Application of power amplifier in the study of defect location of curved plate of piezoelectric sensor

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Application of power amplifier in the study of defect location of curved plate of piezoelectric sensor [Copy link]

Experiment name: Research on defect location of curved panels based on piezoelectric sensors

Research direction:

Curved structures such as aircraft skin, aircraft wings, and wind turbine blades have always been difficult to detect. In order to identify minor damage to aircraft skin as early as possible and reduce the occurrence of aviation accidents, in-service non-destructive testing is very important during aircraft operation.

Ultrasonic Lamb wave flaw detection makes up for these shortcomings very well in the flaw detection of thin plate structures. As an ultrasonic guided wave, Lamb wave has very little attenuation when propagating in thin plate structures. The detection effect is still very obvious after propagating for a very long distance. Moreover, Lamb wave can simultaneously detect defects on a line of thin plate-like structures during one detection process, which greatly improves the efficiency of defect detection in the plate. Moreover, Lamb wave detection technology has a good ability for regional detection. Lamb wave will pass through the area between the two probes during propagation, thereby carrying information of the entire area. Therefore, ultrasonic Lamb wave is most suitable for non-destructive testing of thin plate materials, providing a new method for ultrasonic non-destructive testing of aircraft skins.

Piezoelectric sensors are the main sensing elements for Lamb wave excitation and reception, and are mainly divided into two categories: hard piezoelectric ceramic sensors and various flexible piezoelectric sensors. Hard piezoelectric ceramic sensors are currently the most widely used piezoelectric sensors, and have developed a variety of shapes and functions, as shown in the figure, including piezoelectric ceramic sheets of various shapes, piezoelectric stacks, and piezoelectric actuators. Piezoelectric ceramic materials were the first materials widely used to make ultrasonic sensors. Small piezoelectric chips made of piezoelectric ceramic materials are also used as sensor network units and are widely used in related research on structural health monitoring.

Experimental content:

This experiment is mainly to build a piezoelectric material damage detection system, including signal source, power amplifier, oscilloscope, and host computer. Piezoelectric materials often have a large impedance (MΩ level), and a power amplifier is needed to amplify the excitation signal to stimulate the piezoelectric signal. Therefore, the power amplifier is an indispensable part of the experiment.

Its main purposes are to:

1. Test the displacement/force excitation effect of various piezoelectric materials as excitation sources and the voltage response when used as sensing ends, including the following aspects:

The first step is to test the voltage response followability of various piezoelectric materials. By changing the amplification factor of the voltage amplifier, the voltage between the two stages of the excitation end is changed, and it is observed whether the voltage response of the sensing end changes with the change of the excitation end voltage, and whether it increases or decreases proportionally.

The second step is to detect the consistency of the voltage response frequency of various piezoelectric materials. By changing the frequency of the signal source, the voltage frequency between the two levels of the excitation end is changed, and the frequency of the voltage response at the sensing end is observed to be consistent with that at the excitation end.

Step 3: Detect the effect of different distances between the excitation end and the sensing end on the voltage response amplitude. Keep the position of the excitation end unchanged, change the distance between the piezoelectric sheet at the sensing end and the excitation end, and observe the change in the voltage response amplitude at the sensing end.

2. Locate the damage through the piezoelectric system, realize the damage location of the plate structure through the time delay method and directional response model, and improve the application scope and accuracy of ultrasonic testing of piezoelectric materials.

Purpose of the test:

1. Test the displacement/force excitation effect of various piezoelectric materials as excitation sources and the voltage response when used as sensing ends;

2. The damage is located by the piezoelectric system, and the damage location of the plate structure is achieved by the time delay method and the directional response model.

   Test equipment: Piezoelectric damage monitoring system, including signal source, power amplifier, high-performance oscilloscope and host computer.

   Experimental process:

   Test the voltage response of various piezoelectric materials:

   1. Test the displacement/force excitation effect of various piezoelectric materials as excitation sources and the voltage response when used as sensing ends, including the following aspects:

   (1) Detect the voltage response followability of various piezoelectric materials. By changing the amplification factor of the voltage amplifier, the voltage between the two stages of the excitation end is changed, and it is observed whether the voltage response of the sensing end changes with the change of the excitation end voltage, and whether it increases or decreases proportionally.

   (2) Detect the consistency of the voltage response frequency of various piezoelectric materials. By changing the frequency of the signal source, the voltage frequency between the two levels of the excitation end is changed, and the frequency of the voltage response at the sensing end is observed to be consistent with that at the excitation end.

   (3) Detect the effect of different distances between the excitation end and the sensing end on the voltage response amplitude. Keep the position of the excitation end unchanged, change the distance between the piezoelectric sheet at the sensing end and the excitation end, and observe the change in the voltage response amplitude at the sensing end.

Test results:

1. The voltage response waveform when the frequency is set at 20khz, 40khz, and 80khz has good followability.

2. The voltage response waveforms when the excitation voltage is set at 100V, 80V, and 60V change proportionally.

Conclusion: Under sinusoidal wave excitation, the voltage response waveform is stable, the frequency is consistent, and the amplitude is in the order of hundreds of millivolts, which meets the signal-to-noise ratio requirements.

3. At twice the distance, the voltage response decays to 0.1 times the original value, which is conducive to noise removal and also limits the detection range.

4. For burst excitation signals, the power amplifier can also effectively amplify the voltage and respond well.

5. It also has a good voltage amplification effect for user-defined arbitrary waves. The following figure is a comparison of the theoretical and actual output curves.

Conclusion: Through the signal voltage amplification test of different frequencies, amplitudes, and waveforms, it can be found that it can basically meet the experimental requirements, the waveform retention, frequency tracking are good, and the signal-to-noise ratio is also high.

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Inspection of aircraft skin, aircraft wings, wind turbine blades, etc.

The experiment of the simulation model introduced in the article

Not an actual test

90houyidai

Can you tell me more about the power amplifier and front-end amplifier?