Ultrasonics最新文献

Numerical analyses are performed to investigate ultrasonic wave propagation in fluid–solid half-spaces subject to a directional source. This research is particularly concerned with the behavior of refracted waves within fluid mediums and their utility in determining the acoustic velocities of solid materials. The simulations encompass solids with various mechanical parameters and highlight the influence of incident angles on wave propagation. The analysis reveals that as the disparity between incident and critical angles increases, both the dominant frequencies and amplitudes of the corresponding refracted waves decrease substantially, which is detrimental to the accurate extraction of solid velocities. For the low-velocity solid characterized by its shear wave velocity being less than the fluid’s acoustic velocity, refracted longitudinal waves are susceptible to interference from direct and reflected waves. This interference often results in underestimated velocity measurements. The challenge can be addressed by either extending the source-receiver offset or by adjusting the incident angle closer to the critical angle. Regarding solids with shear wave velocities exceeding the fluid’s acoustic velocity, although the velocity–time correlation (VTC) method can accurately determine longitudinal wave velocities, shear wave velocity extraction may be compromised by the presence of the leaky Rayleigh wave. We further compare velocities calculated by dividing the spacing distance of two receivers by the time difference of their respective wave packet arrivals. Results indicate that the initial trough and peak of the S wave packet are predominantly influenced by refracted shear waves and the leaky Rayleigh wave, respectively. This occurs because refracted shear waves propagate slightly faster than the leaky Rayleigh wave. Consequently, using the first trough of the shear wave packet as the wave onset can mitigate the impact of the leaky Rayleigh wave, yielding precise shear wave velocity measurements. These studies are of considerable importance for applications in geophysical downhole measurements and nondestructive testing.

High-temperature ultrasonic transducer (HTUT) is essential for non-destructive testing (NDT) in harsh environments. In this paper, a HTUT based on BiScO₃-PbTiO₃ (BS-PT) piezoelectric ceramics was developed, and the effect of different backing layers on its bandwidth were analyzed. The HTUT demonstrates a broad bandwidth and excellent thermal stability with operation temperature up to 400 °C. By using a 10 mm thick porous alumina backing layer, the HTUT achieves a broad −6 dB bandwidth of 100 %, which is about 4 times superior to the transducer with an air backing layer. The center frequency (f_c) of the HTUT remains stable with fluctuations of less than 10 % across the temperature range from room temperature to 400 °C. The HTUT successfully detected simulated defects in pulse-echo mode for NDT over 200 °C. This research not only advances high-temperature ultrasonic transducer technology but also expands the NDT applications in harsh environmental conditions.

Underwater inspection is important to ensure the safety, integrity and functionality of underwater structures. Although numerous conventional methods have been adopted for underwater inspection, successful application of most methods relies on the surface condition of the object, which, however, is typically covered by marine growth. Consequently, routine inspection requires thorough cleaning of marine growth, which is time-consuming and costly. Hence a method which can inspect objects without the need for extensive surface cleaning is necessary. Two methods have the potential to achieve this: pulse eddy current (PEC) and electromagnetic acoustic transducer (EMAT). PEC attains a significant lift-off distance, enabling inspection through marine growth. However, it suffers from high sensitivity to environmental conditions and low inspection accuracy due to ‘relative’ property which means its results are interpreted by comparing received signals to reference values. In contrast to PEC, EMAT provides ‘absolute’ measurements, ensuring precise results in the inspection. But it is limited by a small lift-off distance ($<2\sim$3 mm), rendering it unsuitable for underwater applications with marine growth. Therefore, if the lift-off distance can be enhanced to a specific value, this method may offer a superior solution for underwater inspections. In this paper, a quantitative measurement method is proposed through employing a shear wave EMAT with high lift-off performance. A repelling configuration of magnets is introduced to achieve a significantly improved maximum effective lift-off distance of up to 5 mm in both air and seawater conditions with only 400 Vpp applied. This EMAT is then demonstrated to measure thickness through marine growth, showing excellent underwater performance in quantitative thickness mapping for corrosion inspection.

Osteoporosis is a systemic disease with a high incidence in the elderly and seriously affects the quality of life of patients. Photoacoustic (PA) technology, which combines the advantages of light and ultrasound, can provide information about the physiological structure and chemical information of biological tissues in a non-invasive and non-radiative way. Due to the complex structural characteristics of bone tissue, PA signals generated by bone tissue are non-stationary and nonlinear. However, conventional PA signal processing methods are not effective for non-stationary signal processing. In this study, an empirical mode decomposition (EMD)-based Hilbert-Huang transform (HHT) PA signal analysis method, called HHT PA signal analysis (HPSA), was developed to assess the microstructure information of bone tissue, which is closely related to bone health. The feasibility of the HPSA method in bone health assessment was proven by numerical simulation and experimental studies on animal samples with different bone volume/total volume (BV/TV) and bone mineral densities. First, based on adaptive EMD, the different modes correlated with multi-scale information were mined from the PA signal, the correlations between different intrinsic mode function (IMF) modes and BV/TVs were analyzed, and the optimal mode for more efficient PA time–frequency analysis was selected. Second, multi-wavelength HPSA was used to assess the changes in the chemical components of the bone tissue. The results demonstrate that the HPSA method can distinguish bones with different BV/TVs and microstructure conditions adaptively with high efficiency. They further emphasize the potential of PA techniques in characterizing biological tissues in bones for early and rapid detection of bone diseases.

Guided Wave (GW)-based Multiple Signal Classification (MUSIC) damage imaging presents several advantages, such as high resolution, which makes it a promising technique for localizing damage in composite structures. However, the application of this technology in aircraft is confronted with various challenges. The variability in performance of MUSIC array sensors is attributed to material and manufacturing process dispersion. Additionally, the conventional wiring of MUSIC array sensors adds considerable weight and is not compatible with complex structural configurations. Furthermore, within intricate configurations, the attenuation of scattering signals induced by structural damage impacts the accuracy of imaging. Moreover, the manual and individual placement of sensors on structures, along with structural anisotropy, may introduce phase errors in the signals detected by MUSIC array sensors. This can lead to a reduction in the accuracy of MUSIC imaging and result in compromised long-term sensor reliability. This paper proposes a high-precision integrated MUSIC array for the diagnosis of complex composite damage. This approach aims to address the challenges related to damage imaging in materials with complex structures. Impedance curve screening and surface-mount co-curing technology are utilized to manage the performance variation of MUSIC array sensors, enhance layout uniformity, and improve long-term stability. Subsequently, a focus compensation algorithm is proposed within the integrated MUSIC design to enhance precision, reduce weight, and adapt to complex structures. The effectiveness of the proposed method is confirmed through experimental validation on an actual complex composite wing box segment, demonstrating a maximum error of 2 cm in locating impact damage.

Ultrasound Localization Microscopy (ULM) surpasses the constraints imposed by acoustic diffraction, achieving sub-wavelength resolution visualization of microvasculature through the precise localization of minute microbubbles (MBs). Nonetheless, the analysis of densely populated regions with overlapping MB point spread responses introduces significant localization errors, limiting the use of technique to low-concentration conditions. This raises a trade-off issue between localization efficiency and MB density. In this work, we present a new deep learning framework that combines Transformer and U-Net architectures, termed ULM-TransUNet. As a non-linear model, it is able to learn the complex data patterns of overlapping MBs in dense conditions for accurate localization. To evaluate the performance of ULM-TransUNet, a series of numerical simulations and in vivo experiments are carried out. Numerical simulation results indicate that ULM-TransUNet achieves high-quality ULM imaging, with improvements of 21.93 % in detection rate, 17.36 % in detection precision, and 20.53 % in detection sensitivity, compared to previous state-of-the-art deep learning (DL) method (e.g., ULM-UNet). For the in vivo experiments, ULM-TransUNet achieves the highest spatial resolution (9.4 μm) and rapid inference speed (26.04 ms/frame). Furthermore, it consistently detects more small vessels and resolves closely spaced vessels more effectively. The outcomes of this work imply that ULM-TransUNet can potentially enhance the microvascular imaging performance on high-density MB conditions.

The prestige target selectivity and imaging depth of optical-resolution photoacoustic microscope (OR-PAM) have gained attentions to enable advanced intra-cellular visualizations. However, the broad-band nature of photoacoustic signals is prone to noise and artifacts caused by the inefficient light-to-pressure translation, resulting in poor image quality. The present study foresees application of singular value decomposition (SVD) to effectively extract the photoacoustic signals from these noise and artifacts. Although spatiotemporal SVD succeeded in ultrasound flow signal extraction, the conventional multi frame model is not suitable for data acquired with scanning OR-PAM due to the burden of accessing multiple frames. To utilize SVD on the OR-PAM, this study began with exploring SVD applied on multiple A-lines of photoacoustic signal instead of frames. Upon explorations, an obstacle of uncertain presence of unwanted singular vectors was observed. To tackle this, a data-driven weighting matrix was designed to extract relevant singular vectors based on the analyses of temporal-spatial singular vectors. Evaluation on the extraction capability by the SVD with the weighting matrix showed a superior signal quality with efficient computation against past studies. In summary, this study contributes to the field by providing exploration of SVD applied on A-line signals as well as its practical utilization to distinguish and recover photoacoustic signals from noise and artifact components.

Ultrasonic scalpels (USs), as the preferred energy instruments, are facing a growing need to exhibit enhanced performance with the diversification of modern surgical challenges. Hence, we proposed an acoustic black hole ultrasonic scalpel (ABHUS) in longitudinal-bending coupled vibration for efficient surgical cutting. By incorporating an acoustic black hole profile, the local bending wave velocity is reduced and the amplitude is amplified cumulatively, thus creating a high-energy region near the blade tip to enhance the cutting performance of the ABHUS. The precise physical analysis model is established for systematic design of the ABHUS and quick estimation of its frequency characteristics. The vibration simulation and experiments demonstrate that compared with the conventional ultrasonic scalpel (CUS), the output amplitude of the ABHUS significantly increases, particularly a 425% increase in bending vibration displacement. The in-vitro cutting experiment confirms that ABHUS exhibits superior cutting performance. Our design presents vast possibilities and potential for the development of high-performance ultrasonic surgical instruments, serving as an innovative supplement with extraordinary significance for application of acoustic black holes.

The estimation of corrosion induced thickness loss is critical for evaluating the remaining strength of high-strength steel (HSS) structures, particularly due to their emerging applications in ocean platforms and coastal bridges. In this study, an ultrasonic approach based on multimodal guide waves is proposed to identify thickness loss induced by electrical accelerated corrosion (EAC) in Q690E HSS samples. Both pitting corrosion and uniform corrosion were observed in the samples during the EAC testing. The average thickness loss due to corrosion in a plate-like structure can be correlated with the velocity of certain guided wave modes according to their dispersion characteristics. However, in practice, when the frequency-thickness product exceeds 1.5 MHzmm, it becomes difficult to separate a single mode of guided wave. Hence, this paper addresses the use of multimodal guided waves and proposes a stretching factor that could describe the averaged velocity from different guided wave modes. This stretching factor is found to be linearly correlated to the averaged thickness loss from an analytical approach and validated by experiments. The influence of surface roughness due to pitting is found to be negligible due to the large wavelengths of guided waves. This method provides a simple and effective alternative to estimate the average thickness loss due to corrosion damage in HSS structures.