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JPS63139250

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DESCRIPTION JPS63139250
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electromagnetic ultrasonic transducer used for ultrasonic detection of structures and the like.
[Prior Art] A conventional longitudinal wave angle electromagnetic ultrasonic transducer
(hereinafter referred to as EMAT 5) is, for example, as shown in FIG. 6 (A) front view and (B)
bottom view, a magnet 1 and an auxiliary A magnetic field generating portion generating a
magnetic field in a direction parallel to the test surface, and a coil 3 meandering at a pitch T,
when a current of frequency f is supplied to the coil, As shown in the explanatory drawing, an
eddy current J in a direction perpendicular to the paper surface is generated, and the direction of
the eddy current is reversed at a pitch T. On the other hand, a magnetic field B in the horizontal
direction is generated by the magnet 1 and a deer F is generated due to the interaction with the
eddy current J to excite each part of the coil cage. At this time, the direction of the force F is
inverted at the pitch T, and the phases of the ultrasonic waves generated by the excitation differ
by 180 ░. For this reason, the wave fronts of the ultrasonic waves from the respective points
coincide in the following equation (1), and the combined wave front W propagates in the object
10 in the direction of the refraction angle ?. Tssin O = V / (2f) s ииии o fl) where V is the speed of
sound of ultrasonic waves in the subject 1 o. The reception is performed by the reverse
mechanism described above. However, in such a device, as apparent from the equation (1), since
the refraction angle ? and the coil pitch T are fixed, the frequency is constant), and the required
ultrasonic waves can be obtained at other frequencies. I can not. Therefore, only one frequency
can be generated efficiently in one EMAT, and if it is desired to change to another frequency to
investigate the characteristics of the defect, it is necessary to replace two or more EMATs with
different coil pitches. [Problems to be Solved by the Invention] The present invention has been
proposed in view of the above circumstances, and one EMAT can generate ultrasonic waves of a
plurality of frequencies, and accordingly, it is possible to use EM according to the characteristics
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of defects. EMA Ding not need to replace A T. [Purpose of providing a stone] [Means for solving
the problems] Therefore, the present invention is directed to a magnet generating a magnetic
field parallel or perpendicular to the surface to be detected and an h-pitch on the surface of the
magnet. An electromagnetic ultrasonic transducer consisting of three coils, each of which is
arranged in a meandering arrangement, a transmitting circuit for transmitting currents of the
same frequency at a plurality of frequencies, with a phase shift of the three coils, and the three
And a receiving circuit for receiving the received signal of each coil at a delay corresponding to
each transmission phase shift for each of the frequencies. [Operation] According to the abovedescribed configuration, it is possible to generate ultrasonic waves of a plurality of frequencies
by one E M A T T so that an EMAT can be obtained in which the EMAT does not need to be
replaced according to the characteristics of the defect. .
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG. 1 shows the
longitudinal wave angle E MAT main body, FIG. 1 (A) is a front view, FIG. 1 (B) is a bottom view,
FIG. 2 is a system diagram of the entire E MAT device, FIG. 3 is a waveform diagram of the
current flowing through the same coil, FIG. 4 is an explanatory diagram of an oblique incidence
mechanism of the same, and FIG. FIG. First, in FIG. 1 showing the longitudinal wave oblique angle
E MAT main body, a magnetic field Q generating portion is constituted by the magnet 1 and the
pair of interpoles 2 and three coils 3a, 3b. 3C respectively meander in a square wave form at a
pitch T and are disposed so as to be shifted from each other by T / 3 pitches. In FIG. 2 showing
the apparatus configuration when transmitting and receiving using this EMT, each of the
transmitting coils 5a, 3b and 3c is connected to the transmitters 4a, 4b and 4c, respectively. The
transmission controller 5 controls the generation of the repetition pulse for performing the circle
return transmission, and the oscillation frequency and phase to each of the transmitters 4a to 4C.
The receiving coils 3a, 3b and 3c having the same configuration as the transmitting coil are
connected to the amplifiers 6a and 6bs 6C, respectively, and the outputs of the amplifiers are
added by the adding circuit 8 through the delay circuits 7a, 7b and 7c, respectively. It is
displayed on the display 9. The operation when an ultrasonic wave of frequency f is incident at a
refraction angle ? in such an apparatus will be described. The transmitters 4a to 4C, as shown in
FIG. 3, generate transmission currents whose phases are different from each other at frequency f.
At this time, as shown in FIG. 4, eddy currents are generated at points d, e and f, and ultrasonic
waves are generated from this point. Each distance of dg, eh, fi becomes like following (Formula
41) using (1) Formula. dg = T-sin ? = 2,..., +, b; 5 = s' I ?5 sin ? = M conflict ... (3) ? == j-T-sin
? =-... ( Here, ? is the wavelength (= V / f 2) of the ultrasonic wave, and each length is 2/6 (60
in phase) in comparison with the adjacent one, and the phase of the transmission current shown
in FIG. Match Therefore, the phases of the wave fronts of the ultrasonic waves coincide with each
other in the direction of the angle of refraction ? to form a combined wave front, and an
ultrasonic wave of the angle of refraction ? is generated. Next, one operation when the current
of 3f is applied to the coils 3a, 3b and 3c while changing the phase by 180 and the frequency is
multiplied by six and the generated ultrasonic waves are incident at the refraction angle ? will
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be described. In this case, the relationship between the wavelength ?1 and the wavelength ? at
this time is as follows because
?: 3?, e, 5es (51) Substituting these into (2), (3) and (4) gives the following (6) to (8). -3-----f6)
dg =, ? 1 eh-? seems (7) rich = 1 ? (8) These differences are i ? 1 (180 in phase), and the
transmission current Since it matches the phase, an ultrasonic wave is generated in the direction
of the refraction angle ?. Next, the reception will be described. Since the ultrasonic signals
whose phases are shifted as described above are respectively detected reverse to transmission,
they are amplified by the amplifiers 6ae 6b and 6c, respectively, and the phase shifts are delayed
by the delay circuits 7a and 7b, In addition to using 7c, they are combined by the addition circuit
8 and displayed on the display 9. Further, if the angle of refraction ? is 90 and the velocity of
sound is a surface wave (about 2900 m / s), the same operation as a surface wave EMAT can be
performed. Furthermore, if the magnetic structure is made to generate a magnetic field in the
direction perpendicular to the surface to be measured as shown in FIG. 5, the transverse wave
EMAT can be configured and the same effect can be produced. In summary, according to the
present invention, an electromagnetic ultrasonic wave consisting of a magnet generating a
magnetic field in a direction parallel or perpendicular to the surface to be detected and six coils
meanderingly arranged on the surface of the same magnet by 73 pitches A transducer, a
transmitting circuit for transmitting currents of the same frequency at a plurality of frequencies
by shifting the phases of the six coils by a constant phase, and transmission phases of the
received signals of the six coils for each of the frequencies By providing a receiving circuit that
delays the signal according to the frequency, and can generate ultrasonic waves of a plurality of
frequencies by one E MAT, thus replacing the EMAT according to the characteristics of the defect
The present invention is extremely useful industrially because it obtains an EMAT that is not
necessary.
[0002]
Brief description of the drawings
[0003]
1 to 4 show an embodiment in which the electromagnetic ultrasonic transducer device of the
present invention is applied to a longitudinal wave angle EMAT, FIG. 1 shows the main body of
the EMAT, and FIG. A front view, the same figure (B) is a bottom view, FIG. 2 is a system diagram
of the entire EMAT apparatus, FIG. 3 is a waveform diagram of the current flowing through the
coil above, and FIG. 4 is an explanatory diagram of the oblique incidence mechanism above. Fig.
5 is a bottom view of a shear wave EMAT.
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FIG. 6 shows a conventional longitudinal wave oblique angle EMAT, FIG. 6 (A) is a front view, FIG.
6 is a bottom view, and FIG. 7 is an operation explanatory view of the same. DESCRIPTION OF
SYMBOLS 1 ... Magnet 2, 2 ... Capture, 3a, 3b, 3c ... Transmission coil, 3a, 3b ', 3c' ... Reception
carp 4a, 4b, 4c ... Transmitter, 5 ...? Transmission controller, 6a, 6b, 6C ... amplifier, 7a. 7b, 7c:
delay circuit, 8: addition circuit, 9: display. Reinforcement attorney Patent attorney Masaru
Tsukamoto Figure 1 (A) CB) Figure 2 Figure 3 Figure 4 Figure 5 Figure 6
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