JP5456569B2 - Multi-channel flaw detector - Google Patents

Description

  The present invention relates to a multi-channel flaw detection apparatus that has a plurality of channels for transmitting elements and receiving elements, propagates a guide wave to an inspection object, and detects surface defects, internal defects, and the like based on the reflected waves.

  As a flaw detection apparatus that detects an internal defect using ultrasonic waves, there is a multi-channel flaw detection apparatus that includes a plurality of transmission elements that generate ultrasonic waves on an inspection object and reception elements that receive reflected waves. By making the transmission element and the reception element multi-channel, it is not necessary to scan every flaw detection as in the case of a single channel, and the work can be completed in a short time.

  As a multi-channel flaw detection device, for example, one disclosed in Japanese Patent Application Laid-Open No. 2009-36516, and as a single channel flaw detection device, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 10-142201.

JP 2009-36516 A JP-A-10-142201

  However, the conventional multi-channel flaw detector does not sufficiently take measures against crosstalk between channels.

  An object of the present invention is to provide a multi-channel flaw detection apparatus that sufficiently considers measures against crosstalk between channels.

  In order to achieve the above object, a multi-channel flaw detection apparatus according to claim 1 includes an arbitrary waveform generator, a transmission amplifier for amplifying a transmission signal created by the arbitrary waveform generator, and a waveform of the transmission signal amplified by the transmission amplifier. A plurality of channels of transmission elements for generating a guide wave in the inspection object based on the switching means for sequentially supplying the transmission signal amplified by the transmission amplifier to the transmission element, and the guide wave from the inspection region of the inspection object. Multi-channel receiving element for receiving reflected waves, multi-channel receiving amplifier for amplifying the signal received by the receiving element for each channel, and analog / digital conversion for analog / digital conversion of the received signal amplified by the receiving amplifier And an analysis means for performing signal analysis based on the received waveform of the reflected wave, and a connection line between the switching means and the transmission element The connection line between the reception element and the reception amplifier, the connection line between the reception amplifier and the analog / digital converter, and these connectors are independent for each channel, and the reception amplifier is accommodated side by side in one housing. At the same time, noise blocking means is provided between the receiving amplifiers.

  Therefore, the connection line between the switching means and the transmission element, the connection line between the reception element and the reception amplifier, the connection line between the reception amplifier and the A / D converter, and the noise generated in these connector portions are connection lines of other channels. And intrusion into the connector portion.

  In the multi-channel flaw detector according to claim 2, the transmission amplifier is housed in a housing different from the housing. Therefore, it is possible to suppress noise generated in the transmission amplifier from entering the reception amplifier.

  The multi-channel flaw detector according to claim 1 is generated in a connection line between the switching means and the transmission element, a connection line between the reception element and the reception amplifier, a connection line between the reception amplifier and the A / D converter, and a connector portion thereof. Therefore, it is possible to suppress the intrusion of noise into the connection lines and connector portions of other channels, thereby preventing the occurrence of crosstalk between the channels.

  In the multi-channel flaw detector according to claim 2, it is possible to suppress the noise generated by the transmission amplifier from entering the reception amplifier.

It is a block diagram which shows an example of embodiment of the multichannel flaw detector of this invention. It is a block diagram which shows the analysis means of the multichannel flaw detector. The flexible array probe of the multichannel flaw detector is shown, (A) is a front view showing a state where it is in contact with a plate-like inspection object, and (B) is a state where it is in contact with a tubular inspection object. It is a front view. It is a flowchart which shows the procedure of a pulse compression process. FIG. 4A shows a pulse compression process, (A) shows a received signal before pulse compression, and (B) shows a received signal after pulse compression. 6 is a time chart of counter synchronization signal and transmission channel switching.

  Hereinafter, the configuration of the present invention will be described in detail based on the form shown in the drawings.

  1 and 2 show an example of an embodiment of a multi-channel flaw detector according to the present invention. The multi-channel flaw detector includes an arbitrary waveform generator 1, a transmission amplifier 2 that amplifies the transmission signal created by the arbitrary waveform generator 1, and the inspection object 3 based on the waveform of the transmission signal amplified by the transmission amplifier 2. A plurality of channels of transmission elements 4 that generate guide waves, switching means 5 that sequentially supplies the transmission signals amplified by the transmission amplifier 2 to the transmission elements 4, and reflected waves of the guide waves from the inspection region of the inspection object 3 A multi-channel receiving element 6 for receiving the signal, a multi-channel receiving amplifier 7 for amplifying the signal received by the receiving element 6 for each channel, and an analog / digital conversion of the received signal amplified by the receiving amplifier 7 A digital converter 8 and an analysis means 9 for performing signal analysis based on the received waveform of the reflected wave are provided. In the present embodiment, description will be made by taking 8 channels as an example of multi-channel. However, the number of channels is not limited to eight, and can be set as appropriate, for example, 16 channels, 32 channels, and the like.

  The inspection object 3 is not particularly limited in its material and shape as long as a guide wave is excited by the transmitting element 4 and the guide wave and its reflected wave can propagate. As materials, for example, metals, ceramics, resins and the like can be applied. Moreover, as a shape, it can apply about things, such as a shape of a pipe | tube, a board, etc., for example. Further, the detectable defects include surface defects such as thinning, scratches and cracks, internal voids, welding defects, internal defects such as cracks due to clip damage, and the like.

  The transmission element 4 is an element that generates a guide wave in the inspection object 3, is composed of, for example, a piezoelectric element, and is disposed in contact with the inspection object 3. The receiving element 6 is an element that receives a reflected wave propagating through the inspection object 3. The receiving element 6 is composed of, for example, a piezoelectric element, and is disposed in contact with the inspection object 3. In the present embodiment, the transmitting element 4 and the receiving element 6 are shared by one element (hereinafter referred to as a transmitting / receiving element 10). However, the transmitting element 4 and the receiving element 6 may be constituted by different elements.

  The same number of transmitting / receiving elements 10 as the number of channels are provided. In this embodiment, eight channels of transmitting / receiving elements 10 are provided. For example, the eight transmitting / receiving elements 10 are accommodated in a line in a flexible case, and constitute a flexible array probe 11. The flexible array probe 11 can be deformed according to the contact surface of the inspection object 3, and the contact surface can be flat (FIG. 3A) or curved (FIG. 3B). Even if it exists, each transmission / reception element 10 can be made to contact favorably and versatility improves. However, it is not always necessary to make the array probe 11 flexible. When the inspection object 3 having the same shape is always targeted, the array probe 11 does not have to be flexible according to the shape.

  The position of the flexible array probe 11 is measured by the two encoders 12 and 13. The two encoders 12 and 13 are in charge of two directions orthogonal to each other on the contact surface of the inspection object 3. Measurement signals from the encoders 12 and 13 are supplied to the counter 29. The counter 29 is controlled by the control means 9, counts measurement signals from the encoders 12 and 13, and supplies the information to the analysis means 9. The analysis means 9 detects the position of the flexible array probe 11 based on information from the counter 29.

  The arbitrary waveform generator 1 is controlled by the control means 9, creates a transmission signal having a waveform based on the waveform signal supplied from the analysis means 9, and supplies it to the transmission amplifier 2. The arbitrary waveform generator 1 has an amplifier circuit, and a transmission signal is created by the amplifier circuit. The transmission amplifier 2 amplifies the transmission signal supplied from the arbitrary waveform generator 1 and transmits it to the switching means 5. The switching unit 5 sequentially supplies the transmission signal amplified by the transmission amplifier 2 to each transmitting / receiving element 10. For example, a multiplexer or the like can be used as the switching unit 5.

  The reception amplifier 7 amplifies the signal received by the transmission / reception element 10. The same number of reception amplifiers 7 as the number of channels are provided. In this embodiment, reception amplifiers 7 for 8 channels are provided. Each receiving amplifier 7 is connected to the analyzing means 9 through a communication line such as a LAN (local area network), for example, and parameters such as a frequency band and a gain can be set. The analog signal amplified by the receiving amplifier 7 is supplied to an analog / digital converter (hereinafter referred to as A / D converter) 8 controlled by the control means 9, converted into a digital signal, and supplied to the analysis means 9. .

  The reception amplifier 7 is housed in a case 15 different from the case 14 of the transmission amplifier 2, and noise generated by the transmission amplifier 2 is prevented from entering the reception amplifier 7 side. Thereby, it is possible to prevent the noise generated in the transmission amplifier 2 from entering the reception amplifier 7. In this embodiment, the transmission amplifier 2 is accommodated in one casing 14, the reception amplifier 7, the switching means 5, and the control unit are unitized (hereinafter referred to as a transmission / reception unit 18) and accommodated in one casing 15. Further, the arbitrary waveform generator 1, the A / D converter 8, and the counter 29 are accommodated in one housing 16. Each housing 14, 15, 16 is grounded.

  The reception amplifiers 7 are arranged at intervals, and noise blocking means 17 is provided between the reception amplifiers 7. In the present embodiment, an L-shaped plate that is grounded to the housing 15 is used as the noise blocking means 17. However, it is not necessarily limited to the L-shaped plate, and any plate that can block noise can be used. By blocking noise passing between the reception amplifiers 7 by the noise blocking means 17, it is possible to prevent the occurrence of crosstalk between channels.

  The transmission / reception unit 18 and the transmission amplifier 2 are controlled by the control unit 19. The control unit 19 controls the transmission / reception unit 18 and the transmission amplifier 2 based on the synchronization signal from the counter 29. The control unit 19 is realized, for example, by installing a predetermined processing program in a computer. In the present embodiment, the control unit 19 is realized by an FPGA (Field Programmable Gate Array).

  A connection line 20 between the switching means 5 and the transmission element 4, a connection line 21 between the reception element 6 and the reception amplifier 7, a connection line 22 between the reception amplifier 7 and the A / D converter 8, and these connectors are provided for each channel. be independent.

  For example, coaxial cables are used as the connection lines 20, 21, and 22. For example, coaxial connectors are used as the connectors of the connection lines 20, 21, and 22. For example, a BNC connector can be used as the coaxial connector. By making the connection lines 20, 21, 22 and connection connectors of each channel independent, it is possible to prevent noise generated in a line or connector of a certain channel from entering the line or connector of another channel. The occurrence of crosstalk can be prevented. Further, by using a coaxial cable or a coaxial connector, it is possible to eliminate a portion where the signal line is not protected by the shield. From this point, it is possible to prevent noise from being emitted and intruded to prevent occurrence of crosstalk.

  The analysis unit 9 creates a waveform signal to be supplied to the arbitrary waveform generator 1 and analyzes the signal supplied from the A / D converter 8. The analysis unit 9 is realized by installing a predetermined processing program in a computer, for example, and is connected to an input unit 27 such as a keyboard and a mouse and a display unit 28 such as a liquid crystal display device.

  As shown in FIG. 2, the analysis unit 9 includes a pulse compression unit 23, a dispersibility correction unit 24, an aperture synthesis unit 25, and a waveform signal creation unit 26. The function of the pulse compression unit 23 is shown in FIG. The pulse compressor 23 supplies a waveform signal having, for example, a chirp waveform to the arbitrary waveform generator 1 (step S41). When the waveform signal of the reflected wave from the A / D converter 8 is received (step S42), the received waveform is demodulated (step S43), and the received waveform is compressed into a pulse shape (step S44). Here, FIG. 5A shows a received waveform before pulse compression, and FIG. 5B shows a received waveform after pulse compression. By performing pulse compression, the SN ratio can be improved. In addition, since a well-known method (for example, cross-correlation method) is used for pulse compression, the description thereof is omitted.

  The waveform signal compressed into a pulse shape by the pulse compression unit 23 is supplied to the dispersibility correction unit 24. Since the guide wave used for flaw detection has dispersibility, it is necessary to correct the dispersibility before aperture synthesis of the received waveform. Here, dispersibility means that the speed of sound changes depending on the frequency. Due to the dispersibility, the waveform of the guide wave becomes longer in the time direction as the propagation distance increases.

  The dispersibility of the guide wave is corrected by a known method. In the present embodiment, for example, correction is performed as follows. However, the correction method is not limited to this.

ここで、ｆは周波数、ｋｘはｘ方向の波数である。 Now, let the collected received waveform be S (x, z = 0, t). Here, x is a position of the transmitting / receiving element 10 in the scanning direction, z = 0 is a surface of the inspection object 3 on which the transmitting / receiving element 10 is brought into contact, and t is time. When 2D Fourier transform is performed on the received waveform, Equation 1 is obtained.

Here, f is the frequency, and kx is the wave number in the x direction.

ここで、ｉは虚数単位、ｋｚはｚ方向の波数、ｚはz方向の座標である。 Assuming that z has a reflector, Equations 1 and 2 are obtained.

Here, i is an imaginary unit, kz is a wave number in the z direction, and z is a coordinate in the z direction.

ここで、Ｖｐは位相速度である。 Equation 3 is obtained from Equation 2.

Here, Vp is a phase velocity.

ここで、Ωは周波数バンド幅である。 When the frequency components are summed, Equation 4 is obtained.

Where Ω is the frequency bandwidth.

In the case of the guide wave, since the phase velocity depends on the frequency, Equation 3 is rewritten into Equation 5.

ここで、Ｖ_Lは縦波の音速である。

ここで、Ｖ_Sは横波の音速である。

The phase velocity of each mode of the guide wave can be obtained from a known logical expression. The dispersion of the guide wave can be corrected from Equation 5 and the logical equation. Note that the logical expression varies depending on the type of the guide wave. As an example, the logical expression for obtaining the phase velocity of the guide wave (generally referred to as a Lamb wave) propagating through the flat plate is expressed by Expression 6 (in the case of the target mode). ), Formula 7 (in the non-target mode). Here, α (α ² ) is Equation 8, β (β ² ) is Equation 9, k is Equation 10, and h is a half value of the plate thickness.

Here, V _L is the sound velocity of the longitudinal wave.

Here, V _S is the sound speed of the transverse wave.

  The waveform signal whose dispersibility is corrected by the dispersibility correction unit 24 is supplied to the aperture synthesis unit 25. In the aperture synthesis unit 25, aperture synthesis is performed. In addition, since a well-known method is used as aperture synthesis, the description is omitted. By performing aperture synthesis, the signal-to-noise ratio of the waveform signal can be improved. In this embodiment, as described above, pulse compression that can improve the S / N ratio of the waveform signal is also performed, and by performing both aperture synthesis and pulse compression, the S / N ratio is significantly improved due to the synergistic effect of both. Can be expected.

  The waveform signal obtained by aperture synthesis is displayed on the display means 28. Based on this display, the user can detect a defect in the inspection object 3.

  The waveform signal creation unit 26 creates a waveform signal for determining the waveform of the transmission signal created by the arbitrary waveform generator 1 and supplies the waveform signal to the arbitrary waveform generator 1. In the present embodiment, the waveform signal creation unit 26 creates a waveform signal that generates a chirp wave as a transmission signal. By using a chirp wave for the transmission signal, it is possible to perform pulse compression processing of the reception signal and excite a guide wave having a large energy. However, the transmission signal to be used is not limited to the chirp wave, and a sine wave, a square wave, or the like can be used.

  Next, the operation of the multichannel flaw detector will be described.

  When the waveform signal creation unit 26 of the analysis means 9 creates a waveform signal and supplies it to the arbitrary waveform generator 1, the arbitrary waveform generator 1 creates a transmission signal having a waveform corresponding to the waveform signal. In this embodiment, a chirp wave is created as a transmission signal. This transmission signal is sent to the transmission amplifier 2 and amplified, and then supplied to the transmission / reception element 10 via the switching means 5. The switching means 5 switches the channel of the transmitting / receiving element 10 in order and supplies a transmission signal.

  Upon receiving the transmission signal, the transmitting / receiving element 10 vibrates and excites ultrasonic waves on the inspection object 3. The excited ultrasonic wave becomes a guide wave and propagates in the inspection object 3. If the inspection object 3 has a defect, the guide wave is reflected by the defect. The reflected wave propagates in the reverse direction in the inspection object 3 and is received by the transmitting / receiving elements 10 of all channels. The received signal received by each transmitting / receiving element 10 is amplified by each receiving amplifier 7, converted to a digital signal by the A / D converter 8, and supplied to the pulse compression unit 23 of the analyzing means 9.

  The pulse compression unit 23 of the analysis unit 9 performs pulse compression processing on the supplied reception signal. The signal-to-noise ratio of the signal can be improved by performing the pulse compression process. Thereafter, the received signal is supplied to the dispersibility correction unit 24, and the dispersibility of the guide wave is corrected as a pre-process for the aperture synthesis process. By performing this correction, aperture synthesis processing of the received signal becomes possible. The corrected received signal is supplied to the aperture synthesis unit 25, and aperture synthesis is performed by combining the received signals of the respective channels. By performing aperture synthesis, the SN ratio of the received signal can be improved and the azimuth resolution of the flaw detection can be improved. The received signal subjected to aperture synthesis is displayed on the display means 28. The user can determine the presence or absence of a defect in the inspection object 3 based on this display.

  The flaw detection operation described above is performed in synchronization with the synchronization signal generated by the counter 29 (using the synchronization signal as a trigger). Therefore, it is easy to synchronize the operation of each part, and it is possible to increase the flaw detection speed by increasing the repetition frequency of the synchronization signal, and it is easy to shorten the time required for flaw detection. In the present embodiment, the counter 29 generates a synchronization signal having a repetition frequency of, for example, 100 Hz. However, the repetition frequency is not necessarily limited to 100 Hz, and can be appropriately changed according to the distance at which flaw detection is performed, the time required for data processing, and the like.

  FIG. 6 shows a time chart for the synchronization signal of the counter 29 and transmission channel switching. The counter 29 generates a synchronization signal (TTL output low signal) every 10 ms at a repetition frequency of 100 Hz.

  First, transmission signal generation / supply will be described. In order to amplify and transmit the transmission signal created by the arbitrary waveform generator 1 by the transmission amplifier 2, it is necessary to match the timing of the transmission signal creation by the arbitrary waveform generator 1 and the gate creation of the transmission amplifier 2.

  Arbitrary waveform generator 1 starts its own amplification circuit in synchronization with the rise (end) of the synchronization signal and starts creating a transmission signal. However, since it takes about 5 μs until the activated amplifier circuit is actually stabilized, a transmission signal is created after the amplifier circuit is stabilized. The arbitrary waveform generator 1 generates a transmission signal and then transmits an event signal (a TTL output low signal) to the transmission amplifier 2. The transmission amplifier 2 creates a gate at the rising edge of the synchronization signal, and closes the gate by supplying the event signal from the arbitrary waveform generator 1. Thereby, the generation timing of the transmission signal of the arbitrary waveform generator 1 can be kept within the gate period of the transmission amplifier 2, and the transmission signal is normally amplified and supplied to the switching means 5.

  Next, the switching means 5 selects and opens one channel. Channel selection is performed in a predetermined order. The switching means 5 switches the channels in accordance with the fall (start) of the synchronization signal. Thereby, the channel is switched in accordance with the repetition period of the synchronization signal. Here, of 10 ms in which one channel is selected, the first half 5 ms until the transmission signal is supplied is a relay switching period, and the second half 5 ms is a period for flaw detection.

  Note that channel switching is not performed on the reception side as in the transmission side described above. A signal received by the transmitting / receiving element 10 of each channel is supplied to the receiving amplifier 7 of each channel, and is supplied to the analyzing means 9 via the A / D converter 8.

  Control of the transmission amplifier 2, the switching means 5, and each reception amplifier 7 is performed by the control unit 19 in response to a synchronization signal from the counter. The control unit 19 supplies a gate signal to the transmission amplifier 2.

  In the present invention, a high-frequency guide wave having a frequency of 2 MHz, for example, is used as a guide wave for flaw detection. Conventional flaw detectors used a low-frequency guide wave with a frequency of about 0.3 MHz. By using such a high-frequency guide wave, smaller defects can be detected and the flaw detection performance can be improved. Can be improved.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above description, the transmission amplifier 2 and the reception amplifier 7 are accommodated in separate casings 14 and 15, but may be accommodated in the same casing. When the transmission amplifier 2 and the reception amplifier 7 are accommodated in the same housing, it is preferable to provide a shield plate or the like between them to prevent the noise of the transmission amplifier 2 from entering the reception amplifier 7.

DESCRIPTION OF SYMBOLS 1 Arbitrary waveform generator 2 Transmission amplifier 3 Test object 4 Transmission element 5 Switching means 6 Reception element 7 Reception amplifier 8 Analog / digital converter 9 Analysis means 14 Transmission amplifier housing 15 Reception amplifier housing 17 Noise blocking means 20 Connection line between switching means and transmission element 21 Connection line between reception element and reception amplifier 22 Connection line between reception amplifier and analog / digital converter

Claims (2)

  An arbitrary waveform generator, a transmission amplifier for amplifying a transmission signal created by the arbitrary waveform generator, and a plurality of channels for generating a guide wave in an inspection object based on the waveform of the transmission signal amplified by the transmission amplifier Transmitting element, switching means for sequentially supplying the transmission signal amplified by the transmission amplifier to the transmitting element, and a multi-channel receiving element for receiving the reflected wave of the guide wave from the inspection region of the inspection object A reception amplifier of a plurality of channels that amplifies the signal received by the reception element for each channel; an analog / digital converter that performs analog / digital conversion on the reception signal amplified by the reception amplifier; and reception of the reflected wave Analyzing means for performing signal analysis based on a waveform, a connection line between the switching means and the transmitting element, the receiving element, The connection line to the reception amplifier, the connection line between the reception amplifier and the analog / digital converter, and these connectors are independent for each channel, and the reception amplifier is accommodated side by side in one housing. In addition, a multi-channel flaw detector having a noise blocking means provided between the receiving amplifiers.   The multichannel flaw detection apparatus according to claim 1, wherein the transmission amplifier is housed in a housing different from the housing.

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