JPS59173749A - Plate wave transmitter and receiver - Google Patents

Abstract

PURPOSE:To make the replacement of a detecting coil unnecessary when the thickness or the like of a sample plate body is changed, by using multipitch oscillation generating and detecting coils to transmit multimode plate waves and selecting plate waves having a prescribed wavelength in the reception side. CONSTITUTION:A controller 25 excites the first and the second electromagnets 1 and 8 with a command signal Sc to supply vertical static magnetic fields to faces of a sample plate body 16 which face transmitting and receiving transducers 19 and 21. The controller 25 sends a command signal Sd to a pulser 6 to drive it and supplies a pulse current to an oscillation generating coil 20 to induce an eddy current at intervals corresponding to pitches of the coil 20. This eddy current generates the Lorentz force by the interaction with the static magnetic field, and the sample body plate 16 is expanded and contracted in the horizontal direction. This expanding and contracting motion becomes plate waves where plural wavelengths are mixed, and a current is induced in a coil part 22. Only the current, which is induced in the oscillation detecting coil part 22, of the induced current is sent to a discriminating part 24 through a signal processing part 23 to discriminate the material, defects, etc. of the sample.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plate wave transmitting/receiving device using electromagnetic ultrasonic waves.

A conventional device of this type is shown in FIG. In the figure, (1) represents the first excitation coil (2) and the first iron core (
(3) consists of an inner core type first electromagnet that receives current from a first DC power source (4) and generates a magnetic field; (5) is a first electromagnet as shown in FIG.
A vibration generating coil which has a rectangular wave shape as shown in a) in which the coil sides are connected in series or a grid wave shape in which the coil sides are connected in parallel as shown in FIG. 2(b) and receives a signal from the pulser (8). The first electromagnet (1) and the vibration generating coil (5) form a transmission transducer (7). In addition, (8) is the second excitation coil (9) and the second iron core (
The inner core type second electromagnet (12) receives current from the second DC power supply (11) and generates a magnetic field in the same direction as the first electromagnet (1). ), (
A vibration detection coil having one of the shapes shown in b) and sending a detection signal to the determiner (14) via the amplifier (13), which includes the second electromagnet (8) and the vibration detection coil (12).
and form a receiving transducer (15).

Furthermore, (16) is a sample plate made of a conductor, which is connected to the transmitting transducer (7) and the receiving transducer (1).
5) are provided on the sample plate (16) at a distance of a predetermined pressure pt, between which the plate is moved from the transmitting transducer (7) side to the receiving transducer (15) side as shown by the arrow (17). The wave (18) is configured to propagate.

Note that FIGS. 3(a) to 3(d) show the states of the magnetic field, eddy current, etc. when a plate wave is generated in the plate wave transmitter/receiver.

Among these, FIGS. 3(a) and 3(b) relate to plate waves produced by the transverse wave generation method, and FIGS. 3(c) and 3(d) relate to plate waves produced by the longitudinal wave generation method.

In FIG. 3(a), H is a magnetic field horizontal to the surface of the sample plate (16) given by the first electromagnet (1), and J is
i (i = 1.2.3.4) is the difference between the sample plate and Body (16
) Eddy current induced in the surface layer, Fvi (i=1.2,3
．． 4) is the Lorentz force acting in the direction according to Fleming's left-hand rule due to the horizontal magnetic field H and the eddy current Ji, that is, in the vertical direction of the sample plate (16), as shown in Fig. 3(b). ) is excited.

On the other hand, in FIG. 3(c), unlike FIG. 3(a), the direction of the magnetic field V is perpendicular to the sample plate (16) as shown. Therefore, the direction of the eddy current Ji (i=1.2, 3.4) induced by the conduction of the vibration generating coil (5) is the third direction.
Even if it is the same as in Figure (a), the magnetic field ■ and the eddy current J1
The Lorentz force Fhi (i=1
, 2, 3.4) is the sample plate (
16) appears in alternating directions on the plane and the parallel plane. Therefore, Fhi of this Lorentz force is shown in Figure 3(d).
This excites a plate wave (18) as shown in FIG.

Note that typical vibration modes of the plate wave (18) excited in this way include the a mode in which the front and back surfaces of the sample plate (16) vibrate as shown in FIG. 4(a); Furthermore, an S mode in which the front and back surfaces of the sample plate (16) vibrate symmetrically is considered as shown in FIG. 4(b).

Next, the operation of the conventional plate wave transmitter/receiver having the above-described configuration will be explained. In addition, in the following explanation,
Although the plate waves will be explained assuming that they are generated by the longitudinal wave generation method, it goes without saying that the explanation can be made in the same way when the plate waves are generated by the transverse wave generation method.

In order to excite plate waves, first, a static magnetic field V is generated in a direction perpendicular to the surface of the sample plate (16) using the first DC power supply (4) and the first electromagnet (1). After that, Parsa (
When a pulse current P is supplied to the vibration generating coil (5) from 6), an eddy current JIL+ is generated in the surface layer of the sample plate (16) at a pitch equal to the coil pitch D of the vibration generating coil (5).
J2. J3+j4 are induced at equal intervals, and the Lorentz force Fhi (i=1,2
, 3.4) occur in the direction of the arrow shown in FIG. 3(c). Among these Lorentz forces, Lorentz forces Fh1 and Fh
2, and Fb3 and Fh4 are respectively sample plate (16
), and on the other hand, the Lorentz forces Fh2 and F
h3 pulls the constituent particles of the sample plate (16), causing the surface layer of the sample plate (1B) to expand and contract, causing vibrations as shown by the broken line in FIG. 3(d).

At this time, if the sample plate (1B) is thin (for example, 2
mm), the transmitting transducer (7) simultaneously vibrates the back side of the sample plate (18) that does not face it, and vibrates the a-mode (4th
It becomes the plate wave (18) in Figure (a)) and becomes the arrow (1) shown in Figure 1.
7) propagates in the direction of Note that if the coil pitch D of the vibration generating coil (5), the material and plate thickness of the sample plate (16) are constant, and the frequency of the transmission pulse current P is changed, the result shown in Fig. 4 (
a mode, S mode shown in a) and (b), and further,
Various plate waves can be generated and propagated according to the intermediate mode.

On the other hand, plate wave detection can be performed by a receiving transducer having a configuration similar to that of the transmitting transducer (7), based on the opposite principle to plate wave generation and according to Fleming's right-hand rule.

That is, in the receiving transducer (15),
First, DC excitation is performed using the second DC power supply (11) and the second electromagnet (8) to generate a static magnetic field V perpendicular to the surface of the sample plate (16), similar to the transmission side. In this state, vibration detection coil (12) 4.5: Opposing sample plate (1B)
When the plate wave (18) propagates to the part, the static magnetic field ■
An eddy current is generated on the surface layer of the sample plate (16) due to the interaction between the eddy current and the vibration, and the alternating magnetic field generated by the eddy current interlinks with the vibration detection coil (12). A current is induced. This induced current is amplified by an amplifier (13), and a determiner (14) determines the propagation time and the magnitude of the received signal based on the amplified signal. In addition, the sample plate (16)
When the vibration detecting coil (12) vibrates with the maximum amplitude, the eddy current generated in the surface layer becomes maximum, so plate waves can be detected efficiently by matching the coil pitch D of the vibration detection coil (12) to the wavelength of the plate wave. .

In addition, the propagation speed (velocity dispersion) of plate waves changes depending on the thickness of the sample plate (16), and the propagation efficiency 1 also differs. Therefore, when used for flaw detection, it is necessary to There is an optimal plate wave mode and wavelength determined by In other words, in a flaw detection device using plate waves, the sample plate (1
In accordance with the change in plate thickness in step 8), it is necessary to change the wavelength of the plate wave successively, and it is also necessary to change the coil pitch D of the vibration generating coil (5) and the vibration detecting coil (12). Furthermore, when generating a higher-order mode plate wave, it is necessary to change the transmission frequency to a higher frequency side.

As mentioned above, in the conventional plate wave transmitter/receiver, the sample plate (
16) It is necessary to change the coil pitch of the vibration generation/vibration detection coil every time the plate thickness changes.
It is necessary to have a replacement mechanism that allows the vibration detection coil or transmitting/receiving transducer to be freely replaced, which makes the device complicated and bulky, and has the disadvantage that the line has to be stopped during the replacement time. .

The present invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and uses a multi-pitch coil for the vibration generation and vibration detection coil to transmit plate waves in various modes at the same time. The purpose of the present invention is to provide a multi-pitch plate wave transceiver that can receive plate waves of any mode on the receiving side and that can always capture plate waves of the optimum mode even when the thickness of the sample plate (16) is changed. do.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 5, in which the same parts as in FIG. 1 are denoted by the same reference numerals. In the figure, (18) is a transmitting transducer according to the present invention,
The vibration generating coil (20) is different from the conventional case. That is, the vibration generating coil (20) is not arranged at equal pitches as shown in FIG.
a) The part (2) where the coil pitch is Dl (02<Ih)
0b) and the coil pitch is Da (Da < 02
) (1) Part (20c) c7) Formed by series connection. Further, (21) is a receiving transducer having a vibration detection coil (22) having a configuration different from that of the conventional device. Furthermore, (23) is a signal processor that amplifies and processes the signal of the vibration detection coil (22), and (24) determines the properties of the sample plate (16) based on the signal from the signal processor (23). (25) is a controller that controls the operation timing of the DC power supplies (4), (11), the pulser (6), etc. based on the output signal sb of the determiner (24);
26) is a plate wave with this configuration. Among the above-mentioned components, the detailed structure of the vibration detection coil (22), signal pair, and logic device (23) is shown in FIG. In the figure, (22a) to (22c) have coil pitches D, Dl, and D3, respectively, and are clearly separate coil parts forming the vibration detection coil (22), (
2? a) to (27c) are amplifiers provided in the signal processor (23), respectively, and (28) is similarly provided in the signal processor (23).
) is provided with a multiplexer, each coil portion (22a
)~(22c) are the corresponding amplifiers (2?a)~
A detection signal is sent to (27c), and a multiplexer (28) selects the output thereof and sends it to a determiner (24).

Next, the operation of the illustrated embodiment apparatus having such a configuration will be explained in the eighth section.
This will be explained with reference to FIGS.

First, the controller (25) sends the command signal Sc to the first and second command signals.
The DC power supplies (4) and (11) are respectively sent to drive and energize the first and second electromagnets (1) and (8), respectively, and the transmitting/receiving transducer (1!3), < 21)
A perpendicular static magnetic field is applied to the surface of the sample plate (1B) facing the sample plate (1B).

After that, the controller (25) sends the command signal Sd to the pulser (6).
) to drive the vibration generating coil (2o) and supply the pulse-sumi flow P to the vibration generating coil (2o). , which vibration generating coil (20)
As a result of the flow to the surface of the sample plate (16), the sixth
As shown in Figure (b), each coil portion (20a) ~ (
20c) (7) Pychi D1, D2.034.
Eddy currents Jj (j=1 to 10) are induced at corresponding intervals. This eddy current J'' is caused by a low roller Fhj (j=1~
10), and therefore the sample plate (16) performs horizontal expansion and contraction. This expansion/contraction movement occurs at multiple wavelengths D1. D2. The vibration (plate wave) (2B) is a mixture of D3 and propagates in the direction of the arrow (17).

On the receiving side, a determiner (24) gives a command Sa to a multiplexer (28) based on the material and thickness information of the sample plate (16) in advance to select one of the amplifiers.

Assume that the amplifier (27a) is selected now. In this situation, when the above-mentioned plate wave (26) propagates from the transmitting side, an eddy current is induced in the surface layer of the sample plate (16) on the receiving side, and each vibration detection coil portion (22a) to (22
A current is also induced in c). However, the amplifier (27a
) is selected, so each vibration detection coil part (
Among the currents induced in 22a) to (22c), only the current induced in the vibration detection coil portion (22a) is sent to the determiner (24) via the amplifier (2?a). Based on this signal, the determiner (24) captures the propagation time and attenuation amount of the plate wave, and determines the properties of the sample, such as its material and defects.

Next, the criteria by which the above-described determiner (24) selects an amplifier and the necessity of the selection will be explained.

In addition, as a premise for the following explanation, it is assumed that a plate wave of wavelength D1 is optimal for determining the properties of the sample plate (16).

On the receiving side, the magnitude of the eddy current generated in the surface layer of the sample plate (16) is a function of the plate wave amplitude and is maximum at the maximum amplitude, so the maximum amplitude of the plate wave on multiple coil sides A vibration detection coil with a pitch equal to the plate wave wavelength is appropriate in order to simultaneously capture the eddy currents as a medium. That is, as shown in FIG. 8(a), when the pitch D1 of the vibration detection coil (22a) and the plate wave wavelength D1 are equal, at a certain point, each coil ,,(22
The maximum induced voltages eal to ea4 uniformly appear in (22a4) to (22a4), but on the other hand, in FIG. 8(C)
When the pitch D2 of the vibration detection coil (22b) and the plate wave wavelength D1 do not match as shown in FIG. The voltages ebl to eb4 are not uniform, and the point at which the maximum value appears is not clear.

FIGS. 9(a) to (e) show the voltages eal to ea4 induced on each coil side (22al) to (22a4) when the plate wave wavelength D1 and pitch D1 are equal, and the waveform of the composite wave eA. In addition, FIGS. 10(a) to 10(e) show the waveforms of the induced voltages ebl to eb4 and their composite wave eB in the case of mismatch. As shown in the figure, the composite wave eA when the plate wave wavelength and pitch are equal has a symmetrical waveform, and the maximum value is a waveform that can be specified largely, or the composite wave eB in the case of mismatch is:
It is distorted and cannot be identified. Therefore, the vibration detection coil part where the plate wave wavelength and vibration detection coil pitch do not match (
For example, (22b).

(22c)), , etc. Based on the signals from the sample plate (1B)
) is meaningless, so it is necessary to select in advance the amplifier (2?a) corresponding to the vibration detection coil portion (22a) having the same pitch as the plate wave wavelength.

In the above description, the configuration of the vibration detection coil (22) and the signal processor (23) shown in FIG. 7 is used, but the configuration shown in FIG. 11 may be used. That is, single-wire vibration detection coils (22d) to (22k) are installed at arbitrary intervals.
), each signal of the single wire coils (22d) to (22k) is amplified by amplifiers (27d) to (27k), and a multiplexer (28) is selected from the amplifiers (2?d) to (27k). Select some amplifiers so that the coil pitch constitutes an arbitrary coil pitch, and send their output signals to an adder (2
8) may be added and input to the determiner (24).

Furthermore, since the plate wave mode that propagates easily is determined by the thickness of the sample plate (16), even if the vibration detection coil (22) has the same configuration as the vibration generation coil (20), Only plate waves can be received. Furthermore, if a hand-pass filter is used as part of the signal processor (23), an improvement in the S/N ratio can be expected.

Although the above explanation has been made regarding plate waves produced by the longitudinal wave generation method, it goes without saying that the present invention can also be applied to plate waves produced by the transverse wave generation method. Incidentally, the longitudinal wave generation method is not limited to the method shown in FIG. 3(b), but similar effects can be expected even if the method is based on a method that does not apply a magnetic field.

In addition, in the above embodiment, both the vibration generation and detection coils are linear mianta line coils, but the +21st;
ff It may be possible to use a curved mean-line coil or a grid-like coil as shown in (a) and (c), or it may be a linear multi-pitch grid-like coil as shown in FIG. 12(b). A coil may be used.

As described above, according to the present invention, a multi-pitch vibration generation/vibration detection coil is used to transmit a multi-mode plate wave, and on the receiving side, a plate wave of a predetermined wavelength, that is, a plate wave of a predetermined mode is transmitted. Since it has a configuration that allows selection, even if the material, thickness, etc. of the sample plate is changed, there is no need to replace it with a vibration generating coil and a vibration detection coil with different coil pitches, making it easy to operate and inexpensive. This has the effect that it is possible to obtain a device with a high degree of accuracy.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional plate wave transmitter/receiver;
The figures are a schematic diagram showing the shape of the vibration generation/vibration detection coil in the device shown in Figure 1, Figure 3 is a diagram explaining the principle of plate wave generation, and Figure 4.
The figure is an explanatory diagram showing a typical mode of plate wave vibration mode, Figure 5 is a block diagram showing a plate wave transmitter/receiver according to an embodiment of the present invention, and Figure 6 shows the shape of the vibration generating coil in the apparatus shown in Figure 5. 7 is a detailed configuration diagram showing an example of the vibration detection coil and signal processor in the device shown in FIG. 5, and FIG. 8 is a diagram showing the plate wave wavelength and coil pitch. 9 and 10 are respectively induced voltage waveform diagrams of the vibration detection coil, and FIG. 11 is a detailed configuration showing another embodiment of the vibration detection coil and signal processor. Figure 12 shows vibration generation and
7 is a schematic diagram showing the shape of another embodiment of the vibration detection coil. FIG. (1), (8)...electromagnet, (4,), (11
)...DC power supply, (6)...Pulser,
(16)...Sample plate, (17)...Propagation direction, (
19)...Transmission transducer (20)...Vibration generating coil, (21)...Reception transducer, (22)...
Vibration detection coil, (23)...Signal processor, (24
)...determiner, (25)...controller,
(26)...Multimode plate wave. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno -#1 1
Diagram @ 2 Leopard 4WJ No. 1161! ! Figure 7 Figure 8 Figure 9wJ Figure 11 Whistle 12 Amendment to figure procedure (voluntary) Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 58-48283 2,
Name of the invention Plate wave transmitter/receiver 3, representative of the person making the amendment Hitoshi Katayama Department 4, agent 5, name of the invention to be amended, column 9, and u+ ++'t of the invention in the specification
+, '+ WM sword column. 6. Contents of the amendment (1) In the column of the title of the invention in the application that specifies how to read the name of the claimed invention, the part where the furigana is written as "Bampano, Ujushinsouchi" is amended to "Itanami Soujushinsouchi" as in the attached application for correction. . Line 13 on page 3, line 7 on page 5, and line 6 on page 5.
The description "transverse wave" will be corrected to "longitudinal wave." (3) Page 3, line 14 of the specification, and page 5, line 1,
In the fifth line of page 5, each description of "longitudinal wave" is corrected to "transverse wave". ” scribbles, page 6, line 14, ``The description of intermediate modes is ``various higher modes.'''' Page 14, lines 1 to 4, ``Itanami wave, there,''
Delete the statement. (6) The statement "Fig. 3 (b)" on page 15, line 8 of the specification is amended to "Fig. 3 (a)." 7. List of attached documents

Claims (1)

[Claims] a transmitting transducer comprising at least a vibration generating coil having coil sides parallel to the sample plate surface; a magnet mechanism for applying a magnetic field horizontally or perpendicularly to the sample plate surface; a receiving transducer provided with a vibration detecting coil having parallel coil sides and provided spaced apart from the transmitting transducer; and a determiner receiving a signal from the vibration detecting coil; By passing current through the generating coil, the sample plate is vibrated, and the vibration is captured by the vibration detection coil,
In the plate wave transmitting/receiving device in which the determining device determines the properties of the sample plate based on the detection signal, the vibration generating coil has a plurality of coil pitches, and the vibration detecting coil has one coil pitch of the vibration generating coil. It has a corresponding coil part that responds strongly to each determined vibration wavelength,
A board characterized in that the signal from each corresponding coil portion is selected by a signal processing unit and sent to the determination device, 2.
Wave transmitting and receiving device.