JP2007322366A - Ultrasonic flaw detector and ultrasonic flaw detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detector and a flaw detecting method capable of detecting the flaw on the testing surface of the testing body, where the probe of the detector cannot be placed, or the length of the flaw is equivalent or smaller than the wavelength of longitudinal wave or the position of the test body is difficult for oblique flaw detection. <P>SOLUTION: The ultrasonic flaw detector comprises: the probe for converting electrical signal into ultrasonic wave, and transmitting the ultrasonic wave from an end face that is different from both the side faces opposing each other of the inspection object of the test body; and the transducer for driving the ultrasonic probe and receiving the ultrasonic wave that has propagated though the testing object. By utilizing the ultrasonic wave generated by the mode conversion caused when ultrasonic wave which has propagated through the test body becomes incident on the side surface or its opposite side surface, the states of both the side faces themselves are inspected. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method for inspecting a solid interior in a nondestructive manner. In particular, the present invention relates to an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method in which an ultrasonic probe is installed on a surface different from a surface where a surface flaw exists on a specimen, such as a flaw detection on an axle or a bolt of a railway vehicle. .

As a conventional ultrasonic flaw detection method, an oblique probe is installed on the outer surface of the steel pipe, and longitudinal waves are mode-converted in other parts of the outer surface to generate transverse waves. The transverse wave that is reflected and returned is mode-converted again to generate a longitudinal wave, which is received by an oblique probe (see, for example, Patent Document 1).
However, since the ultrasonic probe cannot be installed on the surface to be flawed on the axle of a railway vehicle, the ultrasonic flaw detection method described in Patent Document 1 cannot be applied.

  Therefore, an ultrasonic probe is installed on the shaft end and the shaft surface of the axle as a test body, ultrasonic waves are incident from the ultrasonic probe into the test body, and the ultrasonic probe is not installed. The ultrasonic probe receives the ultrasonic waves that are reflected back from the surface scratches generated from the body surface. Then, vertical flaw detection in which ultrasonic waves are incident perpendicularly to the shaft end portion and the shaft surface or oblique flaw detection in which ultrasonic waves are inclined with respect to the shaft end portion and the shaft surface are appropriately selected according to the flaw detection location ( For example, refer nonpatent literature 1).

JP-A-52-1040392 Japan Nondestructive Inspection Association, “New Nondestructive Inspection Handbook”, first edition, Nikkan Kogyo Shimbun, October 15, 1992, p. 1223-1224

However, when the surface scratch is equal to or less than the wavelength of the ultrasonic wave, there is a problem that the S / N ratio is poor because the echo from the surface scratch is small, resulting in difficulty in detecting the surface scratch.
Therefore, if the oblique wave flaw detection of the transverse wave is applied, it is considered that small surface flaws can be detected because the wavelength is shorter than that of the longitudinal wave, but surface flaws generated from the surface far from the shaft end are installed at the shaft end. When a flaw detector is used to detect flaws, it is necessary to reduce the refraction angle. In this case, not only the transverse wave but also the longitudinal wave is emitted into the test body, so that the shape echo due to the longitudinal wave is received. That is, there is a problem that it is difficult for a transverse wave oblique angle probe having a small refraction angle to detect a surface flaw far away from the transverse wave oblique angle probe.

  The object of the present invention is to install a probe on the surface of a specimen where surface damage occurs, where the surface damage is the same as or less than the wavelength of the longitudinal wave, and where the transverse wave oblique angle inspection is difficult. An ultrasonic flaw detection apparatus and an ultrasonic flaw detection method capable of performing ultrasonic flaw detection on a certain test body are provided.

  The ultrasonic flaw detection apparatus according to the present invention converts an electrical signal into ultrasonic waves, transmits ultrasonic waves into the test body from an end surface different from the side surface to be inspected and the side surface facing the side surface, and the above-mentioned An ultrasonic probe that receives the ultrasonic wave propagated through the test body, converts the ultrasonic wave into an electric signal, drives the ultrasonic probe, and receives an electric signal from the ultrasonic probe. A transmitter / receiver, and using ultrasonic waves generated by mode conversion that occurs when ultrasonic waves propagated through the test body are incident on a side surface to be inspected of the test body or a side surface facing the side surface. Then, the property of the side surface opposite to the side surface of the test body in which the mode conversion has occurred or the side surface itself in which the mode conversion has occurred is inspected.

  The effect of the ultrasonic flaw detector according to the present invention is that an ultrasonic wave is transmitted from an end surface different from a side surface to be inspected or a side surface facing the side surface, and the ultrasonic wave is incident on the side surface to be inspected or the side surface facing the side surface. Since the property is inspected on the side surface of the object to be inspected using the ultrasonic waves generated by the mode conversion that occurs at the time, the ultrasonic probe can be installed at a location different from the surface of the object to be inspected. The size of the echo received by the tentacle is large and the S / N ratio can be increased.

Embodiment 1 FIG.
FIG. 1 is a diagram showing the configuration of an ultrasonic flaw detector according to an embodiment of the present invention.
As shown in FIG. 1, the ultrasonic flaw detector according to the embodiment of the present invention converts an electrical signal into an ultrasonic wave, transmits the ultrasonic wave into the test body 1, and propagates through the test body 1. The ultrasonic probe 5 that receives the ultrasonic wave and converts the ultrasonic wave into an electric signal, the electric signal that drives the ultrasonic probe 5, and the electric signal from the ultrasonic probe 5 are output. And an ultrasonic flaw detector 6 for inputting a signal.

  Then, as a test body 1 that performs ultrasonic flaw detection using the ultrasonic flaw detection apparatus according to this embodiment, a cylindrical rod will be described as an example assuming an axle. Further, only the ultrasonic wave propagating in the cross section including the axis of the cylindrical bar will be described. On one side surface 7 of the two side surfaces of the cylindrical bar, a longitudinal wave is incident from an oblique direction, and mode conversion is performed from the longitudinal wave to the transverse wave. Further, a surface scratch 4 is generated on the other side surface 8. In addition, although the detection target is expressed by the term “surface flaw”, the application range of the ultrasonic flaw detector is not limited to the detection of the surface flaw 4, but the property in the vicinity of the surface of the specimen 1. Covers all inspections.

The ultrasonic probe 5 according to this embodiment is a longitudinal wave ultrasonic probe that transmits a longitudinal wave to the test body 1 and is perpendicular to the one end surface 3 of the test body 1 from a predetermined position. It is a bevel probe that makes longitudinal waves incident at an angle of refraction. That is, the ultrasonic probe 5 is a longitudinal wave oblique angle probe. Hereinafter, the longitudinal wave oblique angle probe 5 is used as the ultrasonic probe 5.
The ultrasonic flaw detector 6 is a transmitter / receiver that excites the ultrasonic probe 5 and receives an electrical signal from the ultrasonic probe 5.

Next, the operation of the ultrasonic flaw detector according to the embodiment of the present invention will be described.
An excitation signal is generated from the ultrasonic flaw detector 6 to excite the longitudinal wave oblique angle probe 5. A longitudinal wave is excited in the test body 1 from the longitudinal wave oblique angle probe 5. Although the transverse wave is also excited, its amplitude is smaller than that of the longitudinal wave, and can be ignored here.

  The longitudinal wave that has propagated through the test body 1 reaches the side surface 7 of the test body 1. Then, the longitudinal wave is mode-converted on the side surface 7 to generate a transverse wave. The transverse wave generated by the mode conversion in the side surface 7 propagates in a direction in which the propagation direction is different because the sound speed is different from the longitudinal wave. In FIG. 1, it propagates in a diagonally downward direction. Thereafter, it propagates in the direction of the side surface 8 of the specimen 1 and enters the surface scratch 4.

  The transverse wave incident on the surface scratch 4 is reflected, propagates along the same path as the incident, returns to the direction of the longitudinal wave oblique angle probe 5, and is received as an echo. That is, on the side surface 7, mode conversion from a transverse wave to a longitudinal wave occurs. The ultrasonic flaw detector 6 receives this echo as an echo from the surface flaw 4. By such an operation, the surface flaw 4 can be detected even if the longitudinal wave oblique angle probe 5 can be installed only on a surface different from the side surface 8 where the surface flaw 4 exists, in this case, the end surface 3. .

  Next, in order to investigate whether or not flaw detection by a transverse wave generated by mode conversion on the side surface 7 is possible, the result of a sound wave simulation performed by the two-dimensional elastic wave FDTD method will be described. FIG. 2 shows a relative positional relationship between the longitudinal wave oblique angle probe 5 and the test body 1 when the sound field simulation is performed. The distance from the longitudinal wave oblique angle probe 5 to the surface scratch 4 was 76.5 mm, and the thickness of the test body 1 was 26.5 mm. Further, the size of the surface scratch 4 was 1.5 mm. The flaw detection frequency was 5 MHz, and the refraction angle was 8 degrees.

FIG. 3 shows the result of sound field simulation. FIG. 3 shows a sound field snapshot every 3 μs from the excitation of the longitudinal wave oblique angle probe 5 to 24 μs. FIG. 3 also shows the ultrasonic mode (longitudinal wave or transverse wave) and the propagation direction.
As can be seen from FIG. 3, when the longitudinal wave emitted from the longitudinal wave oblique angle probe 5 reaches the side surface 7 of the test body 1, a transverse wave is generated by mode conversion. Since the longitudinal wave propagates along the side surface 7, the transverse wave is generated over a wide range. This transverse wave enters the surface scratch 4 on the side surface 8 and is reflected. The reflected transverse wave follows the reverse propagation path and is received by the longitudinal wave oblique angle probe 5. FIG. 4 shows echoes obtained by sound wave simulation. Since various modes and propagation paths exist in the test body 1, the echo is mixed with noise, but the echo from the surface scratch 4 can be clearly identified. Therefore, from this sound field simulation result, it was found that the surface flaw 4 on the side surface 8 can be detected by the transverse wave generated by the mode conversion on the side surface 7. Although it seems that not only the transverse wave but also the longitudinal wave that has undergone mode conversion at the side surface 8 is incident on the surface scratch 4, the transverse wave is assumed to be incident here for the sake of simplicity.

  An experiment was conducted to confirm the validity of the sound field simulation results. The experiment was performed with the relative positional relationship between the longitudinal wave oblique angle probe 5 and the test body 1 being the same as that in FIG. FIG. 5 shows echoes obtained in the experiment. As shown in FIG. 5, an echo is received in the vicinity of 44 μs. Also in the simulation result shown in FIG. 4, the reception time of the echo from the surface flaw 4 is 44 μs, and the experimental result and the simulation result almost coincide. Therefore, the validity of the sound field simulation result was confirmed. That is, it was experimentally revealed that the surface flaw 4 on the side surface 8 of the test body 1 can be detected by echoes caused by transverse waves generated by mode conversion on the side surface 7 of the test body 1. Note that the test body 1 used in the experiment is a cylindrical steel test body.

  Next, the result of comparing the magnitude of echoes in ultrasonic flaw detection according to this embodiment with the magnitude of echoes in conventional ultrasonic flaw detection will be described. In the conventional ultrasonic flaw detection, as shown in FIG. 6, the surface flaw 4 is detected by propagating the vertical wave between the longitudinal wave oblique angle probe 5 and the surface flaw 4 without mode conversion. And the sound field simulation by this conventional ultrasonic flaw detection was performed. FIG. 7 shows the result of a sound field simulation in the conventional ultrasonic flaw detection. FIG. 7 also shows the ultrasonic mode (longitudinal wave or transverse wave) and the propagation direction together with FIG. As shown in FIG. 7, the longitudinal wave is incident on the surface scratch 4, the longitudinal wave is reflected, and is received as an echo by the longitudinal wave oblique angle probe 5.

  FIG. 8A shows an echo received by the longitudinal wave oblique angle probe 5 by the ultrasonic flaw detection according to the embodiment. On the other hand, FIG. 8B shows an echo received by the longitudinal wave oblique angle probe in the conventional ultrasonic flaw detection. FIG. 8A is the same as FIG. In FIG. 8A and FIG. 8B, the vertical axis is normalized. Comparing FIG. 8 (a) and FIG. 8 (b), the magnitude of the echo from the surface flaw 4 is clearly larger in the echo received by the ultrasonic flaw detection according to the embodiment of the present invention. Therefore, it was confirmed that when the ultrasonic flaw detector according to the embodiment of the present invention was used, a large echo was received and a signal having a large S / N ratio was obtained.

  In such an ultrasonic flaw detector, ultrasonic waves are transmitted from an end surface different from the side surface to be inspected or the side surface facing the side surface, and the ultrasonic wave is incident on the side surface to be inspected or the side surface facing the side surface. Since the property is inspected on the side surface of the inspection object using the ultrasonic wave generated by the mode conversion that occurs, the ultrasonic probe can be installed at a location different from the surface of the inspection object, and the ultrasonic probe The size of the received echo is large and the S / N ratio can be increased.

Further, since the longitudinal wave oblique angle probe is used as the ultrasonic probe, it is possible to cause mode conversion by injecting ultrasonic waves obliquely into the side surface to be inspected or the side surface facing the side surface.
Further, since the ultrasonic wave generated by the mode conversion is a transverse wave, it is possible to detect the surface scratch 4 having a short wavelength and a small length.

  In the ultrasonic flaw detection according to the embodiment, the case where the longitudinal wave oblique angle probe 5 is used for transmission and reception has been described. However, as shown in FIG. 9, the transmission and reception are different. A similar effect can be obtained by using a probe. That is, the surface flaw 4 may be detected by using the receiving probe 5b separately from the transmitting probe 5a.

  In the embodiment, the case has been described in which the surface wave 4 on the opposite side surface 8 is detected using the transverse wave generated by the mode conversion on the side surface 7 of the test body 1. The surface scratch 4 on the side surface 7 may be detected using the ultrasonic wave. That is, the same effect can be obtained even if the surface scratch 4 on the side surface 7 or the side surface 8 is detected using ultrasonic waves generated by mode conversion on the side surface 7 or the side surface 8.

It is a figure which shows the structure of the ultrasonic flaw detector concerning embodiment of this invention. It is a figure which shows the relative positional relationship of an ultrasonic probe and a test body in sound field simulation. It is a sound field simulation result of the ultrasonic wave propagating through the test body. It is the echo obtained by the sound field simulation of FIG. This is an echo obtained in the experiment. It is a figure which shows the relative positional relationship of an ultrasonic probe and a test body in the sound field simulation of the conventional ultrasonic flaw detection. It is a sound field simulation result in the sound field simulation of the conventional ultrasonic flaw detection. It is the echo obtained by the sound field simulation of FIG. 3 and FIG. It is a figure which shows the mode of an ultrasonic flaw when the ultrasonic probe for transmission and reception are arrange | positioned separately.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Test body, 3 (End surface of test body), 4 Surface flaw, 5, 5a, 5b Ultrasonic probe, 6 Ultrasonic flaw detector, 7, 8 Side surface (Test body).

Claims (7)

The electrical signal is converted into ultrasonic waves, ultrasonic waves are transmitted into the test body from the side surface of the test object to be inspected and the end surface different from the side surface facing the side surface, and the ultrasonic waves propagated through the test body are received. An ultrasonic probe that converts ultrasonic waves into electrical signals;
A transceiver for driving the ultrasonic probe and receiving an electrical signal from the ultrasonic probe;
With
A test in which the mode conversion has occurred using the ultrasonic wave generated by the mode conversion that occurs when the ultrasonic wave propagated through the test body is incident on the side surface of the test body to be inspected or the side surface facing the side surface An ultrasonic flaw detector which inspects the properties of the side surface facing the side surface of the body or the side surface itself where the mode conversion has occurred. An ultrasonic probe for transmission that converts an electrical signal into ultrasonic waves, and transmits ultrasonic waves into the test body from the side surface to be inspected of the test body and an end surface different from the side surface facing the side surface;
An ultrasonic probe for reception that receives ultrasonic waves propagated through the specimen and converts the ultrasonic waves into electrical signals;
A transceiver for driving the ultrasonic probe for transmission and receiving an electrical signal from the ultrasonic probe for reception; and
With
A test in which the mode conversion has occurred using the ultrasonic wave generated by the mode conversion that occurs when the ultrasonic wave propagated through the test body is incident on the side surface of the test body to be inspected or the side surface facing the side surface An ultrasonic flaw detector which inspects the properties of the side surface facing the side surface of the body or the side surface itself where the mode conversion has occurred.   The ultrasonic flaw detector according to claim 1 or 2, wherein the ultrasonic probe is a longitudinal wave oblique angle probe.   The ultrasonic flaw detector according to claim 1 or 2, wherein the ultrasonic wave generated by the mode conversion is a transverse wave. Transmitting ultrasonic waves into the test body from the side surface different from the side surface of the test object to be inspected and the side surface facing the side surface by the ultrasonic probe;
A test in which the mode conversion has occurred using the ultrasonic wave generated by the mode conversion that occurs when the ultrasonic wave propagated through the test body is incident on the side surface of the test body to be inspected or the side surface facing the side surface Inspecting the properties of the side facing the side of the body or the side where the mode conversion has occurred;
An ultrasonic flaw detection method comprising:   6. The ultrasonic flaw detection method according to claim 5, wherein the ultrasonic probe is a longitudinal wave oblique angle probe.   The ultrasonic flaw detection method according to claim 5, wherein the ultrasonic wave generated by the mode conversion is a transverse wave.

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