JPH0854296A - Stress measuring sensor - Google Patents

Abstract

PURPOSE:To provide a stress measuring sensor optimum for automating the stress measurement whatever the measuring place is. CONSTITUTION:The stress measuring sensor 1 comprises an amorphous wire 11 which varies in magnetostrictive characteristics corresponding to an externally received stress, an exciting coil 12 wound on the periphery of the wire 11, and a detecting coil 13. The coil 13 generates a mutual induction electromotive force responsive to the magnetic strain characteristics by a magnetic field. The wire 11 is embedded in a structural material (FRP member, etc.) 3 in the state that the coils 12, 13 are wound. Incidentally, the coils 12, 13 may be separately wound in the longitudinal direction of the wire 11 or wound together. The wire 11 around which the coil 12 is wound and the wire 11 around which the coil 13 is wound, may be separate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress measuring sensor utilizing the magnetostriction characteristic of an amorphous magnetic material.

[0002]

2. Description of the Related Art When stress is applied to an amorphous magnetic material, the magnetic permeability of the amorphous magnetic material changes. As a stress measuring means utilizing such a magnetostrictive characteristic, there is, for example, one proposed by the present applicant in Japanese Unexamined Patent Publication No. 5-142130. This measuring means is often used to detect the stress state and the presence or absence of internal damage of a FRP (fiber reinforced plastic) member used as a structural material such as a vehicle body.

This stress measuring means is composed of an amorphous magnetic material mixed in a resin in the process of manufacturing an FRP member, and F
The RP member is composed of an exciting coil and a detecting coil which are arranged outside the RP member in close proximity thereto. When an alternating current is passed through the exciting coil to excite it, an alternating electromotive force is induced in the detecting coil by mutual induction. Then, the magnitude of the stress acting on the amorphous wire can be indirectly measured from the magnitude of the AC electromotive force.

[0004]

However, in the above-mentioned stress measuring means, a space for arranging the exciting coil and the detecting coil is required outside the structural material, and such a place where stress can be measured is such a place. There is a problem of being limited to places where space can be secured.

By the way, when the stress measurement means intends to measure the stress in a wide range of the structural material, both coils are appropriately moved along the structural material. Then, such movement of the coil may be automatically performed by a robot or the like. However,
When the shape of the structural material is complicated, it is difficult for the robot or the like to move the coil while properly following the structural material, which is a bottleneck in automating stress measurement.

The present invention has been made in view of the above problems, and an object thereof is to provide a stress measurement sensor which is suitable for automating stress measurement regardless of the measurement location.

[0007]

In order to achieve the above object, the present invention is made of an amorphous magnetic material,
A wire-shaped member whose magnetostrictive characteristics change according to the stress received from the outside, an exciting coil wound around the wire-shaped member to generate a magnetic field passing through the wire-shaped member, and a wire wound around the wire-shaped member. Thus, the stress measuring sensor is composed of a detection coil that generates a mutual induction electromotive force corresponding to the magnetostrictive characteristic by the magnetic field, and the wire-shaped member is a structural member in which the excitation coil and the detection coil are wound. (FRP member, etc.).

In this stress measuring sensor, the exciting coil and the detecting coil may be arranged so as to be separated from each other in the longitudinal direction of the wire-shaped member, or may be wound around the wire-shaped member substantially overlapping each other. . Further, the wire-shaped member around which the excitation coil is wound may be separated from the wire-shaped member around which the detection coil is wound.

[0009]

The above-mentioned stress measuring sensor, that is, the wire-shaped member around which the exciting coil and the detecting coil are wound, is embedded in a structural material (FRP member or the like) as an integral body. As a result, there is no need to provide a space for arranging the coil on the outside of the structural material as in the conventional case, and the measurement place is not limited by the presence or absence of this space. Moreover, since the wire and the coil are integrated, if the arrangement of this sensor inside the structural material is properly devised,
The stress can be easily measured in a wide range of the structural material without moving the detection coil with respect to the structural material. Therefore, the stress measurement can be easily automated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
2 shows the stress measurement sensor of FIG. This stress measurement sensor 1
Is a wire 11 made of an Fe (iron) -based or Co (cobalt) -based amorphous magnetic material, an exciting coil 12 wound around the wire 11, and a longitudinal direction of the wire 11 from the exciting coil 12 The detection coil 13 is wound around the wire 11 at a remote position. Wire 1
1 has a property (magnetostriction property) that the magnetic permeability of the wire 21 changes in response to the magnitude of the stress when a stress acts. An AC power supply 14 is connected to both ends of the exciting coil 12. A voltmeter 15 is connected to both ends of the detection coil 13.

When an alternating current is supplied to the exciting coil 12 by the alternating current power source 14 and this is excited, a magnetic field H which changes its direction every time the polarity of the alternating voltage is reversed through the wire 11.
Occurs. An alternating electromotive force (induced electromotive force) is induced in the detection coil 13 by the mutual induction effect of the magnetic field H. The magnitude of the AC electromotive force depends on the detection coil 13
Corresponds to the magnitude of the inductance, and this inductance also corresponds to the magnetic permeability of the wire 11. For this reason,
If the stress acting on the wire 11 changes and the magnetic permeability changes, the magnitude of the AC electromotive force also changes. Therefore,
If the voltage value of the AC electromotive force generated in the detection coil 13 is measured by the voltmeter 15, the stress acting on the wire 11 (and thus the stress acting on the FRP plate in which the sensor 1 is embedded) can be obtained.

FIG. 2 shows the relationship between the stress (tensile stress) acting on the wire 11 in the stress measuring sensor 1 and the induced electromotive force generated in the detection coil 13. As can be seen from this figure, the magnitude of the induced electromotive force V generated increases as the tensile stress acting on the wire 11 increases. Then, when the tensile stress is within the range E, the induced electromotive force V changes substantially linearly with respect to the tensile stress. Therefore, the stress measurement sensor 1 is suitable for detecting the stress within the range E.

FIG. 3 shows a specific method of using the stress measuring sensor 1. In the stress measurement sensor 1 shown in FIG. 3 (A), the wire 11 has both ends connected to each other and is formed into an elliptical loop shape, and the excitation coil 12 and the detection coil 13 are arranged separately on both sides of this ellipse. Has been done. By thus forming the wire 11 in a loop shape, the leakage magnetic flux from the end portion of the wire 11 can be eliminated, which is effective for improving the sensitivity as a sensor. Then, the plurality of stress measuring sensors 1 thus manufactured are arranged inside the FRP plate 30 so as to be parallel to the upper and lower surfaces of the FRP plate 30 and in the main stress direction (the direction in which the tensile force T acts). It is buried so as to extend.

More specifically, as shown in FIG. 3B, the FRP plate 30 is composed of upper and lower resin layers 31 and an adhesive layer 32 formed between these resin layers 31. Then, in the process of manufacturing the FRP plate 30, when the adhesive material is applied to the upper surface of the lower resin layer 31 to form the adhesive layer 32, the stress measurement sensor 1 (that is, both coils 12,
The wire 11) in a wound state of 13 is embedded in the adhesive layer 32 as a unit. Adhesive layer (adhesive) 32
Until the wire hardens, the wire 11 is subjected to a tensile stress corresponding to the point E0 in FIG. This allows the wire 1
No. 1 is constrained by the cured adhesive layer 32 to the state in which the initial tensile stress acts, and thereafter, the stress corresponding to the point E0 becomes the measurement reference point of the stress acting on the FRP plate 30.

When the tensile force T acts on the FRP plate 30 in which the plurality of stress measuring sensors 1 are embedded in this way as shown in FIG. 3, this is also transmitted to the wire 11 of each stress measuring sensor 1. Therefore, the magnetic permeability of the wire 11 changes and the magnitude of the induced electromotive force V generated in the detection coil 13 is as shown in FIG.
Voltage corresponding to point E0 on the graph (initial voltage)
Will be higher than. When a compressive force acts on the FRP plate 30 in the direction opposite to the tensile force T, the magnitude of the induced electromotive force V becomes lower than the initial voltage. However, as shown in FIG.
When the magnitude of the tensile forces T1 to T3 is different or the magnitude of the compressive force is different depending on each part of the P plate 30, the magnitude of the induced electromotive force is different for each stress measurement sensor 1. Therefore, the direction and magnitude of the stress acting on the FRP plate 30 can be obtained for each embedded position of the stress measurement sensor 1, and the stress distribution of the entire FRP plate 30 can be easily known.

On the other hand, if the adhesive layer 32 of the FRP plate 30 is internally damaged due to a fatigue fracture phenomenon, the constraint of the adhesive layer 32 that holds the wire 11 under the initial stress is loosened and acts on the wire 11. The tensile stress decreases. Therefore, the magnitude of the induced electromotive force V generated in the detection coil 13 is lower than the initial voltage. Therefore, it is possible to know the occurrence of internal damage in the FRP plate 30 through the reduction of the induced electromotive force V, and further by examining the embedding position of the stress measurement sensor 1 where the induced electromotive force V is reduced. The position of the internal damage in the FRP plate 30 in the lateral direction (direction orthogonal to the principal stress direction) can be almost specified.

Incidentally, FIG. 4 shows a plurality of stress measuring sensors 1.
Are embedded in the FRP member 30 'in a grid pattern. In this case, for example, the induced electromotive force V of the sensor indicated by A in the figure among the stress measurement sensors 1 arranged in the vertical direction and the induced electromotive force of the sensor indicated by B in the stress measurement sensors 1 arranged in the horizontal direction. If V and V are decreased, it can be said that internal damage is highly likely to occur within the range indicated by C in the figure, which is close to the intersection of both sensors. Thus, by embedding the stress measurement sensor 1 in a grid pattern, the position of internal damage can be specified in more detail.

(Embodiment 2) In Embodiment 1, the stress measuring sensor in which the exciting coil and the detecting coil are wound separately in the longitudinal direction of the wire has been described. However, as shown in FIG. The stress measuring sensor (second stress measuring sensor according to the present invention) 1'in which the wire 12 'and the detecting coil 13' are wound around the wire 11 'has the same characteristics as the sensor of the first embodiment. The sensor can be used in the same manner as the sensor of the first embodiment. Since the exciting coil 12 'and the detecting coil 13' are each made of an insulated wire, they are not short-circuited. This stress measuring sensor 1'is particularly suitable for detecting stress and internal damage of a small FRP member because the length of the wire 11 'can be shortened because both coils 12', 13 'are wound together.

(Embodiment 3) FIG. 6 shows a third embodiment of the present invention.
2 shows the stress measurement sensor of FIG. This stress measurement sensor 5
Is two wires (first wire 51a and second wire 51b) made of an amorphous magnetic material, an exciting coil 52 wound around the first wire 51a, and a second wire 5.
It is composed of a detection coil 53 wound around 1b. Each wire 51a, 51b has a property (magnetostriction characteristic) that the magnetic permeability of each wire 51a, 51b changes according to the magnitude of the stress when a stress acts. An AC power supply 54 is connected to both ends of the exciting coil 52. Also,
A voltmeter 55 is connected to both ends of the detection coil 53.

When an alternating current is supplied to the exciting coil 52 by the alternating current power source 54 to excite it, the first wire 51a
A magnetic field H that changes its direction each time the polarity of the AC voltage is inverted is generated through the second wire 51b. An alternating electromotive force (induced electromotive force) is induced in the detection coil 53 by the mutual induction effect of the magnetic field H. The magnitude of the AC electromotive force depends on the exciting coil 52 and the detecting coil 53.
Of the first wire 51a and the second wire 51b. Therefore, the first wire 51a and the second wire
If the stress acting on the wire 51b changes and the magnetic permeability changes, the magnitude of the AC electromotive force also changes. Therefore, if the voltage value of the AC electromotive force generated in the detection coil 53 is measured by the voltmeter 55, the stress acting on the first wire 51a and the second wire 51b (and thus on the FRP plate in which the sensor 5 is embedded). The stress acting) is required.

Both wires 51a, 51 of the stress measuring sensor 5
The relationship between the tensile stress acting on b and the electromotive force generated in the detection coil 53 is the same as that in FIG. 2, and thus the description thereof is omitted here.

FIG. 7 shows a specific method of using the stress measuring sensor 5. Stress measurement sensor 5 shown here
In the above, the wires 51a and 51b are each bent into a shape (or zigzag shape) in which three forward and reverse U-shapes are alternately arranged, and are arranged so as to be cut between the respective U-shapes of the other party. The coils 52 and 53 are wound over substantially the entire length of each wire 51a and 51b. In the figure, there is a portion where the exciting coil 52 and the detecting coil 53 intersect with each other, but since both coils 52 and 53 are made by using insulation-coated electric wires, they do not short-circuit.

The stress measuring sensor 5 thus manufactured is arranged inside the FRP plate 70 (the adhesive layer between the upper and lower resin layers) so as to be parallel to the upper and lower surfaces of the FRP plate 70. The long portions of the wires 51a and 51b are embedded so as to extend in the principal stress direction (direction in which the tensile force T acts). An appropriate initial tensile stress is applied to the second wire 51b.

When the tensile force T acts on the FRP plate 70 in which the stress measuring sensor 5 is embedded as shown in FIG. 7, this is also transmitted to the wires 51a and 51b of the stress measuring sensor 5. Therefore, the magnetic permeability of both wires 51a, 51b changes, and the magnitude of the induced electromotive force V generated in the detection coil 13 becomes higher than the initial voltage (see FIG. 2). Also,
When the compressive force in the direction opposite to the tensile force T acts on the FRP plate 70, the magnitude of the induced electromotive force V becomes lower than the initial voltage.
Thereby, the direction and magnitude of the stress acting on the FRP plate 70 can be obtained.

On the other hand, if the adhesive layer of the FRP plate 70 is internally damaged due to the fatigue fracture phenomenon, both wires 51a and 51b will be damaged.
Since the restraint of the adhesive layer, which was held in the state where the initial tensile stress acts, is relaxed, the tensile stress acting on both wires 51a and 51b becomes small. Therefore, the magnitude of the induced electromotive force V generated in the detection coil 53 becomes lower than the initial voltage. Therefore, through the reduction of this induced electromotive force V, F
It is possible to know the occurrence of internal damage in the RP plate 70.

Further, FIG. 8 shows a case where a plurality of the stress measuring sensors 5 are embedded in the FRP plate 70 in the vertical and horizontal directions. In this case, by investigating the embedding position of the stress measuring sensor 5 where the reduction of the induced electromotive force V has occurred, a large F
It is possible to easily specify in which area of the RP plate 70 the internal damage has occurred.

[0028]

As described above, the stress measuring sensor of the present invention is made by winding a coil (excitation coil and detection coil) around a wire-shaped member made of an amorphous magnetic material, and the whole of these is made of a structural material. It is designed to be embedded in and used. Therefore, if this stress measurement sensor is used, it is not necessary to arrange the coil outside the structural material.
The stress measurement can be performed even in a place where such a coil arrangement space is not provided. Further, by appropriately devising the arrangement of the sensor inside the structural material, it is possible to easily measure the stress in a wide range of the structural material without moving the coil along the structural material as in the conventional case. Therefore, the stress measurement can be easily automated.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a first embodiment of a stress measurement sensor according to the present invention.

FIG. 2 is a conceptual diagram showing characteristics of the stress measurement sensor.

FIG. 3 is a conceptual diagram showing a usage state of the stress measurement sensor.

FIG. 4 is a conceptual diagram showing a usage state of the stress measurement sensor.

FIG. 5 is a conceptual diagram of a second embodiment of the stress measuring sensor according to the present invention.

FIG. 6 is a conceptual diagram of a stress measurement sensor according to a third embodiment of the present invention.

FIG. 7 is a conceptual diagram showing a usage state of the stress measurement sensor.

FIG. 8 is a conceptual diagram showing a usage state of the stress measurement sensor.

[Explanation of symbols]

 1, 1 ', 5 Stress measurement sensor 11, 11', 51a, 51b Amorphous wire 12, 12 ', 52 Excitation coil 13, 13', 53 Detection coil 30, 30 ', 70, 70' FRP plate

Claims (4)

[Claims] 1. A wire-shaped member made of an amorphous magnetic material, the magnetostriction characteristic of which changes in response to a stress received from the outside, and a magnetic field which is wound around the wire-shaped member and passes through the wire-shaped member. An excitation coil, and a detection coil that is wound around the wire-shaped member and that generates a mutual induction electromotive force according to the magnetostrictive characteristic by the magnetic field, the wire-shaped member being the excitation coil. A stress measuring sensor, wherein the stress measuring sensor is embedded in a structural material which is a target of stress measurement in a state where the detecting coil is wound. 2. The stress measuring sensor according to claim 1, wherein the exciting coil and the detecting coil are wound around the wire member so as to be separated from each other in the longitudinal direction of the wire member. 3. The stress measuring sensor according to claim 1, wherein the exciting coil and the detecting coil are wound together around the wire-shaped member. 4. The wire-shaped member wound with the excitation coil and the wire-shaped member wound with the detection coil are separate bodies. Stress measurement sensor.