JPS617465A - Ultrasonic wave tester - Google Patents

Abstract

PURPOSE:To enable testing with high precision of a specimen with an extensive sampling period of digitalization, by irradiating a chirp supersonic wave onto a specimen surface and analyzing and processing an envelope of a signal detected from echo. CONSTITUTION:By a chirp signal emittor 510, the chirp signals are irradiated with the specified repetition period and ultrasonic wave is irradiated from a transducer 2 to a specimen 1. The ultrasonic wave reflected by rear surface B, notched part F of the specimen 1 is introduced into an A/D convertor 540, through transducer 2, amplifying circuit 5, envelope extractor 520. On the other hand, on output of the amplifying circuit 5 is introduced into a gate signal forming circuit 350 also and while defective echo or rear surface each is detected, the A/D converted outputs are stored consecutively in a memory 550. Further, by a micro-computer 560 echo of the specimen to be inspected is compared with the rear surface echo which is not provided with the defective part F preliminarily stored and if it is found different, judgement is given as defective and its position is defected by a signal frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a chirp ultrasonic eco one-type ultrasonic inspection apparatus that detects a defective portion directly under the back surface of a material to be inspected.

[Prior art]

A conventional ultrasonic inspection apparatus of this type is one shown in FIG. FIG. 1 is a block diagram showing an example of a conventional ultrasonic inspection apparatus. In the figure, 1 has a thickness of a,
Ultrasonic pulses are transmitted from the surface S of the test material 10 to the inside of the plate-shaped test material 2 with a sound velocity of C, and the surface S of the test material 1 is
Back side B, a transducer that receives echoes from the defective part F; 3 is a propagation medium for the ultrasonic pulse to propagate between the transducer 2 and the test material 1; 4 is for generating the ultrasonic pulse from the transducer 2; transmitting circuit,
5 is an amplifier circuit for amplifying the signal received by the transducer 2; 6 is a surface echo detection circuit for detecting echoes on the surface S of the specimen 1 from the output signal of the amplifier circuit 5; and 7 is the specimen to be detected. A detection range setting device 8 provides a depth range in which the defective portion F of the material 1 exists, and 8 is a gate signal creation circuit that creates a gate signal from the setting value of the detection range setting device 7 and the output of the surface echo detection circuit 6. , 9 is an amplifier circuit for further amplifying the output of the amplifier circuit 5 to make defective echoes more noticeable, and 10 is an amplifier circuit set according to the output of the gate signal generating circuit 8 from among the outputs of the amplifier circuit 9. A gate circuit 11 extracts the echo within the detection range, and a signal processing circuit 11 processes the signal output from the gate circuit 1o to obtain the information necessary for flaw detection, such as the presence or absence of the defect F and its size. Device 12 is a control circuit that generates the timing of transmission and also provides a reference for the surface echo detection circuit 6. In FIG. 1, Al and At are distance ranges for determining the defect detection range.

FIG. 2 is a diagram showing output signal waveforms of each main part for explaining the entire ultrasonic inspection apparatus of FIG. 1.

Next, the operation of the conventional ultrasonic inspection apparatus shown in FIG. 1 will be explained with reference to FIG. generates various pulses,
It is given to the transmitting circuit 4. The transmitting circuit 4 applies a high voltage impulse to the transducer 2 according to the timing of the pulse, thereby generating all ultrasonic pulses. The ultrasonic pulse generated and transmitted in this manner propagates through the propagation medium 3 toward the specimen 1, and a portion is reflected by the surface S of the specimen 1, generating a total surface echo 1-1. A part of it invades into the material 1 to be inspected. If there is a defect F in the material 1 to be inspected, a defect echo will occur. Moreover, the ultrasonic pulse is &rIiJ of the test material 1.
'When Blc is reached, a backside echo occurs.

Each of these echoes is received at transducer 2,
The signal is amplified by the amplifier circuit 5. An example of the output No. 16 waveform of the amplifier circuit 5 is shown in FIG. 2(b), and To shown in FIG. V is the time from the front surface echo to the back surface echo,
There is a relationship of 2a=c, T6. The output of the amplifier circuit 5 is input to the amplifier circuit 9 for further amplification, and is input to the surface echo detection circuit 6.

The propagation medium 3 is usually water, and the transducer 2
Since no echo is generated between the ML and the test material 1, the first echo after transmitting the ultrasonic pulse can be recognized as a surface echo. Therefore, the surface echo detection circuit 6 detects the A rising pulse as shown in FIG. 2(C) is generated. By the way, each distance range A1 and A shown in FIG. 1 are set in the detection range setting device 7.

, At, and the output pulse of the surface echo detection circuit 6 are given to the gate signal generation circuit 8, and a gate signal as shown in FIG. 2 ((f)) is generated. Here, the gate signal shown in FIG. The times T, , T, have the following values.

2AI TI--, T2=L The gate signal for C is controlled to pass through and cut off the gate circuit 10 connected to the output of the amplifier circuit 9 as shown in Fig. 2(e), and the received signal is Preset distance range A from inside
2, the echo-only signal as shown in FIG. 2(f) is extracted. This extracted signal is sent to the signal processing device 11, and the defective portion F is evaluated based on the magnitude of the signal.

The conventional ultrasonic inspection device is configured as described above, and the detection range is determined based on the surface S of the material to be inspected. Change the range to the back side B, υ, that is, distance range AI + A2
t - must be very close to thickness a, but thickness a
There were drawbacks such as a dead zone occurring when the value fluctuated, and backside echoes being mistakenly recognized as all defective echoes. As clearly shown in Fig. 3, when the detection range is set so that normal operation is performed in the part 13 of the test material l, that is, the distance range A indicated by the diagonal line in Fig. 3, the test material is When the thickness a becomes a little thin, as in the case of the part 1b, the back surface B is included in the detection range, and the defective part F does not exist (although the back surface echo will be extracted as a defective echo. , when the thickness a of the material to be inspected is a little thick (as in the case of an IC part), the detection range moves from directly below the back surface B to the inside, and the part shown in Fig. 3 becomes a dead zone, making it impossible to detect the defective part F. There were drawbacks that made it possible.

In order to improve this drawback, we extracted the backside echo of the material to be inspected from the received signal, and on the other hand, we extracted the defective echo of the material to be inspected from the received signal delayed by the delay circuit using the backside echo as a reference. The inventor of the present invention previously proposed an ultrasonic inspection device having a configuration of (Patent application Sho 58-190463
issue).

This will be explained with reference to FIG. FIG. 4 is a block diagram showing another example of a conventional ultrasonic inspection apparatus. The same parts as those in FIG. In the figure, 100 is a back-side echo extraction circuit that extracts back-side echoes from the output of the amplifier circuit 5 using the output of the front-side echo detection circuit 6 as a time reference, and 200 is a received signal in which all defective echoes have been made noticeable by the amplifier circuit 9. A delay circuit 300 delays the backside echo extraction circuit 1
00. This is a defective echo extraction circuit that extracts echoes within the range immediately before the backside echo from the received signal delayed by the output total time reference.

5 and 6 are diagrams showing output signal waveforms of each main part for explaining the entire ultrasonic inspection apparatus of FIG. 4, respectively.

Next, the operation of the conventional ultrasonic inspection apparatus shown in FIG. 4 will be explained. Similar to what is shown in FIG. 1 above,
The control circuit 12 periodically generates pulses as shown in FIG. 5 (Ca) and supplies them to the transmitting circuit 4. The transmitting circuit 4 applies a high voltage impulse to the transducer 2 to generate an ultrasonic pulse according to the timing of the pulse. The ultrasonic pulse generated and transmitted in this manner propagates through the propagation medium 3 toward the specimen 1, a portion of which is reflected by the surface S of the specimen 1, generating all surface echoes, and a portion of which is transmitted. penetrates into the test material 1. If there is a defect F in the material 1 to be inspected, a defect echo is generated. In addition, the ultrasonic pulse
When it reaches the back side B of , a back side echo occurs. Each of these echoes is received by the transducer 2 and sent to the amplifier circuit 5.
is amplified.

An example of the output signal waveform of the amplifier circuit 5 is shown in FIG. 5(b). The output of the amplifier circuit 5 is input to the amplifier circuit 9 for further amplification, and is input to the surface echo detection circuit 6. The output signal waveform of this surface echo detection circuit 6 is as shown in FIG. 5(C). The signal from the front echo detection circuit 6 is given to the back echo extraction circuit 100, which extracts only the back echo from the output signal of the amplifier circuit 5. This extraction is performed as follows. The approximate thickness a of the test material 1 and the sound velocity C in the test material 1 are set in advance, and with reference to the rising edge 5 of the output signal of the surface echo detection circuit 6, ) generates a signal waveform as shown in Time 'l'B1°T shown in Figure 5(d)
a2t! , are given as follows.

TBI ""-・(a-Δa) Here, Δa is the maximum value of the difference between the actual thickness of the material 1 to be inspected and the preset thickness value. Even if the thickness a changes, the position of the backside echo is included in the time TB2. On the other hand, from the output signal of the booster circuit 5, small amplitude signals are removed by a preset threshold value, and only large amplitude signals such as front surface echoes and back surface echoes are removed, as shown in FIG. 5(e). Extracted. Furthermore, this signal is generated during time TB2 by the aforementioned signal as shown in FIG. 5(d), that is, FIG.
) Only the backside echoes shown in () are extracted. The defect echo extraction circuit 300 applies the backside echo extracted in this way.
is input. input to the defect echo extraction circuit 300,
The back surface echo generated is binarized as shown in FIG. 5(a), and as shown in FIG. 5(h), a signal is generated that is active for a time TF from the rising edge of the back surface echo.

On the other hand, the output of the amplifier circuit 5 is further amplified by the amplifier circuit 9, and after making the defective echo noticeable, the output is sent to the delay circuit 20.
0, it is delayed by the time TD as shown in Figure N5 (0. This time TD is given by the following equation, assuming that the depth fd is from the entire back surface B of the object 1 to be inspected. It will be done.

d TD=- Further, the above-mentioned time Tp is set equal to the time TD.

At this time, using the signal shown in FIG. 5(h) as a gate control signal, the output of the delay circuit 200 extracts the peak of the defective echo directly below the back surface B, as shown in FIG. 5(j).

Next, the operation when the thickness a of the test material 1 changes will be explained using FIG. 6. FIG. 6 μ corresponds to FIG. 5, and shows a state in which the thickness a of the specimen 1 is thicker (returning to the back surface BC) and the back surface echo has moved to the right. B indicated by a broken line in FIG. As shown in Figure 6, the gate signal shown in Figure 6 (h) for extracting defective echoes is created just before the backside echo. It is clearly understood that defective echoes can be extracted without producing the dead zone described above. Furthermore, even when the thickness a of the material to be inspected 1 becomes thinner, the gate signal is created based on the backside echo, so the backside echo will not be mistaken as a defective echo.However, as explained above, In addition, in the ultrasonic inspection apparatus shown in Fig. 4 above, the gate signal for extracting all defect echoes is created based on the rising edge of the backside echo, so the amplitude of the defective echo is higher than that of the backside echo. If the amplitude is as large as the amplitude, there is a drawback that the gate signal cannot be created accurately.

[Summary of the invention]

This invention was made with the purpose of improving the above-mentioned drawbacks of the conventional methods. Chirped ultrasonic waves are emitted toward the surface of the material to be inspected, and the envelope of the signal detected from the echoes of the chirp ultrasonic waves is By completely extracting, analyzing and processing this envelope IW, an ultrasonic inspection device is provided which can inspect a test material with high accuracy using a simple device.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 7 is a block diagram showing an ultrasonic inspection apparatus according to an embodiment of the present invention. 1 is a material to be inspected; 2 is a transducer; 5 is an amplifier circuit that amplifies the signal detected by the transducer 2; 510 is a chirp signal generator that generates a chirp signal and drives the transducer 2t; 520
530 is an envelope extractor that detects all the output signals of the amplifier circuit 5 and extracts the envelope; 530 extracts all the echoes on the back surface B of the test material 1 or its vicinity from the output signals of the amplifier circuit 5, and extracts the echo signal. 540 is an analog-to-digital converter (hereinafter referred to as an A/D converter) for digitizing the output of the envelope extractor 520; 550; is A/D converter 5
40 is a memory for capturing and storing the digitalized signal tone while the output of the gate signal generating circuit 530 is active; 560 is for performing signal processing on the contents of the memory 550; This is a microcomputer (hereinafter referred to as microcomputer).

FIG. 8 is an explanatory diagram showing the chirp signal used in the ultrasonic testing device shown in FIG. FIG.

Next, the operation of the ultrasonic inspection apparatus shown in FIG. 7, which is an embodiment of the present invention, will be described. First, the chirp signal generator 510 generates a chirp signal at a predetermined repetition period. This chirp signal is shown in Fig. 8(a).
As shown in , during a predetermined time T, the frequency changes from f to f,
-\ A linearly swept FM wave, for example, a signal with a waveform as shown in FIG. 2(b) above. This signal is a well-known signal that is also used for pulse compression in radar.l)
, is expressed as the following equation.

Here, ω1=2πf1. Shout = 2πf2 (1) = (3
o <"T(a' constant) The above chirp signal C is given to the transducer 2, and this transducer 2
Ultrasonic waves are emitted from the surface S of the specimen 1 into the interior. A power amplifier (not shown) is inserted between the chirp signal generator 510 and the transducer 2 as necessary. The emitted ultrasonic waves advance toward the back surface B of the test material 1 and are reflected by this back surface B. Also, when there is a defective part F,
It is also reflected at this defective portion F, detected by the transducer 2, and amplified by the amplifier circuit 5. In this signal, the defective part F
If there is no echo and there is only a backside echo, it is given by the following equation.

. =b-a(t-r)g''jite・(t-ri+ω・)・
t...(2) Here, τ=gh, h is the thickness of the specimen 1, C is the sound velocity in the specimen 1, b is the ultrasonic reflection characteristic of the back surface B of the specimen 1. It is a constant.

In addition, when the defective part F is located at the distance of the defect position Go...t+ω,)・t+ψ)...
・(3) Jinkode, a6 == bo-a + a, = b
l '' ar bO' constant indicating the ultrasonic reflection characteristics of the back surface B of the test material l, b3. a constant indicating the ultrasonic reflection characteristics of the defective part F;

In this way, the detected signal waveform differs depending on the presence or absence of the defective part F. When only the envelope is extracted by the envelope extractor 520, if there is no defective part F, the B-a-b defective part If F exists, then On the other hand, the output of the amplifier circuit 5 is also input to a gate signal generation circuit 530, which generates a signal that becomes active while a defective echo or a backside echo is being detected. The waveforms of each of the above signals are shown in FIG. 9V. 9th
Figure CH) shows the transmitted ultrasonic wave in the form of a 1,000-fold wave with a duration T.

FIG. 9(b) shows an echo when there is no defective part F, that is, an echo from the back side of the back side B of the material 1 to be inspected.

Fig. 9(C) is a defect echo when there is a u-defect part F, but this defect echo is not observed independently, but as a sum with the backside echo shown in Fig. 9(b). Signal formations similar to those shown in (2) are detected and observed. This signal is processed by the envelope extractor 520 to become as shown in FIG. 9(e) and (f). ).The rise of this signal is at the same time as the rise of the defective echo or the backside echo (1), but this does not require particular precision, and can be seen in Figure 9(d). When there is a defective part F as shown in FIG.
) may be as shown. On the other hand, although the falling edge of the signal coincides with the falling edge of the backside echo, this need not be an exact coincidence either. Therefore, the gate signal generation circuit 53
0 is the extracted envelope f/M which can be easily constructed by a comparator and a flip-flop (not shown),
The D converter 540 samples the signal at a predetermined period, A/D converts it, and inputs it to the memory 550. The contents of the memory 550 are sequentially stored in rows only while the output of the gate signal generation circuit 530 is active.
When the value is 0, predetermined processing is performed. That is, first, the result of the backside echo stored in the memory 550 when there is no defective portion F is stored in the internal memory of the microcomputer 560. Next, the echo to be inspected of the material 1 to be inspected is compared with the backside echo stored in advance when there is no defective part F, and if they are different, it is determined that a defective part F is present. Furthermore, if necessary, all frequencies f of the signals stored in the memory 550 are calculated to determine the defect position Xt. The relationship between the frequency f and the defect position X is obtained from the above equation (4) as follows.

2 (f! fr) f=□・X ・・・・・・・・・・・・
- (5)T Also, since the size of the defective portion F corresponds to the above-mentioned bl, it is evaluated by the difference between the maximum value and the minimum value of the envelope. These processes are difficult even if the rise and fall of the envelope are slightly off (can be done) By the way, in the conventional ultrasonic inspection apparatus shown in Fig. 1 above, the processing as shown in @ Fig. 11 (a) drive the transducer 2 with an impulse,
In addition, when receiving signals, the transducer 2 does not have a sufficiently wide band, so as shown in FIG. The resolution also does not improve.On the other hand, since the ultrasonic inspection apparatus according to the present invention uses a chirp signal waveform as shown in FIG. 12(a), the received signal waveform as shown in FIG. 12(b) is obtained.

For the same reason that the received signal waveform shown in Figure 11 is obtained, the rise is slow and there is some tailing after the chirp signal is cut off, but otherwise a sufficiently large amplitude is obtained in the center. In this invention, the entire envelope of the chirp signal waveform over a predetermined time T is observed and processed.
It is possible to use a large amplitude portion without being affected much by the rise and fall of the signal, and it is possible to test with extremely good S/H. In addition, since the distance between the defective part F and the back surface B of the test material 1 is obtained as the period of the envelope line, a predetermined resolution can be maintained regardless of the sluggish rise and fall of the signal. be able to.

In addition, in the above embodiment, the presence or absence of the defective part F is completely determined by comparing the echo of the inspection object of the inspected material 1 with the backside echo stored in advance when there is no defective part F. As described above, the determination can be made based on whether the envelope is a periodic function or not, without comparing it with the backside echo when there is no defective portion F. because,
This is because if the defective portion F exists, a periodic function is formed as shown in the above equation (4).

Further, in the above embodiment, the gate signal generation circuit 530 is provided to determine the range to be captured into the memory 550, but all signals for a certain period of time from transmission are stored in the memories 5, 50,
It is also possible to search and extract each defect echo and backside echo using the microcomputer 560. In the above embodiment, after extracting the envelope, a signal t with a DC component as shown in FIG. 9 (2) is generated. -I mentioned the method of A/D conversion, but
As shown in FIG. 10 (2) to 0), it is also possible to use a method of cutting the DC component and then binarizing it with a constant darkness value. In this case, a memory 550i and a 1-bit shift register can be used, which helps simplify the device.

Further, in the above embodiment, the signal generated by the chirp signal generator 510 has a constant frequency f, , f, and a time T
' However, as can be seen from equation (5) above, the sensitivity to the defect position X is the same for the same object if;!
For 'l (sound speed C is constant), frequency (f - ft
) and time T, the microcomputer 560 controls the chirp signal generator 510 according to the result of the judgment, and changes the measurement conditions one after another to improve the overall accuracy of the test.
It is also possible to form R.

Further, in the above embodiment, the test material 1 is plate-shaped, and the back surface B
Although we have explained the case of detecting the defective part F directly below, it is also necessary to determine whether or not foreign objects, protrusions, depressions, etc. exist in the vicinity of one reference plane, and to quantify them. It can also be applied to

13 and 14 are diagrams each showing an example in which the ultrasonic inspection apparatus of FIG. 7 is applied as a robot sensor. 1 In each figure, 2 is a transducer, 13 is a robot body, and 14 is an obstacle. , 15 is a floor surface, and 16 is a stepped portion. What is shown in FIG. 13 is a moving robot body 1.
3 is an application example in which an obstacle 14 on a floor surface 15 is detected by ultrasonic waves emitted from a transducer 2. Furthermore, in the robot main body 13 which is also moving, the one shown in Fig. M14 detects the ultrasonic waves emitted from the transducer 2. Like 'jfli
This is an application example of M. In each of the above application examples,
It is possible to detect the presence or absence of the obstacle part 14 or step part 16 and to measure the entire height thereof. A detailed explanation of its operation can be found at
Since the description of the above-mentioned embodiments is clear, the description thereof will be omitted.

Furthermore, the ultrasonic inspection apparatus according to the present invention can also be applied to a case where an object is automatically fed and inspected to see if something is placed on a conveyed table and whether it is A or not. In such cases, it is necessary to confirm that there is no object already on the table before placing it on the table, and also to confirm that there is an object on the table before transporting it. is necessary.

Furthermore, the ultrasonic testing apparatus according to the present invention can be applied to a push button type switch box installed on a wall or the like, to test whether a push button is pressed down or not.

〔Effect of the invention〕

That's all for this invention! i2 On 6I, an ultrasonic inspection device emits chirp ultrasonic waves toward the surface of the material to be inspected,
Since the envelope of the signal detected from the echo of this chirp ultrasound is extracted, and this envelope St-analysis and processing are performed, the signal processing target is the carrier and +i (because it depends on the envelope, the sampling of digitization is The period can be increased, the hardware can be constructed at low cost, and the material to be inspected can be inspected with extremely high precision.
, I4 is used, so it has excellent effects such as improving S/N'<0.

[Brief explanation of the drawing]

Figure 1 shows -f! of a conventional ultrasonic inspection device. , i, FIG. 2 is a diagram showing the output signal waveforms of each main part of the ultrasonic inspection apparatus shown in FIG. 1, and FIG. Figure 4 is a block configuration diagram showing another example of a conventional ultrasonic inspection apparatus;
Figure and M6 figure are respectively the fourth cause of ultrasonic inspection equipment'r.
Figure 7 shows output signal waveforms of each main part for explanation.
Figure G' is a block configuration diagram showing an ultrasonic inspection apparatus which is a simple embodiment of the present invention; Figure 8 is a block diagram showing a chirp signal emitted by the ultrasonic inspection apparatus of Figure 7; 10 is a diagram showing output signal waveforms of each main part for explaining the 71st ultrasonic inspection apparatus, and FIG. 10 is an output signal diagram for explaining an ultrasonic inspection apparatus according to another embodiment of the present invention. A diagram showing waveforms, FIG. 11 is a diagram showing a received signal waveform when driven by impulse in the ultrasonic inspection apparatus of FIG. 1,
Fig. 12 is a diagram showing the received signal waveform when driven by a chirp signal in the ultrasonic inspection apparatus shown in Fig. 7;
14 and 14 are diagrams each showing an example in which the ultrasonic inspection apparatus shown in FIG. 7 is applied as a sensor/sensor for a robot. In the figure, 1...Test material, 2...-Transducer, 3...Propagation medium, 4...Transmission circuit, 5, 9...
- Amplifier circuit, 6... Surface echo detection circuit, 7... Detection range setter, 8, 530... Gate signal creation circuit, 10... Gate circuit, 11... Signal processing device, 1
2... Control circuit, 13... Robot body, 14...
・Obstacle, 15...Floor, 16...Step, 100・
...Back side echo extraction circuit, 200...Delay circuit, 30
0... Defect echo extraction circuit, 510... Chirp signal generator, 520... Envelope extraction section, 540... Analog-digital converter (A, 'D converter), 550
. . . memory, 560 . . . microcomputer (microcomputer). In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] means for emitting chirp ultrasonic waves toward the surface of the material to be inspected;
means for detecting echoes of chirp ultrasound from the surface; means for extracting an envelope of the signal detected from the echo; means for creating a gate signal from the detected signal; An ultrasonic inspection apparatus comprising: means for analyzing and processing the envelope, and detecting whether or not an object is present in the vicinity of the surface, and measuring a distance from the surface.