JPH09280970A - Shearing force detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the measuring error due to the dimensional error between detectors and the phase difference of measuring electric circuits by providing a plurality of electrodes for detecting a strain, polymer piezoelectric films mounted at an equal interval with the electrodes, and an insulating and adhesive protective film for laminating the film at a plate or beam material. SOLUTION: Two sets of electrodes 2, 3 are deposited at a certain interval on both side surfaces of a polymer piezoelectric film 1 of polarized PVDF (polyvinylidene fluoride). The film 1 and electrodes 2, 3 are covered with protective films 4 of epoxy resin used also for insulation of member (material to be detected 8) to be measured such as a beam or plate. When the material 8 is deformed by bending, the film 1 is elongated or contracted, and a voltage proportional to the strain of the member is generated between the electrodes 2 and 3. The shearing force operated at the material 8 is obtained by the difference approximation of the space differentiation of the deformation out of the member. Therefore, wirings 6, 6' are connected to output the difference between the electrodes 2 and 3, and the output is input to a measuring amplifier 10 from leads 7, 7'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shear force detector due to bending deformation at an arbitrary point of a plate material or a beam material.

[0002]

2. Description of the Related Art The shearing force due to the bending deformation of a plate material or a beam material is expressed by equation (1). ^{Fx = D (δ 3 w /} δx 3) ······· (1) However, Fx: shear D: flexural rigidity = Eh ^3/12 beam ^{= Eh 3/12 (1-} v 2) plate E : Young's modulus of beam, plate v: Poisson's ratio of beam, plate h: Height of beam, plate, thickness w: Out-of-plane displacement of beam, plate Conventionally, shear force Fx is a plate material using an accelerometer, etc. The out-of-plane acceleration of the beam is measured, and the spatial differential term (δ ³ w / δ
x ³ ) is approximated by a difference to obtain the shearing force in the equation (1). Since the measurement signal is acceleration, it has to be integrated in order to convert it into displacement.

[0003]

By the way, the measurement of the shearing force of the plate material, the beam material and the like, which is performed by using the conventional acceleration timepiece, is performed by using FIG.
The procedure is shown in the side view. That is, 08 is a plate or beam material, 09 is a plurality of accelerometers, 05
Is an adhesive for attaching the accelerometer 09 to the test material 08, 01
Reference numeral 0 is an amplifier for measurement. As described above, conventionally, the accelerometers 09 are arranged at equal intervals δ on the surface of the plate material or the beam material 08 to be measured, and the spatial differential term of the out-of-plane displacement is obtained by differential approximation as in the equation (2). Is there. (Δ ³ w / δx ³ ) = (w ₄ −3w ₃ + 3w ₂ −w ₁ ) / δ ³ ... (2) However, when using the differential approximation as in Expression (2), each accelerometer 09 The mounting error of the interval δ of has a great influence on the measurement error. Further, since it is necessary to connect the amplifier 010 to each acceleration clock 09, the phase difference between the output signals due to the electric circuit characteristics in the amplifier also causes the measurement error.

The present invention has been proposed in view of the above circumstances, and it is an object of the present invention to provide a high-performance shear force detector which eliminates a dimensional error between detectors and a measurement error due to a phase difference of a measurement electric circuit. To aim.

[0005]

In order to achieve such an object, the present invention provides a plurality of devices for detecting strain as a voltage in order to measure the shear force due to a bending wave propagating through a plate or beam. An electrode, a polymer piezoelectric film in which the plurality of electrodes are attached at equal intervals without dimensional error, and an adhesive protective film that also serves as insulation for attaching the polymer piezoelectric film to the plate material or the beam material It is characterized by being done.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view thereof, and FIG. 2 is a side view of FIG.

That is, in FIG. 1 and FIG. 2, in order to measure the strain of a structure, electrodes 2 are formed on both sides of a polymer piezoelectric film 1 such as polarized PVDF (polyvinylidene fluoride).
Two sets of 2 ': 3,3' are vapor-deposited at intervals δ. The polymeric piezoelectric film 1 and the electrodes 2 and 3 are covered with a protective film 4 such as an epoxy resin that also serves as an insulation from a member to be measured (hereinafter referred to as a material to be measured 8) such as a beam or a plate.

In such a structure, when the test material 8 is bent and deformed, the polymer piezoelectric film 1 expands and contracts, and the strain of the member between the electrodes 2, 2'and 3, 3'is ε = (δw ² / δx ^2). ) Generates a voltage proportional to. At that time, the shearing force Fx acting on the material to be inspected 8 can be obtained by the equation (3) by differential approximation of the spatial derivative of the out-of-plane deformation w of the member. Fx = D (δ ₃ w / δx ³ ) = D [(ε ₂ −ε ₁ ) / δ] (3) Therefore, it occurs between the electrodes 2 and 2 ′ and the electrodes 3 and 3 ′. The electrodes 2 and 3 are connected to each other so that the difference in voltage is output.
′ And 3 ′ are respectively connected by wirings 6 and 6 ′, and the outputs are input to the measurement amplifier 10 through the lead wires 7 and 7 ′ and measured, whereby the center position (x =
The shearing force Fx acting on the surface of the test material 8 in 0) can be measured. This shear force detector has two electrodes 2 and 3
It is composed of the polymeric piezoelectric film 1 that is vapor-deposited and is covered with the protective film 4. By attaching this detector to the test material 8 with the adhesive 5, the strain ε of the member surface at each electrode position A voltage proportional to is generated between the electrodes.
Therefore, by connecting the electrodes 2 and 3'and the electrodes 2'and 3 with the wirings 6 and 6 ', the shearing force at the central position between the electrodes 2 and 3 is the electrodes 2, 2'and the electrodes 3, 3'. The voltage difference between them is output from the wirings 6 and 6'through the lead wires 7 and 7 '.

[0009]

In the device of the present invention, by providing two detection points (electrode positions) on one piezoelectric film, the difference approximation error caused by the detector mounting error at the time of measurement and the measurement electric circuit can be reduced. It is possible to reduce the measurement error caused by the phase difference. Further, by connecting the electrodes so as to directly output a voltage proportional to the shearing force, it is possible to reduce the electric circuit for measurement.

In short, according to the present invention, a plurality of electrodes for detecting strain as voltage in order to measure the shearing force due to a bending wave propagating through a plate or beam, and the plurality of electrodes at equal intervals without dimensional error. Since it is composed of the polymer piezoelectric film attached to the and the polymer piezoelectric film and an adhesive protection film that also serves as insulation for attaching the polymer piezoelectric film to the plate material or beam material, dimensional error between detectors and measurement The present invention is extremely useful in industry because it provides a high-performance shear force detector that eliminates measurement errors due to the phase difference of electric circuits.

[Brief description of drawings]

FIG. 1 is a plan view of a shear force detector showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view taken along the line II-II of FIG.

FIG. 3 is a side view showing a shear force measurement situation by a conventional accelerometer.

[Explanation of symbols]

 1 Polymer Piezoelectric Film 2,2 'Electrode 3,3' Electrode 4 Protective Film 5 Adhesive 6,6 'Wiring 7,7' Lead Wire 8 Test Material (Test Beam or Test Plate) 10 Measurement Amplifier

Claims (1)

[Claims] 1. A plurality of electrodes for detecting strain as a voltage for measuring a shear force due to a bending wave propagating through a plate or beam, and a plurality of electrodes mounted at equal intervals without dimensional error. A shear force detector comprising a molecular piezoelectric film and an adhesive protective film also serving as an insulating material for attaching the polymer piezoelectric film to the plate material or the beam material.