JPS6214057A - Electromagnetic ultrasonic transducer - Google Patents

Abstract

PURPOSE:To enable a highly sensitive flaw detection, by supplying a high frequency power to a plurality of branch conductors, which are arranged in the direction orthogonal to the magnetization of a permanent magnet on the side in the magnetizing direction thereof through an electric insulation layer, by way of a time delay element to judge a defect point in material to be inspected properly by an ultrasonic echo. CONSTITUTION:An electromagnetic ultrasonic transducer B is made up of a permanent magnet 1 and a conducting strip 14 for formation of a high frequency current path fastened on one side thereof through a thin electrically insulating material 2. The strip 14 is formed in a ladder in which a plurality of branch conductors 14a-14n are arranged at a fixed interval in the direction orthogonal to the magnetization of the permanent magnet 1 and one end thereof is respectively connected to time delay elements 15a-15n while the other end thereof is separately to a common ground terminal 21. When a flaw detection test is carried out for a material 4 to be inspected, the time delay elements 15a-15n are connected to a output terminal of a high frequency power source and a signal transmitting/receiving unit 17 separately. This allows the transmission of unidirectional ultrasonic beam thereby assuring accurate judgement on a defect point in the material to be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electromagnetic ultrasonic transducer capable of transmitting and receiving unidirectional ultrasonic waves.

(Technical Disadvantage of the Invention) An ultrasonic transducer is used to conduct an ultrasonic flaw detection test.

One type of ultrasonic transducer is an electromagnetic ultrasonic transducer. This differs from those using magnetostrictive elements in that it uses Lorentz force to generate ultrasonic waves in the material to be inspected, making it possible to perform flaw detection tests without contacting the material to be inspected.

Therefore, even when there are irregularities on the surface of the non-inspected material, the special 51! The test can be conducted without applying IIM.

By the way, such an electromagnetic ultrasonic transducer is
Usually, as shown by the symbol A in FIG. 6, it is composed of a permanent magnet 1 and a conductive band 3 for forming a high-frequency current path, which is fixed to the side surface of the permanent magnet through a thin electrical insulation '@2. There is. The permanent magnet 1 is magnetized in the thickness direction. The conductive strip 3 has a zigzag shape in which branch conductors 3a, 3b, 3c, . I am doing it.

When conducting a flaw detection test on the inspected material 4 using the electromagnetic ultrasonic transducer A configured as described above, the conductive band 3 forming a high frequency current path as shown in FIG. The conductive band 3 is placed facing the surface of the material to be inspected 4 at a predetermined distance, and both ends of the conductive band 3 are exposed to ^frequency! #! and a signal transmitting/receiving device (none of which are shown).

Here, the operation of the electromagnetic ultrasonic transducer A is as follows.

When the electromagnetic ultrasonic transducer A is set with its conductive band 3 facing the surface of the material to be inspected 4, a magnetic force is generated from the permanent magnet 1 as shown by the broken line arrow in FIG. ! 2
2 is incident on the surface of the inspected material 4 at right angles. Therefore, the bias magnetic field 6 perpendicular to the surface of the inspected material 4 is applied thereto. Next, when a high frequency M current is applied to the conductive band 3, the branch conductors 3a of the conductive band 3 are parallel to each other.
, 3b, 3c, . . . , electric currents 17 in opposite directions alternately flow.

Therefore, due to this current 7, an electric current R
High-frequency induced vortices in alternating directions opposite to 7 1! Flow 8 flows. Due to the interaction between the induced eddy current and the bias magnetic field 6, a 0-Lenz force 9 is generated in the material 4 to be inspected, which is parallel to the surface of the material 4. are also alternately in opposite phase. As a result, the ultrasonic wave 10 generated in the material to be inspected 4 is a transverse wave and propagates as an oblique beam oblique to the surface of the material to be inspected 4.

(Problems in the background art) However, the conventional electric power 1ifi configured as described above
In the ultrasonic transducer A, the excited ultrasonic waves are bidirectional. That is, with respect to a direction 11 perpendicular to the surface of the inspected material 4, two ultrasonic beams 1o are transmitted at an angle θ to the left and right of this direction. For this reason, 1
Half of the power input to the t11 ultrasound transducer is wasted, reducing sensitivity. Furthermore, when performing flaw detection on a welded part 26 in the inspected material 4 as shown in FIG. Since an ultrasonic echo is obtained, it becomes difficult to determine whether the echo is from a defect existing in the vicinity of the welded portion 26 or not. For this reason, the advantage of the electromagnetic ultrasonic transducer that non-contact flaw detection is possible is not fully utilized, and the problem arises that it is rather difficult to use.

[Purpose of the invention]

The present invention was made to solve these problems, and its purpose is to be able to accurately determine defective locations in inspected materials using ultrasonic echoes, and to perform highly sensitive flaw detection. An object of the present invention is to provide an electromagnetic ultrasonic transducer.

(Summary of the Invention) In order to achieve the above objects, the present invention provides the following features: A magneto-ultrasonic transducer consists of a permanent magnet and a plurality of conductive branches arranged on one side of the permanent magnet in a direction perpendicular to the magnetization direction of the permanent magnet via an electrical insulating layer. and a time delay element connected to each branch conductor, and transmits a high frequency 1! to each branch conductor via each time delay element. It is characterized by supplying a source of energy.

[Embodiments of the invention]

An embodiment of the present invention will be shown below.

As shown in FIG. 1, the electromagnetic ultrasonic transducer B is composed of a permanent magnet 1 and a conductive band 14 for forming a high-frequency mN flow path, which is fixed to the side surface of the permanent magnet 1 through a thin electrical insulating material 2. has been done. The permanent magnet 1 is magnetized in the thickness direction.

As shown in FIG.
, 14b, 14c, -, 14n wo-2M interval (pitch p
), and is made by photo-etching a printed circuit board.

The branch conductors 14a, 14b, 14c, -, l 4n
One end of each of the time delay elements 15a, 15b, 15c, . . .
・.

15n, and each other end is connected to a common ground terminal 2.
Connected to 1.

When performing a flaw detection test on the inspected material 4 using the electromagnetic ultrasonic transducer 8 configured as described above, as shown in FIG.
, 15c, -, 15n are connected to the output terminal of the high frequency power supply 16 and the signal transmitting/receiving device 17.

Here, the operation of the electromagnetic ultrasonic transducer B is as follows.

The electromagnetic ultrasonic transducer B is connected to its conductive strip 14.
When set facing the surface of the material to be inspected 4 at a predetermined distance as shown in FIG. 4
incident at right angles to the surface of Therefore, the bias magnetic field 6 perpendicular to the surface of the inspected material 4 is applied thereto. Next, time delay elements 15a, 15b, 15c, =.
, 15n to each branch conductor 14a, 14b, 14
c...

When a high frequency current is passed through 14n, these branch conductors 14
A, 14b, 14c, -, 14n all flow in the same direction, and the Wt current 8 sequentially has a delay of one interval. Therefore, due to this current 18, an N current 7 is generated on the surface of the inspected material 4.
A high frequency induced eddy current 19 flows in the opposite direction and has a sequential time delay. Due to the interaction between this induced eddy current and the bias magnetic field 6, Lorentz forces 20a, 20b, 20c, .
On occurs, but these Lorentz forces 20a, 20
b, 20C1..., 2On also have time delays in sequence.

As a result, the ultrasonic wave 1o generated in the material to be inspected 4 is a transverse wave and propagates as an oblique beam oblique to the surface of the material to be inspected 4.

FIG. 5 is a diagram for explaining that an electromagnetic ultrasound transducer can generate a unidirectional beam.

In FIG. 5, the ultrasonic variation U1 (X, y) generated in the inspected material 4 by the Lorentz force 20a is expressed as follows.

ul(x,y)-exp(-jlR@rlexp(jω
t)...(1) r=yx+yy
...(2) kl -, /;'complete a
...(3) R-wkx + yk
y...(4) Here,
A is the amplitude of displacement, X, y are the coordinate axes, ω is the angular frequency of the high-frequency current, t is time, and y.

, are unit vectors in the X direction and y direction, respectively, and j is an imaginary unit. Further, kX, k, is expressed by the following formula.

kx −l 1? l mn l)
・15) k, -l IRl oos
o, , (6)+1RI−2shiλ
(7) Here, λ is the wavelength of the ultrasound beam generated by this electromagnetic ultrasound transducer. Next, the time difference between the time when the Lorentz force 20a is generated and the time when the adjacent Lorentz force 20b is generated is τ
Then, the displacement U2 (x, y) of the ultrasonic wave generated in the inspected material 4 by the Lorentz force 20b is expressed as follows.

Mu...(8) lr, -y(x-p)+yy
-+911 r, I -m ・
・-(l [I where D is the branch conductor 1 shown in FIG.
4a.

The pitches are 14b, 14c, . . . , 14n.

Similarly, the displacement u3 (X, y) of the ultrasonic wave generated in the inspected material 4 by the Lorentz force 20c is expressed as follows.

r2-y(x-2p)+yy
・(17,+
tt+-f seal π7...tl,')1
A similar operation is performed, and the amplitude un (X
, y) is expressed as follows.

'n(x+y) --exp(-j(?・r,-1)・
+l-u+1l-11 ro-1-x(x-(n-+)p)
・-・o511rn-11” J Otome] Music door T7
...1161 Sokote, Lorentz force 20a, 2
0b, 20c, -.

Ultrasonic displacement u (x, y) beam 1 (X, y) generated in the inspected material 4 by 2On.

It is expressed as the sum of U2 (X, y), . . . U (x, y) as follows.

u (x, y) - u, (x, y) + u, (x, y) - + -
un(x,y)-171 now rn-+"&(X-(It-1)p)+yy-zx+y
y-(n-+)px, (-(n-1)l)J
...(1&l, so #<・r,, -+-1(IIr-(n-1)pHr"
un(X+y) xexp(jωt) exp (-jω(,-1)τ
]...((9) So, if we consider it far enough that X, y>> (n-1) p, 1ro-+IIt, 1
...It becomes a mountain, so if you substitute equation (20) into equation (19), 'n(x+y)nee exp (-jlR-r) ex
p (jωt)1.1 xexp (j(n-1)pI<-r) exp(-j
ω(n-+)τ] = u, eXp (j(n-+)
pRl) exp (-jω(n-+)T)-u,
exp (j (n-1)(pTR・z-ωr))・
...21+ Using equations (4) and (5), substituting equation (22) into equation (21) and substituting equation (23) into equation (17), as is clear from equation (24), , Lorentz force 20a,
The conditions for the phases of the displacements of the ultrasonic waves generated by 20b, 20c, -, and 2On to be equal are as follows. If the frequency of the excited ultrasonic wave is f and the sound velocity of the inspected material 4 is V, then (2
5) Equation is expressed as follows.

f[-ken θ-τ)-n
...In the case of Q1ρn-Q, τ--arc θ ...f
271 As is clear from the above equations, if the pitch p of the branch conductor is selected as shown in equation (27) at the delay time, the fifth
A unidirectional ultrasonic beam 25 shown in the figure is obtained.

〔Effect of the invention〕

As described above, according to the electromagnetic ultrasonic transducer of the present invention, it is possible to transmit a unidirectional ultrasonic beam, so the defect location in the inspected material can be accurately determined based on the echoes reflected from the defect. You will be able to do this.

Furthermore, since the power supplied from the signal transmitter/receiver is concentrated into one ultrasonic beam, the sensitivity of the transducer is improved and highly sensitive flaw detection can be performed.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention,
Figure 1 shows i! A side cross-sectional view showing a part of the Iff ultrasonic transducer, Fig. 2 is a diagram showing the connection relationship between the branch conductor and the time delay element of the transducer, and Fig. 3 is a diagram showing the connection relationship between the transducer and the high-frequency power source and signal transmitter/receiver. Figure 4 is a diagram showing the connection relationship, Figure 4 is a diagram explaining the principle of ultrasonic generation of the same transducer, Figure 5 is a diagram explaining the operating principle of the same transducer, and Figures 6 to 9 show conventional examples. , FIG. 6 is a side sectional view showing a part of the electromagnetic ultrasonic transducer, FIG. 7 is a plan view showing the conductive band of the same transducer, and FIGS. 8 and 9 are the same transducer 1-1.
FIG. 2 is a diagram illustrating the principle of ultrasonic wave generation. 1... Permanent magnet, 2... Electrical insulating layer, 14a, 14
b. 14C,..., 14n'... Branch conductor, 15a, 15
b. 15C1..., 15n... time delay element, 16...
- High frequency power supply, 17... signal transmitting and receiving device. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) A permanent magnet, a plurality of branch conductors arranged on one side of the permanent magnet in a direction perpendicular to the magnetization direction of the permanent magnet via an electrical insulating layer, and each branch An electromagnetic ultrasonic transducer comprising: a time delay element connected to each conductor; and a high frequency power source is supplied to each branch conductor via each time delay element. (2) The electromagnetic ultrasonic transducer according to claim 1, wherein the plurality of branch conductors are arranged at equal intervals.