narrowed. Therefore, when correlation processing is performed on the receiving side, a correlation value corresponding to the wave number of the burst wave is obtained, and as a result, a strong transmitted signal can be obtained. In this case, the correlation processing may be performed digitally or analogly.

  Note that the various methods for transmitting strong ultrasonic waves described above may be used alone or in combination of two or more.

  The transmission probe is arranged on either the head side or the foot side of the rail. Here, the “head side” means a position above the position of the horizontal crack generated in the constricted portion of the rail. Further, the “foot side” refers to a position below the position of the horizontal crack generated at the constricted portion of the rail.

  For example, when the transmitting probe is disposed on the rail head side, the transmitting probe may be disposed on the top surface of the rail head or on the side surface of the rail head. May be. Further, when the transmission probe is disposed on the foot side of the rail, the transmission probe may be disposed on the abdomen of the rail, or may be disposed on either of the rail feet. . In particular, if the transmitting probe is arranged on the top surface of the head of the rail, installation work of the transmitting probe is facilitated, and ultrasonic waves can be transmitted vertically toward the constricted portion of the rail, so that the accuracy is high. There is an advantage that a high inspection can be performed.

  In addition, it is desirable to interpose a contact medium for efficiently transmitting ultrasonic waves between the transmission probe and the rail. Specific examples of the contact medium include water, glycerin paste, and machine oil.

  Next, the reception process will be described. The receiving step is a step of placing a receiving probe on the other of the head side or the foot side of the rail and receiving the ultrasonic wave transmitted from the transmitting probe by the receiving probe.

  In the present invention, the structure of the receiving probe is not particularly limited, and probes having various structures can be used. In other words, the receiving probe may be provided with a single piezoelectric element, or an array probe capable of transmitting ultrasonic waves at different timings from a large number of minute piezoelectric elements arranged. It may be a tentacle. In particular, when an array probe in which a large number of piezoelectric elements are arranged in the longitudinal direction of the rail is used as the receiving probe, the step of scanning the receiving probe in the longitudinal direction of the rail can be simplified or omitted. There is an advantage.

  Further, the receiving probe does not necessarily have the same structure as the transmitting probe. In other words, a probe including one piezoelectric element may be used as a transmission probe, and an array probe may be used as a reception probe. Or the reverse may be sufficient. In particular, when an array probe is used for both the transmitting probe and the receiving probe, the inspection speed can be increased and the inspection can be performed efficiently.

  The receiving probe is not particularly limited as long as it can receive the ultrasonic wave transmitted from the transmitting probe. However, if the rail is made of a material with a large attenuation and / or scattering of ultrasonic waves (for example, a casting made of high manganese cast steel), the sensitivity of the receiving probe is made higher than that of the conventional pulse reflection method. Is preferred.

  There are various methods for improving the sensitivity of the receiving probe. The first method is to use a vibrator provided with a highly sensitive piezoelectric element. When a highly sensitive piezoelectric element is used, a weak transmitted wave can be reliably detected. Specific examples of highly sensitive piezoelectric elements include zinc zirconate titanate and composites.

  A second method for improving the sensitivity of the receiving probe is to increase the amplification factor of the receiving amplifier. When the amplification factor of the receiving amplifier is increased, a weak transmitted wave can be reliably detected. Specifically, the amplification factor of the reception amplifier is preferably 60 dB or more, and more preferably 80 dB or more.

  Note that the various methods for improving the sensitivity of the receiving probe described above may be used alone or in combination of two or more. Further, in addition to the method for improving the sensitivity of the receiving probe, various methods for transmitting the above-described strong ultrasonic waves may be used in combination. These combinations may be selected in accordance with the inspection purpose, the structure of the transmission probe, and the like.

  For example, a probe capable of transmitting an ultrasonic wave having the same strength as the ultrasonic wave used in the conventional pulse reflection method is used as a transmission probe, and a highly sensitive probe is used as a reception probe. May be used. Alternatively, a probe capable of transmitting an ultrasonic wave stronger than the conventional method may be used as the transmission probe, and a probe having normal sensitivity may be used as the reception probe. Furthermore, a probe capable of transmitting strong ultrasonic waves may be used as the transmission probe, and a highly sensitive probe may be used as the reception probe. In addition to these, a method of increasing the amplification factor of the reception amplifier may be used in combination.

  The receiving probe is arranged on either the head side or the foot side of the rail and on the opposite side of the transmitting probe with the constricted portion interposed therebetween. Note that the definition of “head side” and “foot side” and the point that it is preferable to interpose a contact medium between the receiving probe and the rail are the same as in the transmission step, and thus the description is omitted. To do.

  FIG. 1 shows an example of the arrangement of transmitting probes and receiving probes. In FIG. 1, the test body is a rail 10, and the rail 10 includes a head 10a, a foot 10c, and an abdomen 10b that connects the head 10a and the foot 10c. In the example shown in FIG. 1, the transmission probe 20 is disposed on the top surface of the head 10 a of the rail 10, and the reception probe 30 is disposed on the foot 10 c of the rail 10.

  In the example shown in FIG. 1, one transmission probe 20 and one reception probe 30 are shown, but this is merely an example, and depending on the purpose, the rail 10 A plurality of transmission probes 20 and / or reception probes 30 may be arranged in the longitudinal direction and / or the width direction. An array probe may be used as the transmitting probe 20 and / or the receiving probe 30.

  Next, the determination process will be described. The discrimination step is a step of discriminating the presence or absence of a defect from the intensity and arrival time of the ultrasonic wave received by the receiving probe after a lapse of a certain time from transmission from the transmission probe.

  Here, the “certain time” is the time from when the ultrasonic wave is transmitted from the transmitting probe to when it is received by the receiving probe when there is no horizontal crack in the vicinity of the constricted portion of the rail (hereinafter referred to as “the predetermined time”) This is referred to as “standard propagation time”). The value of the standard propagation time varies depending on the material and shape of the rail, the material of the contact medium, the structure and arrangement of the transmitting probe and the receiving probe, and the like.

  Normally, when there is no horizontal crack in the vicinity of the constricted portion of the rail, the transmitted ultrasonic wave passes through the constricted portion as it is, so that the ultrasonic wave is received after the standard propagation time has passed. On the other hand, if there is a crack near the constricted part of the rail, but the crack does not penetrate in the horizontal direction, and / or a transmitting probe and a receiving probe are arranged near the end of the horizontal crack. In this case, since the ultrasonic wave bypasses the crack while repeating multiple reflections, the ultrasonic wave reaches the receiving probe with a delay from the standard propagation time. Furthermore, if there is a horizontal crack in the constricted part of the rail and the head and feet are completely separated, the arrival time of the ultrasonic wave will be further delayed, or the supersonic wave received by the receiving probe will be delayed. Sound wave becomes noise level.

  Therefore, even if the reflected echo due to the defect cannot be clearly observed by the conventional pulse reflection method, whether or not the transmitted wave is received by the receiving probe and the arrival when the transmitted wave is received By observing the degree of time delay, it is possible to determine whether or not there is a horizontal crack near the constricted portion of the rail.

  As described above, according to the rail inspection method of the present invention, the presence or absence of a horizontal crack in the vicinity of the constricted portion can be easily determined. In addition, when the intensity of the ultrasonic wave incident on the rail and / or the sensitivity of the receiving probe is optimized, the attenuation and / or scattering of the ultrasonic wave is large as in a cast rail made of high manganese cast steel. In addition, the presence or absence of a horizontal crack in the vicinity of the constricted portion can be easily determined.

  In addition, the rail inspection method according to the present invention only needs to arrange the transmitting probe on one of the head side and the foot side of the rail and the receiving probe on the other side. It is not necessary to remove the rail joint plate. Therefore, even when inspecting at the site where the rail is installed, the inspection can be performed safely in a short time. In addition, an inspection result having a high correlation with the penetrant flaw detection test is obtained, the equipment cost is low, and no inspection skill is required. Furthermore, since an unnatural work posture is rarely taken, an excessive burden is not imposed on the worker.

As shown in FIG. 1, a transmitting probe and a receiving probe were arranged on the top surface and the foot of the head of a cast rail made of high manganese cast steel, respectively, and the transmitted wave was measured. The test conditions are as follows.
Transmitter probe: 2 MHz, broadband, φ20 mm.
Receiving probe: 1 MHz, broadband, φ20 mm.
Contact medium: Sonicoat BS300.
Applied voltage: 400V.

(Comparative Example 1)
A transmitted wave was measured according to the same procedure as in Example 1 except that a probe of 2 MHz, a broadband, and φ20 mm was used as a receiving probe, and the applied voltage was 40V.

  FIG. 2A and FIG. 2B show the reception waveforms (A scope display) of the transmitted waves obtained in Example 1 and Comparative Example 1, respectively. In the case of the comparative example 1 in which the applied voltage is 40 V, the echo height is a noise level and the transmitted wave cannot be detected, whereas in the case of the example 1 in which the applied voltage is 400 V, the transmitted wave can be detected. When the test body is a rail and the probe is arranged at the position shown in FIG. 1, the echo height rapidly increases at an ultrasonic transmission time of about 63 to 73 μs. Therefore, it was found that when a transmitted wave is detected under this condition, the transmitted wave can be detected by setting a monitoring gate in the region of about 63 to 73 μs after transmitting the ultrasonic wave.

  Using test specimens with artificial defects of different depths in the thickness direction of the constricted part of the rail, and using three types of probes as transmission probes and reception probes, respectively. The transmitted wave was measured under the same conditions as in Example 1 except that they were used. In addition, the test body used four types, without a flaw (condition 1), and the depth of the flaw being 50% (condition 2), 75% (condition 3), and 90% (condition 4) of the thickness. . The monitoring gate was set to 63 to 73 μs based on the result of Example 1.

  FIG. 3A shows a schematic cross-sectional view of each specimen. FIGS. 3B and 3C show the maximum echo height and the position where the maximum echo is observed in the monitoring gate, respectively. In FIG. 3B and FIG. 3C, “□”, “Δ”, and “×” are probes A (5 MHz, 12.4φ), A probe B (2 MHz, 20.0φ) and a probe C (1 MHz, 20.0φ) are used, and a probe D (5 MHz, 20.0φ) and a probe E are used as receiving probes. The results obtained using (5 MHz, 12.4φ) and probe F (5 MHz, 12.4φ) are shown.

  From FIG. 3B and FIG. 3C, regardless of which probe is used, the maximum echo height decreases as the flaw depth in the thickness direction increases, and the maximum echo detection. You can see that the time is getting longer. This is because the multiple reflection / detour of ultrasonic waves increases as the flaw depth increases.

  As shown in Fig. 4 (a) and Fig. 4 (b), four artificial flaws (artificial horizontal cracks) with different lengths in the longitudinal direction were introduced near the constricted portion of the rail by machining, and the test was conducted. The body. Next, as shown in FIG. 4 (a), a transmitting probe and a receiving probe are arranged on the top surface and the foot of the head of the rail, respectively, and the transmitted wave after a certain time has passed. The echo height was measured. The test conditions were the same as in Example 1, and the monitoring gate was set to 63 to 77 μs.

  FIG. 4C shows the relationship between the horizontal position (distance in the longitudinal direction of the rail) and the maximum echo height in the monitoring gate. It can be seen from FIG. 4C that the echo height in the region where the artificial flaw is present is lower than the echo heights of the healthy portions on both sides. It can also be seen that the longer the length in the longitudinal direction of the artificial flaw, the lower the echo height in the region with the artificial flaw.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

  The rail inspection method according to the present invention can be used for pre-shipment inspection for presence or absence of defects (particularly horizontal cracks) occurring in the vicinity of a constricted portion of a rail made of various materials, and inspection after installation on site.

It is the schematic which shows the inspection method of the rail which concerns on one embodiment of this invention. FIG. 2A shows the reception waveform (A scope display) obtained in Example 1, and FIG. 2B shows the reception waveform (A scope display) obtained in Comparative Example 1. 3A is a schematic cross-sectional view of the test body used in Example 2, and FIGS. 3B and 3C show the maximum echo height and the maximum obtained in Example 2, respectively. It is a figure which shows the relationship between echo detection time and test conditions. FIG. 4A is a cross-sectional view of the test body (rail) used in Example 3, as viewed from the longitudinal direction, FIG. 4B is a side view thereof, and FIG. It is a figure which shows the relationship between the horizontal position obtained in Example 3, and the maximum echo height.

Explanation of symbols

10 rails (test body)
10a Head 10c Foot 20 Transmitting probe 30 Receiving probe

Claims (4)

A transmission step of arranging a transmission probe on either the head side or the foot side of the rail, and transmitting ultrasonic waves from the transmission probe;
A receiving probe is disposed at a position on the other side of the head side or the foot side of the rail and not coincident with the axis of the ultrasonic wave transmitted by the transmitting probe, and from the transmitting probe. Receiving the ultrasonic wave to be transmitted by the receiving probe; and
During the time from when the transmitting probe transmits an ultrasonic wave until the receiving probe receives the ultrasonic wave, the ultrasonic wave is transmitted to the rail without a horizontal crack near the constricted portion. A determination step of determining the presence or absence of a defect based on a delay from a time from when the probe is transmitted to when it is received by the receiving probe;
Inspection method of rails equipped with.   The rail inspection method according to claim 1, wherein the rail is a cast rail made of high manganese cast steel.   The rail inspection method according to claim 1, wherein a frequency of the ultrasonic wave is 0.5 MHz or more and 5 MHz or less.   The rail inspection method according to any one of claims 1 to 3, wherein the transmitting probe and the receiving probe are array probes.

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