JPS59202060A - Ultrasonic flaw detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to determine a defect area ratio with high accuracy, by detecting a surface echo signal and a defect echo signal by respectively setting predetermined detection levels. CONSTITUTION:The signal from an object 3 to be inspected through a surface echo gate circuit 24 is judged as an ultrasonic surface echo signal when it is equal to or higher than the set detection level of a surface echo comparator circuit 25 and counted by a surface echo count circuit 26 to count the surface area of the object 3 to be inspected. This set detection level is selected as a detection level when the mechanically measured length of the object 3 to be inspected in the transverse direction thereof and the electrically measured length of the object 3 to be inspected during the scanning of a probe 20 in the transverse direction are coincided. Similarily, a defect echo signal is detected by a defect echo counter circuit 19 wherein a detection level coinciding with the measured length of a defect having a preliminarily known length is set and the area of the defect 5 is counted by the defect echo count circuit 29 and a defect area ratio is determined with high accuracy by an area ratio count circuit 30. A similar result is obtained even if a signal is treated with a different amplification degree or attenuation degree.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection device that measures the defect area ratio with respect to the surface area of a specimen by ultrasonic flaw detection.

Background of the Invention Generally, when performing ultrasonic flaw detection on a steel specimen placed underwater, the ultrasonic waves emitted from the probe are reflected by the surface of the specimen due to the law of transmission and reflection at interfaces. The surface echo signal reflected by the defect surface is 20 dB lower than the defect echo signal reflected by the defect surface.
level or higher. The reason for this will be explained below based on FIG.

FIG. 1 shows a surface echo signal 4 from a surface 3s of an object 3 such as steel at the bottom of water 2, and a defect echo signal 6 from a defect 5 inside the object 3, using a probe 1. FIG. 2 is a schematic diagram showing the principle of obtaining .

Here, for example, each acoustic impedance has the following values.

b) Acoustic impedance of water: Z (W) -1,5 [106KP/-'S] c7)
Acoustic impedance of steel: Z(Fe) = 45.4 C106Kp/m''S] C) Acoustic impedance of air: Z(A) = 4 X 10-'CKp/m's) Then, search f(Toyo 1/ l・1〕Hatsugetsu 1: X water water 2 middle 7
Line 1611 - The pseudo-thorn body of the super-salt wave (the reflector S on the plow surface 3s is loud, so the surface echo signal 4 is the sound pressure of the surface echo when the difference in acoustic impedance is particularly large. %, it can be seen that it is 94%.

On the other hand, the sound pressure of the defective echo signal 6 is determined as follows.

a) Passage rate at the interface between water 2 and object 3 1)) Reflectance at the defect 5 surface (assumed to be a mirror surface) inside object 3 c) At the interface between object 3 and water 2 a) with a passing rate greater than or equal to
The product of b) and C) becomes the sound pressure ratio F of the defective echo signal 6.

Therefore, the sound pressure of the defective echo signal 6 is 12%.

Therefore, when the sound pressure of each of the above signals, that is, the echo height, is displayed in A-no-copy mode, an /I waveform as shown in FIG. 2 is obtained.

As explained above, the surface echo signal is detected at a significantly higher level than the defect echo signal.

In addition to the above, since the ultrasonic beam has a certain degree of spread, the following inconvenience occurs when determining the defect area ratio 'AIJ'.

For example, when measuring using a probe with an ultrasonic beam diameter of 2a, as shown in FIG. 3, FIG. , 3rd
Figure (bJ is a side view seen from the side. Figure 3 (c)
1 indicates the height of the surface and defect echo signal corresponding to the position of the probe 1 in FIGS. 3(a) and 3(b). Here, the diffusion and attenuation of the ultrasonic beam will be viewed as #9, and it will be simplified that the beam will proceed with the beam diameter being 2a. Therefore, we will look at the change in echo height when the probe 1 is moved from the left to the right in the figure, that is, from position A to position F.

First, when the center of the probe 1 passes the position A, that is, the position where the beam begins to hit the object surface 3s, a surface echo signal begins to be detected. Position B, that is, the object surface 3s
When the beam reaches the end position, half of the beam is reflected by the object surface 3s. After passing a distance bζ which is the radius of the probe 1 from the position C, that is, the position B, to the right, the entire beam begins to hit the surface 3s of the object.

Then, the height of the surface J echo signal is such that the center of probe 1 is C.
As shown in FIG. 2, it is 94% when in position B, 47%, which is half of that, in position B, and 0% in position A. That is,
;, (r, As shown in Figure 3 (cl), the height of the surface echo signal has a tail near the end of the subject surface 3s.

Next, let's try setting the height of the defect echo signal in the same way. Search;
The center of the dowel 1 is at position D, that is, from the edge of the defect 5 to a
When moving to the right beyond the left position, defective echo signals begin to be detected. When it reaches position E, ie, the edge of the defect 5, half of the beam is reflected by the surface of the defect 5. Beyond position F, that is, a position a distance to the right from position E, the entire beam will hit the surface of the defect 5. Then, the height of the defect echo signal is 12 when it is at the center of probe 1 or at position F, as shown in Figure 2.
%, half of that is 6% at the E position, and 0 at the D position. That is, as shown in FIG. 3(c), the height of the defect echo signal has a tail near the edge of the defect 5 in Table 1 (2).

As described above, since the ultrasonic beam has a spread, even when the center of the probe is located outside the area of the actual object surface and defect surface, each echo signal will have a certain degree of spread. It will have height.

The defect area ratio is measured using a probe. :
The object to be inspected is continuously scanned while generating T-wave pulses, and if the echo signal returned from the surface of the object or defective surface is at a certain height or higher, the object is detected at that position. Alternatively, it is determined that a defect exists, and the area ratio is determined by counting and processing the pulses at that time. Conventionally, the reference level, that is, the detection level, has been set at the same position for both the surface echo signal and the defect echo signal, for example, at about 6%.

The detection level was set at 6% here as shown in Figure 3 (cl.
This is to start counting the defect echo signals when the center position of the probe 1 at that level coincides with the position of the end of the defect 5 (position E) as shown in FIG.

However, for the reasons mentioned above, the surface echo signal has a considerably higher level than the defect Nicol signal, so the 6%
If A is set as the same detection level for both echo signals, the surface echo signal will be detected when the center position of the probe 1 comes to an intermediate position between A and B. That is, with the conventional detection level setting, as shown in FIG. 4, there is no problem with the outer shape 10 of the defect, but on the surface of the object, the detected outer shape 11 is larger than the actual outer shape 12. Therefore, it is very difficult to obtain an accurate area ratio, and there is a drawback that it is necessary to make corrections to the results after measurement.

DESCRIPTION OF THE INVENTION The present invention has been made to eliminate the above-mentioned drawbacks, and detects the surface echo signal and defect echo signal by:
This is done by providing means for setting and comparing different detection levels so that detection is performed only when the center position of the probe coincides with or is inside the edge of the surface of the object to be inspected or the edge of the defective surface. Alternatively, the defect area ratio can be determined with higher accuracy by providing a means for amplifying or attenuating the surface echo signal and the defect echo signal with different amplification degrees or attenuation degrees and then comparing them at the detection level. The purpose is to provide an ultrasonic flaw detection device that can perform

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

FIG. 5 is a block diagram showing a first embodiment of the present invention.

Here, the probe 20 is driven by high-pressure pulses emitted from the pulser receiver 21 and emits ultrasonic pulses over the object 3 provided in an ultrasonic transmission medium such as water. Scans 22 are performed continuously, operated by a probe scanning device. The ultrasonic pulse is applied to the object 3
The signals reflected and returned from the surface of the defect 5 and the surface of the defect 5, that is, the surface echo signal and the defect echo signal, are received by the ultrasonic probe 20, and then amplified and waveform-shaped by the pulser receiver 21. The probe position detection and sampling point designation circuit 23 detects the position signal of the probe 20 sent from the probe scanning device, and places the measurement point by the probe 20 within the scanning range according to a predetermined method. , and instructs the pulser receiver 21 to oscillate an ultrasonic pulse.

The surface echo gate circuit 24 is a circuit that selects and extracts only the surface echo signal from among the surface echo signal and defect echo signal obtained by the pulse receiving receiver 21. The surface echo comparator circuit 25 is the surface echo gate circuit 2.
The surface echo signal obtained in step 4 is compared with the surface echo detection level set by the method described in detail later, and the signal is given to the next stage only when the surface echo signal is at a level higher than the surface echo detection level. . The surface echo count circuit 26 is a circuit that counts signals sent from the surface echo comparator circuit 25, and this count corresponds to the area of the surface of the subject 3 scanned by the probe 20.

On the other hand, the defective echo gate circuit 27
This circuit selects and extracts only the defective echo signal from among the signals obtained in step 1. Defect echo comparator circuit 2
8 compares the defect echo signal obtained by the defect echo gate circuit 27 with a defect echo detection level set to a level different from the surface echo detection level using a method described in detail later, and determines whether the defect echo signal is The signal is sent to the next circuit only when it is at the level below which the defective echo detection signal is detected.
The defect counter count circuit 29 is a circuit that counts the signal sent from the defect echo comparator circuit 28, and this count corresponds to the area of the surface of the defect 5 scanned by the probe 20.

The area ratio calculation circuit 30 processes and divides the defect echo count number obtained above by the surface echo count number to calculate the defect area ratio with respect to the surface area of the object. The video display circuit 31 also displays the position signal of the probe 20 outputted from the probe position detection and sampling point designation circuit 23, the surface echo signal outputted from the surface echo converter circuit 25, defects, This is for displaying the shapes of the object 3 and the defect 5 based on the defect echo signal output from the c-coe comparator circuit 28.

Description of Operation of the Present Invention> Next, the operation of this embodiment having the above block configuration and how to set the above-mentioned detection level will be explained based on the waveform diagram shown in FIG. 6. In each figure in FIG. 6, the vertical axis represents the signal intensity, and the horizontal axis represents the time from the rise of the oscillation echo.

The output waveform after the surface echo signal and the defect echo signal obtained by reflection from the surface of the object 3 and the defect 5 are amplified and waveform-shaped by the balsa receiver 21 is shown in FIG. 6(a).

FIG. 6(b) shows the surface echo gate waveform set by the surface echo gate circuit 24. Surface echocate position S
, G, and P are the times from when the oscillation signal rises as a reference to when the surface echo gate rises. The surface echo gate widths S, G, and W are time gate widths that determine the time range in which surface echo signals are detected. Then, among the various signals output from the balsa receiver 21, the surface echo gate positions S, G, P
After the point set in , only surface echo signals that fall within the time period of the surface echo gate widths S, G, and W are obtained by the surface echo gate circuit 24.

FIG. 6(d) shows how the surface echo signal extracted by the surface echo gate circuit 24 is transferred to the surface echo comparator circuit 2.
5 is an explanatory diagram showing a comparison with surface echo detection levels S, S, and L set in step 5. FIG. Here, the surface echo detection levels S, S, and L are set as follows. For example, in FIG. 3, the length of the subject 3 in the lateral direction is mechanically measured in advance. Next, the surface echo detection level S
, S and L are gradually changed, the length of the subject 3 in four directions is measured by moving the probe in the lateral direction, When the electrical measurement value matches the mechanical d111 constant value, surface echo detection levels S, S, and L are set. In other words, in the case shown in Figure 3, the surface echo detection levels S, S, and L are set to 4.
All you have to do is shift the setting to Section 7. When the surface echo comparator circuit 25 receives an input signal equal to or higher than the surface echo detection bells S, S, and L set as described above, the input signal is converted into a pulse and sent to the surface-n echo detection circuit 26. sent to. The surface echo counting circuit 26 calculates a count corresponding to the surface echo of the object within the scanning range of the probe 20 by counting the number of front echo pulses that are reflected as the probe 20 moves. will have a number.

On the other hand, FIG. 6(c) shows a defective echo gate waveform set by the defective echo gate circuit 27. Here, the defective echo gate positions F, G, and P are the surface echo detected and the bell S,
Using the rising edge of the surface echo signal S, L or higher as a reference, the time from there to the rising edge of the defective echo signal 1 is set. Defective funico gate width F,
G and W are time gate widths that determine the time range in which defective echo signals are detected.

Then, among the multiple signals output by the balsa receiver 21, the defective echo signals that fall within the time period of the defective echo gate widths F, G, and W after the points set by the defective echo gate positions F, G, and P will be obtained by the defective echo gate circuit 27.

FIG. 6(e) is an explanation showing how the defect echo signal extracted by the defect echo gauge 1 circuit 27 is compared with the defect echo detection levels F, S, and L set by the defect echo comparator circuit 28. Figure 1. Here, the defect echo detection levels F, S, and L can be set as follows.

On an object with an artificial defect whose size is known in advance,
The defect size is scanned with a probe and processed by the electric circuit in this device.The defect echo detection levels F, S, and L are gradually changed to determine the size of the defect. Target 611] When the fixed value matches the actual size of the artificial defect, the defect echo detection levels F, S, and L are set. For example, in FIG. 3, if defect 5 is considered to be an artificial defect, an accurate size can be obtained by setting the defect echo detection levels F, S, and L to 6%. When the defect echo counter circuit 28 receives an input signal equal to or higher than the defect echo detection bells F, S, and L set in the above (2 I~), the input signal is converted into a pulse and sent to the defect echo counter circuit 29. Defect echo counting circuit 29
By counting the number of pulses sent as the probe 20 moves, it has a count corresponding to the defect surface area within the scanning range of the probe 20.

Finally, in the area ratio calculation circuit 30, the defect echo count obtained by the defect echo counting circuit 29 is processed and divided by the surface echo count obtained by the surface counting circuit 26. , the defect area ratio is obtained.

As described above, in this embodiment, it is possible to set the surface echo detection level and the defect echo detection level separately, so both can be arbitrarily set to appropriate levels, so that the ultrasonic beat] spreads. It is possible to eliminate the constant error caused by the difference in the level of the rear echo signal and obtain an accurate defect area ratio. Further, in a similar manner, a shape having a more accurate defect area ratio can be formed in the image display circuit 31.

FIG. 7 is a block diagram showing the main parts of a second embodiment of the present invention. In the first embodiment, the surface echo signal and the defect echo signal were detected at different detection levels, but even if the detection levels are the same, the same effect can be obtained by amplifying or attenuating each echo signal to a different height. The results obtained are as follows. Therefore, in this embodiment, an attenuator 40 is provided between the surface echo circuit 24 and the surface echo comparator circuit 25. As mentioned above, since the surface echo signal has a much higher level than the defect echo signal, the gain of the surface echo signal is reduced by using the attenuator 40.
What to do (from 2) Adjust the echo signal and defective echo signal to the same level.

If the attenuator 40 is provided as described above, even if each of the 18 levels is set to the same level, appropriate measurements can be made by adjusting the attenuation rate.For example, in FIG. If the detection level is set to 6,
The height of the surface echo signal is 12 to 13% of the original height.
It is sufficient to set it so that it is attenuated to the level of .

In addition, although the Arati signal generator 40 is used in the above example, an amplifier may be provided between the defective echo gate circuit 27 and the defective echo cosciparator circuit 28, and the gain of the defective echo signal may be increased by the amplifier. Similar/“You can get results.

For example, in FIG. 3, when the detection level is set to 47%, the height of the defective echo signal may be set to be amplified to a level approximately eight times the original height.

Therefore, in the second embodiment, by using an attenuator or an amplifier, it is possible to change the level of the echo signal itself even when the detection level is the same, thereby eliminating measurement errors as in the first embodiment. Accurate defect area ratio can be obtained.

Note that in the first and second embodiments described above, scanning by the probe 20 is performed by specifying a sampling point and using the balsa receiver 21.
However, if the scanning is at a constant speed, there is no need to synchronize if the oscillation interval of the balsa receiver 21 is kept constant and the oscillation interval is sampled.

Next, a case where a focusing type probe is used in the ultrasonic flaw detection apparatus of the present invention will be explained using FIG. 8.

Focused ultrasonic heat is emitted from the focusing probe 50, hits the object surface 3S with a diameter of 2a/, is refracted there, and has a beam diameter of 2V (a>b) at the focus position. . Therefore, in this case, as explained in FIG. 3, if the surface echo detection level and the defect echo detection level are set to the same 6%, the center position of the probe 50 at the point of the surface echo height G is , is further away from the end face of the broken body than in the case of FIG. Therefore, if measures such as those shown in the first or second embodiment of the present invention are taken using the focusing probe 50, the effects of the present invention will be further enhanced.

Moreover, the ultrasonic flaw detection device of the present invention has two planes in contact with each other.7. This method is particularly effective when the relative distances between the scanning surface of the probe, the surface of the object to be inspected, and the defective surface are uniform, such as when measuring a surface with poor adhesion as a defective location in the case of a defective surface.

Therefore, as described above, the present invention eliminates the conventional drawbacks of measurement errors caused by the spread of ultrasonic beats or differences in the level of echo signals, and detects defects with high accuracy. It is possible to measure the area ratio, and in the visualization, it is possible to display the shape with a highly accurate area ratio that corresponds well to the shape of the actual object and defect. It is something.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the principle of obtaining surface and defect echo signals by ultrasonic flaw detection, Figure 2 is a waveform diagram showing the height of each echo signal, and Figure 3 is a defect area ratio by ultrasonic flaw detection. FIG. 4 is a schematic diagram showing the conventional measurement error, FIG. 5 is a block diagram showing the first embodiment of the present invention, and FIG. 6 is a diagram showing the measurement error in the first embodiment of the present invention. FIG. 7 is a block diagram showing the main parts of the second embodiment of the present invention, and FIG.
FIG. 1 is an explanatory diagram when determining the defect area ratio by using a child. 21...Balsa lever 23 -Probe position detection and sampling point designation circuit 24...Surface nicolate circuit 25 -Surface echo comparator circuit 26 -Surface echo count circuit 27 Defect echo gate circuit 28...Defect echo comparator circuit 29... Defect echo counting circuit 30...Area ratio calculation circuit 31...Video display circuit 40 - Arati 50 - Focusing probe whistle 6 Figure 8

Claims (1)

[Scope of Claims] 1. An ultrasonic flaw detection apparatus having a means for processing a surface echo signal and a defect echo signal to obtain a defect area ratio with respect to the surface area of an object by performing ultrasonic flaw detection using a probe, Means for comparing and detecting the signals at different detection levels, or means for amplifying the signals at different amplification degrees or attenuating the signals at different attenuation degrees and then comparing and detecting at substantially the same detection levels. An ultrasonic flaw detection device characterized by having. 2. The ultrasonic flaw detection device according to claim 1, wherein the probe is a focusing probe.