JP2008107165A - Ultrasonic flaw detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detection method capable of efficiently detecting damages to the bottom end of a rail for railroad. <P>SOLUTION: This ultrasonic flaw detection method has an excitation process for exciting the bottom end 5 of the rail 1 for the railroad so as to be made to vibrate in the height direction of the rail 1; and a detection process for detecting the reflected ultrasonic waves, having a prescribed frequency and a prescribed group velocity, generated in the excitation process, and detecting the location of the damage of the rail 1 for the railroad. The prescribed frequency is over 30 kHz or higher and 200 kHz or lower, and the prescribed group velocity is 2,000 m/s or higher and 3,500 m/s or lower. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic flaw detection method for flaw detection of railway rails using ultrasonic waves.

2. Description of the Related Art Conventionally, a flaw detection method using a rail flaw detection vehicle described in Non-Patent Document 1 below is known as a technique for performing flaw detection on railway rails easily and at high speed using ultrasonic waves. Such a rail flaw detection vehicle includes a tire probe that comes into contact with the rail, and ultrasonic waves for flaw detection are incident on the inside of the rail by the tire probe, and a reflected wave is detected.
Mitsunobu Kajikawa, Takuya Motomoto, Tatsuo Otaka, “Improvement of flaw detection capability of rail flaw detection vehicles”, JR EAST Technical Review, No. 02-Winter, 2003, P35.

  However, since the ultrasonic wave from the tire probe enters downward from the rail head, the ultrasonic wave hardly reaches the bottom end of the rail. Therefore, the method using the rail flaw detection vehicle cannot sufficiently detect damage to the bottom end of the rail. The bottom end of the laid rail is strongly fastened to a sleeper and may be buried in the ground at a railroad crossing or the like, so that it is a place where damage due to electric contact or corrosion is likely to occur. Therefore, it is required to detect the damage at the rail bottom end particularly efficiently.

  An object of this invention is to provide the ultrasonic flaw detection method which can detect efficiently the damage of the bottom end part of a rail for railroads.

  The ultrasonic flaw detection method of the present invention is an ultrasonic flaw detection method for flaw detection of railroad rails using ultrasonic waves, and vibrates the bottom portion of the railroad rail so as to vibrate in the height direction of the railroad rail. A vibration process, and a detection process for detecting a position of damage to the rail for railroad by detecting reflected ultrasonic waves having a predetermined frequency and a predetermined group velocity generated by the vibration process, and the predetermined frequency is: It is 30 kHz or more and 200 kHz or less, and the predetermined group velocity is 2000 m / s or more and 3500 m / s or less.

  In this ultrasonic flaw detection method, a vibration process is performed such that the bottom of the railroad rail vibrates in the rail height direction. According to such a vibration process, a guide wave mode in which the bottom end of the rail vibrates in the height direction at a frequency of 30 kHz to 200 kHz and a group velocity of 2000 m / s to 3500 m / s. It has been found by the inventors' diligent research that this occurs. Therefore, according to this method, the vibration in the height direction propagates to the rail bottom, so that damage at the rail bottom end can be detected efficiently, and the damage is based on the group velocity (sound speed). Can be identified.

  In this case, in the vibration process, an ultrasonic probe is installed on the upper surface or the lower surface of the bottom of the rail for rail, and the ultrasonic probe is vibrated in a direction perpendicular to the installation surface to generate ultrasonic waves having a predetermined frequency. May be incident. According to such a method, the bottom end portion of the rail is vibrated so as to vibrate in the height direction by the ultrasonic vibration incident from the ultrasonic probe.

In addition, in the vibration process, an ultrasonic probe forming an oblique probe is installed on the upper surface or the lower surface of the bottom of the rail for the railway, and from the oblique wedge portion of the ultrasonic probe, An ultrasonic wave having a predetermined frequency with respect to the longitudinal direction of the rail is incident on the railroad rail, and the predetermined incident angle θ is determined by the longitudinal wave sound velocity cw in the oblique wedge portion and the phase velocity of the ultrasonic wave. Based on cp, it may be expressed by θ = sin ⁻¹ (cw / cp).

  According to such a method, the bottom end of the rail is vibrated so as to vibrate in the height direction due to the ultrasonic vibration incident on the ultrasonic probe. Further, when an ultrasonic wave is incident at the incident angle θ as described above, the ultrasonic wave propagates in the longitudinal direction of the rail according to Snell's law, so that efficient flaw detection is possible.

  In the excitation process, a plurality of ultrasonic probes including a first probe and a second probe that vibrates at a phase delayed by 90 ° from the first probe are used. The first probe and the second probe are linearly arranged alternately in the longitudinal direction on the upper or lower surface of the rail for rail, and the wavelength of the ultrasonic wave incident from the ultrasonic probe is λ. The first probes are arranged at equal intervals with an interval mλ (where m = 1, 2,...), And each second probe is adjacent to each adjacent first probe. It may be arranged away from the child by (1/4 + n / 2) · λ (where n = 0, 1, 2,...).

  According to the arrangement of the probes and the vibration of the probes, there is a state in which the vibration energy is propagated only in one direction in the longitudinal direction of the rail for the rail and the vibration energy is not propagated in the opposite direction. Produced. Therefore, according to this configuration, ultrasonic waves related to flaw detection can be propagated in the rail with high energy, and reflected waves can be obtained with high energy, so that better rail flaw detection can be performed.

  In the vibration step, the bottom may be vibrated by striking the top or bottom surface of the bottom of the rail for rail. According to this method, vibration with a higher energy than in the case of using a probe can be propagated in the rail and a reflected wave with a high energy can be obtained, so that a good rail flaw detection can be performed.

  The ultrasonic flaw detection method of the present invention is an ultrasonic flaw detection method for flaw detection of railway rails using ultrasonic waves. The ultrasonic flaw detection method according to the present invention applies vibration so as to vibrate the bottom of a railroad rail in the width direction of the railroad rail. And a detection step of detecting a position of damage to the rail for rail by detecting reflected ultrasonic waves having a predetermined frequency and a predetermined group velocity generated by the vibration step, and the predetermined frequency is 70 kHz. It is 200 kHz or less, and the predetermined group velocity is 2400 m / s or more and 3500 m / s or less.

  In this ultrasonic flaw detection method, an excitation process is performed in which the bottom of the railroad rail vibrates in the rail width direction. According to such a vibration process, a guide wave mode in which the bottom end of the rail vibrates in the width direction when the frequency is 70 kHz or more and 200 kHz or less and the group velocity is 2400 m / s or more and 3500 m / s or less. It has been found by the inventors' diligent research. Therefore, according to this method, since the vibration in the width direction propagates to the bottom of the rail, damage at the bottom of the rail can be detected efficiently, and the position of the damage is identified based on the group velocity. can do.

In the vibration process, an ultrasonic probe forming an oblique probe is installed on the side surface of the bottom end of the rail for rail, and the rail of the railway rail is installed from the oblique wedge portion of the ultrasonic probe. An ultrasonic wave having a predetermined frequency at a predetermined incident angle θ with respect to the longitudinal direction is incident on the rail for rail, and the predetermined incident angle θ is determined by the longitudinal wave velocity cw in the oblique wedge portion and the ultrasonic phase velocity cp. , It may be expressed by θ = sin ⁻¹ (cw / cp).

  According to this method, the bottom end of the rail is vibrated so as to vibrate in the width direction due to the ultrasonic vibration incident on the ultrasonic probe. Further, when an ultrasonic wave is incident at the incident angle θ as described above, the ultrasonic wave propagates in the longitudinal direction of the rail according to Snell's law, so that efficient flaw detection is possible.

  In the vibration process, an ultrasonic probe is installed on the side of the bottom end of the rail for rail, and the ultrasonic probe is vibrated in a direction perpendicular to the installation surface to input ultrasonic waves of a predetermined frequency. It is also possible to make it. According to such a method, the ultrasonic wave incident on the ultrasonic probe can be vibrated so that the bottom of the rail vibrates in the width direction.

  In the excitation process, a plurality of ultrasonic probes including a first probe and a second probe that vibrates at a phase delayed by 90 ° from the first probe are used. The first probe and the second probe are arranged in a straight line alternately in the longitudinal direction on the side surface of the bottom end portion of the rail for rail, and the wavelength of the ultrasonic wave incident from the ultrasonic probe Where λ is λ, the first probes are arranged at equal intervals at an interval mλ (where m = 1, 2,...), And each second probe is adjacent to each adjacent first probe. It may be arranged to be separated from the probe by (1/4 + n / 2) · λ (where n = 0, 1, 2,...).

  According to the arrangement of the probes and the vibration of the probes, there is a state in which the vibration energy is propagated only in one direction in the longitudinal direction of the rail for the rail and the vibration energy is not propagated in the opposite direction. Produced. Therefore, according to this configuration, ultrasonic waves related to flaw detection can be propagated in the rail with high energy, and reflected waves can be obtained with high energy, so that better rail flaw detection can be performed.

  Further, in the vibration step, the bottom portion may be vibrated by hitting the side surface of the bottom end portion of the rail for rail. According to this method, vibration with a higher energy than in the case of using a probe can be propagated in the rail and a reflected wave with a high energy can be obtained, so that a good rail flaw detection can be performed.

  Moreover, you may further provide the impact detection process of detecting the moment when the impact in the vibration process was added. By such a hit detection process, the moment when an ultrasonic wave related to flaw detection is generated can be recognized, and the received signal waveform can be displayed. In addition, when the impact of the bottom of the vibration process is repeated multiple times, the received signal waveforms of each time are added together and averaged to obtain a clean waveform with no random noise. Identification can be performed satisfactorily.

  According to the ultrasonic flaw detection method of the present invention, it is possible to efficiently detect damage at the bottom end of a rail for railroad.

  Hereinafter, preferred embodiments of an ultrasonic flaw detection method according to the present invention will be described in detail with reference to the drawings. In the following description, as shown in FIG. 1 and the like, the width direction of the rail 1 for rail is defined as the x direction, the height direction of the rail 1 is defined as the y direction, and the longitudinal direction of the rail 1 is defined as the z direction. Moreover, such a rail 1 for rails is comprised from the site | part of the head 1a, the abdominal part 1b, and the bottom part 3, and the site | part 5 close | similar to both ends among the bottom parts 3 is called a bottom end part. In the present invention, the upper and lower concepts in the case of using words such as “upper surface 5a of bottom 3 (or bottom end 5)”, “lower surface 5b of bottom 3 (or bottom end 5)” It is assumed that the rail 1 as shown in FIG.

(First embodiment)
In the rail 1 for rails as shown in FIG. 1, it is desired to efficiently detect damage to the bottom end portion 5 of the bottom portion 3. In such a rail 1, in order to efficiently detect damage to the bottom end 5, a mode of a guide wave propagating in the longitudinal direction of the rail 1 while energy is concentrated on the bottom end 5 is generated in the rail 1. It is necessary to let As one of such modes, the present inventors set a guide wave mode in which the bottom end portion 3 of the rail 1 vibrates up and down in the height direction (y direction) of the rail 1 as shown in FIG. Pay attention. By numerical analysis based on the cross-sectional shape data of the rail 1, the inventors first of all have a group velocity dispersion curve (FIG. 3) and a phase velocity dispersion curve (guide velocity mode) for a guide wave mode in which the bottom portion 3 of the rail 1 greatly vibrates up and down. Fig. 4) was created.

  Then, the present inventors have conducted various experiments, and among the guide waves corresponding to the group velocity dispersion curve, in particular, the frequency range of 30 kHz to 200 kHz and the group velocity of 2000 m / s to 3500 m / s. Has found that the bottom end portion 5 efficiently vibrates up and down (vibrates in the height direction) and is suitable for flaw detection of the bottom end portion 5. Furthermore, among them, it has been found that a guide wave corresponding to a region having a frequency of 50 kHz to 100 kHz and a group velocity of 2500 m / s to 3500 m / s is particularly suitable for flaw detection of the bottom end portion 5. It was. If the frequency of the guide wave exceeds 200 kHz, the guide wave is greatly attenuated and is not suitable for flaw detection. Also, if the frequency of the guide wave is less than 30 kHz, inspection in a near field of several meters from the incident position is impossible due to incident noise, and the defect detection capability is reduced, which is suitable for flaw detection. Absent.

  Based on such knowledge, the inventors select a point Q1 having a frequency of 50 kHz and a group velocity of 2840 m / s from the group velocity dispersion curve (FIG. 3), and the guide wave corresponding to this point is selected. The mode 1 was used to perform ultrasonic flaw detection on the rail 1.

  In this ultrasonic flaw detection method, as shown in FIG. 1, a vertical probe for exciting a longitudinal wave is installed on the upper surface 5 a of the bottom end portion 5 of the rail for rail 1. Here, two types of vertical probes, that is, vertical probes 7a to 9a and vertical probes 7b to 9b, are alternately arranged on a straight line parallel to the longitudinal direction (z direction) of the rail 1. The The detailed positional relationship between the vertical probes 7a to 9a and 7b to 9b will be described later. Then, when drive signals from a control device (not shown) are transmitted to the vertical probes 7a to 9a and 7b to 9b, the vertical probes 7a to 9a and 7b in the direction of arrow A perpendicular to the upper surface 5a. ˜9b vibrates at a frequency of 50 kHz, and ultrasonic waves are incident on the rail 1.

  When such ultrasonic waves are incident, the bottom end portion 5 is vibrated in the vertical direction by ultrasonic vibration, and as described above, the guide wave that causes the bottom end portion 5 of the rail 1 to vibrate up and down in the y direction. Mode occurs (vibration process). The frequency of this guide wave is 50 kHz, and the group velocity (sound velocity) is 2840 m / s. Subsequently, the vertical probes 7a to 9a and 7b to 9b receive the reflected waves (reflected ultrasonic waves) reflected by the damage of the rail 1, respectively. Then, information on the time position of the received reflected wave is processed by a computer or the like. Since the group velocity of the guide wave used for flaw detection is specified as described above, the position of the damage can be identified here by measuring the time position at which the reflected wave from the damage of the rail 1 appears (detection) Process).

  In the phase velocity dispersion curve of the rail 1 shown in FIG. 4, this guide wave corresponds to the point Q2, and the phase velocity is 2590 m / s. The wavelength λ of the guide wave is λ = 2590 (m / s) / 50 (kHz) = 52 (mm) as calculated from the frequency and the phase velocity. As shown in FIG. 1, the arrangement of the vertical probes 7a to 9a and 7b to 9b is determined as follows based on the wavelength λ of the guide wave. That is, the probes 7a, 8a, 9a are arranged at equal intervals, and the interval P1 is an integral multiple of the wavelength λ (P1 = mλ: m = 1, 2,...). For example, when m = 2 is adopted, P1 = 104, so that the probes 7a, 8a, 9a may be arranged at intervals of 104 mm. The distances P2 between the adjacent probes 7a and 7b, the probes 8a and 8b, and the probes 9a and 9b are all set to P2 = (1/4 + n / 2) · λ ( n = 0, 1, 2, ...). For example, when n = 0 is adopted, P2 = 13. Therefore, the interval between adjacent probes 7a and 7b, probes 8a and 8b, and probes 9a and 9b may be set to 13 mm.

  Further, the same drive signal is branched and inputted to the probes 7a, 8a and 9a, and the probes 7a, 8a and 9a vibrate in the same phase. Similarly, the same drive signal is branched and input to the probes 7b, 8b, and 9b, and the probes 7b, 8b, and 9b vibrate in the same phase. The drive signals input to the probes 7b, 8b, and 9b invert the drive signals input to the probes 7a, 8a, and 9a, and have a phase of T / 4 (T is one cycle with respect to the center frequency). The waveform is delayed by (hour). Accordingly, the probes 7b, 8b, and 9b vibrate with a phase delayed by 90 ° from the probes 7a, 8a, and 9a. Further, the drive signal is controlled so that the amplitudes of the probes 7b, 8b, and 9b and the amplitudes of the probes 7a, 8a, and 9a are the same. Due to the above arrangement of the drive signal and the probe, vibration energy propagates only in the direction of arrow B in the longitudinal direction of the rail 1 from these probes 7a to 9a and 7b to 9b. A state is created where no energy propagates in the direction.

  As for reception of reflected waves, the reflected waves are independently received by the probes 7a, 8a, 9a and the probes 7b, 8b, 9b, and the waveforms received by the probes 7b, 8b, 9b are used. What is necessary is just to perform the process which delays and adds 90 degree phases. According to such a configuration, since ultrasonic waves related to flaw detection can be propagated in the rail 1 with high energy and a reflected wave can be obtained with high energy, it is possible to perform better flaw detection on the rail 1. Note that the vertical probes 7a to 9a and 7b to 9b may be installed on the lower surface 5b of the bottom end portion 5 at the intervals described above, or may be installed on both the upper surface 5a and the lower surface 5b.

  According to the ultrasonic flaw detection method as described above, when the ultrasonic wave is incident on the rail 1, the rail 1 generates a guide wave mode that propagates in the longitudinal direction of the rail 1 while the bottom end portion 5 vibrates up and down. Therefore, damage to the bottom end portion 5 of the rail 1 can be detected efficiently.

  In the above-described region S1 (FIG. 3), two curves are mainly seen. One of them is a mode in which the left and right bottom ends 5 vibrate up and down in the same direction as shown in FIG. The other one corresponds to a mode in which the left and right bottom end portions 5 vibrate up and down in opposite directions as shown in FIG. Actually, these two modes are mixed and the difference in group velocity is small, so that they propagate simultaneously on the rail 1. From this, for example, when the vertical probes 7a to 9a and 7b to 9b are installed and excited only in the right bottom end portion 5 of the rail 1, only the excited right bottom end portion 5 vibrates and becomes long. Propagate in the direction. This is because the right bottom end 5 of the rail is excited, and as a result of the addition of the above two modes, the vibration of the left bottom end 5 is suppressed and the vibration of the right bottom end 5 is increased. It is. Similarly, it is also possible to vibrate only the left bottom end 5. As can be seen from FIG. 3, these two modes have a small difference in sound velocity (dispersibility) depending on the frequency. This means that the waveform collapse due to propagation is small, and if such a guide wave mode is used, a waveform with a large SN ratio can be obtained even after long-distance propagation.

  The present inventors conducted a flaw detection test of the rail 1 by the above-described ultrasonic flaw detection method. The rail 1 used for the test was a JIS50N standard having a length of 4 m, and damage to the bottom end 5 was present at a position of about 1.9 m from the end of the rail 1. The probes 7a to 9b are installed in the vicinity of the end of the rail 1, and the parameters m and n relating to the arrangement of the probes are set to m = 1 and n = 0. As shown in FIG. 6, according to the received waveform obtained by this test, a large reflected wave is detected in the vicinity of time 1300 μs. This reflected wave is converted into a distance based on the group velocity of 2840 m / s, and it can be seen that it corresponds to damage of the bottom end 5 at a position of about 1.9 m from the end of the rail 1. Thus, according to the above-described ultrasonic flaw detection method, it has been found that the damage of the bottom end portion 5 can be detected and the position of the damage can be identified.

(Second Embodiment)
As another example of the mode of the guide wave propagating in the longitudinal direction of the rail 1 while energy is concentrated on the bottom end portion 5, the present inventors have shown that the bottom end portion 3 of the rail 1 is a rail as shown in FIG. 7. Attention was focused on a mode of a guide wave that oscillates in the width direction (x direction). The inventors first created a group velocity dispersion curve (FIG. 8) and a phase velocity dispersion curve (FIG. 9) for a mode in which the bottom 3 of the rail 1 is greatly expanded and contracted in the x direction by numerical analysis.

  Then, the present inventors have conducted various experiments, and among the guide waves corresponding to this group velocity dispersion curve, in particular, the frequency: 70 kHz to 200 kHz, and the group velocity: 2400 m / s to 3500 m / s. It has been found that the bottom end portion 5 efficiently expands and contracts in the x direction and is suitable for flaw detection of the bottom end portion 5. It has been found that the guide wave corresponding to the region of the frequency: 70 kHz to 120 kHz and the group velocity: 2400 m / s to 3200 m / s is particularly suitable for the flaw detection of the bottom end 5 among the above regions. . If the frequency of the guide wave exceeds 200 kHz, the guide wave is greatly attenuated and is not suitable for flaw detection. On the other hand, if the frequency of the guide wave is less than 70 kHz, the wavelength is increased and the ultrasonic energy is not concentrated in the vicinity of the bottom end side surface 5c.

  This mode is a propagation mode similar to the Rayleigh wave that propagates on the surface of the material at a speed of sound about 10% slower than the sound speed of the transverse wave, and it is clear that the wave has the property that energy is concentrated at about half the wavelength of the surface of the material. became. When a mode similar to the Rayleigh wave is excited on the bottom end side surface 5c of the rail 1, energy concentrates and propagates in the vicinity of the side surface 5c, so that the ability to detect scratches on the side surface 5c is excellent.

  In addition, the rail 1 in use is fastened up and down by a pandroll type or dog nail type fastening device. In this mode, the side 5c is vibrated in the width direction so that the attenuation due to fastening is small. Therefore, the flaw detection in this mode can be applied to a place where a fastening device in a strong fastening state is used.

  Based on such knowledge, the present inventors select a point Q21 on the group velocity dispersion curve (FIG. 8) with a frequency of 100 kHz and a group velocity of 2760 m / s, and a guide wave mode corresponding to this point. Was used to perform ultrasonic flaw detection on the rail 1. This guide wave mode corresponds to point Q22 on the phase velocity dispersion curve (FIG. 9), and the phase velocity is 3300 m / s.

  In this ultrasonic flaw detection method, as shown in FIGS. 10A and 10B, the above-described guide wave mode (point Q21 in FIG. 8) is excited on the bottom end side surface 5c of the rail 1 for railway. Two oblique angle probes, namely, a transmission oblique angle probe 37a and a reception oblique angle probe 37b are arranged. A bevel wedge portion 31 made of acrylic for transmitting ultrasonic waves to the rail 1 is provided at the tips of the bevel probes 37a and 37b. The inclined wedge portion 31 has the inclination of the inclined front end surface adjusted in accordance with a desired ultrasonic incident angle θ, and the inclined front end surface is installed along the bottom end upper surface 5 a of the rail 1. The oblique angle probe 37a can make an ultrasonic wave incident on the rail 1 at an incident angle θ. The oblique angle probe 37b having the same configuration as the oblique angle probe 37a is installed in parallel in the vicinity of the oblique angle probe 37a and used for receiving reflected ultrasonic waves. In this ultrasonic flaw detection method, the bevel angle probes 37a and 37b are arranged such that the tip of the bevel wedge 31 points in the longitudinal direction (z direction) of the rail 1, and the emission direction of the ultrasonic wave is the zx plane. It is installed with the posture that is parallel to.

In this method, a preferable incident angle θ of the ultrasonic wave from the oblique angle probe 37a is determined as follows. The incident angle θ is the acoustic velocity cw of the oblique wedge 31 (here, the longitudinal acoustic velocity of acrylic: cw = about 2600 m / s), the phase velocity cp of the guided wave mode corresponding to the point Q21 = cp = 3300 m / s, Is determined as θ = 52 ° by the equation θ = sin ⁻¹ (cw / cp). If the ultrasonic wave is incident on the rail 1 at the incident angle θ determined in this way, the refraction angle becomes 90 ° according to Snell's law, that is, a guide wave propagating in the longitudinal direction (z direction) of the rail 1 is obtained. Therefore, flaw detection can be performed efficiently by high energy ultrasonic waves.

  In such an arrangement, when a drive signal is transmitted to the oblique angle probe 37a, the probe 37a applies ultrasonic vibration to the side surface 5c. At this time, the mode corresponding to Q21 of cp = 3300 m / s is greatly excited according to Snell's law. Then, the oblique probe 37a vibrates at a frequency of 100 kHz in the direction of arrow D perpendicular to the side surface 5c, and an ultrasonic wave is incident on the rail 1. When such ultrasonic waves are incident, a guide wave mode in which the component that the bottom end portion 5 of the rail 1 vibrates in the x direction is dominant as described above is generated, and the vibration in the width direction of the bottom end portion 5 is generated. Propagates in the B direction. Next, the receiving oblique angle probe 37b can receive a reflected wave of high energy according to Snell's law. Then, the reflected wave can be analyzed, and the position of damage of the rail 1 can be identified based on the group velocity.

  According to the ultrasonic flaw detection method as described above, a mode of a guide wave that propagates in the longitudinal direction of the rail 1 while causing the bottom end portion 5 to expand and contract in the width direction (x direction) can be generated in the rail 1. Therefore, damage to the bottom end portion 5 of the rail 1 can be detected efficiently. Note that in the ultrasonic flaw detection method according to this embodiment, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals in the drawings, and description thereof is omitted.

  Note that the oblique angle probes similar to the oblique angle probes 37a and 37b described above may be used for both transmission and reception, and one oblique angle probe may be arranged on the bottom end side surface 5c. Further, a plurality of such oblique transmission / reception probes may be arranged in the z direction on the bottom end side surface 5c. In this case, similarly to the first embodiment, the first oblique angle probes are arranged at equal intervals with an interval mλ (where m = 1, 2,...), And more than the first probe. The second probe oscillated with a phase delayed by 90 ° is separated from each adjacent first probe by (1/4 + n / 2) · λ (where n = 0, 1, 2,...). It is good also as arranging. According to such a method, ultrasonic waves related to flaw detection can be propagated in the rail 1 with high energy, and a reflected wave can be obtained with high energy, so that better flaw detection on the rail 1 can be performed.

  The present inventors conducted a flaw detection test of the rail 1 by the above-described ultrasonic flaw detection method. Although the rail 1 used for the test is the same as the flaw detection test of the first embodiment, the test was performed with the rail 1 being fastened by a fastening device. In addition, when such fastening is performed, the defect echo cannot be obtained by the flaw detection method of the first embodiment. As shown in FIG. 11, according to the received waveform obtained by this test, a large reflected wave is obtained in the vicinity of time 1500 μs. This reflected wave is converted into a distance based on the above group velocity of 2760 m / s, and it can be seen that it corresponds to the damage of the bottom end 5 at a position of about 2 m from the end of the rail 1. As described above, according to the ultrasonic flaw detection method described above, even when the bottom end portion 5 is tightened by the fastening device, damage to the bottom end portion 5 can be detected and the position of the damage can be identified. It was.

(Third embodiment)
In order to excite the guide wave mode (frequency: 50 kHz, group velocity: 2840 m / s, phase velocity cp: 2590 m / s) in which the bottom end portion 5 vibrates in the y direction as shown in the first embodiment. As shown in FIG. 12, the oblique angle probes 37a and 37b used in the second embodiment can be used. In this ultrasonic flaw detection method, the oblique angle probes 37 a and 37 b are attached to the bottom end upper surface 5 a of the rail 1. The oblique angle probes 37a and 37b are provided with an oblique wedge 31 that is adjusted so that the ultrasonic incident angle θ = sin ⁻¹ (cw / cp) = sin ⁻¹ (2600/2590). The bevel wedge 31 is arranged such that the tip of the oblique wedge 31 points in the longitudinal direction (z direction) of the rail 1, and 50 kHz ultrasonic waves are transmitted and received.

  According to such a method, high energy ultrasonic waves propagating in the z direction can be generated according to Snell's law. Since the rail 1 can generate a mode of a guide wave that propagates in the longitudinal direction of the rail 1 while the bottom end 5 vibrates up and down in the y direction, the bottom end 5 of the rail 1 is efficiently damaged. Can be detected. Note that in the ultrasonic flaw detection method according to this embodiment, the same or equivalent components as those of the above-described embodiments are denoted by the same reference numerals in the drawings, and description thereof is omitted.

(Fourth embodiment)
Further, as shown in the first embodiment, the guide wave mode (frequency: 50 kHz, group velocity: 2840 m / s, phase velocity cp: 2590 m / s) in which the bottom end portion 5 vibrates in the y direction is excited. For this purpose, instead of the vertical probes 7a to 9a and 7b to 9b, as shown in FIG. 13, it is possible to employ a method of hitting the bottom end top surface 5a downward with a hammer 41. . In this case, a reception-only oblique probe 47 designed to receive ultrasonic waves of 50 kHz is installed on the bottom end upper surface 5a.

As in the second embodiment, the oblique angle probe 47 has an oblique wedge adjusted so that the ultrasonic incident angle θ = sin ⁻¹ (cw / cp) = sin ⁻¹ (2600/2590). 31, and the bevel wedge 31 is arranged so that the tip of the oblique wedge 31 points in the longitudinal direction (z direction) of the rail 1. According to the hammer hit as described above, waves of various frequencies including the above modes are mixed and propagated, but only the ultrasonic waves of a desired mode of 50 kHz are transmitted from the waves by the oblique probe 47. Can be selectively received.

  In order to identify the location of damage based on the group velocity from the received reflected ultrasound using a computer, it is necessary for the computer to recognize the moment when the guide wave is generated, that is, the moment when the hammer is hit. There is. For this reason, the vertical probe 48 for detecting the stress wave by hammering is installed in the bottom end part upper surface 5a. When a hammer hit is performed, a stress wave generated by the hit is detected by the vertical probe 48, and a trigger signal is transmitted to the computer related to the identification of the position of damage (hit detection step). By such a hit detection process, the computer can recognize the moment when the guide wave is generated, so that the received signal waveform can be displayed and the calculation for identifying the position of damage can be performed. . In addition, the hitting at the bottom as described above may be repeated multiple times, and by averaging the received signal waveforms at each time, a clean waveform with no random noise can be obtained, and the position of the rail damage is well identified Can be done. In order to detect the moment of hammering, an impact hammer incorporating a piezoelectric sensor may be used instead of the hammer 41, and an electrical signal from the piezoelectric sensor may be transmitted to the computer.

  According to this ultrasonic flaw detection method, it is possible to generate a guide wave having a larger energy by using hammer hitting than when a probe is used. Then, the bottom end portion 5 of the rail 1 is selectively received by the oblique probe 47 by the bevel wave probe 47 receiving the mode of the guide wave propagating in the longitudinal direction of the rail 1 while the bottom end portion 5 vertically vibrates in the y direction. Can be efficiently detected. Note that in the ultrasonic flaw detection method according to this embodiment, the same or equivalent components as those of the above-described embodiments are denoted by the same reference numerals in the drawings, and description thereof is omitted.

(Fifth embodiment)
Further, as shown in the second embodiment, the guide wave mode (frequency: 100 kHz, group velocity: 2760 m / s, phase velocity cp: 3300 m / s) in which the bottom end portion 5 vibrates in the x direction is excited. For this purpose, as shown in FIG. 14, the vertical probes 7a to 9a and 7b to 9b of the first embodiment can be used. In this ultrasonic flaw detection method, vertical probes 7 a to 9 a and 7 b to 9 b that vibrate at 100 kHz perpendicular to the installation surface are attached to the bottom end side surface 5 c of the rail 1. The parameters P1 and P2 relating to the arrangement of the vertical probes 7a to 9a and 7b to 9b are determined in the same manner as in the first embodiment.

  Also by such an ultrasonic flaw detection method, a mode of a guide wave that propagates in the longitudinal direction of the rail 1 while the bottom end portion 5 expands and contracts in the width direction can be generated in the rail 1. Damage to the end 5 can be detected efficiently. Note that in the ultrasonic flaw detection method according to this embodiment, the same or equivalent components as those of the above-described embodiments are denoted by the same reference numerals in the drawings, and description thereof is omitted.

(Sixth embodiment)
Further, as shown in the second embodiment, the guide wave mode (frequency: 100 kHz, group velocity: 2760 m / s, phase velocity cp: 3300 m / s) in which the bottom end portion 5 vibrates in the x direction is excited. For this purpose, as shown in FIG. 15, a method of hitting the bottom end side surface 5c with the hammer 41 in the x direction can be employed. In this case, a reception-only oblique probe 67 designed to receive 100 kHz ultrasonic waves is installed on the bottom end side surface 5c. This bevel angle probe 67 is, similarly to the bevel angle probes 37a and 37b of the second embodiment, an ultrasonic incident angle θ = sin ⁻¹ (cw / cp) = sin ⁻¹ (2600/3300). The bevel wedge 31 is adjusted so that the tip end of the bevel wedge 31 points in the longitudinal direction (z direction) of the rail 1.

  According to the hammer hit as described above, waves of various frequencies including the above modes are mixed and propagated, but only ultrasonic waves of a desired mode of 100 kHz are transmitted from the waves by the oblique probe 67. Can be selectively received. Further, a vertical probe 68 that detects a stress wave caused by hammering and sends an electrical signal is provided on the bottom end side surface 5c. When hammering is performed, a stress wave generated by the hammering is detected by the vertical probe 68 and transmitted to a computer related to damage position identification (hit detection step). By such a hit detection process, the computer can recognize the moment when the guide wave is generated, and can perform an operation for identifying the position of damage.

  According to this ultrasonic flaw detection method, it is possible to generate a guide wave having a larger energy by using hammer hitting than when a probe is used. The bottom end portion 5 of the rail 1 is selectively received by the oblique probe 67 by the bevel wave probe 67 receiving the mode of the guide wave propagating in the longitudinal direction of the rail 1 while the bottom end portion 5 expands and contracts in the width direction. Can be efficiently detected. Note that in the ultrasonic flaw detection method according to this embodiment, the same or equivalent components as those of the above-described embodiments are denoted by the same reference numerals in the drawings, and description thereof is omitted.

  The present invention is not limited to the embodiment described above. For example, in the first and fifth embodiments, six probes are used. However, if a plurality of probes are arranged at intervals according to the wavelength λ of the guide wave, the number of probes is increased. May be increased or decreased. In general, JIS 60kg and JIS 50N exist as main types of rails for rails. However, since there is no significant difference in cross-sectional shape and material between the two types, the present invention is applicable to both types of rails for rails. Can be applied in the same way.

It is a perspective view of the rail for railroads which shows 1st Embodiment of the ultrasonic flaw detection method of this invention. It is sectional drawing showing one form of the vibration of the bottom end part of the rail for railroads. It is a figure which shows the group velocity dispersion | distribution curve of the mode of the guide wave which the bottom part of a rail for rails vibrates up and down greatly. It is a figure which shows the phase velocity dispersion curve of the mode of the guide wave which the bottom part of a rail for rails vibrates up and down greatly. It is sectional drawing showing the vibration of the bottom end part of the rail for railroads. It is a figure which shows the received waveform obtained by the flaw detection test of the rail for rails which concerns on 1st Embodiment. It is sectional drawing showing the other form of the vibration of the bottom end part of the rail for railroads. It is a figure which shows the group velocity dispersion | distribution curve of the mode of the guide wave which the bottom part of a rail for rails vibrates greatly in the width direction. It is a figure which shows the phase velocity dispersion | distribution curve of the mode of the guide wave which the bottom part of a rail for rails vibrates greatly in the width direction. (A) is a perspective view of the rail for railroads which shows 2nd Embodiment of the ultrasonic flaw detection method of this invention, (b) is the top view. It is a figure which shows the received waveform obtained by the flaw detection test of the rail for rails concerning 2nd Embodiment. (A) is the perspective view of the rail for railroads which shows 3rd Embodiment of the ultrasonic flaw detection method of this invention, (b) is the figure which looked at the bevel probe in (a) from the side. . It is a perspective view of the rail for railroads which shows 4th Embodiment of the ultrasonic flaw detection method of this invention. It is a perspective view of the rail for railroads which shows 5th Embodiment of the ultrasonic flaw detection method of this invention. It is a perspective view of the rail for railroads which shows 6th Embodiment of the ultrasonic flaw detection method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rail for rails, 3 ... Bottom part, 3a ... Upper surface of bottom part, 3b ... Bottom face of bottom part, 5 ... Bottom end part, 5c ... Side surface of bottom end part, 7a, 8a, 9a ... Vertical probe (1st Probe),
7b, 8b, 9b ... vertical probe (second probe), 31 ... bevel wedge portion, 37a, 37b, 47, 67 ... bevel probe.

Claims (11)

In the ultrasonic flaw detection method for flaw detection of railroad rails using ultrasonic waves,
An excitation step of exciting the bottom of the rail for vibration so as to vibrate in the height direction of the rail for the rail;
A detection step of detecting a reflected ultrasonic wave having a predetermined frequency and a predetermined group velocity generated by the vibration step to detect a position of damage to the rail for the railway, and
The ultrasonic flaw detection method, wherein the predetermined frequency is 30 kHz to 200 kHz, and the predetermined group velocity is 2000 m / s to 3500 m / s.   In the excitation step, an ultrasonic probe is installed on the upper surface or the lower surface of the bottom of the rail for rail, and the ultrasonic probe is vibrated in a direction perpendicular to the installation surface to generate ultrasonic waves having the predetermined frequency. The ultrasonic flaw detection method according to claim 1, wherein: In the vibration step, an ultrasonic probe constituting an oblique probe is installed on the upper surface or the lower surface of the bottom of the rail for the railway, and the railway is used for the railway from the oblique wedge portion of the ultrasonic probe. Making the ultrasonic wave of the predetermined frequency incident on the rail for rail at a predetermined incident angle θ with respect to the longitudinal direction of the rail,
The predetermined incident angle θ is
It represents with (theta) = sin < ^-1 > (cw / cp) based on the longitudinal-wave sound velocity cw in the said bevel wedge part, and the phase velocity cp of the said ultrasonic wave, It is characterized by the above-mentioned. Ultrasonic flaw detection method. In the excitation step, a plurality of the ultrasonic probes including a first probe and a second probe that vibrates at a phase delayed by 90 ° from the first probe are used. ,
The first probe and the second probe are arranged in a straight line alternately in the longitudinal direction on the upper surface or lower surface of the rail for railroad,
When the wavelength of the ultrasonic wave incident from the ultrasonic probe is λ,
The first probes are arranged at equal intervals with an interval mλ (where m = 1, 2,...),
Each of the second probes is arranged away from each of the adjacent first probes by (1/4 + n / 2) · λ (where n = 0, 1, 2,...). The ultrasonic flaw detection method according to claim 2 or 3.   2. The ultrasonic flaw detection method according to claim 1, wherein, in the vibration step, the bottom is vibrated by striking the upper surface or the lower surface of the bottom of the rail for rail. In the ultrasonic flaw detection method for flaw detection of railroad rails using ultrasonic waves,
An excitation step of exciting the bottom of the rail for vibration so as to vibrate in the width direction of the rail for the rail;
A detection step of detecting a reflected ultrasonic wave having a predetermined frequency and a predetermined group velocity generated by the vibration step to detect a position of damage to the rail for the railway, and
The ultrasonic flaw detection method, wherein the predetermined frequency is 70 kHz to 200 kHz, and the predetermined group velocity is 2400 m / s to 3500 m / s. In the excitation step, an ultrasonic probe forming an oblique probe is installed on the side surface of the bottom end of the rail for the railway, and the railway probe is used from the oblique wedge portion of the ultrasonic probe. Making the ultrasonic wave of the predetermined frequency incident on the rail for rail at a predetermined incident angle θ with respect to the longitudinal direction of the rail,
The predetermined incident angle θ is
It is represented by (theta) = sin < ^-1 > (cw / cp) based on the longitudinal-wave sound velocity cw in the said oblique angle wedge part, and the phase velocity cp of the said ultrasonic wave. Ultrasonic flaw detection method.   In the excitation step, an ultrasonic probe is installed on the side surface of the bottom end of the rail for rail, and the ultrasonic probe is vibrated in a direction perpendicular to the installation surface to generate ultrasonic waves of the predetermined frequency. The ultrasonic flaw detection method according to claim 6, wherein: In the excitation step, a plurality of the ultrasonic probes including a first probe and a second probe that vibrates at a phase delayed by 90 ° from the first probe are used. ,
The first probe and the second probe are arranged in a straight line alternately in the longitudinal direction on the side surface of the bottom end portion of the rail for rail,
When the wavelength of the ultrasonic wave incident from the ultrasonic probe is λ,
The first probes are arranged at equal intervals with an interval mλ (where m = 1, 2,...),
Each of the second probes is arranged away from each of the adjacent first probes by (1/4 + n / 2) · λ (where n = 0, 1, 2,...). The ultrasonic flaw detection method according to claim 7 or 8.   The ultrasonic flaw detection method according to claim 6, wherein in the vibration step, the bottom portion is vibrated by hitting a side surface of a bottom end portion of the rail for rail. The ultrasonic flaw detection method according to claim 5 or 10, further comprising an impact detection step of detecting an instant at which the impact is applied in the vibration step.

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