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DESCRIPTION JPS61248700

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DESCRIPTION JPS61248700
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe for detecting a defect generated in a solid using ultrasonic waves. [Background
of the invention] To detect a defect occurring in a part or member and obtain as detailed and
accurate information as possible about the defect such as the position and size of the defect, not
only the part or member but also the part or member In order to know the strength and the life
etc. of the device constituted by the above, it is an important matter of impossible 3-page
missing. For this reason, various ultrasonic probes for flaw detection have conventionally been
researched and provided, and provided to the market. For example, other materials with
improved transmission / reception characteristics, acoustic impedance, mechanical Q, etc. have
been used for vibrator materials in which quartz has been mainly used in the past, and the shape
of the vibrator is made circular or semicircular. The probe with improved directivity is provided,
and the shape of the probe is elongated, the incident angle of ultrasonic waves is variable, or
water is used according to the shape of the object, the roughness of the flaw detection surface,
etc. The material and shape of the ultrasonic probe, such as a technique of performing flaw
detection via a heat-resistant material so that the temperature of the subject is not transmitted to
the probe using a probe of A number of techniques have been provided, including up to the
construction and handling considerations. However, in the ultrasonic probe conventionally
provided, the thickness of the transducer as an electroacoustic transducer for converting the
electric vibration and the ultrasonic wave to each other is usually the wavelength of the
ultrasonic wave converted as described above It has become 2 of. This is for resonating the
vibrator in the thickness direction to generate an ultrasonic wave having a frequency close to the
resonance frequency to increase sensitivity and use. However, when the resonance occurs, the
vibration of the vibrator continues and does not stop, and the width of the generated ultrasonic
wave increases, the resolution decreases, and the required flaw detection can not be performed.
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Therefore, although the sensitivity decreases, it is necessary to absorb the resonance and stop
the vibration of the vibrator as quickly as possible, and a damper made of a material such as
Bakelite or epoxy resin with large attenuation of ultrasonic waves is provided on the back of the
vibrator to vibrate. Is absorbed. And in the case of a normal bare crystal probe or the like, the
degree of absorption of vibration causes vibration damping by transmission from the probe to
the subject and damping by the damper in the probe. I am balanced. The structure of a
conventional general ultrasonic probe for flaw detection will be described with reference to FIG.
9 by taking a vertical probe as an example. The figure is a cross-sectional view showing the
outline of the structure. Reference numeral 11 denotes a transducer, which is often in the form of
a rectangular or circular flat plate having a constant thickness, which is two of the wavelength of
the electroacoustically converted ultrasonic wave as described above.
The material is single crystal quartz, lithium sulfate, lithium niobate. Barium titanate-based
porcelain, zircon tita-5, lead-phosphate-based porcelain, lead niobate-based porcelain, and the
like are mainly used. The back surface of the vibrator 11 is held by the Dan f 12 so that the
vibration generated by the vibrator 11 is absorbed. The vibrator 11 and the Dan 12 are housed
in a case 13. The case 13 is usually made of metal and a plug 14 is attached to a part of the case
13. The plug 14 is electrically connected to the vibrator 11 via an electrode 15 attached to the
back of the case 11 Not connected via ultrasonic flaw detector and high frequency cable. An
electrode 16 connects the vibrator and the case 13. On the other hand, there are a wide variety
of flaw detection targets, depending on the material, shape, size, surface roughness, etc. of the
object, it is necessary to perform flaw detection with a high sensitivity probe, and conversely, the
performance of Danno 4 is enhanced to lower the sensitivity. There are some which can not be
detected unless the resolution is improved by narrowing the width of the generated ultrasonic
wave. This is based on the mutually opposing characteristics of using the high damping and high
sensitivity to keep the resonance as low as possible and the high damping to absorb the vibration
as fast as possible. There is no St or 1 --- O-- page in some. In addition, when both of these
contradictory characteristics are subjected to Fourier analysis to examine the frequency
component, it becomes a mountain-shaped graph including frequency components before and
after the center frequency. And in the case where the resonance state is sustained and the case
where the vibration is absorbed, the mountain shape of the graph is narrow in the former and
narrow in the shape of a narrow curve of the frequency band where the top is sharp, and the
latter is wide. And it becomes the shape of a broad curve of the frequency band where the top is
gentle. For example, when the frequency band of a narrow band high sensitivity probe with a
center frequency of 5 MT (z narrow band high sensitivity and the same (5 MHz wide band low
sensitivity probe) commercially available is investigated by Fourier analysis, the 1? figure is
obtained. It was done. That is, the left side of the figure is the former, and the right side is the
latter. The horizontal axis of the figure is the frequency (in MHz), the vertical axis is the output
(sensitivity), and the unit is Delto (b). From this figure, increasing the performance of the damper
and making it high damping broadens the frequency and frequency band of the ultrasonic wave
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and improves the resolution, but at the same time absorbs the vibration so as to quickly stop the
vibration, so the sensitivity decreases. I know what to do. Thus, sensitivity and resolution are
opposite characteristics. If this is put together in a table, it will be 7 pages. For example, when the
flaw detection surface is rough, the influence of the water immersion method is small, but when
the size of the object is large and the weight is large, direct contact method flaw is used, and in
this case, the contact medium is devised However, it is better to use a probe that emphasizes
sensitivity because the sensitivity necessarily decreases. Also, if the subject has a curvature, there
is a decrease in sensitivity due to the curvature of the flaw detection surface. Focus on sensitivity.
On the other hand, cast iron products with coarse crystal structure, artificial graphite, glass fiber
reinforced plastic (abbreviated as FRP) materials, but metal and non-metal materials such as
welds of metal, plastic and austenitic stainless steel, etc. In the case of materials that are difficult
to transmit ultrasonic energy in a solid, and so-called high attenuation materials that have large
attenuation due to the scattering of ultrasonic waves, the duration of vibration is made as short
as possible, and a probe focusing on resolution in a wide frequency band If it is not used, the
ultrasonic permeability is bad and flaws can not be made. As described above, the conventional
ultrasonic probe can not have the characteristics of high sensitivity and high resolution, and the
probe can be used properly depending on the object to be detected, and one kind of search It was
impossible to use the feeler for various purposes in a multipurpose manner. [Object of the
Invention] The present invention solves the problems which could not be achieved by the prior
art, and by combining both high sensitivity and high resolution characteristics, minute defects of
material with high attenuation of ultrasonic waves. It is an object of the present invention to
provide an ultrasonic probe that can be accurately flawed. [Summary of the Invention] The
present invention relates to an ultrasonic probe in which a vibrator whose back surface is held by
a sheet or material and which converts electric vibration and ultrasonic waves to each other is
accommodated in a case together with a damper material. The vibrator is shaped so as to be
sequentially changed to a thickness that is an integral multiple of 2 of the wavelength of the
converted supersonic 9-page wave, and simultaneously output the frequency component of each
changed thickness It is possible to simultaneously detect both a wide band and a high sensitivity
characteristic so that even a minute defect of the high damping material can be accurately
detected. DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present
invention will be described with reference to FIGS. 1 to 3 for a vertical probe as in the prior art.
FIG. 1 is a cross-sectional view showing a schematic structure thereof, and FIG. 2 is a view taken
along the line II--II of FIG. Reference numeral 1 denotes a vibrator, the thickness of which is
sequentially changed to a thickness different from an integral multiple of the two wavelengths
described in FIG. 9 in which the back surface is stepped, and the back surface is bakelite
Alternatively, it is held by a damper 2 made of a material such as epoxy resin. The vibrator 1 and
the damper 2 are housed in a metal case 3, and the plug 4 attached to one end of the case 3 and
the vibrator 1 are electrodes attached to the back of the vibrator 1. It is electrically connected
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through 5 and is -10-. The vibrator 1 and the case 3 are electrically connected via the electrode
6. The material of the vibrator 1 is a single crystal material or a porcelain material, and the same
as in the explanation in FIG. 9 is used.
When an electric pulse is applied to the vibrator 1 from an ultrasonic flaw detector (not shown)
via a plug, the vibrator 1 resonates, but the manner of the resonance differs depending on the
step-like different thickness. A resonance state occurs, and ultrasonic waves of frequency
components corresponding to the resonance are simultaneously generated. For example,
assuming that the frequency of the ultrasonic wave generated from the thinnest portion in FIG. 2
is 8 MHz, the portion with 6 has a frequency of 6 MHz, the portion with a square has 4 MHz, and
the portion with 2 has 2 MHz. It becomes like. FIG. 3 shows the results of measurement of the
relationship between the distribution of the generated frequency and the output (4 degrees)
using the bottom surface of a 20 tm thick quartz as a reflection surface, using the probe of this
embodiment. The horizontal axis is the frequency (in MHz), the vertical axis is the output
(sensitivity), and the unit is gel (V). In the figure, the frequency band corresponds to the
frequency band for each thickness of the vibrator 1, 2 MHz, 4 MHz, 6 MHz and 8 MHz in the
form of an overlapping broadband, while the sensitivity is Dan-11. High sensitivity is maintained
as it is due to low damping that does not improve the performance of the page and mother. As
described above, the ultrasonic probe in the present embodiment has high sensitivity and high
sensitivity by forming the back surface of the transducer 1 in a step-like shape and sequentially
changing the thickness to an integer multiple of two wavelengths. It is possible to have two
contradictory characteristics of wide band. Next, a second embodiment of the present invention
will be described with reference to FIGS. 4 and 5 taking a vertical probe as an example. FIG. 4 is a
cross-sectional view showing a schematic structure. The same reference numerals as in FIG. 1
denote the same components in the figure. The vibrator 7 tilts the back surface thereof so that
the slope thereof changes sequentially to a thickness that is an integral multiple of two
wavelengths as described in the first embodiment, and the entire shape of the vibrator 7 is
wedged. It has become. That is, the thickness of the vibrator 7 which is stepwisely changed
intermittently as shown in FIG. 1 is continuously changed. This shape corresponds to a state in
which a plurality of transducers 7 having a thickness that is an integral multiple of the two
wavelengths are continuously disposed. FIG. 5 is a graph showing the results of measurement of
the relationship between the distribution of the frequency generated in the same reflector as in
the first embodiment and the output (sensitivity) using the probe of this embodiment. In the
figure, the frequency band is a continuous wide band from about 2 MHz to 9 MHz, and the
sensitivity is the same as the first embodiment, and since the damper performance remains low
damping, high sensitivity is maintained as it is. . However, unlike the first embodiment, the
sensitivity is substantially constant in the entire frequency band of 2 to 9 MHz, and the
unevenness as shown in FIG. 3 occurs due to the stepwise changing thickness of the vibrator 1.
Because the part is wrong, the sensitivity is so stable.
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Next, a third embodiment of the present invention will be described with reference to FIGS. The
present embodiment also relates to a vertical probe, and FIG. 6 is a cross-sectional view showing
a schematic structure thereof, and FIG. 7 is a view taken along the line II--II in FIG. In the
drawings, the same reference numerals as in FIGS. 1 and 4 indicate the same. The vibrator in the
first and second embodiments is different from that in the integral type, the vibrator in the
present embodiment has a plurality of vibrators 10a. The vibrators 10 b, 10 c and 10 d are
arranged concentrically in the form of concentric circles. The vibrator 10m is a circular vibrator
provided at the center of a concentric circle, and a ring-shaped imaging moving member 10b is
provided around the circumference, a ring-shaped vibrator 10a is provided around the
circumference, and a ring-shaped vibration is provided around the vibrator 10c A child 10d is
provided. Each of these vibrators has the same plane area, and the thickness thereof is changed
to a different thickness which is an integral multiple of two wavelengths as in the case of the
above embodiment, and the back surface of each vibrator is sequentially It has a step-like shape.
It has a so-called Fresnel ring shape. The back surfaces of the vibrators 10a, 10b, 10e and 10d
are held by a damper as in the embodiment described above, and are housed together with the
damper 8 in a cylindrical case 9. Electrodes 5a, 5b, 5e and 5d are attached to the back of each
vibrator, respectively, and all are electrically connected to the plug 4 and electrodes 6m and 6b.
It is connected to case 9 through 6e and 6d. The material of the vibrator is the same as that
described above. When an electric pulse is sent to each of the vibrators 10m, 10b, 10a and 10d,
these vibrators vibrate at the same time, and as in the case of the first embodiment, 1--! 4-One
page different resonance state, an ultrasonic wave of frequency component corresponding to the
resonance is generated at the same time. For example, assuming that the frequency component
generated from the vibrator 10d is 8 MHz, the vibrator 10a is 6 MHz, the vibrator 10b is 4 MHz,
and the vibrator 10m is 2 MHz. The result of having measured the relationship between the
frequency which generate | occur | produces with the same reflector as the said Example, and an
output (sensitivity) in FIG. 8 using the probe of a present Example is shown. The figure shows the
frequency distribution and output (sensitivity) of и and turns similar to Fig. 3. The frequency band
is wide band, and the sensitivity is maintained high as it is, and it has both opposing
characteristics. It is understood that The above embodiment has been described by taking the
vertical probe as an example, but the present invention is not limited to the above embodiment,
and it goes without saying that the present invention can be applied to oblique angle probes and
other probes. .
[Effects of the Invention] As described above, according to the present invention, the vibrator is
formed into a shape in which the thickness is sequentially changed to an integral multiple of 2 of
the wavelength of the ultrasonic wave generated by electroacoustic conversion. Since the
frequency component corresponding to the page size is output, the ultrasonic probe of the
present invention can have both high-sensitivity and wide-band opposite characteristics, and has
poor ultrasonic wave permeability. It has the remarkable effect that the minute defects of the
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material and the high damping material can be accurately detected in the same manner as the
conventional flaw detection method.
[0002]
Brief description of the drawings
[0003]
1 to 3 show a first embodiment of the present invention, and FIG. 1 is a cross sectional view
showing a schematic structure thereof, FIG. 2 is a view as seen from the arrow of FIG. 1, and FIG.
It is a graph which shows the relationship between frequency distribution and output (sensitivity)
in, when the probe of an Example is used.
FIGS. 4 and 5 show a second embodiment of the present invention, and FIG. 4 is a cross sectional
view showing a schematic structure thereof, and FIG. 5 shows frequency distribution and output
(sensitivity) when this embodiment is used. Is a graph showing the relationship of FIGS. 6 to 8
show a third embodiment of the present invention, and FIG. 6 is a cross sectional view showing a
schematic structure thereof, FIG. 7 is a view as seen from the arrow of FIG. 6, FIG. It is a graph
which shows the relationship between the frequency distribution at the time of using an
Example, and an output (sensitivity). FIG. 9 is a schematic structural view showing an example of
a conventional ordinary ultrasonic probe, and FIG. 10 is a narrow band high sensitivity probe and
a wide band low sensitivity probe of the structure of FIG. It is a graph which shows the
relationship between the frequency distribution in a case, and an output (sensitivity). 1, 7. 10a,
10b, 10c, 10d, 11-vibrator, 2.8.12 иии Damper, 3, 9.13 и и и Case, 4 ░ 14 и и и Plugging, 5.5a, 5b, 5c,
5d, 15 = electrode.
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