JPH0886698A - Surface stress sensor - Google Patents

Abstract

PURPOSE: To obtain a surface stress sensor for detecting stress on the surface of a plane structural member accurately over a wide range. CONSTITUTION: The surface stress sensor comprises a plurality of amorphous wires 2 embedded in a plane structural member 4 while being arranged in open loop parallel with each other, and coils 3 wound around the amorphous wires 2. The coils 3 are selected sequentially and excited with a high frequency current and the power induced in other coil 3 by the leakage flux of an excited coil 3 is measured thus detecting stress on the surface of the plane structural member 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface stress sensor for a planar structure material capable of detecting fatigue fracture of a planar structure material such as a fiber reinforced plastic (FRP) member in advance.

[0002]

2. Description of the Related Art As a conventional method for detecting surface stress of a planar structure material, as described in Japanese Patent Laid-Open No. 5-142130, a planar shape is formed on a surface layer of an FRP member in which an amorphous wire which is a magnetic material is embedded. A pickup type sensor composed of an exciting coil and a flat detecting coil is installed in a contact state or a non-contact state, a high frequency current is supplied to the exciting coil, and induction is generated in the detecting coil by a magnetic flux passing through the FRP member. It is known that the electromotive force is detected and the stress generated in the amorphous wire is detected as a change in mutual inductance.

[0003]

According to the conventional technique, the exciting coil and the detecting coil, which are the detecting means, are mounted on the planar structure material, and thus an installation space is required.
Therefore, a new detection method is desired when the installation space cannot be taken up so much.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to automatically detect the surface stress of a planar structural material in a wide range and with high accuracy. The present invention is intended to provide a surface stress sensor that can be used.

[0005]

In order to solve the above-mentioned problems, the present invention provides a plurality of amorphous wires arranged in parallel in an open loop and embedded in a planar structural material, and coils wound around these amorphous wires. And sequentially selecting these coils to excite them with a high-frequency current, and detecting the surface stress of the planar structure material by measuring the induced electromotive force induced in other coils by the leakage magnetic flux of the excited coils. It is a thing.

[0006]

The coil wound around each of the plurality of amorphous wires embedded in the planar structure material is sequentially selected and excited by the high frequency current. On the other hand, the induced electromotive force induced in another coil by the leakage magnetic flux of the excited coil is measured, and the surface stress of the planar structure material is detected accurately in a wide range.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a conceptual diagram of a surface stress sensor according to the present invention, and FIG. 2 is a circuit diagram of a surface stress measuring circuit to which the surface stress sensor is applied.

As shown in FIG. 1, a surface stress sensor 1 is formed by winding a coil 3 around each of a large number of open loop amorphous wires 2, and the amorphous wires 2 around which the coils 3 are wound are arranged in parallel. 2 sheets of F
It is configured with the planar structure material 4 formed by being sandwiched by the RP members.

Both ends of each coil 2 are exposed to the outside of the planar structure material 4 as lead wires 5.

In the measuring circuit for detecting the surface stress of the planar structural member 4 by the surface stress sensor 1, as shown in FIG. 2, the six coils 3 arranged at the site for detecting the surface stress are used. The voltage measuring device 6 for measuring the induced electromotive force is connected in parallel.

Further, an output terminal 7b of a scanner (for example, a rotary switch) 7 is connected to one end of each coil 3, and a ground (GND) is connected to the other end of each coil 3.
A high-frequency current power source 8 is connected in parallel to the input terminal 7a of the scanner 7 and the ground (GND).

When detecting the surface stress of the planar structure member 4,
First, the coil 3 connected to the output terminal 7b electrically connected to the input terminal 7a of the scanner 7 is selected as the exciting coil.

Then, the high-frequency current power source 8 causes a high-frequency current to flow through the coil 3 selected as the exciting coil.

Then, as shown in FIG.
Magnetic flux A indicated by the dotted line is generated, and a magnetic circuit in which the magnetic flux A passes through the amorphous wire 2, the FRP member, and the like is configured.

Generally, the magnetic resistance Rm of the magnetic circuit is determined only by the shape and material of the magnetic circuit and is expressed by the following equation.

Rm = 1 / (μ · s), where 1 is the length of the magnetic path, s is the cross-sectional area of the magnetic path, and μ is the magnetic permeability. Therefore,
The larger the magnetic permeability μ and the shorter the magnetic path length l, the smaller the magnetic resistance Rm of the entire magnetic circuit.

Further, the magnetic flux A is expressed by the following equation.

A = NI / Rm, where N is the number of turns of the exciting coil, and I is the high frequency current flowing in the exciting coil.

The stress applied to the planar structure material 4 is also applied to the amorphous wire 2 embedded in the FRP member, and changes the shape of the amorphous wire 2.

Therefore, the shape of the amorphous wire 2 is changed by the stress applied to the planar structure member 4, and the magnetic resistance Rm of the magnetic circuit is changed especially by the shape change of the amorphous wire 2.

Then, the magnetic flux A changes due to the change in the magnetic resistance Rm, and the coil 3 connected to the output terminal 7b which is not electrically connected to the input terminal 7a of the scanner 7 which acts as a detection coil due to the change in the magnetic flux A. Induced electromotive force V
(V = -dA / dt) changes. If the number of turns of the detection coil is n, the induced electromotive force induced in the detection coil is nV.

Therefore, it is possible to measure the change in the induced electromotive force V by the voltage measuring device 6 and then detect the stress applied to the planar structural member 4. Similarly, if an exciting coil is sequentially selected from the coils 3 by the scanner 7 and the induced electromotive force V induced in another coil 3 acting as a detection coil is measured by the voltage measuring device 6, it is set as a measurement target. The surface stress of the planar structure material can be detected in a wide range and with high accuracy.

[0023]

As described above, according to the present invention, when the coils wound around the plurality of amorphous wires are sequentially selected and excited by the high frequency current, the surface stress of the planar structure material is wide and the accuracy is high. It can be detected well.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a surface stress sensor according to the present invention.

FIG. 2 is a circuit diagram of a surface stress measuring circuit to which a surface stress sensor according to the present invention is applied.

[Explanation of symbols]

1 ... Surface stress sensor, 2 ... Amorphous wire, 3 ... Coil, 4 ... Planar structure material, 6 ... Voltage measuring device, 7 ... Scanner,
8 ... High-frequency current power supply.

Claims (1)

[Claims] 1. A plurality of amorphous wires embedded in a planar structure material arranged in parallel in an open loop and coils wound around these amorphous wires respectively, and these coils are sequentially selected to generate a high-frequency current. A surface stress sensor which is excited and detects a surface stress of the planar structural material by measuring an induced electromotive force induced in another coil by a leakage magnetic flux of the excited coil.