CN100439929C - Method and system for measuring transverse piezoelectric strain constant of piezoelectric material by quasi-static method - Google Patents

Abstract

The invention relates to a method and system for measuring the transverse piezoelectric strain constant of a piezoelectric material (referred to as the d ₃₁ piezoelectric constant). The method uses a quasi-static method (different from the previous dynamic method and static method) to measure the d ₃₁ piezoelectric constant , by applying a low-frequency alternating force to the tested sample and measuring the low-frequency alternating voltage generated by the tested sample due to the positive piezoelectric effect, the d ₃₁ piezoelectric constant of the tested sample is obtained. The system is mainly composed of a force-applying device It is composed of two parts: the force applying device and the circuit device. The force applying device provides the force required for measurement to the sample to be tested through a special force-applying attachment. On the one hand, the low-frequency alternating voltage signal generated by the positive piezoelectric effect of the tested sample under the low-frequency alternating force is amplified and processed, and finally the obtained tested sample d ₃₁ piezoelectric constant is displayed and output, and the measurement operation is simple , fast, accurate and reliable measurement results.

Description

Method and system for measuring transverse piezoelectric strain constant of piezoelectric material by quasi-static method

technical field

The present invention relates to a method for measuring the piezoelectric constant of piezoelectric materials, in particular to a method and system for measuring the transverse piezoelectric strain constant of piezoelectric materials (abbreviated as _d31 piezoelectric constant).

technical background

Piezoelectric constant is the important parameter that characterizes the piezoelectric performance of piezoelectric material, mainly comprises longitudinal piezoelectric strain constant d ₃₃ (measurement method can refer to the patent " quasi-static method longitudinal compression method that the applicant was authorized on February 6, 99 Electrical strain constant measuring instrument, patent number: ZL97231420.2), transverse piezoelectric strain constant d ₃₁ , tangential piezoelectric strain constant d ₁₅ and isostatic piezoelectric constant d _h , etc. For transverse piezoelectric strain constant d ₃₁ In the past, the dynamic method and the static method were used to measure the transverse piezoelectric strain constant d ₃₁ , which was calculated by measuring the resonant and anti-resonant frequencies of the tested sample. It is currently internationally recognized that the measurement accuracy is relatively high A high d ₃₁ piezoelectric constant measurement method, but the test process of the dynamic method is cumbersome, and certain boundary conditions and shielding requirements are required to be met during the measurement, which has great limitations and can only measure standard samples that meet specific shape, specification and size requirements (For example: thin strips or thin discs), poor practicability. Static method to measure the d ₃₁ piezoelectric constant is to use the positive piezoelectric effect of the piezoelectric material to measure its force after applying a unidirectional force to the tested sample. The value of d ₃₁ can be obtained by using the piezoelectric voltage value, but in the measurement, the static force applied to ensure the measurement sensitivity is relatively large, due to the nonlinearity and pyroelectric drift of the piezoelectric material, resulting in large measurement errors and poor repeatability .

Contents of the invention

The purpose of the present invention is to solve the previous dynamic method to measure the piezoelectric material d ₃₁ piezoelectric constant test process is cumbersome, the defect of poor practicability, and to solve the static method to measure the d ₃₁ piezoelectric constant error and poor repeatability, thereby providing a suitable The d ₃₁ piezoelectric constant quasi-static measurement method and system can measure piezoelectric materials of various shapes, are simple and practical, and can meet the measurement accuracy requirements.

According to the definition of d ₃₁ piezoelectric constant:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="31"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Here, D ₃ , E ₃ are electric displacement and electric field intensity respectively, T ₁ , S ₁ are stress and strain perpendicular to the polarization direction, when the force provided to the tested sample is a low-frequency sine wave alternating force , when its frequency is much lower than the natural resonant frequency of the sample, the stress and strain in the sample are basically evenly distributed, so it is regarded as quasi-static. Equation (1) can be simplified as:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="31"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; B</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; QA</span>}}{\mathrm{<span\; class="notranslate">\; Facebook</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; CVA</span>}}{\mathrm{<span\; class="notranslate">\; Facebook</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Here, A is the area where the stress is applied, B is the area where the charge Q is generated, F is the applied low-frequency alternating force, and C is a large capacitor connected in parallel with the sample to meet the constant electric field boundary condition when measuring d ₃₁ , where C The value is determined by the size of the sample; V is the piezoelectric voltage generated across the large capacitor C due to the piezoelectric effect.

According to the d ₃₃ piezoelectric constant is defined as:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="33"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="S"\; filenames="C20051012622500122.png"\; state="\{\{state\}\}">S</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Here, D ₃ , E ₃ are the electric displacement and electric field strength respectively, T ₃ , S ₃ are the stress and strain consistent with the polarization direction, similarly, under quasi-static measurement conditions, formula (3) can be simplified as:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="33"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; cv</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Here, A is the area where the stress is applied and the charge Q is generated (since the stress and strain are consistent with the polarization direction), F is the applied low-frequency alternating force, and C is the large capacitance connected in parallel with the sample to be tested, also in order to provide a It meets the constant electric field boundary condition when measuring d ₃₃ , and its C value is determined by the size of the sample; V is the piezoelectric voltage generated at both ends of the large capacitor C due to the piezoelectric effect.

The object of the present invention is achieved like this, according to the definition of d ₃₁ piezoelectric constant, adopt the quasi-voltage method of directly applying low-frequency alternating force to the tested sample and measuring the low-frequency piezoelectric voltage produced by the positive piezoelectric effect of the tested sample The d ₃₁ piezoelectric constant of the tested sample is obtained by the static method. In order to make the measurement simple and feasible, the internal comparison sample is introduced, and the longitudinal piezoelectric constant d ₃₃ value of the internal comparison sample is used as the benchmark, and the d of the tested sample is obtained by the comparison method. ₃₁ piezoelectric constant.

The piezoelectric material quasi-static method transverse piezoelectric strain constant measurement method provided by the present invention (adopting comparative method), comprises the following steps:

1) Connect the tested sample and the internal comparison sample (the value of the longitudinal piezoelectric constant d ₃₃ is known) in series mechanically, so that the magnitude of the force on the two is consistent, and at the same time, the force direction of the internal comparison sample and its polarization The direction is consistent to meet the force requirement of its longitudinal piezoelectric constant d ₃₃ ; the force direction of the tested sample is perpendicular to the polarization direction to meet the force requirement of its transverse piezoelectric constant d ₃₁ ;

2) A large capacitor with the same capacity is connected in parallel between the two ends of the tested sample and the internal comparison sample to meet the constant electric field conditions required for the measurement of d ₃₁ and d ₃₃ ;

3) Apply the same low-frequency alternating force to the tested sample and the internal comparison sample. Due to the positive piezoelectric effect, a transverse piezoelectric charge is generated on the polarized electrode surface of the tested sample, and on the polarized electrode surface of the internal comparison sample A longitudinal piezoelectric charge is generated, and the two piezoelectric charges are converted into two piezoelectric voltage signals through respective parallel capacitors;

4) Use the known longitudinal piezoelectric constant _d33 value of the internal comparison sample and the measured and compared two-way piezoelectric voltage values obtained by applying the same low-frequency alternating force and the geometric dimensions of the tested sample (the area of the polarized electrode and force area), according to the following formula:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="31"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; B</span>}}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Calculate the d ₃₁ piezoelectric constant of the tested sample.

The working principle of the quasi-static transverse piezoelectric strain constant measurement method provided by the present invention is as follows: for the tested sample, assume that the applied force is F ₁ , the force-bearing area is A, the area of the polarized electrode is B, and the tested The large capacitor connected in parallel at both ends of the sample is C ₁ , the piezoelectric charge generated on the electrode surface B due to the piezoelectric effect is Q ₁ , and the piezoelectric voltage generated by the parallel connection of the large capacitor C ₁ is V ₁ , according to the formula (2 )’s d ₃₁ piezoelectric constant can be defined as:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="31"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; B</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

For the internal comparison sample, let the applied force be F ₂ , the force area and the area of the polarized electrode are both A (since the force direction of the sample is the same as its own polarization direction), and the large capacitance connected in parallel at both ends is C ₂ , the piezoelectric charge generated on the electrode surface A due to the piezoelectric effect is Q ₂ , and the piezoelectric voltage generated on the parallel large capacitor C ₂ is V ₂ , which is defined according to the d ₃₃ piezoelectric constant of formula (4) Available:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="33"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Since the capacitances connected in parallel at both ends of the tested sample and the internal comparison sample are the same, that is: C ₁ =C ₂ ; and because the tested sample and the internal comparison sample are mechanically connected in series, the force on both is the same, then: F ₁ =F ₂ ; The ratio of the d ₃₁ piezoelectric constant of the tested sample to the d ₃₃ piezoelectric constant of the internal comparison sample is shown in the following formula:

$\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="33"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}}<span\; class="notranslate">\; =</span>\frac{\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; B</span>}}}{\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; B</span>}}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Since the internal comparison sample is unchanged in the measurement, its d ₃₃ piezoelectric constant value is known, and because the force-bearing area of the tested sample and the area where the charge is generated can be directly measured with a caliper, it can be measured by measuring The test sample is compared with the internal piezoelectric voltage values _V1 and _V2 on the parallel capacitors at both ends of the sample to obtain the _d31 piezoelectric constant of the tested sample, see the following formula (or formula 5 and the formula in claim 1).

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="31"\; label="d"\; filenames="C20051012622500132.png,C20051012622500141.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; B</span>}}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

In the above technical solution, the frequency of the low-frequency alternating force is about 110 Hz, the amplitude of the low-frequency alternating force is 0.2 Newton, and the large capacitors connected in parallel at both ends of the tested sample and the internal comparison sample are both 1 micron Law.

The piezoelectric material quasi-static method transverse piezoelectric strain constant measurement system (see Figure 2) provided by the present invention includes a force applying device and a circuit device, wherein the force applying device includes: an electromagnetic driver, a special force adding accessory (see Figure 3) and internal comparison samples;

Described electromagnetic driver is made of magnetic steel 33, yoke iron core 36, outer yoke iron 34, yoke iron base 35, coil 32, piston 31 and centering strut 30, and wherein the upper end of coil 32 links to each other with the lower end of piston 31, The centering strut 30 is fixed on the end face of the outer yoke 34, and the effective part (winding part) of the coil 32 is suspended in the magnetic field gap formed by the magnetic steel 33, the yoke core 36 and the outer yoke 34. When the coil 32 When the low-frequency sine wave drive signal is connected, it can move up and down linearly in the above-mentioned magnetic field and generate a low-frequency sine wave alternating force in the vertical direction through the piston 31;

The special booster accessories are made of insulating materials, the upper booster disc 1 and the lower booster disc 3, the positioning connector 16, the fixed probe 17, the moving probe 18, the moving probe fixing screw 19, the base 20 and the base Composed of fixing screws 21, wherein the upper force disc 1 is fixed at the end of the beam extension of the positioning slider 25 in the force applying device, and the lower force disc 3 passes through the center of the circular positioning diaphragm 28 and the insulating connecting column 4 Connected; the positioning connector 16 is inserted on the positioning hole of the lower force disc 3, and the fixed probe 17 with threads can be rotated and positioned through the screw hole of the positioning connector 16; the base 20 is stuck on the main shell 22 and the fixed ring 29, fixed by the base fixing screw 21, the moving probe 18 passes through the round hole on the base 20 and is positioned and fixed by the moving probe fixing screw 19; the upper booster disc 1 and the lower booster disc 3 of the special booster attachment For applying vertical vertical force to the tested sample 2, the position of the fixed probe 17 and the adjustment of the movable probe 18 can be used to make the two probes close to the two electrode surfaces of the tested sample 2 (direction B in Fig. 3 and Fig. 4). Contact and lead out the piezoelectric signal generated by the piezoelectric effect of the tested sample. The special force attachment can provide a longitudinal force and a horizontal (or radial) Obtain the piezoelectric signal (see Figure 3);

The internal comparison sample is made of piezoelectric ceramic material (also can be made of other piezoelectric materials), has stable piezoelectric performance, and its d ₃₃ piezoelectric constant has very little influence with time, temperature, and humidity changes. As the benchmark for the measurement of the piezoelectric constant of the tested sample d ₃₁ , it is installed inside the force application device and connected in series with the tested sample mechanically, and the two are under the same force.

Described circuit device is made up of two-way preamplifier 9 and 10, oscillator 11, power amplifier 12, data input part 13, data processing part 14 and display output part 15, wherein the output of oscillator 11 and the output of power amplifier 12 The input is connected; the input of the preamplifier 9 and 10 is connected with the large capacitance connected in parallel at both ends of the tested sample 2 and the comparative sample 6 respectively, and the output of the preamplifier 9 and 10 is connected to the data processing part 14 with the data input part 13, The output of the data processing section 14 is connected to the display output section 15 .

The oscillator 11 is a sine wave voltage signal generator with an oscillation frequency of about 110 Hz;

The power amplifier 12 has an output power of only 5 watts and is continuously adjustable. The output signal of the sine wave signal generator is amplified by the power amplifier and connected to the coil of the electromagnetic driver, so that the electromagnetic driver can generate a maximum of 1 Newton of low-frequency sine wave wave alternating force;

The two-way preamplifiers 9 and 10 are respectively used to amplify the measured and compared two-way piezoelectric voltage signals _V1 and _V2 , the input impedance is about 200KΩ, and the gain range is 60-80db;

Described data input 13 is used for inputting the stressed area and the polarized area (A and B) of the sample to be tested, and is three-digit decimal number input, and its input content is the stressed area of the tested sample and the ratio of the polarized area (The force area and polarization area can be easily measured with a caliper);

The data processing 14 is composed of a synchronous linear detector, an analog divider and an A/D conversion part, and is used to process and calculate the amplified V ₁ and V ₂ and other existing or input data to obtain The tested sample d ₃₁ piezoelectric constant. The amplified two-way low-frequency alternating voltage V ₁ and V ₂ are first converted into two-way DC voltage signals through a synchronous linear detector, and then compared with the input force area A, polarization area B and internal comparison of the sample The d ₃₃ piezoelectric constant value is sent to the analog multiplier and divider to calculate the analog value of the d ₃₁ piezoelectric constant according to formula (5), and then the calculated d ₃₁ piezoelectric constant analog value of the tested sample is converted through A/D conversion be a digital value;

The display output 15 is composed of 4 LED digital tubes plus a sign bit, and can display and output the measured piezoelectric constant value and polarity of the tested sample d ₃₁ .

The main working process of the piezoelectric material quasi-static method transverse piezoelectric strain constant measurement system provided by the present invention is as follows: first, the oscillator in the circuit device provides a low-frequency sine wave signal of about 110 Hz, which is amplified by the power amplifier and then sent to the force applying device The medium electromagnetic driver generates a low-frequency sine wave alternating force of about 0.2 Newton and applies it to the tested sample (the direction of the applied force is perpendicular to the polarization direction of the sample itself) and the internal comparison sample (the direction of the applied force is consistent with the polarization direction of the sample itself). Due to the piezoelectric effect, the two piezoelectric voltage signals generated on the tested sample and the internal comparison sample are amplified by the preamplifier and then processed together with the input tested sample size, and the finally obtained tested sample d ₃₁ voltage The electrical constant value and polarity are directly displayed on the output.

The advantages of the present invention are: the frequency of the sine wave low-frequency alternating force selected in the measurement is about 110 Hz, which is far lower than the natural resonance frequency of the general tested sample, so the stress and strain in the tested sample are basically evenly distributed, and the measured The required boundary conditions are guaranteed; since the magnitude of the low-frequency alternating force applied to the sample during measurement is only about 0.2 Newtons, which is far lower than the force of tens of Newtons in the static method measurement, effectively avoiding the piezoelectric material The occurrence of inherent nonlinearity and pyroelectric drift phenomenon reduces the measurement error and ensures the measurement accuracy; and because the comparison method is used in the measurement, the tested sample and the internal comparison sample are mechanically connected in series, and the d ₃₁ is calculated during the data processing The sine wave low-frequency alternating force applied at the piezoelectric constant can not only be reduced (see Equation 8 and Equation 5), but also the static pressure deviation caused by adjusting the tightness of the force-applying device to the tested sample during the force application process can also be reduced. can be offset, and at the same time, since the piezoelectric constant of the tested sample d ₃₁ is based on the internal comparative sample d ₃₃ piezoelectric constant, the measurement can not only obtain the d ₃₁ piezoelectric constant value of the tested sample but also obtain the d 31 piezoelectric constant of the tested sample The polarity of ₃₁ piezoelectric constants makes the measurement results practical and effective.

Description of drawings

Fig. 1 is the schematic diagram of _d31 piezoelectric constant quasi-static measurement method of the present invention

Fig. 2 is the structure schematic diagram of _d31 piezoelectric constant quasi-static measurement system of the present invention

Fig. 3 is a schematic diagram of the structure of the d ₃₁ piezoelectric constant quasi-static measurement special force attachment of the present invention

Fig. 4 is a structural schematic diagram of the d ₃₁ piezoelectric constant quasi-static measurement force application device of the present invention

Fig. 5 is the schematic diagram of the structure of the quasi-static measurement embodiment of the _d31 piezoelectric constant of the present invention

Graphic description

1-upper force disc 2-test sample 3-lower force disc

4-Insulation connection post 5-Comparison upper probe 6-Comparison sample

7-Comparative probe 8-Electromagnetic driver B-Electrode surface of the tested sample

9-First preamplifier 10-Second preamplifier 11-Oscillator

12-power amplifier 13-data input 14-data processing

15-Display output 16-Fixed probe positioning connector 17-Fixed probe

18-Movement probe 19-Movement probe fixing screw 20-Base

21-base fixing screw 22-main housing 23-positioning guide rail

24-Guide rail slot cover 25-Positioning slider 26-Adjusting rod

27-Adjusting hand wheel 28-Circular positioning diaphragm 29-Fixed ring

30-Spacer 31-Piston 32-Coil

33-Magnet 34-Outer yoke 35-Yoke base

36-Yoke core 37-Signal input connection socket

Detailed ways

Now, the measurement method and system of the present invention will be further described in detail with reference to the above-mentioned figures and embodiments.

Referring to Figures 2 and 5, an embodiment of a piezoelectric material quasi-static transverse piezoelectric strain constant measurement system consisting of a force applying device and a circuit device is produced.

Referring to Figure 4, the electromagnetic driver in the force applying device of this embodiment is composed of a magnetic steel 33, a yoke core 36, an outer yoke 34, a yoke base 35, a coil 32, a piston 31 and a centering strut 30, wherein the outer yoke The iron 34 is fixed on the yoke base 35, the upper end of the coil 32 is connected with the lower end of the piston 31, and is fixed on the end face of the outer yoke 34 by the centering strut 30, and the winding part of the coil 32 is suspended by the magnetic steel 33, In the magnetic field gap formed by the yoke core 36 and the outer yoke 34 , when a low-frequency sine wave drive signal is connected, it can move up and down linearly in the above-mentioned magnetic field and generate a vertical low-frequency alternating force through the piston 31 .

Referring to Fig. 3, the special booster attachment of this embodiment consists of an upper booster disc 1 and a lower booster disc 3 made of epoxy boards, a fixed probe 17 made of stainless steel and its positioning connector 16, moving The probe 18 and its fixing screw 19, the base 20 and the base fixing screw 21 are composed, the upper booster disc 1 is fixed at the end of the beam extension of the positioning slider 25 in the force applying device, and the lower booster disc 3 passes through the circle The center of the type positioning diaphragm 28 is connected with the insulating connecting column 4; the positioning connecting piece 16 is inserted on the positioning hole of the lower force-applying disk 3, and the fixed probe 17 with thread can pass through the screw hole of the positioning connecting piece 16 to perform rotational positioning The base 20 is stuck on the main housing 22 and the fixed ring 29, fixed by the base fixing screw 21, and the mobile probe 18 can move horizontally through the round hole on the base 20 and be fixed by the fixing screw 19. The signal input connection socket 37 is installed on the outer wall of the main housing 22 . The upper force disc 1 and the lower force disc 3 are used to apply a longitudinal vertical force to the tested sample 2, and the position of the fixed probe 17 by rotation and the position of the movable probe 18 can be adjusted so that the two probes are aligned with the two sides of the test sample 2. The electrode surface (direction B in Figure 3 and Figure 4) is in close contact, leading to the piezoelectric signal generated by the piezoelectric effect of the tested sample. The test sample provides the longitudinal force and obtains the piezoelectric signal from the transverse direction (or radial direction) (see Figure 3)

Internal comparison sample 6 is borne by a cylindrical piezoelectric ceramic element made of PZT-5 piezoelectric ceramic material. Its diameter is 6 mm and its height is 5 mm. After sufficient aging time, its d ₃₃ piezoelectric The constant is stable at 400pC/N. The polarized electrode surface is the upper and lower end surfaces of the cylinder, and the upper end surface is the positive electrode of the polarization, which is connected to the comparison probe 5; the lower end surface is the negative electrode of the polarization, which is in phase with the comparison probe 7. connect.

The two ends of the fixed probe 17 and the moving probe 18 and the two ends of the upper and lower probes 5 and 7 are respectively connected in parallel with a capacitor of 1 microfarad to be connected to the preamplifiers 9 and 10 (referring to Fig. 1 ) in the circuit device through a cable. The input impedance of the two preamplifiers is 200KΩ, and the gain is exactly the same, which is 80db.

Referring to FIG. 2 , the circuit device of this embodiment includes an oscillator 11 , a power amplifier 12 , a data input part 13 , a data processing part 14 and a display output part 15 in addition to two preamplifiers 9 and 10 with identical performance.

Here, the process of measuring the d ₃₁ piezoelectric constant of a square sample (length, width, and height) made of a PZT-5 piezoelectric ceramic material is as follows:

With reference to Fig. 5, at first the force applying device and the circuit device in the piezoelectric material quasi-static method transverse piezoelectric strain constant measurement system are connected (can refer to the relevant description in embodiment 1), then the block type tested sample (2 ) is placed in the middle of the upper force disc (3), when the sample is polarized, one end of the positive electrode is connected to the fixed probe (17), while the other end of the negative electrode is connected to the moving probe (18). Adjust the moving probe (18) ) Make the two electrode surfaces of the square-shaped sample to be tested (2) closely contact with the fixed probe (17) and the moving probe (18), and fix it with the moving probe fixing screw (19), then, rotate the adjustment of the force applying device The hand wheel (27) moves the positioning slide block (25) up and down and drives the upper force disc (1) to move up and down to press the square-shaped test sample (2), open the switch of the circuit device in the system, and the oscillator (11 ) work, the sine wave oscillation signal with an oscillation frequency of 110 Hz is amplified by the power amplifier (12) and then sent to the electromagnetic driver in the force applying device, which is converted into an alternating force of the same frequency and acts on the inside of the cylindrical type to compare the sample (6) and the square type On the tested sample (2), due to the piezoelectric effect, the two low-frequency alternating voltages generated on the parallel capacitors at both ends of the square-shaped tested sample (2) and the cylindrical internal comparison sample (6) pass through the respective connected preamplifiers. After amplifiers (9) and (10) are amplified, they are respectively sent to the synchronous linear detector in the data processing part (13) for detection, and the DC voltage V1 corresponding to the low-frequency alternating voltage of the square-shaped tested sample (2) is obtained. The polarity is negative, and the DC voltage V2 corresponding to the low-frequency alternating voltage of the cylindrical internal comparison sample (6) has a positive polarity. Since the square-shaped tested sample (2) has the same stress area as the polarization area (15mm ×15mm) with a ratio of 1, input "1.00" through the dial of the data input (13) and the d ₃₃ piezoelectric constant "400pC/N" of the cylindrical internal comparison sample (6) and send it to the analog multiplier and divider according to the quasi-static The d ₃₁ calculation formula of the comparative method in the method measurement, calculates the d ₃₁ piezoelectric constant of the square-shaped test sample (2) and performs A/D conversion, and the final measurement result is "-212pC/N". The above is a complete process of measuring the piezoelectric constant of the square-shaped sample d ₃₁ using the piezoelectric material quasi-static method transverse piezoelectric strain constant measurement system in Embodiment 1 of the present invention, and the square-shaped sample is put into the measurement system as required After the special force-adding accessories in the force-applying device are fixed, the circuit device in the measurement system is activated to complete the whole process from oscillation drive output, signal input amplification, data processing to final measurement result display and output. It only takes a few seconds, up to ten a few seconds.

Claims (3)

1. a quasi-static method transverse piezoelectric strain constant measuring method of piezoelectric material, comprises the following steps: 1) The tested sample and the internal comparison sample are mechanically connected in series so that the magnitude of the force on the two is consistent. At the same time, the force direction of the internal comparison sample is consistent with its polarization direction to satisfy its longitudinal piezoelectric strain constant d ₃₃ The added force requirement; the force direction of the tested sample is perpendicular to the polarization direction, so as to meet the added force requirement of its transverse piezoelectric strain constant d ₃₁ ; 2) A large capacitor with the same capacity is connected in parallel between the two ends of the tested sample and the internal comparison sample to meet the constant electric field conditions required for the measurement of d ₃₁ and d ₃₃ ; 3) Apply the same low-frequency alternating force to the tested sample and the internal comparison sample, the frequency of the low-frequency alternating force is 110Hz; the amplitude of the low-frequency alternating force is 0.2 Newton; due to the positive piezoelectric effect in the tested Transverse piezoelectric charges are generated on the polarized electrode surface of the same sample, and longitudinal piezoelectric charges are generated on the polarized electrode surface of the internal comparison sample. The two piezoelectric charges are converted into two piezoelectric voltage signals through their respective parallel capacitors. ; 4) Use the known longitudinal piezoelectric strain constant d ₃₃ value of the internal comparison sample, and the measured and compared two-way piezoelectric voltage values obtained by applying low-frequency alternating force, as well as the area of the polarized electrode of the tested sample and force-bearing area, according to the following formula: ${\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; B</span>}}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}$ Calculate the transverse piezoelectric strain constant d ₃₁ of the tested sample; Among them, A is the area where the stress is applied, and B is the area where the charge Q is generated; V ₁ is the piezoelectric voltage generated by the tested sample; V ₂ is the piezoelectric voltage generated by the internal comparison sample. 2. by the quasi-static method transverse piezoelectric strain constant measuring method of piezoelectric material according to claim 1, it is characterized in that, described internal comparative sample is the cylindrical piezoelectric element that piezoelectric ceramic material makes. 3. a quasi-static method transverse piezoelectric strain constant measurement system of piezoelectric material, comprises force applying device and circuit device; Described circuit device is made of two-way preamplifier (9,10), oscillator (11), A power amplifier (12), a data input part (13), a data processing part (14) and a display output part (15); wherein the two-way preamplifiers (9, 10) have an input impedance of 200 kiloohms and a gain range of 60 -80db is used to amplify the measured and compared two-way piezoelectric voltage signals; the data input part (13) is a three-digit decimal number input, which is used to input the ratio of the stressed area of the tested sample to the polarized area; the data The processing part (14) is composed of a synchronous linear detector, an analog divider and an A/D conversion part electrically connected, and is used to calculate the tested sample according to the measured and compared two-way piezoelectric voltage signals obtained in the measurement, and other relevant parameters. The transverse piezoelectric strain constant d ₃₁ value; display output part (15) is made up of four LED nixie tube plus sign bit, is used for displaying the final result of measurement; Oscillator (11) and power amplifier (12) are used for applying The electromagnetic driver in the force device provides the driving signal; The force applying device is composed of an electromagnetic driver used to generate low-frequency alternating force, an internal comparison sample used as a comparison method measurement benchmark, and an accumulator used to provide the required force for measurement and obtain a piezoelectric signal for the tested sample. The electromagnetic driver is composed of magnetic steel (33), yoke iron core (36), outer yoke iron (34), yoke iron base (35), coil (32), piston (31) and centering support The upper end of the coil (32) is connected to the lower end of the piston (31), and is fixed on the end face of the outer yoke (34) by the centering strut (30), and the winding part of the coil (32) is suspended Placed in the magnetic field gap formed by magnetic steel (33), yoke iron core (36) and outer yoke iron (34); it is characterized in that, The booster attachment is composed of an upper booster disc (1) and a lower booster disc (3) made of insulating material, a fixed probe (17), a positioning connector (16), a moving probe (18), a moving The probe fixing screw (19), the base (20) and the base fixing screw (21) are composed; the upper force disc (1) is fixed at the beam extension end of the positioning slider (25) in the force applying device, The lower booster disc (3) passes through the center of the circular positioning diaphragm (28) and is connected with the insulating connecting column (4); the positioning connector (16) is inserted in the positioning hole of the lower booster disc (3), with The threaded fixed probe (17) is fixed through the screw hole of the positioning connector (16); the base (20) is clamped on the main shell (22) and the fixing ring (29), and fixed by the base fixing screw (21) , the mobile probe (18) can move horizontally in the circular hole on the base (20), and be positioned and fixed by its fixing screw (19).

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