JPH0619341B2 - Electronic scanning ultrasonic flaw detector - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an electronic scanning ultrasonic flaw detector for flaw detection inside a subject such as a metallic material or a non-metallic material.

TECHNICAL BACKGROUND OF THE INVENTION An ultrasonic flaw detector using ultrasonic waves has been generally used as a means for inspecting the inside of a subject of a metallic material or a non-metallic material. When the crack is perpendicular to the surface, as shown in FIG. 5, an oblique probe with a wedge 2 attached to the ultrasonic transducer 1 is used to make the crack as perpendicular as possible to the surface of the crack 4. Ultrasonic beam 5
An oblique angle flaw detection method capable of incident light is advantageous. Further, as shown in FIG. 6 (b) which is a perspective view of FIG. 6 (a) and a sectional view taken along the line AA of FIG. 6 (c), ultrasonic waves dedicated for ultrasonic transmission and reception Transducer 1a, 1b
In the split-type bevel probe attached to the wedge 2, the transmitting and receiving ultrasonic transducers 1a and 1b are slightly tilted with respect to each other, and the ultrasonic beams 5a and 5b on the central axis of the probe, respectively.
An ultrasonic flaw detection method in which b is crossed to improve the defect detection capability of the specific area 7 is also often used. With this flaw detection method, even for vertical cracks near the surface of the subject, if a split-type bevel probe is selected so that the ultrasonic transmission / reception focusing area matches the defect position, it can be used as a normal bevel flaw detection method. Higher defect detection accuracy can be obtained.

However, on the other hand, as shown in FIG. 7, when l is the distance and P is the reception power, the distance-amplitude characteristic of the split type probe shows that the level of reflected ultrasonic waves is high only in the focused region of ultrasonic wave transmission / reception. In other cases, the level of reflected ultrasonic waves was significantly reduced, indicating that the detectability of defects was poor. Therefore, if the defect position cannot be predicted in advance, ultrasonic wave transmission
There is no choice but to deal with the problem by using a plurality of probes having different focus areas, which not only deteriorates workability but also makes it difficult to maintain the inspection accuracy.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances. Even if the defect inside the object is a crack perpendicular to the surface of the object, and the defect exists at any depth position. It is an object of the present invention to provide an electronic scanning ultrasonic flaw detector having good flaw detection performance.

[Summary of the Invention] In order to achieve the above object, an electronic scanning ultrasonic flaw detector according to the present invention is a reception ultrasonic beam which is applied to a subject, transmits a transmission ultrasonic beam to the subject, and reflects from the subject. And an array type 2 in which a transmitting ultrasonic transducer group and a receiving ultrasonic transducer group are separately arranged.
A division probe, a transmission system for transmitting and driving each transducer of the transmission ultrasonic transducer group to generate a transmission ultrasonic beam to be transmitted to the subject, and reception reflected from the subject. A reception system for receiving a reception signal from each transducer of the reception ultrasonic transducer group to receive an ultrasonic beam; and a transmission in the transmission system for controlling a transmission aperture in the transmission ultrasonic transducer group. In addition to controlling the number of transducers to be driven, it also controls the transmission delay amount of the transducers to be driven for transmission in order to change the transmission deflection angle of the transmission ultrasonic beam and control the transmission focusing point of the transmission ultrasonic beam. Controlling the number of transducers driven to be received in the receiving system to control the receiving aperture in the group of ultrasonic transducers for receiving, and changing the receiving deflection angle of the receiving ultrasonic beam and the receiving ultrasonic wave. Transmission / reception control means for controlling the reception delay amount of the transducer driven for reception to control the change of the reception focusing point of the system, and the reception obtained via the reception system in order to obtain the ultrasonic information of the subject. A signal processing system that performs signal processing on the signal, and was obtained in advance by measurement in order to correct the fluctuation of the maximum amplitude value of the received signal due to the change of the setting condition by the transmission and reception focusing points and the transmission and reception aperture. Based on the maximum amplitude value of the distance amplitude characteristic for each setting condition by the transmission and reception focusing point and the transmission and reception aperture, the maximum amplitude value of the reception signal obtained from the reception system is changed every time the setting condition is changed. It is characterized by comprising an amplitude correcting means for correcting, and a display system for displaying the ultrasonic wave information obtained by the signal processing system.

With these, it becomes possible to send and receive ultrasonic waves with the focusing point positions of the ultrasonic wave transmitting beam and the receiving wave beam at the same point on the central axis of the probe.
The lateral resolution characteristic and the defect detection sensitivity characteristic in the focused region of the received beam are excellent. Further, while repeatedly shifting the focusing point position of the ultrasonic wave transmitting / receiving beam on the central axis of the probe to transmit / receive ultrasonic waves,
When the focal point position is close to the probe surface, ultrasonic waves are transmitted.
By reducing the number of transducer groups that contribute to reception and increasing the number of transducer groups as the distance increases and transmits and receives ultrasonic waves, it is possible to always focus on the ultrasonic waves that are focused at any position on the center axis of the probe. It is possible to detect flaws with a sound beam,
Furthermore, the aperture of the transducer group in ultrasonic transmission and reception is changed according to the focal point position, so that the focusing intensity can be made approximately constant regardless of the focal point position, and stable regardless of the defect depth position. The azimuth resolution characteristic and the defect detection sensitivity characteristic are obtained, and it becomes possible to improve the detectability of the defect, the defect position, and the dimensional accuracy.

Embodiments of the Invention Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an electronic scanning ultrasonic flaw detector according to the present invention. Array type two-division probe 20
Is an ultrasonic transducer group 1a dedicated to transmitting ultrasonic waves and an ultrasonic transducer group 1b dedicated to receiving ultrasonic waves, which are linearly arranged in one probe. Transducer group 1a
Are respectively coupled to an ultrasonic transmitter group 21 for generating a transmission pulse, and this ultrasonic transmitter group 21 selects all or several transmitters by a pulse generation trigger signal from a transmission delay setting unit 22. Then, a transmission pulse is sent to each corresponding ultrasonic transducer 1a, and in response to this, the ultrasonic transducer 1a is configured to transmit an ultrasonic wave.
On the other hand, the ultrasonic wave transmitted from the ultrasonic transducer 1a dedicated to transmission is reflected inside the subject, and the ultrasonic transducer 1 dedicated to reception is used.
reach b. The ultrasonic transducer 1b dedicated to receiving waves generates an electric signal corresponding to a change in sound pressure of ultrasonic waves and has a receiving function. After being amplified by the ultrasonic receiver group 23 corresponding to each, A /
It is input to the D converter 24.

The A / D converter 24 converts an ultrasonic signal into a digital signal at high speed, and can faithfully convert a received waveform into a digital amount. The A / D converter 24 receives a trigger signal for starting digital conversion of the received signal,
It is supplied from the reception delay setting device 25. All or some of the A / D converters 24 that have received this trigger signal convert the ultrasonic wave reception waveform into a digital signal in synchronization with the input time of the trigger signal.

The signal controller 26 selects, for the reception delay setting device 25 and the transmission delay setting device 22, a transducer group related to ultrasonic wave reception and a transducer group related to transmission, and sets a preset ultrasonic wave transmission and The trigger signal output timing is given according to the receiving direction and the focal point distance.

The outputs of the respective A / D converters 24 are added to the digital waveform and stored in the addition memory 27. That is, the digital waveform of the ultrasonic wave received signal once held in the A / D converter 24 is stored by digitally adding the received signals by the transducer group 1b dedicated to each ultrasonic wave signal at the same time when they are converted into digital waveforms. Will be. These operations are controlled by the signal controller 26. The received waveforms added by the addition memory 27 are input to the signal processor 28. The signal processor 28 detects the added waveform, converts it into a detected waveform, adjusts the signal level of the detected waveform based on the amplitude correction data preset by the signal controller 26, and displays it on the waveform display 29 such as a CRT. Output and display A scope. The most characteristic configuration of the present invention resides in transmission / reception control and amplitude correction of a received signal. That is, the transmission / reception control of the present invention controls the number of transducers driven to be transmitted in the ultrasonic transmitter group 21 so as to control the transmission aperture in the transmitting ultrasonic transducer group 1a, and at the same time, the transmission deflection of the transmitting ultrasonic beam is controlled. A transmission delay amount of a transducer that is driven to transmit is controlled in order to control the angle change and the transmission focus point of the transmission ultrasonic beam. Similarly, the reception control of the present invention controls the number of transducers driven to be received in the ultrasonic wave receiver group 23 to control the reception aperture in the ultrasonic wave transducer group 1b for reception, and receives the ultrasonic wave beam for reception. This is to control the reception delay amount of the transducer driven for reception in order to control the deflection angle and control the reception focusing point of the reception ultrasonic beam.

Further, the amplitude correction in the present invention, the transmission and reception obtained by measuring in advance, in order to correct the fluctuation of the maximum amplitude value of the received signal due to the change of the setting condition by the transmission and reception focusing point and the transmission and reception aperture. Correcting the maximum amplitude value of the received signal obtained from the receiving system every time the setting condition is changed, based on the maximum amplitude value of the distance amplitude characteristic for each setting condition by the reception focus point and the transmission and reception apertures. Is.

In this way, the ultrasonic flaw detector shown in FIG. 1 repeats the above-mentioned operation every time the ultrasonic transducers for transmission and reception are selected and the directions of the transmitted and received ultrasonic beams and the focal point distance are changed. Perform the operation.

Next, regarding the operation of the ultrasonic flaw detector shown in FIG. 1, the ultrasonic flaw detection method according to this embodiment will be described with reference to FIGS. 2, 3, and 4.

As shown in FIG. 2, an oblique angle two-divided probe composed of dedicated array type transducers 1a and 1b separated by a shield plate 6 provided on the wedge 2 is used for each of transmission and reception of ultrasonic waves. The case will be described. That is, the propagation path of the ultrasonic beam in the cross section perpendicular to the array direction is, as shown in FIG. 2A, the central axis of the ultrasonic beam transmitted from the transducer 1 propagates through the wedge 2 and The ultrasonic beam is incident on the subject 3 at an incident angle α with respect to the surface of the subject 3. At this time,
Assuming the sound velocity C _{w of the} wedge 2 and the sound velocity C _M of the subject, the refraction angle θ to the subject 3 is expressed by the following equation according to Snell's law, and is uniquely determined.

By increasing this refraction angle θ as much as possible, in a defect 4 such as a crack having a surface perpendicular to the surface of the object inside the object 3, the incident angle of the ultrasonic beam approaches the angle of the defect surface. It is well known that the ultrasonic reflection intensity from the defect 4 is increased, which is advantageous.

Transducer group 1a for ultrasonic wave transmission and transducer group 1 for wave reception only
Focusing of the ultrasonic wave by b can be considered by considering the cross section in the array direction on the central axis of the ultrasonic beam shown in FIG. 2 (b), which is shown in FIG. 3 (a).

That is, in FIG. 3 (a), in order to focus the transmitted ultrasonic wave beam and the received ultrasonic wave beam at point F on the central axis of the array type two-divided probe, in order to focus each ultrasonic vibration wave 1 ai. , 1bj and the ultrasonic focus point F in the propagation path, the angles αi, θi and α formed by the boundary between the wedge 2 and the subject 3
If the ultrasonic wave incident points C and D such that j and θj satisfy Snell's law are determined, the transmitted ultrasonic wave is transmitted from the wedge propagation distance l ₁ i and the subject propagation distance l ₂ i. The transmission delay time of each transducer required for beam focusing can be calculated by the following equation.

However, l _1: probe center in a wedge on the axis distance l _2: distance within the object on the probe central axis C _W: Kusabinai sound velocity C _M: in the subject sound velocity Similarly reception ultrasonic beam The receiving delay time of each transducer required for focusing is calculated by the following equation.

However, the formulas for obtaining the incident points C and D at the boundary between the wedge 2 and the subject 3 that satisfy Snell's law in the sound ray path that passes through the ultrasonic transducer and the focusing point are implicit functions and cannot be obtained by direct calculation. Therefore, the incident points C and D are given on a trial basis. The incident points C and D are determined.

When the transmission / reception delay time, which is the ultrasonic transmission / reception timing obtained in this way, is set in the transmission delay time setting device 22 and the reception delay time setting device 25 by the signal controller 26 and ultrasonic waves are transmitted / received, the focus is converged. The transmitted ultrasonic beam and the received ultrasonic beam focused at the point F intersect at the focusing point F. Therefore, as shown in FIGS. 3B and 3C, the detection sensitivity characteristic 31 and the azimuth resolution characteristic 32 are different from those of the normal two-division probe 31a and 32a (shown by broken lines) in which electron focusing is not performed. In the case of the array-type two-division probe with electron focusing, excellent characteristics can be obtained in the vicinity of the focusing points 31b and 32b (shown by solid lines). However, it becomes worse as the position deviates from the focus point, so that if the position of the defect cannot be estimated in advance, sufficient detection capability can be obtained for the defect at the position outside the focus region.

Therefore, as shown in FIG. 4 (a), the focusing points are sequentially set to F ₁ , F ₂ ... F _n along the center axis of the probe by the transmission delay setting unit 22 and the reception delay. The ultrasonic wave transmission / reception timing is set / changed in the setter 25 to transmit / receive ultrasonic waves. As a result, a defect at any depth position inside the subject can be inspected by the focused ultrasonic beam.

Further, when the defect depth position is shallow, that is, when the focusing point distance is short, sufficient focusing characteristics can be obtained even with a small number of transducers of the array-type transducer 1 operating, and when the focusing point distance is long. In order to obtain good focusing characteristics,
Since we have to do many oscillators that work,
At the same time as setting / changing the ultrasonic transmission / reception delay time associated with the change of the focus point, the signal controller 26 selects and changes the ultrasonic transducer group 1a, 1b to be operated based on the transducer aperture correction data set in advance. And are performed on the transmission delay setting device 22 and the reception delay setting device 25.

Further, the signal controller 26 corrects the fluctuation of the maximum received signal level due to the change of the focus point and the change of the aperture of the ultrasonic transducer group, so that the distance amplitude under each focus condition obtained by measurement in advance is corrected. Based on the maximum value of the characteristic, the amplitude correction data is set / changed in the signal processor 28 every time the focus point is changed so that the maximum amplitude value becomes substantially constant regardless of the focus condition.

As a result, the apparent ultrasonic transmission / reception focusing region 41 is equivalent to being focused on the center axis of the probe, and excellent lateral resolution and detection sensitivity characteristics can be obtained regardless of the depth position of the defect. become.

Note that FIG. 4 (b) is a diagram for explaining the total detection sensitivity characteristic 31 (t), and it takes the envelope of the distance amplitude characteristics 31 (1) to 31 (n) of ultrasonic wave transmission / reception under each focusing condition. It can be represented by a shape, indicating that flaw detection can be performed with substantially constant detection sensitivity regardless of the defect depth position.

In the embodiment described above, the case of using the oblique angle two-division probe with a wedge has been described, but the present invention can be applied to a vertical two-division type or a water immersion flaw detection method in which a liquid is used instead of the wedge. Are included in.

In the above description, the case where the received signal waveform of ultrasonic waves is subjected to high-speed A / D conversion and waveform addition is performed in a digital amount has been described.
It goes without saying that the same can be realized by performing waveform addition with an analog amount using a Coupled Device) or an analog delay line.

[Effects of the Invention] As described in detail with reference to the above embodiments, the present invention applies a transmission acoustic beam to a subject and receives a reception ultrasonic beam reflected from the subject. An array type two-division probe in which a transmitting ultrasonic transducer group and a receiving ultrasonic transducer group are separately arranged, and a transmitting ultrasonic beam transmitted to the subject. A transmission system for transmitting and driving each transducer of the transmission ultrasonic transducer group, and each of the reception ultrasonic transducer group for receiving the reception ultrasonic beam reflected from the subject. A reception system for receiving a reception signal from each of the transducers, and controlling the number of transducers driven to be transmitted in the transmission system to control the transmission aperture in the transmission ultrasonic transducer group, and transmitting the transmission ultrasonic beam Deflection angle change control and transmission The reception delay in the reception system is controlled so as to control the transmission delay amount of the transducer that is driven to transmit to control the change of the transmission focusing point of the ultrasonic beam and to control the reception aperture in the ultrasonic transducer group for reception. A transmission / reception control unit that controls the number of transducers and also controls the reception delay amount of the transducers that are driven to receive to change the reception deflection angle of the reception ultrasonic beam and change the reception focusing point of the reception ultrasonic beam. A signal processing system for processing the received signal obtained through the receiving system in order to obtain the ultrasonic information of the subject, and the setting conditions of the transmitting and receiving focusing points and the transmitting and receiving apertures. In order to correct the fluctuation of the maximum amplitude value of the received signal due to the change, the maximum of the distance amplitude characteristic for each setting condition by the transmission and reception focusing points obtained by measuring in advance and the transmission and reception aperture An amplitude correction unit that corrects the maximum amplitude value of the reception signal obtained from the reception system every time the setting condition is changed based on the width value, and a display system that displays the ultrasonic information obtained by the signal processing system. And an electronic scanning ultrasonic flaw detector.

According to the present invention having such a configuration, the array type 2
Using a divided probe, the ultrasonic transmission / reception beam is focused / crossed on the central axis of the probe, and the focusing / crossing point position is repeatedly set / changed stepwise on the central axis of the probe. Furthermore, each time the focus point setting is changed, each transducer group involved in ultrasonic wave transmission / reception is selected / changed, and a focus area that is apparently equivalent to focusing on the center axis of the probe can be obtained. Since this is done, there is an advantage that defects at any depth position inside the subject can be detected by the focused ultrasonic beam.

Also, regardless of the focal point position of the ultrasonic beam, the aperture of the ultrasonic transducer group that operates according to the focal position is changed so that the focal point is approximately constant, and the distance amplitude characteristic at each focal depth is Since it is configured to perform the sensitivity correction based on the maximum amplitude data for each focus point position, the azimuth resolution and the detection sensitivity characteristics can be made substantially constant regardless of the depth position inside the subject, It is possible to provide an electronic scanning type ultrasonic flaw detector which is extremely advantageous in practical use and can accurately detect the position of a defect.

[Brief description of drawings]

1 to 4 are all diagrams for explaining an electronic scanning ultrasonic flaw detector according to one embodiment of the present invention. FIG. 1 is a configuration diagram of the ultrasonic flaw detector, and FIG. FIG. 3 is a diagram illustrating an array-type oblique-angle two-division probe used in this embodiment, FIG. 3 is a diagram illustrating ultrasonic wave transmission / reception of an array-type oblique-angle two-division probe, and FIG. 4 is this embodiment. FIG. 5 to FIG. 7 are diagrams for explaining the operation of the above, and FIGS. 5 to 7 are diagrams for explaining the conventional ultrasonic flaw detection method. 1 ... Ultrasonic transducer, 2 ... Wedge, 3 ... Test material, 4 ...
Defect, 5 ... Ultrasonic beam, 6 ... Shield plate, 20 ...
... array type two-division probe, 21 ... ultrasonic transmitter group, 2
2 ... Transmission delay setting device, 23 ... Ultrasonic wave receiver group, 24
... A / D converter, 25 ... reception delay setting device, 26 ...
Signal controller, 27 ... Addition memory, 28 ... Signal processor, 29 ... Waveform display.

Claims (1)

[Claims] 1. A method for transmitting a transmission ultrasonic beam to a subject and receiving a reception ultrasonic beam reflected from the subject, comprising: Array type 2 in which ultrasonic transducers are arranged separately
A division probe, a transmission system for transmitting and driving each transducer of the transmission ultrasonic transducer group to generate a transmission ultrasonic beam to be transmitted to the subject, and reception reflected from the subject. A reception system for receiving a reception signal from each transducer of the reception ultrasonic transducer group to receive an ultrasonic beam; and a transmission in the transmission system for controlling a transmission aperture in the transmission ultrasonic transducer group. In addition to controlling the number of transducers to be driven, it also controls the transmission delay amount of the transducers to be driven for transmission in order to change the transmission deflection angle of the transmission ultrasonic beam and control the transmission focusing point of the transmission ultrasonic beam. Controlling the number of transducers driven to be received in the receiving system to control the receiving aperture in the group of ultrasonic transducers for receiving, and changing the receiving deflection angle of the receiving ultrasonic beam and the receiving ultrasonic wave. Transmission / reception control means for controlling the reception delay amount of the transducer driven for reception to control the change of the reception focusing point of the system, and the reception obtained via the reception system in order to obtain the ultrasonic information of the subject. A signal processing system that performs signal processing on the signal, and was obtained in advance by measurement in order to correct the fluctuation of the maximum amplitude value of the received signal due to the change of the setting condition by the transmission and reception focusing points and the transmission and reception aperture. Based on the maximum amplitude value of the distance amplitude characteristic for each setting condition by the transmission and reception focusing point and the transmission and reception aperture, the maximum amplitude value of the reception signal obtained from the reception system is changed every time the setting condition is changed. An electronic scanning ultrasonic flaw detector, comprising: an amplitude correction unit that corrects; and a display system that displays ultrasonic information obtained by the signal processing system.