JPH0240976B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention improves accuracy in vertical crack-like defects that are internal to a plate-shaped object to be inspected or open to the surface of the object to be inspected, that is, the bottom surface. Moreover, it relates to an ultrasonic flaw detection method and its probe for high-speed detection.

[Background of the invention]

Vertical crack defects are defined as cracks that propagate in a direction perpendicular to the surface of the plate, that is, vertical cracks, and similar defects. They tend to have a high reflectance to sound waves, and so-called oblique transducers, surface wave transducers, or plate wave transducers are now being used to detect such defects. For the same reason, even if the angle to the surface is the same, depending on the direction of the defect, if ultrasonic waves are transmitted and received from a direction close to perpendicular to the defect surface, a high level of echo will be received. When ultrasonic waves are transmitted and received from parallel directions, almost no echoes are detected.
That is, in order to detect a vertical crack-like defect, it is necessary to perform pendulum scanning to perform ultrasonic flaw detection from various directions around the defective site. However, since pendulum scanning may reduce the flaw detection speed and become an obstacle, automatic flaw detection uses a so-called X-shaped transducer (oblique) as shown in Fig.
The TTRR method is now being used to detect flaws in welded pipe welds.

Now, referring to FIG. 1, transducers 1 and 3 are used for transmitting ultrasonic waves, and transducers 2 and 4 are used for receiving ultrasonic waves, and are operated simultaneously. If there are no defects in the inspection area U of the weld seam 5, no received echo will be obtained, but if there is a vertical crack defect 7 parallel to the direction of the weld seam 5, a vertical crack defect 6 perpendicular to that direction, or no defect. If a directional defect exists, the received echoes are detected as defective echoes by the transducers 2 and 4.

Although the TTRR method has thus become effective in detecting flaws in welded pipe welds, it can sometimes cause problems. As shown in FIG. 2a, if the inspected area U where the defect 7 exists is away from the weld center line A-A' and the weld bead width is wide, the ultrasonic waves will be incident on each of the transducers 1 to 4. Among points 8 to 11, ultrasound incidence point 10,
11 becomes close to the weld bead, which may cause the transducers 3 and 4 to ride on the weld overlay. The transducers 1 to 4 arranged in an X-shape are mechanically fixed in mutual position so that their ultrasonic wave incident points 8 to 11 are on the circumference of the circle 12. In order to prevent the transducers 1 to 4 from riding on the weld build-up, it is conceivable to arrange the transducers 1 to 4 at a distance of one skip distance from the inspection site U. When placed one skip distance apart, the transducers 1 to 4 are placed so that their ultrasonic incidence points lie on the circumference of the circle 13. In FIG. 2a, the new placement positions of the transducers 3 and 4 are indicated by dotted lines, and the transducers 1 and 2 are also placed in the same manner.

FIG. 2b shows the front view of FIG. 2a as a plane. However, the transducers 3, 4 are shown as having been placed in a new position. The skip (reflection) point will be explained with reference to FIG. 2b. The skip point is defined as the reflection position of the ultrasonic wave on the top and bottom surfaces of the object to be inspected. Since the transducer 3 cannot actually be placed at the skip point 14, the transducer 3 is placed at the skip point 10' as a new ultrasound incidence point. The situation is exactly the same for the other transducers 1, 2, and 4.

However, if the transducers 1 to 4 are arranged so that the distance to the inspected part U of each of the transducers 1 to 4 is separated by one skip distance, the number of parts that cannot be detected due to the approach limit will be reduced. Become. However, on the other hand, the flaw detection sensitivity and its stability are significantly lowered, and the flaw detection accuracy is undeniably lowered.

[Purpose of the invention]

Therefore, an object of the present invention is to use ultrasonic waves to detect vertical crack-like defects that are internal to the body to be inspected or that are open on the surface of the body to be inspected, that is, the bottom surface, without reducing the flaw detection accuracy. The flaw detection method and its probe are provided.

[Summary of the invention]

For this purpose, in order to detect vertical crack-like defects on the inner bottom surface of the weld seam, the present invention provides an X-shape arrangement on the surface of the object to be inspected other than the weld seam so that the inspected area within the weld seam is located in the center. Ru,
Of the four oblique transducers related to the TTRR method, one or two adjacent transducers are placed on the surface of the object to be inspected at a distance of 1 skip distance from the area to be inspected. Each time the part is updated, the part to be inspected is subjected to ultrasonic flaw detection. Furthermore, the present invention provides an ultrasonic flaw detection probe by mechanically coupling the transducers arranged in this manner. Furthermore, in order to expand the flaw detection range, two ultrasonic flaw detection probes are mechanically combined and connected.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 3 to 7.

First, the ultrasonic flaw detection method according to the present invention will be explained. FIG. 3 shows a state in which three or four transducers are arranged in one group near the welded portion of the second group of welded pipes.
The transducers 15 to 18 form a first group, and the remaining transducers 19 to 22 form a second group. It is designed to cover. In this case, the transducers 17, 18 in the first group and the transducers 21, 22 in the second group are placed at positions separated by one skip distance from their original positions.

To perform ultrasonic flaw detection by the first and second groups, first, the ultrasonic flaw detection is performed by the first group as follows.

That is, first, the transducer 15 performs an ultrasonic transmission/reception operation. After this, the transducers 16 to 18 perform ultrasonic transmission and reception operations in sequence.
After ultrasonic flaw detection using the probe method is performed, ultrasonic flaw detection using the two-probe method is performed next. As the ultrasonic waves from the transducer 15 are received by the transducer 16, the operation of transmitting and receiving ultrasonic waves is performed sequentially between adjacent transducers. Once the ultrasonic flaw detection by this two-probe method is completed, the ultrasonic flaw detection by the second group is carried out in the same manner as the first group, and the ultrasonic flaw detection by the second group is completed. This marks the end of one cycle of flaw detection operation. Note that the number of transducers in the first and second groups is not necessarily 4, as described later.
You don't need more, three is enough. Although the transducers 18 and 22 shown in dotted lines are shown to be unnecessary, it is also possible to make the others unnecessary. Further, the distance X indicates the deviation between the first and second groups in the scanning direction. Furthermore, in this example, it is assumed that the width of the weld seam 5 is relatively large, so there are two groups of transducers, but if the width is small, the weld seam of the transducer Since flaw detection can be carried out without causing any run-up on the surface of the surface of the surface, only one group is required.

FIG. 4 shows a schematic configuration of an ultrasonic flaw detection apparatus according to the present invention. Although the group arrangement of the transducers is shown in FIG. 4 for convenience, they are actually arranged as shown in FIG. 3.

According to this, transducers 15, 16, 18 in the first group are connected to pulsers 23-25 and preamplifiers 26-28, and transducers 19, 20, 22 in the second group are connected to pulsers 29-31 and preamplifiers. 32 to 34 are connected as shown in the figure. In this case, the controller 48 determines which of the transducers 15, 16, 18-20, 22 the high voltage pulse is applied to. The controller 48 triggers the trigger circuit 36 during ultrasonic transmission, and the trigger output is sent to the pulser 2 via the (de)multiplexer 35 under the control of the controller 48.
Among the voltage pulses 3 to 25 and 29 to 31, the high voltage pulse is applied to the one that should generate the high voltage pulse. In addition, transducer 15, 16, 18
20 and 22 are amplified by preamplifiers 26 to 28 and 32 to 34, but which reception output is selectively taken in depends on the controller 48. The multiplexer 37 is configured to selectively output one of the received outputs under the control of the controller 48 and then input it into the receiver 38 . Therefore, while the controller 48 emits ultrasonic waves from the target transducer, it is also possible to capture the reception output of the target transducer.

By controlling the trigger circuit 36 and the multiplexers 35 and 37 in this way, various ultrasonic transmission/reception operations can be performed, but here, when the ultrasonic waves transmitted from the transducer 22 are received by the transducer 19, The operation of the device will be explained below using an example.

That is, the controller 48 is configured so that the trigger circuit 36 first generates a trigger signal that determines the ultrasonic wave generation timing. Prior to this occurrence, the multiplexer 35 is controlled by the controller 48 to output the output of the trigger circuit 36 to the pulser 31, so the trigger signal is converted into a high voltage pulse and then applied to the transducer 22. It will be a place where you can be taught. This allows transducer 2
Ultrasonic waves are emitted from 2 toward the inspection site 50, but if any defect exists there, the ultrasonic waves will be reflected by the defect. If the direction of the defect is perpendicular to the welding line direction, the reflected ultrasonic wave from the defect can be received by the transducer 19, and the reception output is received by the receiver 38 via the preamplifier 33 and multiplexer 37. This is where the waves are detected. The detected reception output is subjected to processing after noise components are removed by a gate circuit 39 whose gate is opened only for a certain period of time after a certain period of time has elapsed from the time of ultrasound transmission.

In processing the received output, first, the beam path calculator 41 precisely measures the time from the trigger signal generation point to the reflected ultrasound reception point, and calculates the ultrasonic propagation distance (beam path) using the known sound speed. It's becoming like that. The defect location calculator 42 also includes transducers 15, 16, 18-20,
Transducer position information from the scan control device 40 that performs automatic scanning and position detection of 22, and the input/output direction of ultrasonic waves determined by the selected transducer (transducer 22, 19 in this case). The position of the defect is calculated based on the entrance and exit points and the beam path length from the beam path calculator 41. On the other hand, the amplitude detector 4
3, the peak voltage of the received output is detected and held, but the discriminator 44 discriminates whether or not the peak voltage is above a preset threshold. The peak value is output only when the The memory 45 stores the peak voltage from the discriminator 44 and the defect position information from the defect position calculator 42 for each transmitting/receiving transducer only when the peak voltage is below a threshold value. Defect identification circuit 46
Then, for each flaw detection operation, the information obtained is combined with previous information, especially information obtained from the same transducer combination, and with other transducer combinations from the same or previous cycle of flaw detection. By comparing the received information with the obtained information, it is possible to identify whether the received output is related to a defect or the shape of the object to be inspected.
If the defect is related to a defect, the defect is recorded and displayed on the recording display 47 based on the defect information. Incidentally, reference numeral 49 is a part to be inspected for the first group.

As can be seen from the flaw detection operations described above, when a transducer group consists of four transducers, in addition to the transmission and reception directions of each transducer (total of four directions), the two-probe method has line symmetry. This is equivalent to flaw detection from the directions of the symmetry axes of two adjacent transducers (total of 4 directions), so various directional defects can be detected by performing flaw detection from a total of 8 directions. .

The ultrasonic flaw detection method according to the present invention has been described above. Next, the ultrasonic flaw detection probe according to the present invention will be explained. FIGS. 5 and 6 show the configuration of an example thereof. First, referring to FIG. 5, this is a device in which the transducers in the second group or the first group in FIG. 3 are mechanically coupled. Ordinary links and gimbals can be used as the mechanical coupling means 51 for fixing the transducers to each other, but as shown in the figure, each transducer is It is desirable to fix the distances Ya, Yb, and Yc (Ya=Yb) to the sound wave incidence point, and to press the contact surface of each transducer so that it follows the flaw detection surface (not shown). In addition, in this embodiment, if the type of defect is limited to one that is almost perpendicular to the bottom surface, the detection performance can be improved even if one of the transducers 21 and 19 in FIG. Since there is almost no drop in the number of transducers, one of the four transducers in each transducer group, e.g. However, of course, no inconvenience will occur even if the four transducers are configured in a similar manner. In this case, the distance Yc is 1 compared to the distances Ya and Yb.
Of course, the distance is set longer by the skip distance. In addition, in this case, with respect to the weld line center line,
Although the scanning range is not symmetrical on both sides, by using two of the devices shown in FIG. 5, it is possible to scan a symmetrical range. However, if the width of the weld seam 5 is small, using one of the devices shown in FIG. It is possible to scan a range equivalent to the width of the camera while holding the camera. Ultrasonic flaw detection is performed while moving the entire transducer as an ultrasonic flaw detection probe in the left and right direction. Once the flaw detection in that direction is completed, the flaw detection position is updated in the front and back direction and the ultrasonic flaw detection is performed in the left and right direction again. It is sufficient if the flaw detection operation is repeated.

Furthermore, the one shown in FIG. 6 is one in which two transducer groups are coupled using a mechanical coupling means 52 that fixes the distance X mentioned above.

When using two of the devices shown in Fig. 5, the above-mentioned The one shown in FIG. 6 is effective when the width is fixed, and when a plurality of types of coupling means are prepared, it becomes possible to deal with differences in plate thickness, etc. In particular, the method shown in Fig. 6 is effective when the width of the weld seam 5 is relatively large, and the flaw detection areas on the left and right of the weld center line are divided into flaw detection areas using the corresponding ultrasonic flaw detection probes. In this way, a range corresponding to the width of the weld seam 5 can be easily detected without significantly moving the entire ultrasonic flaw detection probe in the left-right direction.

Finally, a display example of the flaw detection results according to the present invention will be explained with reference to FIG. 7. As shown in FIG. 7a, the ultrasonic waves transmitted from the transducer 19
3 and received by the transducer 20, a line segment of length l corresponding to the peak value of the received output is reflected by the C scope parallel to the scanning direction, as shown in FIG. (Plane image) is now displayed. Furthermore, when the transducer 17 transmits ultrasonic waves as shown in FIG. 7c and receives reflected ultrasonic waves from the defect 54, the inclination θ from the scanning direction is as shown in FIG. 7d. With the angle set at 45 degrees, a line segment of length l corresponding to the peak value of the received output is similarly displayed on the C scope. Since the C-scope image formed as the transducer scans is represented by a collection of the line segments, the directionality of the defect can be clearly displayed.

〔Effect of the invention〕

As explained above, the present invention has the effect of quickly detecting vertical crack-like defects that are internal to the object to be inspected or open on the surface of the object to be inspected, without reducing the flaw detection accuracy. .

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the flaw detection method using the TTRR method in which transducers are arranged in an X-shape, Figures 2a and b are diagrams for explaining the defects of the flaw detection method, and Figure 3 4 is a diagram showing the arrangement of the transducer according to the present invention, FIG. 4 is a diagram showing the schematic configuration of the ultrasonic flaw detection apparatus according to the present invention,
5 and 6 are diagrams showing the configuration of an example of the ultrasonic flaw detection probe according to the present invention, and FIG. 7a
- d are diagrams for explaining display examples of flaw detection results according to the present invention. 5... Welding seam, 15-22... Transducer, 51, 52... Mechanical coupling means.

Claims (1)

[Scope of Claims] 1. An ultrasonic flaw detection method for detecting vertical crack-like defects on the inner bottom surface of a weld seam, the weld seam portion on the surface of an object to be inspected so that the inspected area within the weld seam is located in the center. In addition, one or two of the four oblique transducers related to the TTRR method, which are arranged in an X shape, are moved one skip distance away from the above-mentioned inspected area on the surface of the inspected object. An ultrasonic flaw detection method characterized by performing ultrasonic flaw detection on a part to be inspected each time the part to be inspected is updated. 2. It is an ultrasonic flaw detection probe for detecting vertical crack-like defects on the inner bottom surface of the weld seam, and includes four angle transformers related to the TTRR method, which are arranged in an X shape on the surface of the object to be inspected other than the weld seam. Mechanically coupling the four bevel transducers with one or two adjacent transducers separated from the virtual intersection center by one skip distance on the surface of the object to be inspected. An ultrasonic flaw detection probe characterized by the following configuration. 3. It is an ultrasonic flaw detection probe for detecting vertical crack-like defects on the inner bottom surface of the weld seam, and includes four angle transformers related to the TTRR method, which are arranged in an X shape on the surface of the object to be inspected other than the weld seam. Mechanically coupling the four bevel transducers with one or two adjacent transducers separated from the virtual intersection center by one skip distance on the surface of the object to be inspected. An ultrasonic flaw detection probe characterized by a structure in which two of the above are mechanically coupled with their virtual intersection centers shifted to avoid duplication of the flaw detection areas.