JPS5837506B2 - Ultrasonic flaw detection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection device, and more particularly to an ultrasonic flaw detection device suitable for detecting, recording, and displaying the position and size of a defect existing in an object with high precision.

In ultrasonic flaw detection, the accuracy of locating a defect position or evaluating the size of a defect largely depends on the azimuth resolution and distance resolution of the ultrasonic beam.

The lateral resolution can be improved by focusing the ultrasound beam.

For this reason, various types of probes have been conventionally available, such as a probe using a single concave transducer and a multi-probe in which a large number of transducers are arranged.

In particular, multi-probes are widely used as observation devices for tomographic images of living bodies in the medical field because, in theory, it is possible to focus an ultrasound beam on a predetermined position on a subject.

A conventional example of focusing an ultrasound beam using multiple probes will be described below with reference to FIGS. 1 and 2.

Regarding Fig. 1, in order to narrow down the ultrasonic beam to below a point, the transducers 11 to 17 that make up the multi-probe 1 are arranged in an arc shape, and each transducer is simultaneously excited with the transmission pulse P. good.

Another method is to arrange the transducers 11 to 17 in a straight line on the surface of the subject 3, and delay the acceleration time for each transducer so that the ultrasonic beam is focused on point F, as shown in Fig. 2. Element 21
~27.

Note that the number of transducers and delay elements is determined by the flaw detection conditions, but here, for simplicity, it is set to seven.

Such multi-probe methods have been developed for medical use.

In the medical field, the surface of a living body can be assumed to be smooth and constant, and the medium can be considered to be water, so there is no need to particularly consider the shape of the surface of the subject.

However, since welded parts of steel often have uneven surfaces, the results obtained in actual flaw detection vary greatly depending on whether the surface shape is accurately determined.

Therefore, the conventional method of fixing the delay time of the delay element to the initial value cannot focus the ultrasonic plate beam to a predetermined position due to the influence of the surface shape, and cannot be applied to steel welds with uneven surfaces. Difficult.

1. Medical equipment using multi-probes directly displays the tomographic image of the living body on a CRT and records it as a screen, so it can be used to detect the location and location of defects (reflectors), which is generally required in flaw detection of steel materials. Automatic recording of ultrasound echo amplitude was not performed.

An object of the present invention is to provide an ultrasonic flaw detection device that can accurately grasp the shape of the surface of a test object and at the same time detect, record, and display the defect position with high precision. Based on the results, the transmission to each transducer of the multi-probe and the reception time from each transducer are automatically controlled, and the azimuth resolution is improved by narrowing the ultrasound beam to a predetermined position. This is to accurately orient the position.

Control of transmission (or reception) time will be explained using FIG. 3.

In this figure, the same parts as those in the previous figure are given the same numbers and symbols.

If the surface of the object 3 is uneven, the time to apply the pulse to the i-th transducer facing the multi-probe 1 is longer than the time to apply the pulse to the leftmost transducer in the figure, as shown in equation (1). The time of the delay element is changed so that it becomes earlier by the time τi shown.

The time τi will be hereinafter referred to as a delay time for convenience.

Here, gi is the gap between the i-th transducer and the surface of the subject,
(xiyyi) is the position of the vibrator when the origin is below the point, and (x1, yi) is the position of the leftmost vibrator.

. is the speed of sound in the medium in the gap, and c8 is the speed of sound toward the subject.

The basis for deriving equation (1) is that the wavefronts of the ultrasonic waves from each vibrator are made to coincide at one point F.

When receiving an ultrasonic echo from point F, the i-th transducer only needs to be placed earlier than the leftmost transducer by 1 time, just as when transmitting.

Equation (1) can be easily calculated because only gi is a variable and the others are known constants.

Examples according to the present invention will be described below.

FIG. 4 shows a schematic structure.

The clock pulse generator 4 sends pulses P of a constant period to the pulse generator 5, the delay time control circuit 10, and the surface shape detection circuit 9.

give.

The pulse transmitter 5 transmits a pulse P for vibrating the multi-probe 1 in synchronization with the clock pulse Po.

The pulse P is applied to the vibrators 11 to 17 via the delay circuit 2 in which the time τi of the above equation 1) is set.

The applied pulses P, -P7 cause the ultrasonic beam to enter the subject.

Ultrasonic echoes from defects (reflectors) on the object are received by transducers 11 to 17, and transmitted to the surface via preamplifiers 61 to 67 and delay elements 71 to 77 connected after each transducer. The signal is input to a shape detection circuit 9 and an adder 8.

The surface shape detection circuit 9 detects the interval gi directly below each transducer of the multi-probe, and sends this information to the delay time control circuit 1.
0 and the defect position locating circuit 31.

The delay time control circuit 10 sets the delay time τi of the delay circuits 2 and 7 to zero in synchronization with the odd-numbered pulse of the clock pulse PC, thereby creating conditions for detecting the surface shape.

Clock pulse P. For even pulses of (
Mr. 0 is at home for a time τi, and the ultrasound beam is focused on a predetermined position F (X, Y) on the subject.

The defect position locating circuit 31 uses a gap gi between the transducer and the surface of the object to be inspected, and a propagation time t of the ultrasonic echo Ro from the defect inputted via the adder 8.

and amplitude p. and from the probe position Xp to the defect position (
Xo, Yo ) is calculated.

At the same time, the defect position (X.,Yo) and the amplitude p.

Edit the basic data of a pair of .

In actual flaw detection, since the multi-probe 1 scans over a separately determined inspection range, a large amount of basic data can be obtained.

The display device 33 and the recording device 34 each display and record a large amount of basic data.

Next, the operation of the present invention will be explained using a specific example of a circuit.

Figure 5 shows Kugutsuku Pulse P. and the transmission and reception signals of each vibrator (here, three vibrators are used for simplicity) R1, R2, R
Ultrasonic echo Ro that combines the received signals of 3 and each transducer
FIG.

At odd-numbered clock pulses PC, the delay time τi is set to zero, the echo from the surface of the object is grasped, and the gap gi between the surface and each transducer is detected. At the next even-numbered clock pulse, the delay time τi is set to zero. is chosen to be a value determined by the gap gi.

6 and 7 are detailed diagrams of a part of the surface shape detection circuit 9 for detecting the gap gi and its operation.

Figure 6 shows a circuit for one vibrator, 91 is a waveform shaping circuit, 92 is a monostable multivibrator, and 93 is an N
AND gate, 94 is AND gate, 95 is counter,
96 is a pulse transmitter, and 10 and 31 are the aforementioned delay time control circuit and defect position locating circuit.

The waveform shaping circuit 91 catches the first echo of the received signals of the transducer, that is, the echo from the surface of the subject, and sends a signal P91 to the NAND gate 93.

On the other hand, the monostable multivibrator 92 generates a signal P92 for every odd numbered clock pulse Po.

Furthermore, the pulse oscillator 96 sends a pulse with a period determined by the gap detection resolution to the AND gate 94 .

For example, if the resolution is 0.1 mm, the period is approximately 15
It is 0 nsec.

The AND gate 94 outputs a signal P94 with a pulse number proportional to the gap g1.

The counter 95 counts the number of pulses and provides it to the delay time control circuit 10 and the defect position locating circuit 31 as gap information.

The delay time control circuit 10 calculates equation (1) using the gap gi and known constants to determine the time τj.

Specifically, it may be executed by a microcomputer.

FIG. 8 shows an example of one delay element in delay circuits 2 and 7.

In the figure, the operation will be explained by selecting the fifth element on the transmitting side.

Delay element 25 is of the tap-switching type, and this switching is performed by electronic switches 251-257.

The delay time control circuit 10 sends a closing signal to the electronic switch corresponding to the time τ.

As a result, the transmission pulse P is delayed by a time τ5,
It passes through the adder 2Q5 and is applied to the vibrator 15.

FIG. 9 shows one specific example of the defect position locating circuit 31.

FIG. 10 is a time diagram regarding amplitude detection of ultrasonic echoes, which is one function of the defect position locating circuit 31.

In FIG. 9, the ultrasonic echo Ro is clock pulse P.

Via an electronic switch 312 that is closed every even number of times,
It is sent to the peak detector 313.

The peak detector 313 detects the peak value of the echo that exceeds a predetermined threshold H.

The peak value is then converted into a digital value by an A/D converter 314 and stored in a data memory 315.

Output signals P3, 1, Ro', Ro'' of each circuit in FIG.
and R.

The phrase-time relationship is as shown in Figure 10.

Flip-flop 311 and pulse oscillator 316 in FIG.
, AND gate 317 and counters 324 to 326 are
This is a circuit for determining the propagation time of an echo Ro'' that is equal to or greater than a threshold value H.

When an even numbered clock pulse PC is input, counters 324-326 start counting from pulse P316.

The number of counters to be installed is determined depending on how many pulses for ultrasonic echoes are to be stored in the data memory 315, but here, for simplicity, it is assumed to be three.

The counter hold circuit 318 consists of two flip-flops 319 and 320 and three AND gates 321 to 3.
23.

The AND gate 322 holds the counter 324, the AND gate 321 holds the counter 325, and the AND gate 323 holds the counter 326, but the hold start time is
This is the rise time of echo Ro'.

In this way, the propagation time t of the echo Ro'.

A value proportional to is stored in data memory 315.

The calculation circuit 327 calculates the echo propagation time t.

, the center position of the multi-probe (probe position)
From (X, Y), the defect position (XO, YO) is determined by (2) bar 4.
Ask according to martial arts.

The display device 33 displays the defect position (Xo, Yo) and the echo amplitude p.

are displayed on a CRT as, for example, B-scope and C-scope.

The recording device 34 also records the flaw detection results in a format suitable for display.

The collection of defect positions obtained by scanning by moving the probe on the almost equal.

As explained above, according to the present invention, the gap between the multi-probes and the surface of the subject is detected during scanning of the probes, and the delay time of transmitting and receiving ultrasonic waves is controlled. It becomes possible to focus the beam and accurately locate the defect position.

As a result, the size of the defect can be detected with high precision, and the mechanical strength calculation of materials for plant structures and equipment, quality control of materials, etc. can be improved.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of how to focus an ultrasound beam using multiple probes, Figures 3 to 5 are an example of the principle of the present invention and circuit configuration, and time diagrams of waveforms; Figure and 7th
The figure shows an embodiment of the surface shape detection circuit which is a component circuit of the present invention and an operation explanatory diagram, FIG. 8 shows an embodiment of the delay circuit, and FIGS. 9 and 10 show an embodiment of the defect position locating circuit and It is an operation explanatory diagram. DESCRIPTION OF SYMBOLS 1... Multi-probe, 2... Delay circuit, 3... Subject, 4... Clock pulse oscillator, 5... Pulse oscillator, 6... Preamplifier, 7... Delay circuit, 8・・・
- Adder, 9... Surface shape detection circuit, 10... Delay time control circuit, 11-17... Vibrator, 31... Defect position locating circuit, 33... Display device, 34... Recording device.

Claims (1)

[Claims] 1 Ultrasonic flaw detection equipment injects ultrasonic waves into a test object via a probe, detects ultrasonic echoes from defects existing in the test object, and detects the size of the defects. Means for detecting a gap between the probe and the surface of the subject using a multi-probe consisting of a transducer, a time for transmitting pulses to the transducer according to the gap, and a time for receiving ultrasonic echoes from the transducer. means for controlling the ultrasonic beam and focusing the ultrasonic beam to a predetermined position, means for locating the defect position from the propagation time of the ultrasonic echo and the probe position, and means for displaying and recording the defect position and the amplitude of the ultrasonic echo. This ultrasonic flaw detection device is unique in that it is equipped with: