Application Cases

【Overview】
In this study, the Aigtek ATA-2022B high-voltage amplifier was used to build an experimental system for ultrasonic guided wave full wavefield imaging (UGWI). UGWI has attracted widespread attention in industrial nondestructive testing and evaluation applications due to its ability to non-contact record full wavefield data containing information about structural inhomogeneities. By utilizing the thickness-wavenumber dispersion relationship of guided waves and the wavenumber spectrum, the size, location, and depth of defects can be quantitatively characterized from the full wavefield. However, a major challenge in UGWI is the trade-off between noise immunity and imaging efficiency. To simultaneously achieve noise immunity and high efficiency, a computationally efficient method called adaptive spatial wavenumber estimation (ASWE) was proposed for depth-resolved detection. By modifying the fixed spatial window in local wavenumber estimation (LWE) to an adaptive spatial window, the imaging process is significantly accelerated without sacrificing depth resolution and robustness. Furthermore, to improve the depth accuracy of imaging results, a reference wavefield-based filter was introduced to isolate the detection wavefield from other accompanying wavefields, and an inverse procedure for longitudinal and transverse wave velocities was designed to calibrate dispersion. Validation experiments were conducted on several metal plate specimens with various shaped artificial thinning defects, steps, and linear depths. The results demonstrate that the proposed ASWE method is an accurate and efficient approach for depth-resolved detection, advancing the industrial application of UGWI.

Experiment Name: Application of Power Amplifier in Full Wavefield Corrosion Imaging Using Ultrasonic Guided Waves

Research Direction: Ultrasonic Nondestructive Testing

Experimental Content:
Corrosion-induced thickness loss poses a significant threat to the integrity of shell structures, making quantitative assessment of thinning depth critically important. Ultrasonic Lamb wave testing is widely used for detecting various defects in thin-walled structures due to its advantages of convenience, low cost, safety, sensitivity to damage at any position on the cross-section of the waveguide structure, and the ability to inspect the entire structure from a single probe location. A scanning laser vibrometer can acquire the full guided wavefield in the propagation region. By analyzing the relationship between frequency and wavenumber in the ultrasonic Lamb wave full wavefield, features corresponding to different structural depths can be separated, thereby improving diagnostic accuracy. In this experiment, a Hanning window-modulated 5-cycle sinusoidal pulse signal with a center frequency of 400 kHz was generated using an arbitrary waveform generator. The signal was further amplified by an ATA-2022B high-voltage amplifier to drive a PZT piezoelectric patch to generate ultrasonic guided waves. A laser vibrometer was used to record the full wavefield data of the ultrasonic guided waves on the specimen surface for signal processing and defect imaging.

Testing Equipment:
Arbitrary waveform generator, ATA-2022B high-voltage amplifier, PZT piezoelectric patch, laser vibrometer, data acquisition card, etc.

Experimental Procedure:

Figure: Physical Setup of the Experimental Test System

In this experiment, a narrowband pulse signal modulated by a Hanning window (center frequency 400 kHz, 5 cycles) was used to excite Lamb waves propagating in a plate structure. The signal design, through time-domain envelope optimization, achieves spectral energy focusing (-6 dB bandwidth 320–480 kHz), effectively suppressing side-lobe interference. When Lamb waves propagate to a corrosion defect region, multiple physical responses are excited, including scattered wave generation, S0/A0 mode conversion, and wave velocity changes. A laser vibrometer (displacement resolution 0.1 μm, scan step 1 mm) was used to non-contact capture the full wavefield space-time matrix (typical dimensions: 200×200 spatial points × 10,000 time points) on the specimen surface. The experimental system used an arbitrary waveform generator to generate the excitation signal, which was amplified by an ATA-2022B high-voltage amplifier (gain 40×, output 200 Vpp) to drive a 4 mm × 4 mm × 4 mm PZT piezoelectric patch to generate ultrasonic Lamb waves. Finally, a local wavenumber estimation algorithm was used for defect imaging, achieving a spatial resolution of λ/2 (approximately 2 mm in aluminum at 400 kHz), significantly  the physical limitations of traditional point-sensing methods.

Experimental Results:

Figure: Experimental Results

Tests were conducted on three aluminum plates with different defects. The imaging results show that the obtained images accurately represent the spatial distribution characteristics of the defects. Not only was the defect morphology well characterized, but the defect depth information was also obtained. The defect location and depth were consistent with the actual values, with slightly expanded boundaries due to the minimum window width being set to one wavelength, which helps suppress wavenumber leakage errors. In shallow defect regions, some imaging methods suffer from reduced resolution. The robustness of local wavenumber estimation in such areas is affected by wavefield interference, especially in regions where boundary reflections and defect scattering overlap. For samples with relatively uniform defect depth distribution, the detection exhibited high computational efficiency. In areas with sharp depth variations, the computational time correspondingly increased. Thanks to the stable output and high-voltage amplification of the ATA-2022B high-voltage amplifier, the signal-to-noise ratio of the imaging results was extremely high. Almost no significant artifacts were observed in the background area, with only weak diffraction streaks appearing at the defect edges, slightly deviating from the incident direction, which is a physical scattering phenomenon that is difficult to completely suppress.

Advantages of Aigtek Amplifiers in This Application:

1. High voltage output capability (200 Vpp) – Drives PZT to generate Lamb waves with sufficient energy to penetrate defect regions.

2. Wide bandwidth and low distortion – Accurately reproduces the 5-cycle narrowband pulse modulated by a Hanning window at 400 kHz.

3. High stability and low noise – Achieves extremely high signal-to-noise ratio imaging.

Recommended Product: ATA-2022B High-Voltage Amplifier

Figure: ATA-2022B High-Voltage Amplifier Specifications and Parameters