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JPH09318606

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH09318606
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe that can be used for flaw testing of complex thin-walled welds.
[0002]
2. Description of the Related Art The prior art will be described with reference to FIGS. 3 to 8 and
10. FIG. FIG. 3 is a top view (No. 1) of a seal weld portion of a reactor pressure vessel upper lid
nozzle. FIG. 4 is a top view of a seal weld portion of a reactor pressure vessel upper lid nozzle
(Part 2). A top view (3) of the seal weld portion of the reactor pressure vessel upper lid nozzle,
FIG. 6 is a top view (4) of the seal weld portion of the reactor pressure vessel upper lid nozzle,
and FIG. FIG. 8 is an explanatory view of ultrasonic wave diffusion by the conventional probe, and
FIG. 10 is an explanatory view of a wave mode.
[0003]
During periodic inspections of nuclear power plants, ultrasonic flaw testing is performed on
welds of major equipment. One of such inspection target points is the seal weld portion of the
reactor pressure vessel upper lid nozzle.
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[0004]
FIGS. 3 and 5 show the shape of the seal weld of the reactor pressure vessel upper lid nozzle. 4
and 6 are enlarged views of them. In FIG. 4 and FIG. 6, 11 and 12 are seal welding parts.
[0005]
The thicknesses t1 and t2 of the base material of the welded portion are as thin as about 2 mm,
and the curvature radii R1 and R2 are as small as 3 mm. In the normal ultrasonic flaw detection,
the oblique angle method by the direct contact method is used, and the refraction angle is
generally 45 ° in the transverse wave.
[0006]
However, when the oblique angle method by the normal direct contact method is applied to the
inspection object having a small radius of curvature like the seal welded portion, the lens effect
of the curved surface of the object 21 as shown in FIG. Because of the significant diffusion of the
ultrasound beam 23 due to
[0007]
In order to improve this, as shown in FIG. 7, ultrasonic flaw detection by local water immersion
was applied.
In FIG. 7, reference numeral 12 denotes a seal welding portion to be inspected, and 5 denotes a
defect to be inspected. The probe 13 is fixed by a holder 15 filled with water 16 in order to
detect a defect 5.
[0008]
A lens 14 is attached to the probe 13 in order to prevent the diffusion of the ultrasonic wave
when entering the curved surface, whereby the ultrasonic beam 18 is narrowed narrowly in the
vicinity of the surface to be detected.
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[0009]
In addition, the flexible film 17 is attached to the holder in the vicinity of the test surface where
the ultrasonic waves are incident, and the flexible film 17 adheres along the curved surface.
The refraction angle .theta.2 is such that the transverse wave 45.degree. Is maintained.
[0010]
Straverse wave 45 ° means a wave whose wave mode is transverse wave and the angle of
refraction is 45 °. The "wave mode" has types as shown in FIG.
[0011]
However, when such a conventional localized water immersion method is applied, since the
shape and size of the holder become relatively large, there is a sufficient space in the periphery
as shown in FIG. Although it can be applied in some cases, there is a problem that the application
is not easy if there is an interference near the seal weld as shown in FIG. 4 and there is not
enough space for it.
[0012]
In addition, the flexible membrane is broken, water leaks, etc., and there is a problem in
durability, and it takes a long time to replace the flexible film, and there is also a problem in
maintenance.
An object of the present invention is to solve these problems, and to provide an ultrasonic probe
capable of detecting a thin-walled seal weld having a complicated shape with a small radius of
curvature, even in a narrow space.
[0013]
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[Means for Solving the Problems] (First Means) An ultrasonic probe according to the present
invention is a direct contact type probe, which has (A) a vibrator, a shoe, a wedge, and a holder.
(B) the holder holds the wedge, (C) the vibrator is adhered to the wedge for generating a plate
wave, and (D) the wedge has a shoe shaped to conform to the contact surface. (E) The angle i of
the wedge is equal to the angle of incidence i to the object, and is an angle at which a plate wave
is generated. (Second means) In the ultrasonic probe according to the present invention, in the
first means (A), the shape of the shoe (2) is three-dimensionally examined in order to efficiently
generate a plate wave. It is characterized in that it is shaped to conform to the shape of the
surface, and the material of (B) the shoe (2) is the same as the material of the wedge material.
[0014]
Therefore, it works as follows. An object to be measured is a thin portion of the seal welded
portion, but when the wall thickness becomes thin and the refracted waves interfere with each
other in the subject, a plate wave is generated.
[0015]
The ultrasonic probe according to the present invention is in a direct contact type, and the shape
of the shoe is added so as to follow the contact surface, and the angle of the transducer is
arranged so as to generate a plate wave. Plate waves are generated on the curved surface.
Therefore, a defect can be detected by this plate wave.
[0016]
DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The first embodiment of
the present invention will be described based on FIGS. 1, 2 and 9. FIG. FIG. 1 is a longitudinal
sectional view of an ultrasonic probe according to a first embodiment of the present invention,
and FIG. 2 is a top view of the ultrasonic probe according to the first embodiment of the present
invention, 9 is a diagram showing the relationship between the angle i of the acrylic wedge, the
mode of the plate wave, the plate thickness, and the flaw detection frequency.
[0017]
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The term "plate wave" refers to a wave generated by a thin plate in which the wave mode is a
plate wave. There are types shown in (d) or (e) of FIG. In FIG. 1, the vibrator 1 is bonded to a
wedge 3 for generating a plate wave.
[0018]
To the wedge 3 is added a shoe 2 shaped to follow the contact surface. The angle i of the wedge
is equal to the angle of incidence i on the object and is the angle at which the plate wave is
generated.
[0019]
The angle i of the wedge is determined by the equation (1) from the velocity of sound vw of the
wedge and the velocity of plate wave v of the object. sin (i) = (vw / v) (1) Here, "the sound
velocity vw of the wedge material" means the velocity at which the sound propagates in the
wedge material, and "plate wave velocity v" means the plate wave Speed of propagation of
[0020]
For example, when using acrylic as the wedge material, the sound velocity of the wedge material
is vw = 2730 m / sec, and the plate wave velocity v is determined by the plate wave mode, plate
thickness, flaw detection frequency and can be calculated theoretically .
[0021]
FIG. 9 shows the relationship, for example, mode of plate wave = S4 mode flaw detection
frequency = 5 MHz (= 5 Mc) incident angle to acrylic wedge i = approximately 20 °
[0022]
It should be noted that the S4 mode has a feature that the attenuation is small even in water,
since there are many longitudinal wave components.
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As shown in FIG. 2, the shoe 2 has a shape three-dimensionally following the shape of the test
surface in order to generate a plate wave efficiently.
[0023]
The material of the shoe 2 is the same as the material of the wedge material.
In a probe of such a shape, the longitudinal wave transmitted from the vibrator 1 is efficiently
converted to a plate wave (in the above example, the S4 mode) when it is refracted in the subject.
[0024]
By this plate wave, it is possible to easily detect a defect of a thin plate object having a
complicated shape. Moreover, since it is the structure as mentioned above, the shape of the
holder 4 can also be made small and it becomes applicable also in a narrow space like FIG.
[0025]
Since the present invention is configured as described above, the following effects can be
obtained. (1) According to the present invention, in the direct contact probe, a shoe that follows
the contact surface is added, and the wedge and the vibrator are disposed so that the incident
angle is an angle that generates a plate wave. As a result, it is possible to obtain (2) an ultrasonic
probe capable of detecting a thin-walled seal weld of a complicated shape having a small radius
of curvature. (3) Because of the above-described structure, the shape of the holder 4 can be
reduced.
[0026]
Brief description of the drawings
[0027]
1 is a cross-sectional view of an ultrasound probe according to a first embodiment of the present
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invention.
[0028]
2 is a top view of the ultrasound probe according to the first embodiment of the present
invention.
[0029]
[Fig. 3] A top view of the seal weld portion of the reactor pressure vessel upper lid nozzle (Part
1).
[0030]
4 is a top view (part 2) of the seal weld of the reactor pressure vessel top lid nozzle.
[0031]
5 is a top view of the seal weld portion of the reactor pressure vessel upper lid nozzle (Part 3).
[0032]
6 is a top view (No. 4) of the seal weld portion of the reactor pressure vessel upper lid nozzle.
[0033]
FIG. 7 is a cross-sectional view of a conventional localized immersion probe.
[0034]
Explanatory drawing of the spreading ¦ diffusion of the ultrasonic wave by the conventional
probe.
[0035]
9 is a diagram showing the relationship between the angle i of the acrylic wedge, the mode of the
plate wave, the plate thickness, and the flaw detection frequency.
[0036]
10 is an explanatory view of a wave mode.
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[0037]
Explanation of sign
[0038]
DESCRIPTION OF SYMBOLS 1 ... Vibrator 2 ... Shoe 3 ... Wedge 4 ... Holder 5 ... Defect 6 ... Wiring
11 ... Seal welding part 12 ... Seal welding part 13 ... Probe 14 ... Lens 15 ... Holder 16 ... Water 17
... Film 18 ... Ultrasonic wave Beam 21 ... object 22 ... probe 23 ... ultrasonic beam i ... incident
angle θ2 ... refraction angle
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