JPH09113249A - Ultrasonic flaw detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the dimension of a defect, etc., even when the dimension is small at the time of measuring the dimension by using an ultrasonic flaw detecting method. SOLUTION: An ultrasonic flaw detecting device 21 is provided with a point convergent-type probe 22 which transits and receives ultrasonic waves and a CRT display 23 which displays the relation between the magnitude of received ultrasonic wave energy and required reflecting time in a waveform. The probe 22 performs ultrasonic flow detection on a plate 24 by scanning the plate 24 in the direction along the incident and reflecting direction of the ultrasonic waves while the probe 22 obliquely transmits the ultrasonic waves toward the other surface 26 of the plate 24 from one surface of the plate 24. The time interval between the time when the magnitude of the received ultrasonic wave energy becomes the maximum and the time when the magnitude of the received ultrasonic wave energy to the maximum magnitude becomes a preset ratio which is determined by taking the results of preliminary experiments into consideration against the time when the magnitude of the energy becomes the maximum is found from a waveform which is received by means of the probe 22 and displayed on the display 23 and the depth of a defect 27 is calculated based on the time interval and the ultrasonic wave transmitting angle from the probe 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses ultrasonic waves to measure the depth dimension of defects and the like formed on the back surface of a solid.
The present invention relates to an ultrasonic flaw detection method.

[0002]

2. Description of the Related Art An ultrasonic flaw detection method has been conventionally used in which an ultrasonic wave is incident from one surface of a solid body and the reflected wave thereof is inspected for the presence of a defect or the like opened on the back surface of the solid body.

By the way, recently, a point-focusing type probe capable of emitting and receiving ultrasonic waves focused in a narrow range of about 2 mm in diameter has been developed. By using such a point-focusing type probe, Attempts have been made to measure the depth dimension of defects and the like.

Measurement of the depth dimension of a defect using such a point-focusing type probe (hereinafter, simply referred to as a probe) is performed as shown in FIG. 8, for example.

In FIG. 9, 1 is a plate material as a solid, a point focusing probe 3 is arranged on the front surface 2 side of the plate material 1, and the back surface 4 side of the plate material 1 is opened to the back surface 4 side. There are crack-like defects 5.

Then, the probe 3 transmits a predetermined ultrasonic wave in an oblique direction at an angle θ (for example, 45 degrees leftward in the figure) and receives a reflected wave (echo) from the same direction. ing.

In the figure, a indicates a region where the sound waves emitted from the probe 3 are focused. In addition, hereinafter, the opening of the defect 5 is referred to as a corner 5a, and the upper end of the defect 5 is referred to as an end 5b.

The probe 3 as described above is scanned in the direction of the arrow on the surface 2 side of the plate member 1. The echo received by the probe 3 takes a reflection time in the horizontal axis direction, and the reflection required. A waveform formed by arranging echoes according to time is displayed on the CRT screen. In addition, since the required reflection time has a unique relationship with the distance, it is hereinafter referred to as a road length.

In such a CRT screen, an echo 6 (hereinafter referred to as a corner echo) in a state where the center line O of the ultrasonic wave from the probe 3 coincides with the corner 5a.
Alternatively, the waveform is displayed including the echo 7 in the state where the center line O of the ultrasonic wave coincides with the end 5b (hereinafter, referred to as end echo).

Here, the waveform including the corner echo 6 of the defect 5 is called a corner waveform 11 and the waveform including the end echo 7 is called an end waveform 12.

The echo 6 from the corner 5a displayed on the CRT screen is displayed at the position of the road length LC in the corner waveform 11 and the sonic energy of the corner echo 6 is large. Therefore, the echo on the CRT screen is displayed. The height is displayed large.

Also, the end portion 5 displayed on the CRT screen.
The echo 7 from b is displayed at the position of the path Lto in the end waveform 12 and is displayed at an echo height smaller than that of the corner echo 6.

Since the corner waveform 11 and the end waveform 12 including the corner echo 6 and the end echo 7, respectively, are displayed in a separated state, the corner echo from each of the waveforms 11 and 12 is displayed. 6 and end echo 7
Can be identified and grasped on the CRT screen, and the road difference W can be obtained by subtracting the road distance Lto from the road distance LC.

Therefore, the depth dimension d of the defect 5 is as shown in FIG.
Can be calculated by the road difference W × sin θ.

[0015]

By the way, when the dimension of a defect or the like is measured by such a method, if the depth dimension d of the defect 5 becomes smaller, the path difference W between the echoes 6 and 7 becomes smaller, Since the corner waveform 11 and the end waveform 12 are combined as shown in FIG. 10 or FIG. 12, it is difficult to measure the road difference W, and it becomes impossible to measure the dimension such as a defect by the above method.

This is because, as shown in FIG. 11 or FIG. 13, the size of a defect or the like is reduced, so that the ultrasonic wave from the probe 3 is present at both the corner 5a and the end 5b of the defect 5. This is because there is a situation in which the corner echo 6 and the end echo 7 are simultaneously generated by the simultaneous reflection.

The present invention has been made under such circumstances, and is a method for measuring the size of a defect or the like by an ultrasonic flaw detection method. Even when the size of the defect or the like is small, the size of the defect or the like can be measured. It is an object to provide what can be measured.

[0018]

In order to solve such a problem, the invention according to claim 1 proposes a point-focusing type probe for generating and receiving a sound wave, and the strength and reflection of the received sound wave energy. An ultrasonic flaw detector having a display for displaying a relationship with a required time in a waveform, wherein the probe is pressed against one surface of a solid and transmits sound waves obliquely toward a back surface including a defect. In addition, in the ultrasonic flaw detection method in which the scanning direction of the probe is along the incident direction of the sound wave,
The waveform was received by the probe and displayed on the display when the magnitude of the sonic energy was maximum, and when the waveform was the maximum of the sonic energy, it was performed in advance. The time interval between the time and the ratio set in consideration of the test result is obtained, and the defect size is calculated based on the time interval and the transmission angle of the sound wave from the probe. This is an ultrasonic flaw detection method.

The invention according to claim 2 is the ultrasonic flaw detection method according to claim 1, wherein the ratio is set in a range of 0.05 to 0.3.

Further, in a third aspect of the present invention, when the waveform displayed on the display has a set ratio time at a plurality of positions, the ratio time on the position side separated from the maximum position is set. 3. The ultrasonic flaw detection method according to claim 1 or 2, characterized in that the time interval is calculated with respect to the selected time.

Further, in a fourth aspect of the invention, when the waveform displayed on the display device has set ratio times at a plurality of positions, the ratio time on the position side separated from the maximum position is set. Is selected to obtain a first time interval with respect to the ratio time, and a second time interval with respect to the ratio time on the position side closer to the maximum time position. And calculating the first dimension and the second dimension of the defect based on each of the second time interval, and when the distance between the probe and the defect end is within the effective focusing range of the probe. The first dimension is the dimension of the defect, and the second dimension is the dimension of the defect if the distance between the probe and the defect end is outside the effective focusing range of the probe. It is the ultrasonic flaw detection method according to claim 1 or 2.

Further, according to a fifth aspect of the present invention, the focusing range of the point-focusing type probe is 1 mm smaller than the thickness of the measuring object to twice the thickness of the measuring object or the thickness of the measuring object. The beam width of the point-focusing type probe is 2.5 mm.
The ultrasonic flaw detection method according to any one of claims 1 to 4, wherein the ultrasonic flaw detection method has a thickness of less than or equal to mm.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the embodiments shown in the drawings. First, the structure of an apparatus used in this ultrasonic flaw detection method will be described with reference to FIG.

In FIG. 2, reference numeral 21 denotes an ultrasonic flaw detector, which has a point-focusing type probe 22 and a CRT display 23 for displaying the echo received by the probe 22.

The probe 22 transmits a predetermined ultrasonic wave at an angle θ.
(For example, in the figure 45 degrees to the left) Send diagonally,
It receives a reflected wave (echo) from the same direction.

The probe 22 has a condition that the ultrasonic beam diameter is in the range of 2.2 mm to 3.0 mm and the ultrasonic beam focusing range is in the range of 3.0 mm to 26.0 mm. Is selected from the range.

The probe 22 is a portable pulse reflection type ultrasonic flaw detector (type
USL-38) is used to perform flaw detection operations such as scanning.

The CRT display 23 takes a reflection time in the horizontal axis direction, and displays on the screen a waveform in which echoes received by the probe 22 are arrayed according to the reflection required time. The waveform of the displayed echo is displayed with the echo height corresponding to the magnitude of the sound wave energy and the path length indicated by the required reflection time as coordinates.

Such an ultrasonic flaw detector 21 has a back surface 2
The probe 22 is used to scan the probe 22 in the direction of the arrow on the surface 25 of the plate member 24 where the crack-like defect 27 exists on the 6 side to display a waveform by echo on the CRT display 23.

The scanning of the probe 22 is performed in a direction along the emission direction of the sound wave from the probe 22, that is, so that the emission direction of the sound wave and the scanning direction are on the same side in the same plane. To do.

The waveform 31 on the screen of the CRT display 23 thus obtained is as shown in FIG. 1, for example.

The waveform 31 is Lt0 in FIG.
The case where the direct wave indicated by 1 produces an end echo (hereinafter referred to as the first method), and the one-time reflected wave Lt1 produces an end echo (hereinafter referred to as the second method). ) Will be described later.

This waveform 31 is a combination of the corner waveform 11 and the end waveform 12 due to the defect 27. In this waveform 31, the position of the corner echo 6 at which the echo height becomes the maximum value should be grasped. However, the position of the end echo cannot be grasped as it is, and therefore the path difference W necessary for calculating the size of the defect 5 cannot be directly obtained.

Therefore, in the method of the present application, the following preliminary experiment is carried out, the coefficient relating to the ratio of the end echo to the corner echo 6 with respect to the echo height is determined in consideration of the result of the preliminary experiment, and this coefficient is used. The waveform 31
The position of the end echo is calculated from.

That is, in the preliminary experiment, the defect 2 to be measured
The known defects, which are expected to be about the same degree as No. 7, were formed on the back surface of the plate material, and the surface of such a plate material was similarly scanned by the probe 22, which was obtained on the screen of the CRT display 23. The waveform is matched to a known defect size, which defines a factor for the ratio of end echo to corner echo.

When determining the coefficient relating to such a ratio, in addition to the above, the content of the preliminary experiment may differ from that of the object to be measured under various conditions (eg, plate thickness, structure, etc.). Since it is considered, the numerical value calculated as described above may be adjusted in consideration of the conditions when the coefficient relating to the above-mentioned ratio is determined.

With respect to the waveform 31 shown in FIG. 1, the coefficient relating to the ratio thus determined is 0.1,0.
If the positions of the end echoes are obtained from the waveform 31, assuming that there are three types of 2 and 0.5, it is as follows.

That is, when the coefficient relating to the ratio is 0.1, the echo height of the end echo is 0.1H with respect to the echo height H of the corner echo 6,
In FIG. 1, W0.1 is the road difference in that case.

Similarly, the coefficient relating to the ratio is 0.2,0.
In case of 5, the echo heights are 0.2H and 0.5, respectively.
It becomes the position of H, and the road difference at that time is W0.2, W respectively
0.5.

Then, depths of 0.5 mm, 1.0 mm,
For the known defect of 1.5 mm, the depth d of the defect is measured by the method of the present application by using the difference W0.1, W0.2, and W0.5 of the difference in path obtained as described above and the difference W × sinθ in the path. The value was calculated.

The results are shown in FIG. 3, and the highest accuracy is obtained when the coefficient relating to the ratio is 0.1.
The accuracy was the worst when the coefficient was 0.5.

In the case of the second method shown in FIG. 1 in which the once-reflected wave Lt1 causes the end echo, the waveform 32 as shown in FIG. 4 is formed on the CRT display 23.

Also in this waveform 32, the corner waveform 11 and the end waveform 12 'due to the defect 27 are combined, and it is not possible to directly obtain the path difference W necessary for calculating the size of the defect 5. Is the same as the case of the waveform 31, except that the end waveform 12 'is formed by the once-reflected wave Lt1.

Also in grasping the position of the end echo for such a waveform 32, a preliminary experiment is conducted in the same manner as in the case of the first method, and the echo height is determined in consideration of the result of the preliminary experiment. A coefficient relating to the ratio of the end echo to the corner echo 6 is determined, and the position of the end echo is determined from the waveform 31 by this coefficient.

The position of the end echo according to the second method corresponds to a position separated from the maximum time position according to the present invention, and the position of the end echo according to the first method corresponds to the maximum time position according to the present invention. It corresponds to a closer position.

Also for this waveform 32, if the road difference is obtained from the waveform 32 assuming that there are three types of coefficients relating to the ratio, 0.1, 0.2 and 0.5, W0.1 and W0.2 in FIG. 4 are obtained. , W
It seems to be 0.5.

Then, depths of 0.5 mm, 1.0 mm,
FIG. 5 shows the correlation between each defect and the measured value calculated using each of the path differences W0.1, W0.2, and W0.5 obtained as described above for the known defect of 1.5 mm. It is as follows.

From the measurement values obtained by the first method and the second method, the coefficient relating to the ratio is 0.05 to
If it is set within the range of 0.3, it is possible to obtain a highly accurate measured value in practical use.

Various kinds of defects are measured by using the first method and the second method, and the correlation between the actual size of the defect and the measured value by these methods is as shown in FIG.

Particularly, regarding the beam path length Lt (including both Lt0 and Lt1) and the focusing range Lmin of the probe 22,
In the range of Lt / Lmin <1, the second method accurately measures the defect, and in the range of Lt / Lmin ≧ 1, the first method is conversely the first method.
It can be seen that the method of (1) measures accurately.

This means that when the defect is measured by the method of the present application, it is possible to improve the measurement accuracy by properly using the first method and the second method. Is.

However, since the beam path length Lt cannot be calculated unless the dimension of the defect is known, it is possible to measure with good accuracy by using the first method and the second method together in the following procedure. Becomes

The beam path length LC from the plate thickness to be measured to the defect corner is calculated, and the beam focusing range lower limit Lmin is calculated.
Is smaller than the beam path LC.

The corner echo is obtained by using such a probe, and the end echo is obtained by the second method.
The defect size is calculated from the difference in road length by the method of.

This is to avoid overlooking large defects that are difficult to measure by the first method.

The measured value is used to calculate the path length to the edge of the defect according to the first method.

Then, Lt / Lmin is calculated, and Lt / Lmin
In the case of <1, the measured value obtained above is used as the measured value of the defect.

On the contrary, when Lt / Lmin ≧ 1, the defect is measured by the first method, and the measured value obtained by this is used as the measured value of the defect.

When a measurement object similar to that shown in FIG. 6 is measured in this procedure, only the measurement values shown in FIG. 7 are obtained, and these measurement values are ± 0.5 mm with respect to the actual depth of the defect. It is found that the value is within the range and the accuracy is extremely good.

Note that, for example, in order to measure the dimension of a defect with good accuracy by the method of the present invention with respect to a relatively thin plate material having a plate thickness of 10 mm or less, the focusing range of the probe 22 is the thickness of the object to be measured. The diameter of the probe 22 is less than 2.5 mm and the beam width of the probe 22 is 2.5 mm or less. Is preferred.

[0061]

As described above, according to the first aspect of the invention, in this type of ultrasonic flaw detection method, the sound wave energy of the waveform received by the probe and displayed on the display is displayed. Since the time interval between the time when the magnitude becomes the maximum and the time when the magnitude of the sound wave energy becomes the ratio set in consideration of the test result performed in advance with respect to the maximum time, is obtained, Even when the corner waveform and the end waveform are combined to make it difficult to distinguish between the corner echo position and the end echo position, a reasonable time interval can be obtained.

Therefore, it becomes possible to calculate an appropriate size of the defect based on the time interval thus obtained and the known transmission angle of the sound wave from the probe.

[Brief description of the drawings]

FIG. 1 is a waveform explanatory diagram according to a first method.

FIG. 2 is a schematic view of an ultrasonic flaw detector and a usage state thereof.

FIG. 3 is a correlation diagram between a measured value by the first method and an actual depth of a defect.

FIG. 4 is an explanatory diagram of waveforms according to a second method.

FIG. 5 is a correlation diagram between a measured value by the second method and an actual depth of a defect.

FIG. 6 is a correlation diagram between measured values of various defects and actual depths obtained by mixing the first method and the second method.

FIG. 7 shows a first method and a second method according to the procedure proposed by the present application.
FIG. 6 is a correlation diagram between measured values of various defects and actual depths when the above method is used properly.

FIG. 8 is a waveform diagram of a conventional measurement method using an ultrasonic flaw detection method.

FIG. 9 is an explanatory diagram of a conventional measurement method using an ultrasonic flaw detection method.

FIG. 10 is a waveform diagram from a small defect in the conventional measurement method using the ultrasonic flaw detection method.

FIG. 11 is an explanatory diagram when a conventional measuring method is applied to a small defect.

FIG. 12 is a waveform diagram from a smaller defect in the conventional measurement method using the ultrasonic flaw detection method.

FIG. 13 is an explanatory diagram when a conventional measurement method is applied to smaller defects.

[Explanation of symbols]

 21 Ultrasonic Testing Equipment 22 Point Focusing Probe 23 CRT Display 24 Plate Material 25 Front Surface 26 Back Surface 27 Defects 31, 32 Waveform

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 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masazumi Iwata 2109 Yashima Nishimachi, Takamatsu City, Kagawa Prefecture 8 Shikoku Research Institute, Inc. (72) Inventor Masayuki Matsuura 2-5 Marunouchi Takamatsu, Kagawa Prefecture Shikoku Electric Power Co., Inc. In the company

Claims (5)

[Claims] 1. An ultrasonic flaw detector comprising a point-focusing type probe for generating and receiving a sound wave, and a display for displaying the relationship between the intensity of the received sound wave energy and the required reflection time in a waveform. , The probe is pressed against a solid surface,
In an ultrasonic flaw detection method in which a sound wave is obliquely transmitted toward a back surface including a defect, and the scanning direction of the probe is a direction along the incident direction of the sound wave, the ultrasonic wave is received by the probe, and the display is When the magnitude of the sound wave energy is maximized in the waveform displayed in Fig. 3, and the proportion of the sound wave energy in the waveform is set in consideration of the result of the test conducted in advance with respect to the maximum time. The ultrasonic flaw detection method is characterized in that the time dimension of the defect is calculated, and the dimension of the defect is calculated based on the time interval and the transmission angle of the sound wave from the probe. 2. The ultrasonic flaw detection method according to claim 1, wherein the ratio is set within a range of 0.05 to 0.3. 3. When the waveform displayed on the display has a set ratio time at a plurality of positions, a ratio time on a position side separated from the maximum time position is selected and The ultrasonic flaw detection method according to claim 1 or 2, wherein the time interval is obtained between the two. 4. When the waveform displayed on the display device has a set ratio time at a plurality of positions, a ratio time on a position side apart from the maximum time position is selected to set the ratio time. Between the maximum time position and the second time interval between the maximum time position
Is calculated, and the first dimension and the second dimension of the defect are calculated based on each of the first and second time intervals, and the distance between the probe and the defect end is determined by the probe. If the distance between the probe and the defect end is outside the effective focusing range of the probe, the second dimension is set as the dimension of the defect. The ultrasonic flaw detection method according to claim 1 or 2, wherein the dimension is the dimension of the defect. 5. The focusing range of the point-focusing type probe is within a range from 1 mm smaller than the thickness of the measuring object to twice the thickness of the measuring object or 5 mm larger than the thickness of the measuring object. 5. The ultrasonic flaw detection method according to claim 1, wherein the point-focusing type probe has a beam width of 2.5 mm or less.