JPS6315549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection method and an ultrasonic probe.

Ultrasonic testing is a non-destructive method for detecting internal defects in steel materials. In this method, a dielectric material such as crystal is sandwiched between a pair of electrodes, and a pulse voltage is applied to the electrodes to generate vibrations specific to the dielectric material, and these vibrations are propagated to the material being inspected to produce reflected waves from inside the defect. Flaw detection is performed by detecting. When detecting defects in a near-field sound field using a so-called vertical probe that propagates ultrasonic waves perpendicular to the detection surface of the test material and measures the reflected waves, the A complex sound field is formed due to the interference of sound waves, and along with this, the reflected waves due to defects (hereinafter referred to as flaw echoes) also become complex, and instead of only one flaw, there are now two or three, as if there were multiple flaws. There is a risk that misleading measurement results may be obtained, or the height of the flaw echo, that is, the flaw evaluation, may be misjudged, which significantly impairs detection accuracy.

For this reason, in the ultrasonic flaw detection method, the shape of the electrode of the vibrator, the structure of the vibrator, the back damper member,
Attempts have been made to simplify the sound field by making various improvements to the form, etc., and eliminating the interference fringes as much as possible. For example, a so-called chrysanthemum-shaped electrode vibrator was proposed, in which the electrode shape was formed into the shape of eight petals, and although such a vibrator was highly expected to have excellent performance at the prototype stage, the shape of the electrode was Due to its complexity, there were problems with reproducibility in terms of manufacturing technology, and it was never put into practical use. For this reason, at present, despite the above-mentioned interference problem, probes with circular planar electrodes are still used as practical devices.

The present invention has been made to solve the above-mentioned problem by a completely new attempt, and involves forming a perforated plate mask in which a large number of holes of a predetermined diameter are bored in a plate material made of the same material as the test material, and An ultrasonic flaw detection method in which a plate mask is interposed between the test material and the contact surface of an ultrasonic transducer, and the perforated plate mask is placed in close contact with the contact surface of the probe. The present invention provides an ultrasonic probe.

The present invention will be described in detail below based on one embodiment of the accompanying drawings.

In FIG. 1, a perforated plate mask 1 is made of a member made of the same material as the industrial material to be inspected, such as various types of steel, alloy steel, etc., and has through holes 2 of a predetermined size and diameter d arranged at a predetermined pitch l in all directions. A large number of holes are drilled evenly. However, the homogeneous member here is not limited to a material of the same standard, but may be any material that has an acoustically equivalent effect to the material to be tested. for example,
If the material to be tested is a steel material made of SUS304,
The material for the mask may be made of ordinary carbon steel, austenitic steel, or the like, in addition to SUS304, which is of the same quality as this. In addition, the thickness of the perforated plate mask is preferably 1 mm or less, preferably 0.2 mm or less.
~0.7mm is suitable. Furthermore, the diameter d of the holes 2 formed in the perforated plate mask 1 is set to be approximately the same length as the wavelength of the ultrasonic wave determined by the material of the material to be examined, etc., and a large number of such holes 2 are formed. and,
The arrangement of each hole is at a pitch l (=2d) that is 2 to 5 times the hole diameter.
(Here, the pitch l refers to the distance between the centers of adjacent holes.) It is appropriate to arrange the holes evenly in the vertical and horizontal directions. For example, if a steel material with a flaw detection depth of 20 mm is to be tested and a vibrator with an ultrasonic frequency of 5 MHz is used, the wavelength of the ultrasonic wave in the steel material is approximately
It becomes 1.2mm. Therefore, it is appropriate for the perforated plate mask 1 used for flaw detection of such materials to be inspected to be one in which holes of about 1.0 mm in diameter are evenly bored vertically and horizontally at a pitch of about 2 mm. In this way, the optimum perforated plate mask 1 is formed according to the wavelength of the ultrasonic wave of the transducer used.

The porous plate mask 1 formed in this way is
As shown in the figure, the ultrasonic vibrator 5 is placed in close contact with the specimen 3 via machine oil 4, and the contact surface 5a of the ultrasonic vibrator 5 is brought into close contact with the porous plate mask 1.
Then, this ultrasonic vibrator 5 is moved while being in close contact with the porous plate mask 2 to detect defects.
In this case, the propagation of the ultrasonic waves can be improved by filling the holes 2 of the porous plate mask 1 with a lubricant such as wax or grease, if necessary.

FIG. 3 is a diagram showing an embodiment of the ultrasonic probe of the present invention, in which a transducer 5 is installed in a casing 6,
A perforated plate mask 1 is disposed in close contact with the contact surface 5a. The protection plate 7 is for protecting the perforated plate mask 1, and can be detachably attached to the casing 6, and is designed to protect the perforated plate mask 1 from the contact surface 5.
Fix it tightly to a. This protective plate 7 is made of a durable hard metal thin plate. Of course, vibrator 5
The porous plate mask 1 may be removably attached to the contact surface 5a, or may be fixed. In this way, the ultrasonic probe 8 is constructed.

Next, an example will be shown in which the ultrasonic flaw detection method and ultrasonic probe of the present invention are used to detect defects in a near-field sound field. Scanning pattern test piece 1 used for defect detection
0 is material SM42, size 100 as shown in Figure 4
As shown in the figure, a 4φ flat-bottomed drill hole 10c was drilled from the bottom surface 10b at a depth of 25 mm from the top surface 10a in a board measuring 100.times.30 mm, and this hole was used as a suspected defect. Then, the position 0 directly above the defect is set as zero, and the probe is scanned left and right (in the directions of arrows A and A') without changing the sensitivity. Note that the measurement sensitivity is set so that the maximum echo is 80%. The results of flaw detection on such a test piece using a conventional circular plane electrode type probe are as shown in the graph shown in FIG.
FIG. 6 is a graph showing the flaw detection results when the perforated plate mask 1 of the present invention was interposed between the test material and the conventional probe. Further, the flaw detection results when using the ultrasonic probe of the present invention equipped with the perforated plate mask 1 also show a graph similar to that shown in FIG. 6.
As is clear from the graphs in FIGS. 5 and 6, according to the flaw detection method and probe of the present invention, there is only one peak echo, and the peak echo is located directly below the probe. On the other hand, in the case of conventional flaw detection methods and probes, there are clearly multiple peak echoes (2
(one) exists and is identified as if two defects were present side by side. Moreover, these positions are apparently located several millimeters away from the actual position of the defect.

FIG. 7 shows the hole diameter d and pitch l of the perforated plate mask 1 from d=1 mm and l=2 mm in the case of FIG.
2 is a graph showing the shape of an echo when the distance is changed to =2 mm and l =3 mm. As is clear from the graphs in FIGS. 6 and 7, good results are obtained when the diameter d of the holes formed in the perforated plate mask 1 is close to the wavelength of the ultrasonic waves used. The pore diameter is preferably set to the wavelength of the ultrasonic wave used or a value close to this. Further, as mentioned above, the thickness of the perforated plate mask 1 is desirably 1 mm or less, preferably about 0.2 to 0.7 mm from the viewpoint of interference effects, workability, durability, etc.

As explained above, according to the present invention, although it is an extremely simple means of inserting a perforated plate mask between the test material and the contact surface of the vibrator, this perforated plate mask is a kind of mechanical filter. As a result, it can significantly reduce the sonic interference that degrades inspection accuracy in ultrasonic flaw detection.
This has the excellent effect of greatly improving inspection accuracy and fully utilizing the inspection performance inherent in ultrasonic flaw detection.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the ultrasonic flaw detection method according to the present invention and a perforated plate mask used in an ultrasonic probe, and Fig. 2 is a plan view showing an embodiment of the ultrasonic flaw detection method according to the present invention. 3 is a sectional view showing an embodiment of an ultrasonic probe according to the present invention, and FIG. 4 is a diagram showing an embodiment of a test piece for detecting defects in a near-field sound field.
FIG. 5 is a graph showing an example of a defect detection signal in a near-field sound field by a conventional ultrasonic probe, and FIGS. It is a graph which shows an example of a defect detection signal in a distance sound field. 1... Porous plate mask, 2... Hole, 3... Test material, 4... Machine oil, 5... Ultrasonic vibrator, 6...
...Casing, 7...Protective cover, 10...Test piece.

Claims (1)

[Claims] 1. A perforated plate mask in which through holes having a diameter approximately corresponding to the wavelength of the ultrasonic waves to be used are formed two-dimensionally at a predetermined pitch in a thin plate made of the same material as the material to be tested is tested. An ultrasonic flaw detection method characterized by placing the material in close contact with the contact surface of an ultrasonic vibrator. 2. A perforated plate mask in which through-holes with a diameter approximately corresponding to the wavelength of the ultrasonic waves to be used are bored two-dimensionally at a predetermined pitch in a thin plate made of the same material as the material to be tested is placed on the contact surface of the ultrasonic transducer. An ultrasonic probe characterized by being disposed in close contact with.