CN105651818A - Device and method for measuring shearing-directional flexoelectric coefficient through torsion of half-cylindrical structure - Google Patents

Abstract

Disclosed is a device and method for measuring the shearing-directional flexoelectric coefficient through torsion of a half-cylindrical structure. The device comprises: a flexoelectric material, exposed cores in fixed connection with two ends of the half-cylindrical flexoelectric material, electrodes symmetrically distributed about an axis of symmetry, arranged on the left and right sides of the axis of symmetry, and located on a lateral plane of the half-cylindrical flexoelectric material, a charge-amplifier electrically connected to the electrodes, a signal processing module electrically connected to the charge-amplifier, a driving power supply connected to the signal processing module, and an actuator connected to the driving power supply. A control signal is output through the signal processing module to the driving power supply, and the driving power supply amplifies the control signal power and controls the actuator to output torque. The flexoelectric material deforms because of torsion and generates shearing strain gradient in a half-cylindrical radial direction, thereby generating electric polarization due to a shearing flexoelectric effect. Polarization charges are sent to the charge-amplifier through the electrodes and are converted to corresponding voltage. According to the control signal, discharge output quantity, and material parameters, shearing flexoelectric response of the flexoelectric material can be obtained through calculation.

Description

The device and method of shearing flexoelectric coefficient is measured by reversing semi-cylindrical in configuration

Technical field

The present invention relates to the stress-electric coupling technical field in Materials science, it is specifically related to measure by reversing semi-cylindrical in configuration the device and method of shearing flexoelectric coefficient.

Background technology

Flexoelectric effect is a kind of stress-electric coupling characteristic being extensively present in all dielectric materialss, specifically refers to and produces electropolarization or the behavior due to electric-force gradient generation material deformation due to strain gradient. As the emerging research point of intelligent structure and intelligent material, flexoelectric effect has potential using value widely in every field such as aerospace, military science, bio-pharmaceuticals. The research of flexoelectric effect also partly stops at theory stage at present, one of main contents of research flexoelectric effect are exactly the research of flexoelectric coefficient, and due to charge number magnitude in the measurement of flexoelectric coefficient little, strain gradient is difficult to the existence of the problems such as applying, is the Focal point and difficult point of research always.

Flexure electricity is present in all dielectric mediums, and its principle has just been suggested as far back as the sixties in last century and has obtained great development within the specific limits, and the simplified characterization equation containing the material electropolarization of piezoelectric effect is:

$P_i=e_{ijk}{\mathrm{\σ}}_{jk}+{\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(4\right)$

Wherein P_i,e_ijk,��_jk,��_jk,��_ijkl,x_lIt is respectively degree of polarization, piezoelectric constant, stress, strain, flexoelectric coefficient and gradient direction, on the right of equation, Section 1 is the piezoelectric effect that stress causes, Section 2 is the flexoelectric effect of the gradient direction caused because of strain gradient, owing to there is not piezoelectric effect in centrosymmetry crystal, therefore only Section 2 exists, namely

$P_i={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(1\right)$

By formula (1) it may be seen that when the condition such as material, test specimen is certain, bends electroluminescent electropolarization degree and be directly proportional to electric-force gradient. Therefore, present invention employs that it produces uniform shearing strain gradient and corresponding electropolarization thereof to ensure by contrived experiment and test specimen.

Summary of the invention

In order to fill the blank in relevant field, it is an object of the invention to provide the device and method measuring shearing flexoelectric coefficient by reversing semi-cylindrical in configuration, namely bending electric material applying torsional load by semicircle column makes it that deformation occur, produce the strain gradient of shearing, thus measure the electropolarization caused by tangential strain gradient, then measure the flexoelectric coefficient of material.

For reaching above object, the present invention adopts following technical scheme:

A kind of measuring apparatus obtaining shearing flexoelectric coefficient by reversing semi-cylindrical in configuration, comprise flexure electric material 2, it is fixedly connected on the clamping end 1 at semicircle column flexure electric material 2 two ends, it is positioned in flexure electric material 2 lateral plane along the electrode 3 of the symmetrical distribution of symmetry axis, the electric charges amplify device 4 being electrically connected with electrode 3, the output terminal of electric charges amplify device 4 is electrically connected with signal processing module 5, the input terminus of power supply 6 is electrically connected signal processing module 5 with driving, and drives the output terminal of power supply 6 to be electrically connected with actuator 7; Actuator 7 clamps the clamping end 1 of flexure electric material 2 upper end and applies moment of torsion by clamping end 1 to flexure electric material 2, and flexure electric material 2 radially produces shear strain gradient, and therefore produces electropolarization.

The structure of described flexure electric material 2 is semicircle column; Its geometric centre overlaps to ensure that flexure electric material 2 is only subject to torsional load with the geometric centre of clamping end 1.

Described flexure electric material 2 structural parameter mate mutually with the load output area of material parameter and actuator 3, to ensure that flexure electric material 2 is when being subject to load effect, and enough big elastic deformation occurs.

Described electrode 3 has the rigidity far below flexure electric material 2 and possesses good electroconductibility.

The measuring accuracy of described electric charges amplify device 4 can meet the deformation of flexure electric material 1.

Described above is a kind of by reversing the measuring method that semi-cylindrical in configuration obtains the measuring apparatus of shearing flexoelectric coefficient, flexure electric material 2 upper end clamping end 1 will be fixed on be connected with actuator 7, the clamping end 1 of flexure electric material 2 times ends is fixed, when signal processing module 5 exports control signal, power supply 6 is driven by this control signal power magnification and to make actuator 7 output torque, moment of torsion is passed to flexure electric material 2 by clamping end 1 and flexure electric material 2 is twisted distortion, in the radial electropolarization producing shear strain gradient and thus produce that shear flexure conductance causes along flexure electric material 2, polarization charge exports the input terminus of electric charges amplify device 4 to by electrode 3, and by electric charges amplify device 4, this charge signal is converted into voltage signal, the output control signal of binding signal processing module 5, input voltage signal, material parameter and structural parameter, and after actuator's parameters, just the flexoelectric coefficient that can calculate material measures the device and method of shearing flexoelectric coefficient by reversing semi-cylindrical in configuration.

There is not piezoelectric effect in (namely bending electric material) in centrosymmetry crystal, being simply described as of material electropolarization:

$P_i={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(1\right)$

Wherein P_i,��_jk,��_ijkl,x_lIt is respectively degree of polarization, strain, flexoelectric coefficient and gradient direction;

And electropolarization can be described as the ratio of electric charge and charge distribution area, namely

$\frac{Q_i}{A}={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(2\right)$

Wherein Q_i, A is the area of the quantity of electric charge and counter electrode respectively;

For half cylinder, the relation of its unit length torsion(al)angle and strain gradient can be written as

Wherein �� is unit length torsion(al)angle, and �� is radial direction vector,It is that ring is to vector.

Deform owing to flexure electric material (2) is subject to load effect and is longitudinally producing shear strain gradient because of the structural performance of its variable cross-section, thus produce plan electric charge on the surface in flexure electric material (2), thus calculate shearing flexoelectric coefficient.

Compared to the prior art, tool has the following advantages in the present invention:

1) the present invention has filled up the blank reversed and measure shear flexure electrostrictive coefficient fields of measurement.

2) compared to reporting other coefficient measurement patterns, the present invention adopts and reverses the measurement that semi-cylindrical in configuration realizes shear flexure electrostrictive coefficient, has lower processing request and experiment difficulty.

In a word, the present invention can realize the inverse flexoelectric coefficient measuring the device and method acquisition material of shearing flexoelectric coefficient by reversing semi-cylindrical in configuration, compensate for the blank of prior art with not enough.

Accompanying drawing explanation

Accompanying drawing is present configuration schematic diagram.

Embodiment

Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.

As shown in drawings, the present invention measures the device and method of shearing flexoelectric coefficient by reversing semi-cylindrical in configuration, to be connected with actuator 7 with flexure electric material 2 upper end clamping end 1, the clamping end 1 of flexure electric material 2 times ends is fixed, the plane of flexure electric material 2 is symmetrically arranged electrode 3 along symmetry axis, electrode 3 is electrically connected with the input terminus of electric charges amplify device 4, the output terminal of electric charges amplify device 4 is electrically connected with signal processing module 5, the input terminus of power supply 6 is electrically connected signal processing module 5 with driving, the output terminal of power supply 6 is driven to be connected so that actuator 7 output torque with actuator, when signal processing module 5 exports control signal, power supply 6 is driven by this control signal power magnification and to make actuator 7 output torque, moment of torsion is passed to flexure electric material 2 by clamping end and flexure electric material 2 is twisted distortion, in the radial electropolarization producing shear strain gradient and thus produce that shear flexure conductance causes along flexure electric material 2, polarization charge exports the input terminus of electric charges amplify device 4 to by electrode 3, and by electric charges amplify device 4, this charge signal is converted into voltage signal, the output control signal of binding signal processing module 5, input voltage signal, material parameter and structural parameter, and after actuator's parameters, just the flexoelectric coefficient of flexure electric material can be calculated.

The method of calculation of the inverse flexoelectric coefficient of described flexure electric material are as follows:

There is not piezoelectric effect in (namely bending electric material) in centrosymmetry crystal, being simply described as of material electropolarization:

$P_i={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(1\right)$

Wherein P_i,��_jk,��_ijkl,x_lIt is respectively degree of polarization, strain, flexoelectric coefficient and gradient direction.

And electropolarization can be described as the ratio of electric charge and charge distribution area, namely

$\frac{Q_i}{A}={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(2\right)$

Wherein Q_i, A is the area of the quantity of electric charge and counter electrode respectively.

For half cylinder, the relation of its unit length torsion(al)angle and strain gradient can be written as

Wherein �� is unit length torsion(al)angle, and �� is radial direction vector,It is that ring is to vector.

Deform owing to flexure electric material (2) is subject to load effect and is longitudinally producing shear strain gradient because of the structural performance of its variable cross-section, thus produce plan electric charge on the surface in flexure electric material (2), thus calculate shearing flexoelectric coefficient.

As the preferred embodiment of the present invention, described flexure electric material 2 has higher specific inductivity and bigger elasticity distortion scope.

As the preferred embodiment of the present invention, described electrode 3 has good conductivity and lower attachment rigidity.

Claims (7)

1. the device of shearing flexoelectric coefficient is measured by reversing semi-cylindrical in configuration, it is characterized in that: comprise flexure electric material (2), it is fixedly connected on the clamping end (1) at semicircle column flexure electric material (2) two ends, it is positioned in flexure electric material (2) lateral plane along the electrode (3) of the symmetrical distribution of symmetry axis, the electric charges amplify device (4) being electrically connected with electrode (3), the output terminal of electric charges amplify device (4) is electrically connected with signal processing module (5), the input terminus of power supply (6) is electrically connected signal processing module (5) with driving, the output terminal of power supply (6) is driven to be electrically connected with actuator (7), actuator (7) clamps the clamping end (1) bending electric material (2) upper end and applies moment of torsion by clamping end (1) to flexure electric material (2), flexure electric material (2) radially produces shear strain gradient, and therefore produces electropolarization.

2. the device measuring shearing flexoelectric coefficient by reversing semi-cylindrical in configuration according to claim 1, it is characterised in that: the structure of described flexure electric material (2) is semicircle column; Its geometric centre overlaps to ensure that flexure electric material (2) is only subject to torsional load with the geometric centre of clamping end (1).

3. the device measuring shearing flexoelectric coefficient by reversing semi-cylindrical in configuration according to claim 1, it is characterized in that: described flexure electric material (2) structural parameter mate mutually with the load output area of material parameter and actuator (3), to ensure that flexure electric material (2) is when being subject to load effect, and enough big elastic deformation occurs.

4. the device measuring shearing flexoelectric coefficient by reversing semi-cylindrical in configuration according to claim 1, it is characterised in that: described electrode (3) has the rigidity far below flexure electric material (2) and possesses good electroconductibility.

5. the device measuring shearing flexoelectric coefficient by reversing semi-cylindrical in configuration according to claim 1, it is characterised in that: the measuring accuracy of described electric charges amplify device (4) can meet the deformation of flexure electric material (1).

6. according to claim 1 by reversing the measuring method that semi-cylindrical in configuration measures the device of shearing flexoelectric coefficient, it is characterized in that: flexure electric material (2) upper end clamping end (1) will be fixed on and be connected with actuator (7), the clamping end (1) of flexure electric material (2) lower end is fixed, when signal processing module (5) exports control signal, power supply (6) is driven by this control signal power magnification and to make actuator (7) output torque, moment of torsion is passed to flexure electric material (2) by clamping end (1) and flexure electric material (2) is twisted distortion, in the radial electropolarization producing shear strain gradient and thus produce that shear flexure conductance causes along flexure electric material (2), polarization charge exports the input terminus of electric charges amplify device (4) to by electrode (3), and by electric charges amplify device (4), this charge signal is converted into voltage signal, the output control signal of binding signal processing module (5), input voltage signal, after material parameter and structural parameter and actuator's parameters, just the flexoelectric coefficient of material can be calculated.

7. measuring method according to claim 6, it is characterised in that: the method for the flexoelectric coefficient of described Calculating material is as follows:

There is relation in the shear strain gradient of the electric charge that flexure electric material (2) produces and material;

Namely centrosymmetry crystal bends does not exist piezoelectric effect in electric material, material electropolarization is simply described as:

$P_i={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(1\right)$

Wherein P_i,��_jk,��_ijkl,x_lIt is respectively degree of polarization, strain, flexoelectric coefficient and gradient direction;

And electropolarization can be described as the ratio of electric charge and charge distribution area, namely

$\frac{Q_i}{A}={\mathrm{\μ}}_{ijkl}\frac{\∂{\mathrm{\ϵ}}_{jk}}{\∂x_l}---\left(2\right)$

Wherein Q_i, A is the area of the quantity of electric charge and counter electrode respectively;

For half cylinder, the relation of its unit length torsion(al)angle and strain gradient is written as

Wherein �� is unit length torsion(al)angle, and �� is radial direction vector,It is that ring is to vector;

Deform owing to flexure electric material (2) is subject to load effect and is longitudinally producing shear strain gradient because of the structural performance of its variable cross-section, thus produce plan electric charge on the surface in flexure electric material (2), thus calculate shearing flexoelectric coefficient.