CN105571756A - High-sensitivity bending electric sensor used for shock wave detection - Google Patents

Abstract

A high-sensitivity flexoelectric sensor that can be used for shock wave detection, including a left metal electrode and a right metal electrode respectively arranged on the left and right surfaces of a flexoelectric dielectric material; the left metal electrode and the right metal electrode are respectively connected with two output measurement charges The other ends of the two lead wires are connected to two external metal electrodes, and the epoxy resin seals the flexible dielectric material, metal electrodes and lead wires; the metal screen has a pressure channel for the shock wave to apply pressure; the shell is bonded to the metal screen Connected together, epoxy resin is consolidated inside; the present invention measures the shock wave pressure by the linear relationship between the strain gradient produced by the flexoelectric dielectric material under shock wave compression and the charge generated based on the flexoelectric dynamic effect the size of.

Description

A high-sensitivity flexoelectric sensor for shock wave detection

technical field

The invention relates to the technical field of sensors, in particular to a high-sensitivity flexoelectric sensor that can be used for shock wave detection.

Background technique

The phenomenon of electromechanical coupling widely exists in various artificial and natural materials. Traditional piezoelectric sensors are made using the phenomenon that certain dielectric materials have a piezoelectric effect when they are stressed. The piezoelectric effect refers to the phenomenon that when some dielectrics are bent or deformed by external forces in a certain direction, charge accumulation occurs on the surface due to the polarization of internal charges. Piezoelectric sensors are used to measure the surface charge and use the electromechanical coupling relationship to realize other non-electrical measurements, and are widely used in mechanics, acoustics, medicine, aerospace and national defense.

Although piezoelectric materials have superior electromechanical conversion effects, in crystallography, piezoelectric effects only exist in crystals with non-centrosymmetric structures, which greatly limits the selection and utilization of materials. The piezoelectric effect of naturally occurring piezoelectric materials is very weak, and the piezoelectric rate is too low to be used in practical detection. The widely used piezoelectric materials are mainly composed of quartz crystals, piezoelectric polymers and piezoelectric ceramics. In practical industrial applications, most of the piezoelectric materials used are piezoelectric ceramics like lead titanate. However, lead titanate contains heavy metal lead, which is easy to cause harm to the environment and human health.

Different from the piezoelectric effect, the flexoelectric effect refers to the phenomenon of electrical polarization generated by a non-uniform strain field or strain gradient. Even for centrosymmetric crystals, the flexoelectric effect can also generate electrical polarization in materials. Due to the relatively relaxed requirement on crystal structure symmetry, the flexoelectric effect is ubiquitous in all dielectrics, including non-piezoelectric and isotropic materials.

When a shock wave passes through a flexoelectric dielectric material, high-strain-rate deformation occurs, producing a time-dependent strain gradient that produces a polarization displacement of the ions; for shock-compression waves, the acceleration of the atoms is proportional to the strain gradient , the acceleration of ions of different masses produces an additional polarization displacement, which results in a flexoelectric dynamic effect, which creates a polarized charge. The flexoelectric dynamic effect is usually defined as:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}\frac{<span\; class="notranslate">\; \&part;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}{<span\; class="notranslate">\; \&part;</span>\mathrm{<span\; class="notranslate">\; x</span>}}$

where μ _d =-χcM/ρ is the dynamic flexoelectric coefficient. M is a coefficient calculated from lattice dynamics. ε is the elastic strain of the material, x is the direction of the gradient, P is the polarization resulting from the strain gradient due to the flexoelectric effect, ρ is the density, and c is the elastic constant. Under the International System of Units, the unit of flexoelectric coefficient is C/m.

The choice of flexoelectric materials is wider, and environmental and human-friendly materials can be used to prepare functional devices such as flexoelectric sensors and drivers. Another notable feature is that the flexoelectric effect is related to size. Studies have shown that the strain gradient increases as the size of the structure decreases. Small-sized and high-sensitivity flexoelectric micro-devices are feasible in practice, and Measurements are more precise.

Contents of the invention

In order to overcome the above-mentioned problems in the prior art, the object of the present invention is to provide a high-sensitivity flexoelectric sensor that can be used for shock wave detection. A linear relationship between charges is generated to measure the magnitude of the shock wave pressure, and the pressure measurement can be realized accurately and simply.

In order to achieve the above object, the present invention adopts following technical scheme:

A high-sensitivity flexoelectric sensor that can be used for shock wave detection, including a left metal electrode 2 and a right metal electrode 4 respectively arranged on the left and right surfaces of a flexoelectric dielectric material 3; the left metal electrode 2 and the right metal electrode 4 are respectively There are two lead wires 5 that output the measured charge, and the other ends of the two lead wires 5 are connected to the external metal electrodes 8; the flexible dielectric material 3, the left metal electrode 2, the right metal electrode 4 and the lead wires 5 are sealed in the ring epoxy resin 7; the shell 7 and the metal screen 1 are bonded together to consolidate the epoxy resin 7; the metal screen 1 has a pressure channel through which the shock wave applies pressure.

The left metal electrode 2 and the right metal electrode 4 are evaporated metal electrodes.

The lead wire 5 is connected to the left metal electrode 2 , the right metal electrode sheet 4 and the external metal electrode 8 by wire bonding.

The flex dielectric 3 is a block of barium strontium carbonate.

The external metal electrodes 8 are two copper rods.

When a high-speed shock wave passes through a flexoelectric dielectric material 3, high-strain-rate deformation occurs, producing a time-dependent strain gradient that produces a polarization displacement of the ions; for shock-compression waves, the acceleration of the atoms is proportional to The strain gradient, the acceleration of ions of different masses produces additional polarization displacements, resulting in a flexoelectric dynamic effect, resulting in a polarization charge, whose expression is:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>\frac{<span\; class="notranslate">\; \&part;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}{<span\; class="notranslate">\; \&part;</span>\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}}{{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

U=kQ

where μ _d = -χcM/ρ is the dynamic flexoelectric coefficient, M is the coefficient calculated by lattice dynamics, ρ is the density, c is the elastic constant; μ is the static flexoelectric coefficient, ε is the elastic strain of the material , x is the direction of the gradient, P is the polarization generated by the strain gradient caused by the flexoelectric effect, Q is the output charge of the metal electrodes of the left metal electrode 2 and the right metal electrode sheet 4, k is the charge amplification factor, and U is the voltage The output of the value, H is the side length of the lower surface of the material specimen. It can be seen from the above formula that as long as the output charge value is measured, the linear relationship between the strain gradient generated by the flexoelectric dielectric material through the shock wave compression and the charge generated based on the flexoelectric effect can accurately and simply realize the measurement of the shock wave pressure .

Compared with the prior art, the present invention has the following advantages:

1) The present invention uses the flexoelectric dynamic effect to measure the shock wave pressure. Different from the traditional pressure sensor, the material selection range of the flexoelectric sensor is wider.

2) Compared with the piezoelectric pressure sensor, it has high sensitivity and has a size effect, and the sensitivity increases with the decrease of the block size.

3) Since the flexoelectric effect is mainly caused by the strain gradient, it is difficult to measure the strain in the case of small deformation, but the large strain gradient still exists, and the electrical signal can be detected very easily, and even the electrical signal can be directly output for analysis. It provides the possibility for the on-site inspection of the structure.

Description of drawings

The accompanying drawing is a structural schematic diagram of the sensor of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in the drawings, a high-sensitivity flexoelectric sensor that can be used for shock wave detection in the present invention includes left metal electrodes 2 and right metal electrodes 3 respectively arranged on the left and right surfaces of flexoelectric dielectric materials 3, the left metal electrodes The electrode 2 is in contact with the left surface of the flexible dielectric material 3; the right metal electrode 4 is in contact with the right surface of the flexible dielectric material 3; the left metal electrode 2 and the right metal electrode 4 are respectively connected with Two lead wires 5 that output the measured charge, the other ends of the two lead wires 5 are connected to the external metal electrodes 8, and the epoxy resin 7 seals the flexoelectric dielectric material 3, the metal electrodes 2, 4 and the lead wires 5; the metal screen 1 has a pressure channel through which the shock wave exerts pressure; the shell 7 is bonded to the metal screen 1, and the epoxy resin 7 is consolidated inside.

The left metal electrode 2 and the right metal electrode 4 are evaporated metal electrodes.

The lead wire 5 is connected to the left metal electrode 2 , the right metal electrode sheet 4 and the external metal electrode 8 by wire bonding.

The flex dielectric 3 is a block of barium strontium carbonate.

The external metal electrodes 8 are two copper rods.

When a high-speed shock wave passes through a flexoelectric dielectric material 3, high-strain-rate deformation occurs, producing a time-dependent strain gradient that produces a polarization displacement of the ions; for shock-compression waves, the acceleration of the atoms is proportional to The strain gradient, the acceleration of ions of different masses produces additional polarization displacements, resulting in a flexoelectric dynamic effect, resulting in a polarization charge, whose expression is:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>\frac{<span\; class="notranslate">\; \&part;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}{<span\; class="notranslate">\; \&part;</span>\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}}{{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

U=kQ

where μ _d = -χcM/ρ is the dynamic flexoelectric coefficient, M is the coefficient calculated by lattice dynamics, ρ is the density, c is the elastic constant; μ is the static flexoelectric coefficient, ε is the elastic strain of the material , x is the direction of the gradient, P is the polarization generated by the strain gradient caused by the flexoelectric effect, Q is the output charge of the metal electrodes of the left metal electrode 2 and the right metal electrode sheet 4, k is the charge amplification factor, and U is the voltage The output of the value, H is the side length of the lower surface of the material specimen. It can be seen from the above formula that as long as the output charge value is measured, the linear relationship between the strain gradient generated by the flexoelectric dielectric material through the shock wave compression and the charge generated based on the flexoelectric effect can accurately and simply realize the measurement of the shock wave pressure .

Claims (5)

1. can be used for a high sensitivity flexure electric transducer for shock-wave detection, it is characterized in that: comprise the left metal electrode (2) and right metal electrode (4) that are separately positioned on surface, the electric dielectric material of flexure (3) left and right; Described left metal electrode (2) and right metal electrode (4) are connected to two and export the lead-in wire (5) measuring electric charge, and the other end of two lead-in wires (5) is connected with external metal electrode (8); The electric dielectric material of described flexure (3), left metal electrode (2), right metal electrode (4) and lead-in wire (5) are sealed in epoxy resin (7); Shell (6) and metallic screen (1) bond together, in epoxy resin (7) is cemented in; Described metallic screen (1) has shock wave and executes stressed pressure channel.

2. a kind of high sensitivity flexure electric transducer that can be used for shock-wave detection according to claim 1, is characterized in that: described left metal electrode (2) and right metal electrode (4) are evaporation metal electrode.

3. a kind of high sensitivity flexure electric transducer that can be used for shock-wave detection according to claim 1, is characterized in that: described lead-in wire (5) and left metal electrode (2) and right metal electrode film (4) and external metal electrode (8) are connected by the mode of wire bonding.

4. a kind of high sensitivity flexure electric transducer that can be used for shock-wave detection according to claim 1, is characterized in that: the electric dielectric material of described flexure (3) is strontium carbonate barium block.

5. a kind of high sensitivity flexure electric transducer that can be used for shock-wave detection according to claim 1, is characterized in that: described external metal electrode (8) is two copper rods.