JP4171130B2 - Ultrasonic rail flaw detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic rail flaw detector that detects a defect in a rail.
[0002]
[Prior art]
Conventionally, this type of ultrasonic rail flaw detector is shown in FIG. In FIG. 4, an ultrasonic probe 32 is in contact with the head surface of the rail 1, and a transmission / reception circuit 36 is connected to the ultrasonic probe 32. When the electric pulse output from the transmission / reception circuit 36 is sent to the ultrasonic probe 32, it is converted into an ultrasonic pulse by the ultrasonic probe 32 and is incident obliquely into the rail 1 with a certain refraction angle. . The ultrasonic pulse that enters the rail is reflected when there is a discontinuous surface of acoustic impedance, that is, a defect. Therefore, the ultrasonic pulse 32 that is reflected and returned is received by the ultrasonic probe 32 to detect the defect. ing.
[0003]
The reflection direction from the defect is affected by the angle and position of the defect serving as the reflection surface. Therefore, when the ultrasonic probe 32 that is used for both transmission and reception shown in FIG. 4 is used, the defect 3 opened at the bottom as shown in FIG. 4A and the natural defect 4 having an uneven surface as shown in FIG. On the other hand, since the ultrasonic wave returns to the ultrasonic probe 32, the presence of a defect can be detected from the received signal. However, as shown in FIG. 4C, when the flat surface defect 5 perpendicular to the rail longitudinal direction exists in the rail 1, the reflection directivity is sharp and the ultrasonic wave is different from the incident direction. There is a problem that the signal cannot be received because it does not return to the direction of the ultrasonic probe 32 because it is reflected in the direction of. There is also an ultrasonic component that is scattered and reflected at the edge of the defect 5, but this is very low in signal level and difficult to receive.
[0004]
For this reason, in the flaw detection of the welded portion in which the flat surface defect 5 is predicted to be present in the rail, as shown in FIG. 5, the transmitting probe 42 and the receiving probe are formed on the head surface of the rail 1. It has been proposed to use a tandem flaw detection apparatus in which the probe 44 is arranged in tandem in the rail longitudinal direction.
[0005]
[Problems to be solved by the invention]
However, this tandem type flaw detection apparatus has a problem that the flaw detection area is determined by the relative positional relationship between the transmission probe 42 and the reception probe 44. For example, as shown in FIG. 5A, when the distance between the transmission probe 42 and the reception probe 44 is small, the transmission probe has a deep flaw detection area. When the distance between the child 42 and the receiving probe 44 is large, a shallow flaw detection area is provided. Therefore, flaw detection must be performed while adjusting the positions of the two probes 42 and 44. When flaw detection is performed while traveling like an ultrasonic flaw detection vehicle, the flaw detection travel speed is accompanied by the above-described position adjustment. There is a problem that it can be restricted.
[0006]
The present invention has been made in view of such conventional problems, and the inventions of claims 1 and 2 have a flat surface shape in a wide flaw detection region without moving the relative positions of the transmission probe and the reception probe. An object of the present invention is to provide an ultrasonic rail flaw detector capable of detecting a defect.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 has a single transmitting probe and a receiving probe which are in contact with the rail and are aligned in the longitudinal direction of the rail. The ultrasonic signal radiated from the child is incident on the rail obliquely in the direction away from the receiving probe, and the ultrasonic signal reflected by the defect is received by the receiving probe, thereby In the ultrasonic rail flaw detector for detecting defects,
The refraction angle θ of the ultrasonic signal radiated from the transmitting probe to the rail and the beam length L in the longitudinal direction of the rail of the ultrasonic signal are set to the height d of the rail.
[0008]
[Expression 2]
d = L / tan θ (1)
And the length of the receiving surface of the receiving probe in the longitudinal direction of the rail is set to L or more.
[0009]
Assuming a virtual reflecting surface having the same length as the rail height in the rail and orthogonal to the rail longitudinal direction, by satisfying the above equation, the ultrasonic signal emitted from the transmitting probe is virtually Cover the entire reflective surface. Therefore, if there is a flat defect on any one of the virtual reflection surfaces, the ultrasonic signal from the transmission probe is always reflected by the defect. Also, by setting the receiving probe to a length equal to or longer than L, the reflected ultrasonic signal can be reliably received by the receiving probe.
[0010]
The receiving probe may be arranged at a position where all the ultrasonic signals reflected by the virtual reflecting surface can be received, and the relative positional relationship between the receiving probe and the transmitting probe is It can be fixed.
[0011]
The receiving probe may be a single probe having one transducer. The invention according to claim 2 is the one according to claim 1, wherein the receiving probe is the same as the receiving probe. Is an array type probe composed of a plurality of array elements aligned in the longitudinal direction of the rail, and is characterized by detecting the depth of a defect by identifying whether an ultrasonic signal is received by any of the array elements. To do.
Since the reception position in the rail front-rear direction depends on the reflection depth position of the virtual reflection surface, the depth of the defect can be detected based on whether it is received by any of the array elements.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram viewed from the side of a rail representing an embodiment of an ultrasonic rail flaw detector according to the present invention, and FIG. 2 is a perspective view.
[0013]
The ultrasonic rail flaw detector 10 has a transmitting probe 12 and a receiving probe 14 that are in contact with the head surface of the rail 1 and are aligned in the rail longitudinal direction.
The transmission probe 12 has a refraction angle θ of the ultrasonic pulse emitted from the transducer to the rail 1 and a beam length L in the longitudinal direction of the ultrasonic pulse emitted from the transmission probe 12. , For the depth region length d of the rail 1 to be flawed,
[0014]
[Equation 3]
d ≦ L / tan θ (1)
Is set to satisfy. By setting so as to satisfy the expression (1), the ultrasonic signal radiated from the transmission probe 12 can cover the entire virtual reflection surface 6 of FIG. That is, the virtual reflecting surface 6 is a flat surface having the same length d as the depth region to be detected and orthogonal to the rail longitudinal direction.
[0015]
Also, the length of the receiving surface of the receiving probe 14 in the longitudinal direction of the rail is set to be equal to or longer than the beam length L. The reception probe 14 is set at a position where it can receive an ultrasonic signal emitted from the transmission probe 12 and reflected by the virtual reflecting surface 6, and the transmission probe 12 and the reception probe. The relative position between the child 14 is fixed. When the depth region d to be flawed is substantially equal to the length from the head to the bottom as in the example of the figure, the reception probe 14 is disposed in close contact with the transmission probe 12. The
[0016]
As the value of the refraction angle θ increases, L increases in the above equation (1) and the overall size of the transmission probe 12 increases, so that the refraction angle θ represents the conversion efficiency at the interface with the rail 1. It should be selected so that the angle is as small as possible within a good range.
[0017]
For example, when flaw detection is performed using a transverse wave of ultrasonic waves, if the refraction angle at which the longitudinal wave is a critical angle is set, the conversion of the longitudinal wave is eliminated, so that efficient flaw detection is possible. When the rail is a steel material, the shear wave velocity is 3230 m / s and the longitudinal wave velocity is 5900 m / s. Therefore, from Snell's law, the relationship between the refraction angle θ _{S of the} transverse wave and the refraction angle θ _{D of the} longitudinal wave is
[0018]
[Expression 4]
sin θ _S / 3230 = sin θ _D / 5900
When θ _S when the longitudinal wave becomes the critical angle and θ _D = 90 ° is obtained, θ _S = about 33 °. Therefore, if a transverse wave having a refraction angle of 33 ° or more is used, longitudinal wave conversion is eliminated and efficient flaw detection is possible. More preferably, about 35 ° having the highest conversion efficiency of the transverse wave is selected. In addition, when using longitudinal waves, it is known that the refraction angle can be used from 0 to 30 °. However, it is not possible to use reflection on the plane of the defect unless it is oblique inspection, and conversion efficiency. In consideration of the above, 15 to 20 ° is preferably selected.
[0019]
For example, when using a transverse wave ultrasonic wave, if the refraction angle θ is 35 ° and the rail height corresponding to the depth region length d of the rail 1 to be flawed is 160 mm, L is
[0020]
[Equation 5]
L = 160 × tan35 ° = 112 (mm)
It becomes. The length of the transmission probe 12 in the longitudinal direction of the rail may be substantially equal to L. Further, the length of the receiving surface of the receiving probe 14 in the longitudinal direction of the rail may be set to this dimension L (or L or more), and the length of the receiving probe 14 in the longitudinal direction of the rail is also substantially L (or L or more). ).
[0021]
The transmission probe 12 and the reception probe 14 are each connected to a transmission / reception circuit 16. The transmission / reception circuit 16 includes a transmission pulser 18 that is connected to the transmission probe 12 and transmits an electric pulse, and an amplification detection unit 20 that is connected to the reception probe 14 and amplifies a reception signal to detect the presence or absence of a defect. have.
[0022]
In the ultrasonic rail flaw detector 10 configured as described above, the transmission probe 12 and the reception probe 14 are mounted on an ultrasonic flaw detection vehicle in a state where the relative positional relationship is maintained. The flaw detection is performed continuously while moving in the direction of the arrow in FIG. When an electric pulse is transmitted from the transmission pulser 18 to the transmission probe 12, the transmission probe 12 converts the pulse into an ultrasonic pulse, and an ultrasonic beam having a length L in the longitudinal direction of the rail is received by the reception probe. In the direction away from 14, the light enters the rail 1 at the refraction angle θ.
[0023]
If there is no defect anywhere in the virtual reflecting surface 6, the ultrasonic pulse proceeds forward (in a direction away from the receiving probe 14) and is received by the receiving probe 14. Never happen.
[0024]
On the other hand, when the flat surface-like vertical defect 5 exists somewhere in the virtual reflection surface 6, the ultrasonic wave is reflected and reflected toward the bottom surface. The reflected echo is further reflected from the bottom surface, received by the receiving probe 14, and converted into an electrical signal. This received signal is amplified and detected by the amplification detector 20, and it is detected that the inherent flat surface-like vertical defect 5 is present in the flaw detection area d.
[0025]
Since the intensity of the received signal received at this time is considered to be proportional to the size of the reflecting surface, the area (size) of the defect 5 may be estimated by measuring the signal intensity with the amplification detector 20. it can. The estimation of the area can be performed based on the relationship between the strength and the area obtained in advance for the reference defect.
[0026]
Note that the defects that can be detected are not limited to the flat surface-like vertical defect 5, but the defect 3 opened at the bottom (see FIG. 4A) and the natural defect 4 having an uneven surface (see FIG. 4B). Similarly, since a part of the reflected wave is received by the receiving probe 14, a defect can be detected.
[0027]
Next, FIG. 3 is a view corresponding to FIG. 1 showing the second embodiment of the present invention. In the figure, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this embodiment, an array-type probe comprising a plurality of array elements 14-1, 14-2, 14-3 aligned in the rail longitudinal direction is used as the receiving probe 14 '. 14-1, 14-2, and 14-3 are individually connected to the amplification detection unit 20 ′. The amplification detection unit 20 ′ includes a deep amplification detection unit 20-1, an intermediate amplification detection unit 20-2, and a shallow amplification detection unit 20-3. The array elements 14-1, 14-2, and 14-3 are respectively included. It is connected to the array element according to the position where a receivable defect exists.
[0028]
The length in the rail front-rear direction of each receiving surface of the array elements 14-1, 14-2, 14-3 is relative to the beam length L in the rail front-rear direction of the ultrasonic signal radiated from the transmitting probe 12. , Each having the same length L / 3.
[0029]
In the ultrasonic rail flaw detector 10 ′ configured as described above, if a flat surface-like vertical defect 5 exists somewhere in the virtual reflecting surface 6, the array element 14-1 according to the position of the vertical defect 5. , 14-2, or 14-3, the reflected echo is received. Therefore, it is identified whether the electrical signal corresponding to the reflected echo is detected by any of the detection units 20-1, 20-2, and 20-3. Thus, the depth of the defect 5 can be known. For example, when a reflected echo is received by the array element 14-1, it can be seen that the defect 5 is in the range of (2/3) · d to d.
[0030]
In this example, three array elements have been described for the sake of simplicity, but the resolution of the defect depth can be improved by configuring the receiving probe with a large number of array elements.
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, the refraction angle θ of the ultrasonic signal radiated from the transmitting probe to the rail and the beam of the ultrasonic signal in the longitudinal direction of the rail. The length L is set to the rail height d.
[0032]
[Formula 6]
d = L / tan θ (1)
And the relative length between the transmitting probe and the receiving probe is moved by setting the length of the receiving surface of the receiving probe in the rail front-rear direction to L or more. Therefore, it is possible to reliably and efficiently detect a flat surface-like defect perpendicular to the rail longitudinal direction existing in the rail at the rail height d which is a wide flaw detection area.
The defect area can also be estimated by measuring the intensity of the received signal received by the receiving probe.
[0033]
According to the second aspect of the present invention, the receiving probe is an array type probe including a plurality of array elements aligned in the rail longitudinal direction, and an ultrasonic signal is received by any of the array elements. The depth of the defect can be detected by identifying whether or not.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram viewed from the side of a rail, showing an embodiment of an ultrasonic rail flaw detector according to the present invention.
FIG. 2 is a perspective view of FIG.
FIG. 3 is an explanatory diagram viewed from the side of a rail, showing a second embodiment of the ultrasonic rail flaw detector according to the present invention.
FIG. 4 is an explanatory view seen from the side of a rail representing a conventional ultrasonic rail flaw detector.
FIG. 5 is an explanatory view seen from the side of a rail representing another conventional ultrasonic rail flaw detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rail 10, 10 'Ultrasonic rail flaw detector 12 Transmitting probe 14 Receiving probe 14' Receiving probe (array type probe)
14-1, 14-2, 14-3 Array element

Claims (2)

A receiving probe that has a single transmitting probe and a receiving probe that are in contact with the rail and aligned in the longitudinal direction of the rail, and that receives ultrasonic signals emitted from the transmitting probe. In the ultrasonic rail flaw detector that detects a defect in the rail by making it incident into the rail obliquely in a direction away from the rail and receiving the ultrasonic signal reflected by the defect with the receiving probe,
The refraction angle θ of the ultrasonic signal radiated from the transmitting probe to the rail and the beam length L in the longitudinal direction of the rail of the ultrasonic signal are set to the height d of the rail.

The ultrasonic rail flaw detector is characterized in that the length of the receiving surface of the receiving probe in the longitudinal direction of the rail is set to be L or more.   The receiving probe is an array type probe composed of a plurality of array elements aligned in the longitudinal direction of the rail, and the depth of the defect is determined by identifying whether an ultrasonic signal is received by any of the array elements. The ultrasonic rail flaw detector according to claim 1, wherein the ultrasonic rail flaw detector is detected.

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