Abstract
Noncontact ultrasonic detection technology is an effective method to detect damage in time. This paper proposes a noncontact damage detection system based on air-coupled ultrasound and full-field laser vibrometer, which realizes the excitation of relatively single-mode guided waves and the wavefield automatic detection. The system performance is verified through experiments, and the experimental wavenumber is consistent with the theoretical dispersion characteristics of the Lamb wave in the A0 mode. Based on this system, the topography reconstruction algorithms, including the Wavenumber Filtering Algorithm and Spatial Wavenumber Algorithm, were tested and compared with the aluminum alloy plate and the carbon fiber reinforced polymer plate. The results show that, based on the air-coupled ultrasound and full-field laser vibrometer detection system, the Spatial Wavenumber Algorithm has better imaging error and contrast, and the damage edge detection is smoother.
Highlights
System Composition and FunctionMainly includes an air-coupled ultrasonic transmitter and a full-field laser vibrometer
Introduction on AirCoupled Ultrasound and Ultrasonic technology is widely used in structural damage assessment due to its advantages of nondestructive and fast testing [1,2,3]
Wavenumber Filtering Algorithm (WFA) processes the full wavefield information through filtering in the wavenumber domain, and the filtered time domain wavefield is obtained through the inverse Fourier transform, and the damage situation is reflected by the time domain energy signal [20]
Summary
Mainly includes an air-coupled ultrasonic transmitter and a full-field laser vibrometer. Snell’s law of refraction, the ultrasonic angle of the transducer is easy to accurately adjust. The signal generator outputs a ms, Vpp, cycles, kHz sine pulse train, frequency of the probe. The signal generator outputs a 1 ms, 4 Vpp, 5 cycles, 200 kHz sine and 50 times amplified to realize the air-coupled ultrasonic excitation. The signal receiving component of the system is shown, which is performed by a full-field laser Doppler vibrometer (PSV-500-V). The He-Ne laser of the system has a wavelength of 633 nm, the velocity resolution is 0.01 μm/s (1 Hz), a minimum displacement resolution can be up to pico-meter level, and the frequency measurements range greatly reducing the complexity of the experiment operation and improving the spatial resolution of the signal.
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