JPH01262465A - Ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To suppress external noises by storing a noise waveform, generating a defect echo gate generated by removing the position of a noise echo larger than a constant level from the noise waveform, and detecting the maximum value of the echo height in the defect echo gate. CONSTITUTION:The titled device is provided with a noise sensor 2, a noise signal amplifier 7, a noise waveform storage part 8, a defect echo gate generation part 11, a maximum value detecting circuit 12, etc. Then a reflection echo from a probe 1 is written in a waveform storage part 9 through a receiving amplifier 8 and an external noise signal detected by the sensor 2 is written in the storage part 9. Then the data in the storage part 8 is read out and a flaw detection waveform is read out of the storage part 9 with slight delay and compared with a decision value by a generation part 11 to generate the defect echo gate. Then the echo gate is used and a maximum value detecting circuit 12 detects the maximum echo height from the flaw detection waveform outputted from the storage part 9.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an ultrasonic flaw detection device.

[Conventional technology]

As stated by Ayachi O, ultrasonic flaw detection equipment used to detect flaws in metal materials has traditionally been carried out manually, but in recent years automatic ultrasonic flaw detection equipment has rapidly increased in order to improve reliability and conduct efficient testing. It is well known that it has become popular. However, there are several issues in automatically determining defects. One of these is the issue of external noise. If electrical noise from the outside enters the amplifier that amplifies the flaw detection signal or the processing system for this signal, it will reduce the reliability of the test. Management Association) Publication C296-298
Page] This is a well-known fact. Moreover, it is extremely rare that all of these external noises can be removed.

Therefore, when manufacturing an automatic ultrasonic flaw detection device with high flaw detection processing capacity, reliability of automatic judgment results is ensured by adding some kind of noise suppression device. These noise suppression devices are mostly targeted at random noise generated by motors and bath water heaters. Hereinafter, conventional methods for suppressing external noise will be explained.

Figure 3 is a configuration diagram of an ultrasonic flaw detection device with a countdown function, which is a simple noise suppression circuit, and Figure 4 Fi.
A configuration diagram of an ultrasonic flaw detection device with a noise suppression circuit that utilizes the gradient of the envelope edge of the MA scope. Figure 5 is an explanatory diagram of the relative positional relationship between the probe and the defect. Figure 6 is a supersonic diagram of Figure 4. FIG. 3 is a diagram showing the operating state of the noise suppression circuit as detected by the sonic flaw detection device.

In Figure 3, (1) is a probe for detecting defects in the test specimen, (3) is a transmission pulse generator connected to probe (1), and (4) is the transmission pulse of (3). A synchronous timing generator for controlling generation timing, (5) a gate circuit for determining a flaw detection section in synchronization with the synchronous timing generator (4), and 61 an ultrasonic signal from the probe (11). a maximum value detection circuit for detecting the maximum value of the ultrasonic signal output from the reception amplification section (6) within the interval determined by Q3Fi gate circuit (51), αJ is the maximum a level determination circuit for determining the maximum value of the ultrasonic signal output from the value detection circuit a3;
α knob is a level judgment circuit (level judgment value setting means for setting a judgment value to +3, α9#'i level judgment circuit α3
A countdown circuit that holds the judgment results output from the circuit twice or more and outputs a defect when the countdown judgment value or more is consecutively defective.

(Ie is a countdown judgment value setting means for setting a judgment value in the countdown circuit. In the conventional device, after the ultrasonic signal from the probe (1) is amplified by the reception amplification section (6), , a sample hold circuit and an A/
The maximum value detection circuit α2 using a D converter or the like converts it into a digital quantity, which is used as the defect echo height. Up to this point, it is the same as the gate analog function included in general flaw detectors. In this case, as external noise,
If random noise mixes into the reception amplifier section (61) at the timing within the gate signal, the output of the maximum value detection circuit a3 will indicate the level of random noise. Therefore, the following measures are taken to determine it as random noise. First, the defect echo height output from the mosquito large value detection circuit Q3 is converted to a level judgment circuit using a digital comparator or the like based on the defect judgment value set from the level judgment value setting means 4 using a Nuitch or a microcomputer, etc. a3
Determine the size.

If the defect echo height is greater than or equal to the defect determination value, it is determined that there is a defect. The result is stored in the countdown judgment circuit aX5 using a shift register or the like.
In this case, two or more judgment results including the previous judgment result are stored.

Random noise depends on the cause of occurrence, but there are almost no cases where it is continuously mixed into the gate.

The issue of false detection due to external noise is addressed by comprehensively determining that there is a defect only when the results stored in the shift register etc. continue to be greater than or equal to the countdown determination value set by the countdown determination value setting means (Ie).

Figure 4 is an explanatory diagram of the conventional extraneous noise suppression method shown in, for example, "Nondestructive Inspection" (published by the Japan Nondestructive Inspection Association), Vol. 29, No. 10 [pages 132 to 136], and (1) is the test object. probe for detecting defects in.

(3) is a transmission pulse generator connected to the probe (1);
(4) is a synchronous timing generator for controlling the timing of transmission pulse generation in 31, (5) is a gate circuit for determining the flaw detection section in synchronization with the synchronous timing generator circuit +41, and +6 is a probe. Receiving amplification section for amplifying the ultrasonic signal from the child (1), a2U gate circuit (5)
A maximum value detection circuit for detecting the maximum value of the ultrasonic signal output from the reception amplification section (6) within the interval, αii is n71 output from the maximum value detection circuit a3.
A previous maximum value storage section that uses a running register etc. to hold the maximum value of the ultrasonic signal of the times, the output of the arrVibJ times maximum value storage section αg and the current maximum value output from the maximum value detection circuit az are digitally stored. A comparison circuit that calculates the deviation using a converter, adder/subtractor, etc., a9 is a comparison circuit aη
This is an arithmetic unit that uses an adder, etc. that adds a deviation to the deviation value calculated in and the previous maximum value output from the previous maximum value storage unit +Ill within the step range set by the follow-up step amount setter ■. .

Figures 5 and 6 are diagrams for explaining the operation of the conventional extraneous noise suppression method shown in Figure 4. In Figure 1, (1)
is the probe, t2nd test specimen 2 is a slit-shaped defect made on the bottom of the test specimen, IF is the change in the defect echo level due to changes in the relative position of the defect and the probe, The change in the output of the noise suppression circuit is represented by H, and H indicates external noise. An ultrasonic flaw detection device with a noise suppression function that utilizes the slope of the envelope of a conventional MA scope is configured as described above.
After the ultrasonic signal from the probe (1) is amplified by the reception amplifier (6), the maximum value of the ultrasonic signal within the flaw detection interval signal (hereinafter referred to as gate signal) generated by the gate circuit (5) In order to detect this, the maximum value detection circuit α2 using a sample and hold circuit and an A/D converter converts it into a digital quantity, and this is taken as the defective echo height. Up to this point, it is the same as the gate analog function included in general flaw detectors. In this case, the probe (1
1 moves on the surface of the test specimen Ca1l in the direction of the arrow, the change in the reflected echo level from the defect @ roughly changes as shown by F in FIG. 6. Figure 6? The data shown in was measured under the following conditions. A bevel probe (model name 5ZIQX10A3B) is used for the probe fl+, and the slit-like defect a! For No. 1, an N-notch defect with depth Q, 3 m depth, and 25 lengths was used. In this case, the 9 reflected echo heights were expressed in dB.

In the case of automatic flaw detection, the relative position of the probe and the defect changes every moment, and the movement of the transmitted pulse once per transmission is called the pulse density, and the moving speed of the probe is V (m/8θC). and the repetition frequency f(yH2) of the transmission pulse.

Pulse density (sm) Pp=v/r ・+1+
There is a certain relationship between the pulse density per pulse and the change in reflected echo height depending on the combination of probe and defect. In the case shown in FIG. 6, it can be seen that when the pulse density is 15 m, there is a maximum change in BQ of 2 dBQ per pulse. This fact shows that when the pulse density is set to 0.5H, the change in the reflected echo from the defect for each repetition frequency is always within 2 dB. Tsuma fi 2
If a change of dB or more occurs, there is a high possibility that the echo is not a reflected echo from a defect, and can be determined to be mostly external noise. The calculated maximum amount of change in this case is used as the follow-up step amount in the calculator α3, which will be described later.

If random noise is mixed into the reception amplifier (6) K as external noise at a timing within the gate signal, the output of the maximum value detection circuit a3 will indicate the level of the random noise. Therefore, we take the following measures to judge it as random noise.

The data output from the maximum value detection circuit α2 is stored in the maximum value storage unit αg using registers etc. in the comparison circuit aη.
The deviation from the maximum value of the previous reflected echo taken from is calculated. The calculation is performed using a subtractor or the like. Next, the calculated deviation data is sent to the calculator I. Arithmetic unit α
The follow-up step amount setting device compares the set maximum change amount (hereinafter referred to as follow-up step amount) with the output deviation from the comparison circuit αη, and if the deviation is smaller than the follow-up step amount, the maximum value is detected. Output the output from circuit az as is.

If the deviation exceeds the follow-up step amount, data obtained by adding or subtracting the follow-up step amount from the previous maximum value in the previous maximum value storage section 08 is output as the maximum echo height. At the same time, it is stored in the previous maximum value storage section α as the previous maximum value. As a result, the external noise that has entered the external reception amplification section (61) can be suppressed even at the tracking step i. In this case, external noise is suppressed to a change of 2 dB.

[Problem to be solved by the invention]

Although the extraneous noise suppression circuit shown in Figure 3 is effective to some extent in terms of judgment results, when recording reflected echoes, the maximum value detection circuit (Iz output) in which the BM sound is not suppressed has no choice but to be used. It cannot be used in automatic ultrasonic flaw detection equipment, which requires recording of inspection records after the inspection is completed.To compensate for this drawback, the extraneous noise suppression circuit shown in Figure 4 was devised, which eliminates extraneous noise even on records. However, this conventional method of suppressing extraneous noise requires the detection repetition frequency to determine the pulse density and the number of reflected echoes due to changes in the relative position of the defect and the probe to determine the tracking step amount. There is a limit due to the rate of change, which ultimately limits the maximum inspection speed = flaw detection processing capacity to $11.In addition, in recent years, in order to improve defect detection performance, ultrasonic waves sent from the probe have been used to improve defect detection performance. Focus probes, which improve detection sensitivity by focusing the beam, have come into widespread use.This means that the rate of change in reflected echoes due to changes in the relative position of the probe and the defect becomes more rapid than in conventional methods. With a probe, it is sufficient to detect the peak of the reflected echo from the defect if it is transmitted every 5 m, but when detecting with a focus probe, it is necessary to transmit at a fine pitch of 9.25 m or less, otherwise the defect will be detected. It becomes impossible to detect the peak of the reflected echo.
As a result, testing speed has been forced to be cut in half. Of course, it would be better to increase the follow-up step cover, but it is better to suppress external noise! Because ll i becomes smaller in inverse proportion.

It is not possible to simply increase the follow-up step amount.

Therefore, it has been desired to develop an extraneous noise suppression method that is less likely to limit the inspection speed due to the influence of the rate of change in reflected echoes due to changes in the relative position of the probe and the defect. This invention was made to solve the above problem, and even if a focus probe in which the ultrasonic beam is fully focused is used as a probe, the maximum value of the reflected echo from a defect can be detected sufficiently, and the An object of the present invention is to obtain an ultrasonic flaw detection device having an effect of suppressing external noise. [Means for solving the problem] The ultrasonic flaw detection device according to the present invention uses an ultrasonic probe for the purpose of detecting external noise. A noise sensor placed nearby, a noise amplifier that amplifies only external noise, and a waveform storage unit that stores the noise waveform.

A waveform storage section that stores the flaw detection waveform of the ultrasonic waves output from the reception amplifier section at least once, and a waveform storage section control circuit that synchronizes the flaw detection waveform and noise waveform with a gate circuit and controls writing and reading. It consists of a defective echo gate generating section, and a maximum value detection circuit that detects the maximum echo height within the defective echo gate. Generates a defect echo gate that excludes noise echoes that exist in the same part of the flaw detection waveform and extracts them as defect echoes.
The maximum value of the echo height within the defective echo gate is detected and the defective echo height is outputted. [Operation] In this invention, random noise, which is the main source of external noise, is detected in the ultrasonic probe section and By placing a noise sensor near the ultrasonic probe for the purpose of detecting only external noise, taking advantage of the fact that it is easily mixed in from the cables that connect the flaw detection equipment.

Only the external noise that is equivalent to the external noise mixed in the flaw detection waveform is input to the noise amplification section, and the noise waveform is stored in the noise waveform storage section. At the same time, the flaw detection waveform is stored one or more times in the waveform storage unit, and the waveform storage unit control circuit controls reading out the data in synchronization with the gate signal, and the synchronously read out noise waveform is used as a defect echo. In the gate generation section, a defective echo gate is generated that masks the noise at a certain level or higher.
External noise is suppressed by detecting the maximum value of reflected echoes within the defective echo cage excluding noise echoes using a maximum value detection circuit using a sample and hold circuit, etc., and setting it as the defective echo height.

〔Example〕

FIG. 1 is a block diagram of an ultrasonic flaw detection device showing an embodiment of the present invention. (1), +31, (4), (
51 and (6) are exactly the same as the above-mentioned conventional device.

+21 ij A noise sensor having a structure similar to that of the ultrasonic probe +11, for example, placed near the probe (1), (71 is a noise signal amplification unit connected to the noise sensor (2), ( 81 is a noise signal amplification section (an analog or A/
A noise waveform storage section (9) is composed of a D converter and a digital memory, and (9) is composed of an analog or A/D converter and a digital memory for storing the flaw detection waveform outputted by the reception amplifier section (6) one or more times. The waveform storage unit (9) is stored in the waveform storage unit (9) by the synchronization signal from the gate circuit (5).
Writing and reading of the flaw detection waveform to 1, noise waveform storage section +8
1 is a waveform storage control circuit that controls writing and reading of noise waveforms, and αυ is a noise waveform storage unit (81) that detects noise signals of a predetermined level or higher from the noise waveform data read out from the noise waveform storage unit (81). A defective echo gate generating section detects using a comparator or the like and generates a gate to turn off the gate signal at the position where a noise signal is detected according to the synchronization signal from the waveform storage control circuit Q[I. A3 is a maximum value detection circuit that detects the maximum value of the defect echo gate in the flaw detection waveform output from the waveform storage unit (9) using the defect echo gate output from the defect echo gate generation unit Qll.Second
The figure is a diagram for explaining the present invention. In Fig. 2, A is the external noise waveform detected by the noise sensor (21), n-0 is random noise, and Ll is a pre-stored noise signal detection signal. Judgment value.

B is the flaw detection waveform output from the reception amplifier (61), t is the transmission pulse, f is the echo reflected from the defect, n-1 is random noise, and b is the echo reflected from the bottom surface.

C is the gate signal output from the gate circuit (5), D is the defect echo gate output from the defect echo gate generating section αB, E is the current flaw detection waveform extracted by the defect echo gate, and KH is the maximum value detection circuit. It shows the defect echo height detected by az.

In the ultrasonic flaw detection device configured as described above, the synchronous timing generator (4) causes the transmission pulse generator (3) to
is driven, and the transmission pulse generator (3) generates an electric signal necessary for excitation of the ultrasonic pulse and applies it to the probe (11).The probe (1) transmits the ultrasonic signal into the test object. The transmission 1 reflected echo is converted into an electrical signal as a flaw detection waveform and amplified in the reception amplifier (6).The amplified flaw detection waveform B is the output of a gate circuit set in advance in the area where the reflected echo from the defect exists. The waveform storage unit (9) is activated by the write signal output from the waveform storage unit control circuit a1 in synchronization with the signal.
written to. At the same time, an external noise signal detected by a noise sensor (2) having a structure similar to that of the probe (11) installed near the probe fil is amplified by a noise signal amplifier (7).Noise waveform A is the flaw detection waveform B
Similarly, gate times jli! A write signal output from the waveform storage control circuit aa in synchronization with the output signal of f5+ is written into the noise waveform storage (8). Note that the noise waveform storage section (8) and the waveform storage section (9) are converted into digital signals by an OCD memory or A/D converter that can directly store analog signals, and are stored in digital memory or shift registers. It can be used.

Note that the dynamic range required for the noise waveform storage unit +81 is only necessary to create a defective echo gate, so in extreme cases it may be only 1 bit. In that case, the A/D converter is Can be omitted.

Next, the data stored in the noise waveform storage unit (81) is output from the noise waveform storage unit (81) in response to a read command from the waveform storage unit control circuit a0. is relatively simple.Next, the waveform storage section (91) reads out the flaw detection waveform B a little later than the noise waveform reading timing.

As a result of these operations, the external noise waveform A output from the noise signal amplification unit (71) is taken out a little earlier in synchronization with the flaw detection waveform B output from the reception amplification unit (61). The generated external noise waveform A is compared with the judgment value L1 in the defective echo gate generating section a9, and a defective echo gate D is created which turns off only when the judgment value is 51 or more. Taking into consideration the width of the noise waveform and the delay in judgment processing time, the flaw detection waveform B is also taken out from the waveform storage section (9) a little earlier than the flaw detection waveform Bl' (
It is necessary to ensure that the defective echogame kD is synchronized. Therefore, a waveform storage unit (91) is provided for the purpose of temporally delaying the flaw detection waveform B with respect to the external noise waveform A.

A method for determining the judgment value L1 is to use a noise sensor (
Examine the external noise level detected in step 21 and the level of external noise mixed into the flaw detection waveform in that case, and find out that the level of external noise mixed into the flaw detection waveform is about the same level as the ultrasonic noise caused by minute structures and surface textures present in the flaw detection waveform. Set a target for external noise level.

Using the defective echo gate D created as above,
The maximum echo height K)l within the defective echo gate is detected by the maximum value detection circuit αΔ from among the flaw detection waveforms output from the waveform storage unit (9).

Here, we will consider the case where external noise is mixed into the flaw detection waveform B. In that case, what is the intrusion route of external noise?

In most cases, the probe jumps in from the probe (1), so the noise sensor (2), which has a similar structure to the probe +11 installed near the probe (11), also receives a similar noise signal n-. It is easy to think that Q can be detected.In that case, there is an external noise n-1 at the same position in the flaw detection waveform B. Therefore, the defective echo gate D is detected by the external noise n-1.
It does not exist at position 1, and the extraneous noise is cancelled. Furthermore, the judgment value L1 is determined by the noise signal amplification section (
By linking with the average output level of 7), it is possible to improve the detection accuracy of external noise, which is a problem, and it can be expected that the ability to remove external noise will be improved accordingly.

On the other hand, in the case of the defective echo f, as described in the conventional plane 1, the position where the echo 1 is generated hardly changes.

Even if external noise mixes in the same location as the defective echo,
Abnormal data due to external noise originates from cancellation, and due to the nature of external noise, the probability of external noise occurring in the same location is low. Furthermore, in automatic flaw detection where the probe and defect move relative to each other, even if the rate of change in the echoes reflected from the defect increases due to the use of a focused probe, the echoes reflected from the defect reach their peak. Since it is naturally expected that echoes reflected from a defect will appear several times at the same location, tracking is required in the conventional method when determining the pulse readiness to detect the maximum value of the echoes reflected from the defect. Step children can be removed from the constraints),
Ultrasonic flaw detection that detects the maximum value of reflected echoes from defects without slowing down inspection speed even when a focus probe that focuses an ultrasonic beam is used as a probe, and has a high external noise suppression effect. It became possible to obtain the device.

By the way, the above invention is applied to a noise removal method when detecting the height of reflected echo from a defect in an ultrasonic flaw detector, but the defect echo gate D is also used when measuring the beam path to the defect to eliminate external noise. No more erroneous location detection.

Needless to say, it also has the ability to remove extraneous noise when measuring the beam path to a defective echo.

〔Effect of the invention〕

As explained above, the present invention separates and detects an external noise signal using a noise sensor, stores it in a noise waveform storage section, simultaneously stores a flaw detection waveform in a waveform storage section, and detects a defect by detecting the noise waveform. A defective echo gate is generated in the echo gate generating section to remove external noise at a certain level or higher.

By extracting the maximum defect echo height among them using a maximum value detection circuit, the effect of removing random noise, which is the main cause of extraneous noise, can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an ultrasonic flaw detection device showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of Fig. 1, and Fig. 3 is an ultrasonic flaw detection device with a countdown function, which is one of the conventional examples. Fig. 4 is a block diagram of the flaw detection device. Fig. 4 is a block diagram of an ultrasonic flaw detection device that has an extraneous noise removal function using the slope of the envelope of a conventional MA scope. Fig. 5 shows the structure of the probe and FIG. 6 is an explanatory diagram of the relative positional relationship of defects, and FIG. 6 is an explanatory diagram of the operation of the ultrasonic flaw detection apparatus of FIG. 4. In the figure, (2) is a noise sensor, f71 is a noise signal amplification section, I81 is a noise waveform storage section, (9) is a waveform storage section, +1 (l is a waveform storage section il + control circuit, αB is a defective echo gate generation section, az is the maximum value detection circuit. Note that the same symbols in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] Ultrasonic flaw detection equipment that receives reflected pulses from the test specimen with an ultrasonic probe, amplifies them with a receiving amplifier, and determines defects based on the height of the echoes reflected within the section defined by the gate device. a noise sensor disposed near the ultrasonic probe; a noise signal amplification section connected to the noise sensor and amplifying the noise signal;
a noise waveform storage unit that is connected to the output circuit of the noise signal amplifier and stores a noise waveform within an interval determined by the gate device; and a noise waveform storage unit that is connected to the output circuit of the reception amplifier and stores a noise waveform within an interval determined by the gate device. a waveform storage section that stores the flaw detection waveform at least once at least once; a waveform storage section control circuit that controls writing and reading of the waveform storage section and the noise waveform storage section in synchronization with a gate signal; a defect echo gate generation unit that generates a gate for defect echoes by excluding positions of noise echoes above a certain level from the flaw detection waveform read from the storage unit; and a maximum value for detecting the maximum value within the gate for defect echoes. An ultrasonic flaw detection device comprising a detection circuit.