JPH0143906B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a stationary type probe array in which a plurality of probes arranged in a ring is fixedly installed in water, and defects in an object to be inspected are detected by switching and scanning the probe array. This article relates to automatic ultrasonic flaw detection equipment.

In order to enable automatic ultrasonic flaw detection over the entire circumference of steel pipes, etc. without mechanically rotating the probes, the inventors of the present application have developed a probe array in which multiple probes are arranged in a ring shape underwater. A predetermined number of probes are fixedly installed in a group and sequentially switched and scanned in a fixed direction, in order to obtain ultrasonic beam characteristics equivalent to those of a focusing probe in the transmission pulse for the selected probe group by switching scan. In addition, the same delay is applied to the received signals from each probe as during transmission to eliminate differences in reception timing due to differences in propagation distance, and a device is installed that detects defects from the combined received signals. is suggesting.

However, in the switching scan of the probe array in the above-mentioned apparatus, for example, as shown in FIG. After performing flaw detection with B ₁ , shift one probe counterclockwise and select probe groups No. 2 to No. 9 to perform flaw detection with beam B ₂ with the same refraction angle θ. However,
An undetected area A, which is not irradiated with the beam, is created between the beams _B1 and _B2 .

Therefore, it is possible to narrow the mounting pitch of the probes in the probe array 10, but if the pitch is narrowed, the number of probes will increase significantly, the switching scanning circuit will become considerably complicated, and the probe array will also become smaller. It is expensive in terms of cost.

The present invention has been made in view of the above, and an object of the present invention is to prevent the occurrence of undetected areas by simple control processing without increasing the degree of integration of a probe array.

In order to achieve this objective, according to the present invention, each time the probe array is switched and scanned, the amount of transmission/reception delay is switched in multiple stages to sequentially send out ultrasound beams with different refraction angles and swing the beam. It was designed to let you do so.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 is an explanatory view showing a probe array used in the present invention, and FIG. 3 is an axial cross-sectional view.

In FIGS. 2 and 3, reference numeral 10 denotes a probe array, which is constructed by arranging a plurality of probes in a ring shape, and this probe array 10 is fixedly installed in water 11. A tube body 12 as an object to be inspected is transported in the axial direction inside the tube 10 as shown in the figure.

The switching scan of the ultrasonic beam by the probe array 10 is performed by forming one group of eight probes with a predetermined position of the probe array 10 as a reference position, for example.
By delaying the supply of transmission pulse signals to the probes forming one group, ultrasonic beam characteristics equivalent to those of a focusing probe are created, and the switching scan of the probe array is performed in clockwise direction or in the clockwise direction in units of one group. A switching scan is performed in which the probe is sequentially shifted by one probe element in the counterclockwise direction.

FIGS. 4, 5, and 6 are explanatory diagrams showing the oscillation effect of the ultrasonic beam by the probe array of the present invention.

First _, the ultrasonic beam characteristics of the probe array 10 shown in FIG. ing.

That is, by supplying ultrasonic pulse signals to the eight probe groups of the probe array 10 forming one group via the focus delay section 14 and the deflection angle delay section 16A, the tubes are controlled as shown by the broken line. body 1
It is possible to create a characteristic in which the ultrasonic beam is focused at a focus F ₁ on the X axis with an eccentricity d ₁ from the center O of 2.

Here, in the focal beam characteristics shown in FIG. 4, between the angle of incidence i ₁ and the angle of refraction θ ₁ with respect to the tube body 12, the longitudinal sound velocity of water Cw≒1500 m/s, and the transverse sound velocity of steel Cs≒
When the speed is 3230 m/s, the relationship sini ₁ /Cw=sinθ ₁ /Cs (1) holds true.

On the other hand, sini ₁ is given by sini ₁ = d ₁ / r ...(2), so by substituting this equation (2) into the above equation (1), sinθ ₁ = Cs/Cw・d ₁ /r=3230/1500・d ₁ /r≒2.16
The relationship d ₁ /r...(3) is obtained.

That is, if the focus F ₁ of the ultrasonic beam is set on the X-axis with the displacement d ₁ , the incident angle i 1 is determined from the outer diameter 2r of the tubular body 12 by the above equation (2), and the incident angle i ₁ is determined by the above equation (2). The refraction angle θ ₁ with respect to the tube body 12 is also uniquely determined from equation (3), and the setting of ultrasonic beam characteristics equivalent to such a focusing probe is determined by each probe in the focus delay section 14 and the deflection angle delay section 16. This can be achieved by adjusting the amount of delay for each touche.

That is, the focus delay unit 14 is equipped with a delay element for each of the eight probes, and the delay amount increases from both sides toward the center, as shown by the length of the delay element. By setting this delay amount, an ultrasonic beam characteristic is created that focuses the ultrasonic beam from the probe group of the probe array 10 near the center O of the tube body 12.

On the other hand, the declination delay section 16A also includes a delay element for each probe, and the amount of delay is increased stepwise from the left side to the right side as shown by the lengthwise size of the delay element. Depending on the amount setting,
The ultrasonic beam focused near the center O of the tubular body 12 due to the delay of the focus delay unit 14 becomes X with eccentricity d ₁
Creates a declination characteristic that focuses on the focal point F ₁ on the axis.

In FIGS. 5 and 6, the focus delay unit 1 is similar to FIG. 4.
4 and declination delay units 16B and 16C, and the focus delay unit 14 has the same delay setting as in FIG. , mutually different delay amounts are set.

That is, the argument delay section 16B in FIG.
The declination delay unit 16A in the figure is set so that the amount of delay increase of the delay element that increases stepwise from the left side to the right side becomes smaller, so that the focus F ₂ of the ultrasonic beam by the probe group is is tube body 12
It is located at a position of eccentricity d ₂ from the center O of
The delay amount of the yaw angle delay section 16B is determined so that d ₂ is smaller than the eccentricity d ₁ shown in FIG.

Therefore, since d ₂ <d ₁ , the incident angle i ₂ and the refraction angle θ ₂ are also smaller than in FIG. 4, as is clear from equations (2) and (3).

Furthermore, in FIG. 6, the amount of stepwise increase of the delay elements from the left side to the right side in the argument delay section 16C is smaller than that of the argument delay section 16B in FIG.
The eccentricity d ₃ of the focal point F ₃ of _the ultrasonic beam of the probe array ₁₀ is smaller than the eccentricity d ₂ shown in FIG _. Minimum.

That is, in the present invention, the probe array 10
When eight probe groups are selected as one group, the declination delay unit 16
By sequentially switching and connecting A, 16B and 16C to supply an ultrasonic pulse signal, ultrasonic beams B ₁ , B ₂ , whose refraction angles change sequentially as θ ₁ , θ ₂ , θ ₃ are created.
This oscillates the ultrasonic beam that sends out _B3 .

Note that the swing control shown in Figures 4 to 6 was based on the example of transmitting an ultrasonic beam.
Regarding the received signals of reflected echoes from defects caused by B ₁ to _{B 3} , the declination and focus delay are adjusted using similar delay control so that the received signals with different propagation times for each probe become received signals with the same timing. I will start doing it.

FIG. 7 is a block diagram showing one embodiment of the present invention.

First, to explain the configuration, 18 is a control signal generator, which includes a switching signal for swinging the ultrasonic beam and a switching scanning signal for switching and scanning the probe array 10 based on the program control of the microcomputer 44. and outputs control signals for reception timing, etc.

14 is a focus delay unit, in which the same delay amount as the focus delay unit 14 shown in FIGS. 4 to 6 is set for each probe, and the transmission control signal from the control signal generator 18 is a pulse signal. Therefore, the same signal delay as in the case of using an analog delay element is performed by counting and outputting clock pulses by a counter synchronized with the transmission control pulse.

20 is a changeover switch, and the probe array 10
Each time eight probe groups are selected as one group, the switching terminals 20a, 20b, 20c are sequentially switched.
Make the switching connection. Reference numerals 16A, 16B, and 16C are argument delay sections, which are set with the same delay amount as the argument delay sections shown in FIGS. 4 to 6.
Since the signal input via the focus delay section 14 is a pulse signal, a predetermined amount of argument delay is created by counting the counter similarly to the focus delay section 14.

Further, the argument delay amounts of the argument delay units 16A to 16C are set to different values as shown in FIGS. 4 to 6, and the refraction angle of the ultrasonic beam by the argument delay unit 16A is θ. ₁ , the amount of argument delay is set so that the refraction angle by the argument delay unit 16B is θ ₂ and the refraction angle by the argument delay unit 16C is θ ₃ .

22 is a transmitter, which includes argument delay units 16A to 16;
The ultrasonic oscillator is driven by a transmission control signal sequentially output from C, and a transmission pulse signal with a predetermined delay is output for each probe. Reference numeral 24 denotes an analog switch which switches and scans in a predetermined rotational direction one probe at a time at regular intervals, with eight probe groups as one group starting from the reference position of the probe array 10.

Further, the probe groups of the probe array 10 selectively connected by the analog switch 24 are connected to the declination delay section 2 on the reception side.
It is also commonly connected to 6A, 26B, and 26C.

The argument delay units 26A to 26C are set with the same argument delay amount as the argument delay units 16A to 16C on the receiving side, and since the received signal from the probe array 10 is an analog signal, the fourth - The same analog delay element as shown in the argument delay section of FIG. 6 is used.

Reference numeral 28 denotes a changeover switch, which sequentially switches and connects the changeover terminals 28a to 28c in synchronization with the changeover switch 20 on the transmitting side.

30 is a preamplifier, 32 is a focal delay section,
The same delay amount as the focus delay section 14 on the transmitting side is set, and analog delay elements are used in the same manner as shown in the focus delay section of FIGS. 4 to 6 because analog signals are similarly delayed.

34 is an adder that adds and synthesizes the received signals of each probe that are input in parallel from the focus delay unit 32, and 36 is a distance amplitude that corrects the change in signal level with respect to the ultrasonic propagation distance for the combined signal of the adder 34. Since the microcomputer 44 is used for correction and processing of the received signal, it has an A/D converter for converting the combined received signal into a digital signal. The digital reception signal of main amplifier 36 is input to mixing-level comparator 40 via buffer 38a. The mixing level comparator 40 determines that the digital received signal from the main amplifier 36 is a defective received signal when it exceeds the reference level, and removes the signal that falls below the reference level as a noise component and eliminates the excess signal caused by the transmitted pulse signal. Received components due to direct wraparound of the sound wave beam are removed by the control signal generator 18 based on the transmission control signal.

The mixing level comparator 42 also includes a buffer 42,
A distance signal a, a flaw detection mode signal b, and a defect position signal c are inputted via 44 and 46.

Here, the distance signal a uses a pulse signal from a pulse generator driven by the tubular body sent to the probe array 10, and is designed to detect the longitudinal position of the tubular body with respect to the reference position. ing.

Further, the flaw detection mode signal b inputs a signal that identifies any one of θ ₁ , θ ₂ , and θ ₃ due to the swing delay, and is used to instruct reception processing of defect positions and the like.

Further, the defect position signal c is applied to the probe array 10 in order to identify the switching scanning position of the probe array 10, that is, which probe receives the defect signal based on the switching control signal of the analog switch 24.
is given as an angle signal with respect to the reference position.

The output of the mixing-level comparator 40 is connected to a microcomputer 44 via an input interface 42.
The defects and defect positions are calculated based on the input data, and printed and recorded on the printer 48 and CRT 50 via the output interface 46.

Next, the operation of the embodiment shown in FIG. 7 will be explained with reference to the operational flow shown in FIG.

When a tube body as an object to be inspected is sent to the probe array 10 fixedly installed in the water, the control signal generator 18 outputs a switching scanning signal to the analog switch 24 under the control of the microcomputer 44. , eight probe groups with the reference position of the probe array 10 as the starting position are transmitted to the transmitter 22.
and selectively connected to the receiving side argument delay units 26A to 26C.

Subsequently, the control signal generator 18 outputs a transmission control signal and a switching signal for transmitting an ultrasonic beam having a refraction angle θ ₁ . This switching signal causes the switching switches 20 and 28 to switch to the switching contact 20 as shown in the figure.
a, 28a, and then the transmission control signal whose focus is delayed by the focus delay unit 14 according to the transmission control signal is input to the declination delay unit 16A via the changeover switch 20, and after being subjected to a predetermined declination delay. Transmission section 22
The ultrasonic oscillator provided for each probe group is driven, and a transmission pulse signal is supplied to the selected probe group of the probe array 10 via the analog switch 24.

Therefore, from the probe group of the probe array 10, an ultrasonic beam equivalent to the focusing probe with a refraction angle θ ₂₁ shown in FIG. Reflected signals due to defects such as scratches and cracks are received by the same probe group and input to the receiving side declination delay circuit 26A. The received signal subjected to the declination delay in the declination delay circuit 26A is transferred to the switching contact 28.
The signals are preamplified by a preamplifier 30 via a changeover switch 28 that is switched to a, and the difference in reception timing that differs for each probe is removed by a focus delay in a focus delay unit 32, and then combined by an adder 34. After distance amplitude correction in the main amplifying section 36, the signal is converted into a digital signal and mixed via the buffer 38a.
input to the level comparator 40.

At the same time, a distance signal a, a flaw detection mode signal b, and a defect position signal c are also input via buffers 42, 44, and 46, and a received signal exceeding a reference level is compared and determined as a defect signal in a mixing level comparator 40, and the defect position signal is The data are input to the microcomputer 44 via the input interface 42 based on the distance signal a indicating the defect position signal c and the defect position signal c.

Next, when the defect detection using the refraction angle θ ₁ is completed,
The changeover switches 20 and 28 have changeover contacts 20b and 28.
b, and by transmitting and receiving similar ultrasonic waves, defect detection is performed using an ultrasonic beam having a refraction angle of θ ₂ (see FIG. 5).

Furthermore, the changeover switches 20 and 28 are connected to the changeover contact 10.
c, 28c, and detects defects based on the refraction angle θ ₃ by transmitting and receiving similar ultrasonic waves.

By switching the ultrasonic beam at the refraction angle θ ₁ to _{θ 3} in this way, the microcomputer 4
The received signal obtained in step 4 is subjected to a predetermined program calculation to determine whether there is a defect or not, and when a defect is detected, data indicating the size and location of the defect is output via an interface 46 to a printer 48,
Shoot and record on CRT50.

When the defect detection by one beam swing is completed in this way, the switching scanning signal from the control signal generator 18 causes the analog switch 24 to shift the detection by one probe of the probe array 10 in a predetermined direction. A group of probes is selectively connected, and the oscillation control of the ultrasonic beam for the selected group of probes is repeated every time the probe array is shifted in a predetermined direction by one probe.

Therefore, by the ultrasonic beam swing control of the present invention, the undetected area that occurs when the probe array is shifted by one probe element can be completely covered by the ultrasonic beam swing control in three stages. Highly accurate defect detection can be performed by completely eliminating the undetected area of the object to be inspected that is caused by the switching scan of the probe array.

In the above embodiment, the ultrasonic beam is oscillated in three stages, but the number of oscillation stages may be two stages, or may be three or more stages as appropriate.

As described above, according to the present invention, a probe array in which a plurality of probes are arranged in a ring is fixedly installed underwater, and a predetermined number of probes in this probe array are grouped as one group. Switching scans sequentially in the axial direction,
In an automatic ultrasonic flaw detection system that detects defects in an object to be inspected passing through a probe array with ultrasonic beam characteristics equivalent to those of a focused probe by delaying the transmission and reception of a group of probes selected for each switching scan. By switching the transmission/reception delay amount in multiple stages each time the probe array is switched and scanned, ultrasonic beams with different refraction angles are sent out and the beam is oscillated. It is possible to completely eliminate the undetected area of the object to be inspected, and it is possible to obtain the effect that the flaw detection accuracy in a flaw detection apparatus having a structure in which a probe is fixedly installed can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an undetected area caused by switching scanning of a stationary probe array by the present inventor, and FIGS. 2 and 3 are explanatory diagrams showing one embodiment of the probe array used in the present invention. Figures 4, 5, and 6 are explanatory diagrams showing the principle of beam swing according to the present invention, Figure 7 is a block diagram showing an embodiment of the present invention, and Figure 8 is the operation of the embodiment of Figure 7. It is a flow diagram. 10...Probe array, 11...Water, 12...
Tube body, 14... Focus delay section (transmission side), 16A,
16B, 16C... Declination angle delay section (transmission side), 18
. . . Control signal generator, 22, 28 . . . Selector switch, 22 . receiving side), 30...
Preamplifier, 34...Adder, 36...Main amplifier section, 38a, 38b, 38c, 38d...Buffer, 40...Mixing-level comparator, 42...Input interface, 44...Microcomputer, 46... ...Output interface, 48...Printer, 50...CRT.

Claims (1)

[Scope of Claims] 1. A probe array in which a plurality of probes are arranged in a ring is fixedly installed in water, and a probe group is formed in which a predetermined number of probes in the probe array constitute one group. Scans are sequentially switched in the axial circumferential direction, and defects in the tubular metal passing through the probe array are detected with ultrasonic beam characteristics equivalent to those of a focal probe by the transmission/reception delay of the probe group selected for each switching scan. In an ultrasonic automatic flaw detection device, the ultrasonic beam is oscillated by switching the amount of transmission/reception delay for the probe group in multiple stages each time the probe group of the probe array is switched and scanned. An ultrasonic automatic flaw detection device characterized by being provided with a swinging means.