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Name of experiment：application of power amplifier in ultrasonic nondestructive testing

Research direction：structure nondestructive testing and damage monitoring based on ultrasonic guided wave

Content of experiment：PZT(piezoelectric sensor) is used as excitation sensor and receiving sensor to test Lamb wave signal in homogeneous aluminum plate (2024)

Purpose of experiment：the signals of symmetric (S0) and antisymmetric (A0) modes that simultaneously exist in the fundamental frequency of Lamb wave are collected, and the two modes are distinguished by parameter extraction of time domain signals.

The role of the amplifier in this experiment：

By considering the dispersion characteristics of the two fundamental frequency modes of Lamb wave, the time domain model of Lamb wave is strictly derived, and the coupling term that does not change with propagation time is obtained, which can be used for modal discrimination. The conclusion solves the multi-mode problem based on guided wave nondestructive testing technology. In the verification test, the excitation waveform must be strictly controlled, and the power amplifier with excellent performance at high frequency/bandwidth condition is needed.

Test equipment: Ata-2022h (Power Amplifier), PCI-1714(Data acquisition card), PCI-1721(data output card)

Experimental process（1）：

The self-programmed LABVIEW program generates the high-frequency modulation waveform, which is amplified by the power amplifier through the data output card to drive the excitation force sensor, and then receives the waveform signal through the data acquisition card. The measured structure is shown in FIG. 1.a, and the experimental device is shown in FIG. 1.b:

                                                 FIG. 1.a  structure to be tested                                       FIG. 1.b  experimental facilities

Result of experiment（1）:

The results are used to analyze the parameter extraction accuracy under different excitation bandwidths, and the experimental results and fitting results are as follows:

Figure 2.  (a) different excitation waveforms controlled by the bandwidth factor

             (b) the corresponding Fourier transform result

             (c) sampling results (os) and fitting results (RS)

             (d) correlation analysis of fitting results and sampling results

Description：the results are consistent with the theoretical results and reflect that the amplifier satisfies the ideal hypothesis under different bandwidths.

Experimental process（2）： Through the test of the plate structure with large area, the schematic diagram of the measured structure is as follows:

Figure 3: Diagram of the tested structure

Result of experiment：

Figure 4: test signal (blue line) and excitation signal ( red line ) excitation P-P voltage:36V

Description：

The measured signal verifies the correctness of the theoretical derivation, and it can be seen from the signal that the electromagnetic noise of the whole section is very small, which is related to the stability of the amplifier.

The role of the amplifier in this experiment: 

The PZT sensor is excited by providing a stable amplification signal to generate an almost ideal excitation waveform. In the experiment, the capacitance of PZT is 3.42nF.

Below are the frequency response graphs of ATA-2022H high voltage amplifier

                                                            ATA-2021B                                                                       ATA-2022B

                        Magnitude-frequency characteristic                       Small signal amplitude-frequency characteristics

（max. output voltage Vp-p）