Ultrasonic flaw detection device and ultrasonic flaw detection method for rail bottom

Abstract

To provide an ultrasonic flaw detection device that can easily perform ultrasonic flow detection at the ends of a rail bottom.SOLUTION: An ultrasonic flaw detection device for a rail bottom 10 includes: a transmission-side probe 11 that is attached to a head 20a of a rail 20 and transmits ultrasonic waves toward a bottom 20c of the rail 20; a reception-side probe 12 that is attached to the head 20a of the rail 20 at an interval from the transmission-side probe 11 and receives reflection echoes of the ultrasonic waves transmitted from the transmission-side probe 11; and a propagation path determination unit 13 that determines a propagation path of the reflection echoes received by the reception-side probe 12, and the transmission-side probe 11 transmits the ultrasonic waves so that the transmitted ultrasonic waves make a mode conversion in a belly 20b of the rail 20. The reception-side probe 12 receives the reflection echoes from the ends of the bottom of the rail, and determines thinning of the bottom of the rail due to corrosion on the basis of the reflection echoes from the ends of the bottom of the rail 20 received by the reception-side probe 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to an ultrasonic flaw detector and an ultrasonic flaw detection method for the bottom of a rail.

Background Art

[0002] Rails used in railways etc. accumulate water due to rain or leakage, and the bottom corrodes (galvanic corrosion) and thins. The state is shown in FIGS. 11(A) and 11(B). FIG. 11(A) is a view of rail 120 seen from its side, and corrosion parts 127 are shown at the abdomen and the ends of the bottom of rail 120. Further, FIG. 11(B) is an enlarged view showing the corrosion part 127 of rail 120 shown in FIG. 11(A). Inspection of such corrosion locations of rail 120 is performed by placing an ultrasonic probe 131 at the center of the head 120a of rail 120 to confirm the internal situation. Such an ultrasonic flaw detection method for rail 120 is shown in FIG. 12. Referring to FIG. 12, an ultrasonic probe 131 is placed at the center of the head 120a of rail 120, and ultrasonic waves are transmitted toward the bottom 120c of rail 120 by vertical flaw detection. In this case, ultrasonic waves are transmitted to the central part of rail 120 indicated by the width 121 of the straight line in the figure, but ultrasonic waves do not reach the positions of both end faces 120d of the bottom 120c of rail 120.

[0003] FIG. 13 shows a graph showing the flaw detection results in an ultrasonic flaw detection test of a rail when ultrasonic flaw detection is performed by the vertical flaw detection method shown in FIG. 12. Referring to FIG. 13, what is displayed there are only a small reflection 141a in the rail head 120a and repeated echoes 142a to 142c of reflections from the bottom surface of the central part of the rail bottom 120c.

[0004] On the other hand, a method of performing ultrasonic flaw detection on the end of the conventional rail bottom is disclosed, for example, in Japanese Patent Application Laid-Open No. 2018-194384 (Patent Document 1). According to this publication, an ultrasonic flaw detector for a rail is disposed to face the bottom surface of the foot portion of the rail, and has a bottom surface facing portion for fixing a probe of the ultrasonic flaw detector, and is disposed to face the top surface of the foot portion. And a top surface facing portion having a fixing mechanism for movably fixing the ultrasonic flaw detector for the rail along the longitudinal direction of the rail with respect to the foot portion, and a connecting portion connecting the bottom surface facing portion and the top surface facing portion. A through opening into which the probe is inserted is formed in the bottom surface facing portion, and the formation position of the opening is set to a position where the ultrasonic oscillation surface formed at the tip of the inserted probe can contact the bottom surface of the toe portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The ultrasonic flaw detection inspection of the conventional rail bottom has been performed as described above. In the conventional method, there is a problem that flaw detection of the end of the rail bottom cannot be performed, or the configuration of the flaw detection device is complicated, and it takes time and effort to perform ultrasonic flaw detection inspection of the rail bottom.

[0007] This invention has been made to address the above problems, and an object thereof is to provide an ultrasonic flaw detector and an ultrasonic flaw detection method capable of easily performing ultrasonic flaw detection on the end of the rail bottom.

Means for Solving the Problems

[0008] An ultrasonic flaw detector for the bottom of a rail that inspects the bottom of the rail using an ultrasonic probe includes a transmitting probe that is mounted on the head of the rail and transmits ultrasonic waves toward the bottom of the rail, a receiving probe that is mounted on the head of the rail at a distance from the transmitting probe and receives the reflected echo of the ultrasonic waves transmitted from the transmitting probe, and a propagation path determination unit that determines the propagation path of the reflected echo received by the receiving probe. The transmitting probe transmits ultrasonic waves so that the transmitted ultrasonic waves undergo mode conversion in the web of the rail, the receiving probe receives the reflected echo from the end of the bottom of the rail, and based on the reflected echo from the end of the bottom of the rail received by the receiving probe, determines the loss of thickness due to corrosion at the end of the bottom of the rail.

[0009] Preferably, the transmitting probe transmits the ultrasonic waves at a predetermined refraction angle from the head of the rail.

[0010] More preferably, the predetermined refraction angle is 10 degrees to 12 degrees.

[0011] In another aspect of the present invention, an ultrasonic flaw detection method for the bottom of a rail that inspects the bottom of the rail using an ultrasonic probe includes a step of transmitting ultrasonic waves from the head of the rail toward the bottom of the rail, and a step of receiving the reflected echo of the transmitted ultrasonic waves. The step of transmitting ultrasonic waves from the head of the rail toward the bottom of the rail includes a step of transmitting ultrasonic waves so that the transmitted ultrasonic waves undergo mode conversion in the web of the rail. The reflected echo from the end of the bottom of the rail is received, and based on the reflected echo from the end of the bottom of the rail received, the loss of thickness due to corrosion at the end of the bottom of the rail is determined.

Advantages of the Invention

[0012] According to the present invention, the propagation path determination unit irradiates ultrasonic waves that obliquely enter obliquely toward the bottom of the rail, causes mode conversion in the web of the rail, receives the reflected echo from the end of the bottom of the rail, and based on this, determines the loss of thickness due to corrosion at the end. Therefore, the loss of thickness due to corrosion at the end of the bottom of the rail can be detected and evaluated.

[0013] As a result, it is possible to provide an ultrasonic flaw detector that can easily perform ultrasonic flaw detection on the end of the rail bottom.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

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Figure 11

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Figure 13

Embodiments for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for estimating the propagation path of ultrasonic waves passing through a rail when the rail is ultrasonically flaw-detected in the present invention. Referring to FIG. 1, in the present invention, the probe 11 is placed on the head 20a of the rail 20, and its position is not at the center as in the prior art, but the probe 11 is placed at a position slightly deviated from the center, and the ultrasonic wave transmission direction is set to the abdomen 20b of the rail 20. Then, the ultrasonic wave is mode-converted at the abdomen 20b of the rail and changes from a longitudinal wave to a shear wave, the reflection angle of the ultrasonic wave becomes smaller, and the ultrasonic wave propagates to the end 20d of the bottom 20c of the rail 20. In FIG. 1, the longitudinal wave is shown by a solid line and the shear wave is shown by a dotted line. As a result, ultrasonic flaw detection of the end 20d of the bottom 20c of the rail 20 becomes possible.

[0016] Next, the configuration of the ultrasonic flaw detection device and the specific arrangement of the probes will be described. FIG. 2 is a diagram showing the specific arrangement of the probes. FIG. 2(A) is a side view in the length direction of the ultrasonic flaw detection device 10 and the rail 20, and FIG. 2(B) is a plan view of the rail 20 as viewed from the direction of the head 20.

[0017] First, referring to FIG. 2(A), the ultrasonic flaw detection device 10 includes transmitting and receiving probes 11 and 12, and a propagation path determination unit 13. The propagation path determination unit 13 includes propagation path determination software 13a and a display unit 13b that displays the ultrasonic wave propagation path determined by the propagation path determination software 13a. Based on the ultrasonic wave propagation path displayed on the display unit 13b, the reduction in thickness due to corrosion is determined.

[0018] Referring to FIGS. 2(A) and 2(B), the transmitting probe 11 and the receiving probe 12 are placed such that a corrosion part (thickness reduction part) 24 is located at the central part in the length direction of the rail 20. At this time, the angles formed by the transmitting and receiving probes 11 and 12 and the thickness reduction part 24, which are indicated by arrows in FIG. 2(A), are 10° to 40° on the side surface.

[0019] Next, in ultrasonic flaw detection using the mode conversion shown in FIG. 1, the relationship between the estimated propagation path of ultrasonic waves and the reflected echo will be described. FIG. 3(A) is a diagram showing the reflected echo, and FIGS. 3(B) to 3(D) are diagrams showing the estimated propagation paths of ultrasonic waves.

[0020] Referring to FIG. 3(A), there are displayed a waveform 3a surrounded by a large ellipse, a waveform 3b surrounded by an ellipse located on the right side thereof, and a waveform 3c surrounded by an elongated ellipse with a gap therebetween. Here, the waveform 3a is the reflected echo from the center of the rail bottom surface, and its repeated echo appears on the left side of the waveform 3c.

[0021] The reflected echo of the wave that reflects from the abdomen 20b of the rail 20 by a probe (not shown) and goes to the bottom 20c of the rail 20 shown in FIG. 3(B) corresponds to the waveform 3b. The reflected echo of the wave that reflects from the abdomen 20b of the rail by a probe (not shown) and goes to one end 20d of the bottom 20c of the rail 20 shown in FIG. 3(C) corresponds to the left half of the waveform 3c, and the reflected echo of the wave that reflects from the abdomen 20b of the rail 20 by a probe (not shown) and goes to the other end 20e of the bottom 20c of the rail 20 shown in FIG. 3(D) corresponds to the right half of the waveform 3c.

[0022] In FIGS. 3(B) to 3(D), the path indicated by ○ represents the path of longitudinal waves, and the path indicated by ● represents the path of transverse waves.

[0023] In addition, the inventors have confirmed that the estimated propagation path of ultrasonic waves is substantially consistent with the path diagrams shown in FIGS. 3(B) to 3(D) and the travel distance of the flaw detection waveform beam shown in FIG. 3(A).

[0024] Specifically, on AutoCAD (drafting and design software), the estimated path is drawn, and its beam travel distance is calculated and confirmed to be substantially consistent. Also, during flaw detection, the skip points (points where ultrasonic waves are reflected) of ultrasonic waves on the abdomen 20b of the rail 20 and the bottom 20d of the rail 20 are touched with a finger, and it is confirmed that the corresponding echo moves (when touched with a finger, the ultrasonic waves attenuate and the flaw detection waveform moves).

[0025] Next, the corrosion simulation rail will be described. In this embodiment, a corrosion simulation rail was created to examine whether the corrosion depth of the side end portion 20d of the bottom portion 20c of the rail 20 can be evaluated using the reflection echo reaching the side end portion of the bottom portion 20c of the rail 20. Two types shown in FIGS. 4(A) and 4(B) were created as the corrosion simulation rail. FIG. 4(A) is a view in which a corroded portion is provided at one side end portion 20d in the width direction of the bottom portion 20c of the rail, and FIG. 4(B) is a view in which corroded portions are provided at both side end portions 20d and 20e in the width direction of the bottom portion 20c of the rail.

[0026] Referring to FIG. 4(A), as corroded portions at one side end portion 20d in the width direction of the bottom portion 20c of the rail, a corroded portion 25a with a width of 2 mm, a corroded portion 25b with a width of 4 mm, and a corroded portion 25c with a width of 8 mm were created. Also, referring to FIG. 4(B), at one side end portion 20d in the width direction of the bottom portion 20c of the rail, as corroded portions, a corroded portion 25a with a width of 2 mm, a corroded portion 25b with a width of 4 mm, and a corroded portion 25c with a width of 8 mm were created, and at the other side end portion 20e in the width direction, as corroded portions, a corroded portion 26a with a width of 2 mm, a corroded portion 26b with a width of 4 mm, and a corroded portion 26c with a width of 8 mm were created.

[0027] Next, the shape of the corrosion simulation rail in the cross-sectional direction will be described. FIGS. 5(A) to 5(C) are views showing the shape of the corroded portion 25a in the cross-sectional direction of the corrosion simulation rail shown in FIG. 4(A). FIG. 5(A) is a cross-sectional view of the corroded portion, FIG. 5(B) is a view showing the corroded portion as seen from the direction of the web 20b of the rail shown in FIG. 5(A) along the arrow 5B-5B, and FIG. 5(C) is an enlarged view of the corroded portion shown in FIG. 5(B). Referring to FIGS. 5(A) to 5(C), the corroded portion 25a has a length of 40 mm from the end portion 20d of the bottom portion 20c of the rail 20 toward the center, and its shape is a circle with a radius of 2 mm.

[0028] Figs. 6(A) to 6(C) are diagrams showing the shape in the cross-sectional direction of the corroded portion 25b in the simulated rail shown in Fig. 4(A). Fig. 6(A) is a cross-sectional view of the corroded portion, Fig. 6(B) is a diagram showing the corroded portion as viewed from the direction of the web 20b of the rail indicated by the arrow 6B-6B in Fig. 6(A), and Fig. 6(C) is an enlarged view of the corroded portion shown in Fig. 6(B). Referring to Figs. 6(A) to 6(C), the corroded portion 25b has a length of 40 mm from the end of the rail 20 toward the center, and its shape is circular with a radius of 4 mm.

[0029] Figs. 7(A) to 7(C) are diagrams showing the shape in the longitudinal direction of the corroded portion 25c in the simulated rail shown in Fig. 4(A). Fig. 7(A) is a cross-sectional view of the corroded portion, Fig. 7(B) is a diagram showing the corroded portion as viewed from the direction of the web 20b of the rail indicated by the arrow 7B-7B in Fig. 7(A), and Fig. 7(C) is an enlarged view of the corroded portion shown in Fig. 7(B). Referring to Figs. 7(A) to 7(C), the corroded portion 25c has a length of 40 mm from the end 20d of the bottom 20c of the rail 20 toward the center, and its shape is circular with a radius of 8 mm.

[0030] Note that the diagrams in which corroded portions are provided on both sides of the ends of the bottom of the rail shown in Fig. 4(B) are the same as Figs. 5(A) to 7(C), so they are omitted.

[0031] In the following description, these corroded portions are distinguished by the depth of the corroded portion. For example, for the corroded portion 25a, the depth of the corroded portion is d = 2 mm.

[0032] Next, the results of the flaw detection test using these corrosion-simulated rails will be described. Here, the analysis was performed using the propagation path determination software 13a. Figs. 8(A) to 8(D) are graphs showing the flaw detection results when a corroded portion is provided on one side of the bottom of the rail.

[0033] Figure 8(A) is a graph showing the flaw detection result in a sound state without a corroded part. Figure 8(B) is a graph showing the flaw detection result when the depth of the corroded part is d = 2 mm. Figure 8(C) is a graph showing the flaw detection result when the depth of the corroded part is d = 4 mm. Figure 8(D) is a graph showing the flaw detection result when the depth of the corroded part is d = 8 mm.

[0034] First, referring to Figure 8(A), the largest reflected echo 8a is the reflected echo from the center of the rail bottom. The reflected echo 8b adjacent to the reflected echo 8a is the reflected echo from the center of the rail bottom (corresponding to the waveform 3b shown in Figure 3(A)). A large reflected echo 8c different from such repetitions is displayed. This is the reflected echo from one side end of the rail bottom.

[0035] Next, referring to Figure 8(B), even when d = 2 mm, a small reflected echo 8d close to the reflected echo 8c is displayed. Similarly, referring to Figure 8(C) and Figure 8(D), similar reflected echoes 8e and 8f are displayed when d = 4 mm and d = 8 mm.

[0036] Figures 9(A) to 9(D) are graphs showing the flaw detection results when corroded parts are provided on both sides of the rail bottom. Figure 9(A) is a graph showing the flaw detection result in a sound state without a corroded part. Figure 9(B) is a graph showing the flaw detection result when the depth of the corroded part is d = 2 mm. Figure 9(C) is a graph showing the flaw detection result when the depth of the corroded part is d = 4 mm. Figure 9(D) is a graph showing the flaw detection result when the depth of the corroded part is d = 8 mm.

[0037] In Figure 9(A), 9a is the reflected echo from the center of the rail bottom surface, 9b is the reflected echo from the center of the rail bottom surface (corresponding to the waveform 3b shown in Figure 3(A)), and 9c is the reflected echo from both ends of the rail bottom surface. The reflected echoes 9c from both ends of the rail bottom surface include 9c1 and 9c2 surrounded by the left dotted line. 9c1 is the reflected echo from one side end 20d shown in Figure 4(B), and 9c2 is the reflected echo from the other side end 20e shown in Figure 4(B).

[0038] In FIG. 9(B), the reflected echoes 9d from both ends of the bottom surface of the rail include 9d1 and 9d2 surrounded by the dotted line on the left side. 9d1 is the reflected echo from the end 20d where the corrosion part 25a on one side shown in FIG. 4(B) is located, and 9d2 is the reflected echo from the end 20e where the corrosion part 26a on the other side shown in FIG. 4(B) is located.

[0039] The same applies to FIGS. 9(C) and 9(D).

[0040] Referring to FIGS. 9(A) to 9(D), the same results as those shown in FIGS. 8(A) to 8(D) are obtained.

[0041] FIG. 10 is a graph showing an example of a criterion for the ultrasonic propagation path determination unit 13 to determine the metal loss due to corrosion based on the displayed ultrasonic propagation path by the propagation path determination software 13a. Here, the criterion in the case where a corrosion part is provided on one side of the bottom of the rail will be described.

[0042] FIG. 10(A) is a graph showing the case where the bottom of the rail is sound, and also shows the reflected echo 10a from the center of the bottom surface of the rail and the reflected echo 10b from the center of the bottom surface of the rail (corresponding to the waveform 3b shown in FIG. 3(A)) as shown in FIG. 9(A). In the reflected echo 10c from one end of the bottom surface of the rail, if the peak of the reflected echo surrounded by ○ is 70% or more, the rail is determined to be sound.

[0043] FIG. 10(B) is a graph showing the case where the metal loss due to corrosion of the bottom of the rail is 2 mm, corresponding to FIG. 9(B). Here, in the reflected echo 10d from one end of the bottom surface of the rail, the peak of the reflected echo surrounded by ○ corresponds to a 40% metal loss.

[0044] Similarly, FIGS. 10(C) and 10(D) are graphs showing the cases where the metal loss due to corrosion of the bottom of the rail is 4 mm and 8 mm, respectively. In the reflected echoes 10e and 10f, the peaks of the reflected echoes surrounded by ○ correspond to 20% and 10% metal losses, respectively.

[0045] As described above, the corroded part at the end of the bottom of the rail can be detected by an ultrasonic flaw detector, and the depth of the metal loss due to corrosion can be evaluated from the change in the height of the reflected echo.

[0046] Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various changes can be made to the illustrated embodiments within the same scope or equivalent scope of the present invention.

Industrial Applicability

[0047] According to the present invention, since ultrasonic waves are incident from the easily accessible rail head and it is possible to detect the metal loss due to corrosion at the end of the rail, it is possible to provide an ultrasonic flaw detector capable of ultrasonic flaw detection at the end of the bottom of the rail without removing the rail fastening. Therefore, it is effectively used as an efficient inspection device for rail bottom corrosion.

Explanation of Reference Numerals

[0048] 10 Ultrasonic flaw detector, 11 Transmitting probe, 12 Receiving probe, 13 Propagation path determination unit, 13a Propagation path determination software, 13b Display unit, 20 Rail, 20a Head, 20b Belly, 20c Bottom, 20d, 20e Ends, 24 Metal loss part, 25a - 25c, 26a - 26c Corroded parts.

Claims

1. An ultrasonic flaw detector for the bottom of a rail that inspects the bottom of the rail using an ultrasonic probe, a transmitting probe mounted on the head of the rail and transmitting ultrasonic waves toward the bottom of the rail, a receiving probe mounted on the head of the rail at a distance from the transmitting probe and receiving the reflected echo of the ultrasonic waves transmitted from the transmitting probe, and a propagation path determination unit that determines the propagation path of the reflected echo received by the receiving probe, wherein the transmitting probe transmits ultrasonic waves such that the transmitted ultrasonic waves undergo mode conversion in the web of the rail, the receiving probe receives the reflected echo from the end of the bottom of the rail, and an ultrasonic flaw detector for the bottom of a rail that determines the reduction in thickness due to corrosion of the bottom of the rail based on the reflected echo from the end of the bottom of the rail received by the receiving probe.

2. The ultrasonic flaw detector for the bottom of a rail according to claim 1, wherein the transmitting probe transmits the ultrasonic waves at a predetermined refraction angle from the head of the rail.

3. The ultrasonic flaw detector for the bottom of a rail according to claim 2, wherein the predetermined refraction angle is 10 degrees to 12 degrees.

4. An ultrasonic flaw detection method for the bottom of a rail that inspects the bottom of the rail using an ultrasonic probe, comprising the steps of transmitting ultrasonic waves from the head of the rail toward the bottom of the rail, and receiving the reflected echo of the transmitted ultrasonic waves, wherein the step of transmitting ultrasonic waves from the head of the rail toward the bottom of the rail includes the step of transmitting ultrasonic waves such that the transmitted ultrasonic waves undergo mode conversion in the web of the rail, receiving the reflected echo from the end of the bottom of the rail, and an ultrasonic flaw detection method for the bottom of a rail that determines the reduction in thickness due to corrosion of the bottom of the rail based on the reflected echo from the end of the bottom of the rail received.

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