JPH0225165Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] This invention relates to an ultrasonic probe used to non-destructively inspect defects existing on the surface or internal parts of steel pipes, round bars, etc. using ultrasonic waves. [Prior Art] A conventional ultrasonic probe will be explained using FIGS. 1a and 1b. FIG. 1a is a cross-sectional view of a conventional ultrasonic probe and an ultrasonic beam pattern diagram corresponding to the flaw detection distance. FIG. 1b is a diagram of a rectangular transducer used in a conventional ultrasound probe. In Fig. 1a and b, 1 is a conventional rectangular vibrator;
2 is a damper that suppresses the vibration of the rectangular vibrator 1 and absorbs unnecessary ultrasonic waves; 3 is the test material 12 of the rectangular vibrator 1;
4 is a case for storing the rectangular vibrator 1, damper 2, etc., and 5 is a matching layer provided on the opposite surface.
Ultrasonic beam pattern diagram seen at a distance of 0.3X ₀ ,
6 is an ultrasound beam pattern diagram seen at a distance of approximately 0.5X ₀ , 7 is an ultrasound beam pattern diagram seen at a distance of approximately 0.7X ₀ , 8 is an ultrasound beam pattern diagram seen at a distance of approximately X ₀ , 9 is the unevenness difference in the ultrasonic beam pattern due to phase interference observed in the near-field sound field, 10 is the effective beam width, 11 is the amount of decrease from the maximum value of the sound pressure of the ultrasound to define the effective beam width 10, 12 is the material to be tested, 13 is the shape of the electrode on the damper 2 side of the conventional rectangular vibrator 1, 14 is the shape of the electrode on the surface of the conventional rectangular vibrator 1 facing the material to be tested 12, and A is the shape of the electrode of the rectangular vibrator 1. This is the length of the long side. In an ultrasonic automatic wound contact device, it is customary to ensure that the effective beam width 10 of the ultrasonic probe is as wide as is allowable for defect detection ability, and to reduce the number of ultrasonic probes. Furthermore, even if the flaw detection distance is wide, one type of ultrasonic probe is often used. Therefore, most of them are used in the near sound field or in the region spanning from the near sound field to the far sound field. Here, the near-field sound field limit distance X ₀ is given by equation (1). X ₀ = A ₂ /4λ...(1) A = Long side dimension of the oscillator λ = Wavelength (mm) In other words, in order to ensure a wide effective beam width 10, the length A of the oscillator 1 must be increased. Yes, if the length A is increased, the near-field sound field limit distance is determined by equation (1).
X ₀ becomes longer. Furthermore, within the area of this near-field sound field, the test material 12
This is a phenomenon that occurs significantly when the shape of the reflector (defect) inside is small and it is a point reflection source. Even if the depth and distance are the same, the reception sensitivity changes depending on the location of the rectangular oscillator 1, causing unevenness 9 in the beam pattern diagram. . This unevenness difference 9
This can be as high as 6 to 8 dB in some places, so automatic flaw detection equipment that does not always know whether it will capture the maximum value is a big problem because it can overlook defects or have poor reproducibility. A typical beam pattern diagram shows pattern 5 with multimodal characteristics at a distance closer than 0.5X ₀ , pattern 6 with bimodal characteristics at 0.5X ₀ , pattern 7 with unimodal characteristics near 0.7X ₀ , and maximum at X _0. Pattern 8 with dull unimodal characteristics is shown. The cause of the unevenness 9 in the beam pattern is due to phase interference between the ultrasonic waves generated from the ends and the center of the rectangular vibrator 1. Since the electrodes 13 and 14 of the rectangular transducer 1 of a conventional ultrasound probe are located on the entire surface, the rectangular transducer 1 performs a piston movement, and the sound pressure of the ultrasound generated from the ends and the center becomes equal. Therefore, there is a drawback that phase interference is likely to occur. [Summary of the invention] This invention was made with the aim of improving such conventional drawbacks. By removing the four peripheral parts of the electrode on one side of the rectangular vibrator and making it into an octagonal shape, the difference in unevenness of the beam pattern can be reduced. The purpose of the present invention is to provide an ultrasonic probe that reduces flaw detection and achieves stable flaw detection performance. [Example of the invention] The following is an example of this invention as shown in Figures 2a and b.
The details will be explained using . FIG. 2a is a sectional view of the ultrasonic probe according to this invention and an ultrasonic beam pattern diagram corresponding to the flaw detection distance. FIG. 2b is a diagram of a rectangular vibrator used in the ultrasonic probe of this invention. In Figures 2a and b, 1 is a rectangular vibrator according to this invention in which one electrode surface has an octagonal shape, and 2
is the damper, 3 is the matching layer, 4 is the case, and 5 is approximately
Ultrasonic beam pattern diagram seen at a distance of 0.3X ₀ ,
6 is an ultrasound beam pattern diagram seen at a distance of approximately 0.5X ₀ , 7 is an ultrasound beam pattern diagram seen at a distance of approximately 0.7X ₀ , 8 is an ultrasound beam pattern diagram seen at a distance of approximately X ₀ , , 9 is the unevenness difference in the ultrasonic beam pattern due to phase interference observed in the near sound field, 10 is the effective beam width, and 11 is the specified drop from the maximum sound pressure value of the ultrasound to define the effective beam width 10. 12 is the material to be tested, 13 is the shape of the electrode on the damper 2 side of the rectangular vibrator 1 according to this invention, 14 is the shape of the electrode on the surface facing the material 12 of the rectangular vibrator 1 according to this invention, and A is the rectangle. vibrator 1
B is the length of the short side of rectangular vibrator 1,
C is the end effective electrode dimension in the length direction of the short side B of the rectangular vibrator 1. D is the cutting length of the electrode in the direction of the long side A, and θ is the cutting angle of the four circumferences of the electrode 13 of the rectangular vibrator 1. In the ultrasonic probe according to this invention, the effective beam width 10 required for flaw detection processing capacity is the rectangular transducer 1.
In order to make effective use of this dimension, it is very important to set the effective electrode dimension C to the short side B dimension of the rectangular vibrator 1 to be B/2 or more. In addition, in order to reduce the unevenness difference 9 due to phase interference between the ultrasonic beam patterns 5 and 6 in a sound field that is closer than 0.7X ₀ , the specimen 1 of the rectangular vibrator 1 is
The electrode on the surface facing 2 is a full-surface electrode, and the four circumferential parts of the electrode on the other side are the lengths of the long sides A and short sides B of the rectangular vibrator 1, and the surface facing the test material 12. Since the matching layer 3 is removed in an appropriate size depending on whether the structure has only the matching layer 3 or the structure has a wedge, the sound pressure of the ultrasonic wave generated at the end of the rectangular vibrator 1 is weakened. The influence on the ultrasonic waves generated from the central part is reduced. In addition, since the four circumferential electrodes 13 of the rectangular vibrator 1 are removed diagonally, it becomes difficult to match the phases, and as a result, the unevenness difference 9 between the ultrasonic beam patterns 5 and 6 seen at a closer distance than 0.7X ₀ . is significantly reduced, making it possible to reduce the unevenness difference to within 3 dB on average. In addition, experimentally, if the electrode shape 13 is made into an oval shape with the long side A and the short side B, the unevenness difference 9 between the ultrasonic beam patterns 5 and 6 will be extremely reduced, but the effective beam width 10 will be reduced. Therefore, in order to reduce the unevenness difference 9 in the beam pattern without significantly reducing the effective beam width 10, an octagonal electrode 13 is most effective, and the guideline for removing the electrode 13 on the four peripheries is approximately It is thought as follows, but the optimal electrode shape 13 is the long side A of the rectangular vibrator 1.
It is desirable to adjust the length ratio between the short side B and the short side B. D>A/3...(2) and 65°<θ<80°...(3) However, this is the case under the condition of A>B. That is, under the above conditions, it is preferable that the cutting line of the electrode 13 be close to the line of the ellipse represented by the long side A and the short side B. For reference, examples of beam pattern shapes 6 and unevenness differences 9 for various electrode shapes 13 are shown in Table 1.

〔Effect of the invention〕

As explained above, this idea is based on the fact that the electrodes on the surface of the rectangular vibrator facing the test material are full electrodes, and the shape of the electrodes on the other surface is made into an octagon by removing the four circumferences by appropriate dimensions. This provides an ultrasonic probe with stable flaw detection performance and high reproducibility by reducing unevenness of an ultrasonic beam pattern that occurs in a near-field sound field region.

[Brief explanation of the drawing]

Figures 1a and b are a cross-sectional view, beam pattern diagram, and rectangular transducer of a conventional ultrasonic probe, and Figure 2a,
b is a cross-sectional view, a beam pattern diagram, and a diagram of a rectangular transducer of the ultrasonic probe according to this invention. In the figure, 1 is a rectangular vibrator, 2 is a damper, and 3
is the matching layer, 4 is the case, 5, 6, 7, 8 are the ultrasonic beam patterns corresponding to the flaw detection distance, 9 is the difference in unevenness of the beam pattern in the near field, 10 is the effective beam width, and 12 is the material to be tested , 13 is the electrode surface of the rectangular vibrator facing the damper, 14 is the electrode surface of the rectangular vibrator facing the test material, A is the long side dimension of the rectangular vibrator, B is the short side dimension of the rectangular vibrator, C is the end effective electrode dimension of the short side of the rectangular vibrator, D is the electrode cutting length in the long side direction of the vibrator, and θ is the electrode cutting angle. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Scope of utility model registration request] In an ultrasonic probe equipped with a rectangular vibrator having a piezoelectric effect, the electrode shape on the surface of the rectangular vibrator facing the test material is a full-surface electrode, and the electrode shape on other surfaces is the four circumferential parts of the rectangular vibrator. An ultrasonic probe characterized by having an octagonal shape obtained by removing the ridges to appropriate dimensions.