JP6408145B2 - Ultrasonic flaw detection method with differential compensation of interfering factors - Google Patents

Description

  The product of the present invention relates to an ultrasonic flaw detector for a linear body including a rolled plate and a rolled steel bar. The technical solution can be used to inspect the rails of the track at high speed during the service period.

  Currently, transmission ultrasonic inspection based on ultrasonic amplitude attenuation detection is widely used for defects (eg, Aryosin, Belui, Vopirkin, etc., metal acoustic inspection methods, Moscow: Masinostroenje Publishing) 1989, pages 94-96).

  According to the RU2340495C1 patent, an ultrasonic flaw detection method comprising the formation of first and second measurement channels for transmission, movement of the probe system of the flaw detector, ultrasonic scanning of the specimen and processing of the channel output signal is provided. Are known. Moreover, an ultrasonic flaw detection apparatus is known by RU2340495C1 that includes a generator / receiver pair for generating / receiving ultrasonic waves and a data processing device connected to the output of the receiver at the input.

  However, the technical implementation of the transmission method, in particular the technical solution of RU2340495C1, is hampered by malfunctions due to a reduction in the desired signal level for various reasons. The flaw detection surface of the rail (rail) differs from the nominal value of the cross section due to wear, so that a part of the ultrasonic energy is scattered in various directions or due to a change in the ultrasonic propagation path to the receiver, The detection signal from the electroacoustic probe is reduced.

  Scattered reflection occurs due to corrosion of the reflecting side surface (outer surface) of the head of the rail (rail), and the received signal is attenuated for any type of probe. Dirt on the reflection side of the head of the rail causes ultrasonic absorption and desired signal attenuation. Due to the unevenness, the gap between the probe and the flaw detection surface changes, and signal attenuation occurs. In addition, since the ultrasonic attenuation differs depending on the manufacturer and lot of the rail, the amplitude of the received signal is different even if the rail of a certain track has the same defect if the manufacturer or lot differs.

  In the above case, the desired signal level received at the receiver decreases and eventually exceeds the failure determination value. Even if there is no defect, the reception level of the transmitted ultrasonic wave fluctuates due to excessive scattering and absorption of the ultrasonic wave, and erroneous detection occurs. For this reason, transmission methods are not widely used for high-speed inspection of important things such as rails on tracks.

  An object of the present invention is to reduce the number of false detections when performing ultrasonic flaw detection at high speed without degrading the detectability of the flaw detector.

  The positive effect ensured is to increase the selectivity of the ultrasonic inspection device against defects of the specimen during the inspection, as compared with Japanese Patent No. RU2340495C1.

  This includes the steps of forming the first and second measurement channels for the transmission method, the step of moving the probe system of the flaw detector, the step of scanning with the ultrasonic beam of the specimen and the step of processing the channel output signal. In the acoustic flaw detection method, the properties of the electroacoustic path of both channels are the same, but the second measurement channel is spatially separated from the first measurement channel along the operating axis, and the output signal is processed. As a result, differential signal processing is also included.

  In some cases, the distance between measurement channels is selected from a range of 3 mm to 900 mm.

  In other cases, the number N of measurement channels is selected based on an even number and N> 2.

  In other cases, the measurement information signal is obtained by uniformly separating the channels and averaging the signal difference (deviation) between the even and odd channels (in other cases, the measurement information signal Is obtained as the signal difference (deviation) between the averaged even and odd channels.) Alternatively, the channels are separated irregularly and the differential signals are weighted and averaged.

  Furthermore, during the construction of a flaw detector comprising a generator-receiver pair for generating and receiving ultrasound and a data processing device connected at the input to the output of the receiver, the generator and receiver are Arranged in a line, the data processing apparatus has a function of calculating a differential signal.

  In some cases, the generator and receiver pair have the same nature of the electroacoustic path.

  In other cases, the distance between the receivers is equal to the distance between the generators. Alternatively, the generator and receiver pairs are arranged to interfere with each other. Alternatively, the distance between the generators is 3 mm to 900 mm.

  In some cases, all generators and receivers are grouped together with the same type of equipment.

  In other cases, the number N of generator-receiver pairs is an even number and N> 2, but the data processor has the ability to calculate a differential signal based on the alternating measurement channel output.

  In some cases, the pairs are uniformly spaced (regular), and the data processing device has a function of averaging the measurement results.

  In another case, the data processing apparatus has a function of averaging the differential signal with a weighting factor by randomly separating the generator-receiver (element) pairs.

The present invention is illustrated in the following drawings.
FIG. 1 is a top view showing a transmission ultrasonic inspection method on a rail having no defect. FIG. 2 is a diagram illustrating a waveform of a signal at the output of the measurement channel. FIG. 3 is a top view showing a transmission ultrasonic flaw detection method for a defect near the flaw detection surface of the head of the rail. FIG. 4 is a diagram showing a waveform of a signal at the output of the measurement channel. FIG. 5 is a top view showing a transmission ultrasonic inspection method for a defect in the central portion of the rail head. FIG. 6 is a diagram illustrating a waveform of a signal at the output of the measurement channel. FIG. 7 is a top view showing a transmission ultrasonic inspection method for defects on the outside of the head of the rail. FIG. 8 is a diagram illustrating a waveform of a signal at the output of the measurement channel. FIG. 9 is a top view showing detection of longer defects. FIG. 10 is a diagram showing that the width after the decrease of the measurement signal is increased by detecting a longer defect. FIG. 11 is a top view showing an ultrasonic flaw inspection of a rail according to the present invention. FIG. 12 is a cross-sectional view showing the arrangement of the integrated mechanism of the ultrasonic probe with respect to a defect in the head of the rail. FIG. 13 is a side view showing the arrangement of the integrated mechanism of the two-channel ultrasonic probe with respect to the rail head. FIG. 14 shows a functional block diagram of the ultrasonic flaw detector. FIG. 15 is a diagram illustrating a waveform of a signal at the output of the measurement channel 1 when the integrated mechanism is detached from the head of the rail in a short time. FIG. 16 is a diagram illustrating a waveform of a signal at the output of the measurement channel 1 when the integrated mechanism has not detached from the head of the rail in a short period of time. FIG. 17 is a diagram illustrating a waveform of a signal at the output of the measurement channel 2 when the integrated mechanism is detached from the rail head in a short time. FIG. 18 is a diagram illustrating a waveform of a signal at the output of the measurement channel 2 when the integrated mechanism has not detached from the head of the rail in a short time. FIG. 19 is a diagram showing a waveform of a differential signal when the integrated mechanism is detached from the flaw detection surface (side surface / surface) of the rail. FIG. 20 is a diagram showing a waveform of a differential signal when the integrated mechanism has not detached from the flaw detection surface (side surface / surface) of the rail. FIG. 21 is a diagram showing a four-channel integrated mechanism having a uniform distance. FIG. 22 is a diagram showing an integrated mechanism of four channels at irregular distances.

  As shown in FIG. 1, the flaw detector of the transmission ultrasonic flaw detection method for detecting the head of a rail of a track (railway) while traveling is composed of two first and second acoustically connected devices. Electronic acoustic probes 1 and 2 are provided. The probe 1 functions as an ultrasonic generator, and the probe 2 functions as a reflected ultrasonic receiver. Both probes 1 and 2 are disposed on the side surface (work surface) of the rail 3 in contact with the train wheel. According to the transmission ultrasonic inspection method, as shown in FIGS. 3 to 10, the depth and size of the defect inside the rail can be measured by the waveform of the signal.

  The best mode for carrying out the invention will be described in the following examples.

  The flaw detector includes electromagnetic ultrasonic probes (EMAT) 1, 2, 5, and 6. EMAT1, 2 form the first pair of acoustically connected probes. The second pair is formed with EMAT5,6. EMAT 1 and 5 function as an ultrasonic generator, and EMAT 2 and 6 function as an ultrasonic receiver that reflects from an opposing surface (reflection surface) of the head of the rail 3. At this time, as shown in FIGS. 11 and 13, the centers of the acoustic axes of all the EMATs are arranged in a line, and the linear integrated mechanism 7 is structurally formed along the line L-L.

  The work surfaces (generation / reception surfaces) of EMAT 1, 2, 5, and 6 are in the same plane and are suitable for the specimen. Since the first pair of probes and the second pair of probes are alternately arranged, the EMAT pair (s) are arranged to overlap. Due to the interleaving, generators (EMAT) 1, 5 form a first group of equipment of the same type in position and receivers (EMAT) 2, 6 are of the same type remote from the first group. Form a second group of equipment.

  The first pair of EMAT1,2 is part of the first measurement channel, and the second pair of EMAT5,6 is part of the second measurement channel. Both channels are in the same scanning plane, and the generator 1 and the receiver 2 and the transmitter 5 and the receiver 6 are acoustically coupled. In order to carry out this, the generators 1 and 5 propagate the ultrasonic beam obliquely to the test body, and the receivers 2 and 6 determine the distance of the width of the head of the rail 3 and the incident angle of the ultrasonic wave. Release accordingly.

  As shown in FIG. 13, the distance d between the centers of the receivers is equal to the distance between the centers of the generators and is 100 mm. Since EMAT 1, 2, 5, and 6 are the same type and have the same arrangement rule, the properties (characteristics) of the electroacoustic path are completely the same.

  EMAT 1, 2, 5 and 6 are control devices and data mechanically formed as an integrated digital calculator 8 having an analog function unit including an interface unit and a measurement signal differential amplifier (subtractor) 9 at the input and output. Electrically connected to the processing device. An ultrasonic flaw detector is attached to the rail carriage, and the integrated mechanism 7 is brought close to the work surface (contact surface) of the rail 3. By switching to the scanning mode, the flaw detector is advanced along the trajectory, and the rail head 3 is scanned with the ultrasonic beam to detect the presence or absence of the transverse crack type rail internal defect 4. In the figure, the direction of movement is indicated by the arrow V, but due to the identity of EMAT 1, 2, 5, 6 and the symmetry of the scanning pattern, the device can be operated even when moved in the opposite direction.

  The control device propagates electric pulses to the generators 1 and 5 that generate ultrasonic waves at the same angle with respect to the flaw detection surface of the rail. When there is no defect 4, the receivers 2 and 6 continuously receive the acoustic signal reflected from the opposite side surface (bottom surface / reflection surface) of the rail head 3. Defect 4 causes a reduction in the level of the desired signal.

  As shown in FIG. 11, two identical channels having the most closely similar characteristics are formed during scanning. In this case, the second channel is separated from the first channel by a distance d along a motion axis that spatially coincides with the rail (front / rear / vertical) axis.

  15 to 18 show waveforms of electrical signals from the outputs of the receivers 2 and 6. Here, A indicates a light defect (light injury / scratch), B indicates a medium defect (slack / scratch) with separation of the integrated mechanism 7 of the probe from the side surface of the head 3 of the rail, and C indicates a rail. D indicates a serious defect (serious injury / flaw).

  The input of the differential amplifier 9 receives the measurement signal.

  As shown in FIG. 19 or 20, the calculated differential signal compares the level of the calculated differential signal with the pass / fail judgment level from the output of the amplifier 9, or implements another input measurement processing algorithm. Propagated to the input of the calculator 8. If the decrease in the differential signal level exceeds the pass / fail judgment level, the ultrasonic flaw detector displays to the operator that there is a defect 4 in the head 3 of the rail. Since the generator and receiver are arranged along a line in a row, the second measurement channel is spatially separated from the first channel by a distance d along the axis of motion.

  In the case of the mechanism shown in FIG. 11, the defect 4 first intersects with the first ultrasonic beam, and after a while, intersects with the second ultrasonic beam. The time difference (gap) δt between the lowered signals from the outputs of the receivers 2 and 6 is calculated by the following equation:

δt = d / v
d: Distance between channels
v: Probe speed relative to the specimen

  Due to the time difference between the measurement channels, the total amplitude of the reflected signal at the defect 4 is almost doubled for the differential signal. However, any disturbing factors that reduce the received signal level (such as gap change between the probe and the flaw detection surface, scattering, corrosion, rail cross-section change, and differences in properties between the (real) rail and the standard test rail) And since it affects both measurement channels to the same extent, changes in the measurement signal due to interference factors have no time difference. As a result, the signal difference is close to zero, and instead of addressing the factor by increasing the flaw detector's amplification, which leads to not only minor defects (minor injuries) but also minor defects (minor injuries), the noise generated by this factor The signal can be filtered.

  As shown in FIGS. 15 and 16, when the gap change (rattle) between the integrated mechanism 7 and the rail head 3 occurs in the short term, the waveform of the output signal of the first measurement channel is the gap change. It is quite different from the waveform of the signal when there was not. As shown in FIGS. 17 and 18, the same applies to the second channel.

  However, the differential signal curve is almost the same as when the gap change (rattle) occurs (FIG. 19) and when there is no gap change (FIG. 20). Therefore, the gap change between the integrated mechanism 7 and the rail head 3 is important for each channel, but does not significantly affect the resulting signal difference. This means increasing the selectivity of the ultrasonic flaw detector for defects in the specimen during scanning, and the number of false detections during high-speed ultrasonic flaw inspection can be reduced while the sensitivity of the flaw detector remains high. .

  The more equal the properties (characteristics) of the electroacoustic path of the measurement channel being scanned, the better the selectivity of the ultrasonic flaw detector for defects in the specimen. This (path identity) is greatly affected by the accuracy of the difference between the distance between the generators and the distance between the receivers.

  The distance d is determined based on experiments according to requirements such as the detection speed and the size (size) of the detection defect. In practice, it is possible to achieve an improvement in selectivity of the ultrasonic detector against defects in the specimen of the ultrasonic detector by keeping the distance d within the range of 3 mm to 900 mm during scanning.

  If the d-value should not exceed the distance between the generator and receiver of one channel, all generators and receivers are grouped together with the same type of equipment, mutual interference (overlapping) An arrangement of generator / receiver pairs is required. By increasing the number of channels for obtaining measurement information during scanning, it is possible to further improve the selectivity of the ultrasonic flaw detector with respect to the defect of the specimen.

  The conditions for determining the number of generator / receiver pairs are an even number of channels N and N> 2. The number of generator / receiver pairs can be determined by the condition that the number of channels N is even and N> 2. At this time, there are two choices for the possible arrangement pattern of the generator / receiver pair: regular arrangement and irregular arrangement.

  As shown in FIG. 21, in the case of mutual regular arrangement of probe pairs, the measurement information signal can be obtained in the form of the difference between the averaged odd and even channel signals. Thereby, random noise can be removed.

  As shown in FIG. 22, when the channel arrangement is irregular, the differential signal is averaged with a weighting factor for more accurate (high accuracy) selectivity.

  Potential applications of the invention are not limited to the above examples. The technical solution can also be applied to the detection of the entire (track) rail and the detection of the abdomen from the top surface. It is also possible to improve the selectivity of the multiple reflection method in which the receiver is placed at a distance to receive a signal reflected multiple times from the generator parallel plane (flaw detection surface and bottom surface) from the generator. is there.

Claims (14)

An ultrasonic flaw detection method for a transmission method,
Forming first and second measurement channels;
Moving the probe system of the flaw detector;
Irradiating the specimen with an ultrasonic beam;
Processing the channel output signal;
The electroacoustic path properties of both measurement channels are equal and the second measurement channel is spatially spaced along the axis of motion of the probe system with respect to the first measurement channel;
2. The ultrasonic flaw detection method according to claim 1, wherein the signal processing step includes a differential signal processing step.   2. The inspection method according to claim 1, wherein the distance between the two measurement channels is selected within a range of 3 mm to 900 mm.   The inspection method according to claim 1, wherein the number N of measurement channels is selected under an even number and N> 2.   The detection method according to claim 3, wherein the measurement information signal is obtained by uniformly separating the measurement channels and averaging the difference between the even and odd channels.   The detection method according to claim 3, wherein the measurement channels are separated irregularly, and the differential signal is averaged with a weighting factor. A pair of a generator for generating an ultrasonic wave and a receiver for receiving the reflected ultrasonic wave, and a data processing device connected to an output of the receiver at an input;
The generator and the receiver are arranged in a line along the axis of motion ,
The data processing apparatus is an ultrasonic flaw detector having a function of calculating a differential signal.   The flaw detector according to claim 6, wherein the pair of the generator and the receiver has the same property of an electroacoustic path.   The flaw detector according to claim 7, wherein a distance between the receivers is equal to a distance between the generators.   The flaw detector according to claim 6, wherein the pair of the generator and the receiver is arranged to interfere with each other.   The flaw detector according to claim 6, wherein a distance between the generators is in a range of 3 mm to 900 mm.   The flaw detector of claim 6, wherein all the generators and receivers are grouped together with the same type of equipment. The number N of pairs of the generator and the receiver is even and N> 2.
The flaw detector according to claim 6, wherein the data processing device has a function of calculating the differential signal based on an alternate measurement channel output signal. The pair of the generator and the receiver are uniformly spaced;
The flaw detector according to claim 12, wherein the data processing device has a function of averaging measurement results. The pair of the generator and the receiver are randomly spaced;
The flaw detector according to claim 12, wherein the data processing device has a function of adding a weighting coefficient to the differential signal and averaging.

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