Research on imaging localization method for crack damage in concrete based on Lamb wave

Decision fusion for damage localization in CFRP laminate using Lamb wave and acoustic emission

Evaluation of zero-group-velocity Lamb waves induced by local feature variation in directed energy deposition

Measurement of dynamic stress using linear and nonlinear acoustoelastic effects due to colinear wave mixing.

An absolute stress evaluation method based on the lamb waves time-frequency spectrum and residual network for alleviating the effects of inconsistent coupling conditions

Multi-mode dispersion compensation in Lamb wave time-reversal method for high damage sensitivity across frequencies.

Abstract Dry storage canisters (DSC) are used for storing spent nuclear fuel rods for an extended period.Due to their critical role, periodic inspections are necessary for mitigating potential accidents which could cause the release of radioactive material to the environment. Hence, non-destructive methods need to be employed to evaluate the structural integrity of DSC. In this work, helical guided ultrasonic waves (HGUW) are utilized to develop a methodology for the structural health monitoring of DSC. Similar to Lamb waves propagating in thin plate structures, HGUW travel circumferentially in cylindrical waveguides. The proposed methodology is comprised of instrumenting the canister with a permanently attached network of two arrays of piezoelectric (PZT) sensors capable of transmitting and receiving high frequency ultrasonic signals. Using the data collected from the HGUW inspection, a probabilistic imaging technique is employed and optimized to identify and localize defects within the span of the PZT arrays. A numerical study representing experimental setup for a 6' DSC instrumented with the sensor arrays was conducted in order to optimize the defect localization methodology, followed by an experimental verification which successfully identified and localized an artificial "damage" introduced at the DSC wall.

Surface acoustic wave resonators have been widely developed for strain detection due to their advantages of miniaturization, portability, potential to be integrated with microelectronics, and passive/wireless capabilities. A Lamb wave resonator, similar to a surface acoustic wave resonator, transforms the acoustic waves from surface to bulk propagation, enhancing its sensitivity to deformation. Recent research has reported that Lamb wave resonators exhibit high strain sensitivity and multi-modal characteristics in strain sensing. Our study aims to investigate the underlying mechanisms for high sensitivity and the differences in sensitivity across various modes. This study began with the coupling mechanism of Lamb waves and employed computational and simulation software to investigate the reasons behind the differences in strain sensitivity among different modes: shear-wave-dominated modes achieve higher strain sensitivity. Subsequently, experimental testing of strain sensitivity for various modes on fabricated resonators was conducted, yielding trends consistent with theoretical and simulation predictions. Ultimately, the Lamb wave resonator achieved a high strain sensitivity of 1.97 ppm/με, a minimum detection limit of 25 με, and a maximum hysteresis of less than 1% within a 1000 με strain detection range through the laterally excited higher-order symmetric mode (S1-5 mode). All results clearly demonstrate the sensor's significant potential for strain monitoring applications.

Abstract Manual evaluation and interpretation of Impact echo (IE) data is often labor-intensive and time-consuming, motivating the growing interest in applying machine learning (ML) techniques to this non-destructive testing (NDT) method. However, the scarcity of labeled datasets limits the generalizability of ML models to new, unseen data. This study investigates strategies to integrate a-priori knowledge into Convolutional Neural Networks (CNNs) for improved prediction of the S1 Lamb wave frequency from IE signals. To this end, time–frequency representations of IE signals, derived using the Short-Time Fourier Transform (STFT), are used as model inputs. A-priori knowledge is introduced in the form of initial frequency estimates obtained through manual evaluation. Additionally, transfer learning is employed to enrich the limited measurement dataset with data from 2D numerical simulations. The results demonstrate that, although training loss curves remain similar across models, incorporating additional information significantly enhances performance on unseen datasets. Furthermore, pre-training with simulation data accelerates convergence during early fine-tuning stages. The highest predictive accuracy was achieved when the initial guess was directly embedded into the loss function.

This paper experimentally investigates the resonant behavior of the one-way Lamb and SH (shear horizontal) mixing method in composite laminates with inherent quadratic nonlinearity, delamination damage and impact damage. When the fundamental S0-mode Lamb waves and SH0 waves mix in the damage regions of composite laminates, experimental results demonstrate the generation of the resonant SH0 waves with the resonance condition. Meanwhile, the damage localization method in composite laminates is experimentally verified by the time-domain signal of resonant waves. Furthermore, it is found that the one-way Lamb and SH mixing method is sensitive to inherent quadratic nonlinearity and impact damage but insensitive to delamination damage.

In radiofrequency filters, there is an increasing demand for high-frequency, wide-bandwidth operation. Recently, laterally excited A1-mode Lamb wave resonators (XBARs) have attracted significant attention; however, freestanding structures are mechanically fragile, limiting their practical implementation. To address this challenge, a novel bonded membrane structure consisting of a lithium niobate (LiNbO3; LN) thin plate supported by a silicon carbide (SiC) layer is proposed to realize high-frequency, high-performance, and thermally robust acoustic resonators. Finite element simulations were performed to analyze the excitation and propagation of A1-mode Lamb waves in the LN/SiC membrane, clarifying the distinct behavior compared with XBARs. The influence of the bonded SiC thin layer on A1-mode Lamb waves was systematically evaluated in terms of coupling coefficient and phase velocity, and design guidelines were established based on these insights. A fabricated LN/SiC resonator with an interdigital electrode pitch of 12 µm exhibited a clear A1-mode response near 1.2 GHz, showing an effective electromechanical coupling coefficient of 24% and a phase velocity exceeding 14,000 m/s. These results demonstrate the feasibility of the bonded LN/SiC membrane as a promising platform for high electromechanical coupling, high-speed, and thermally stable acoustic devices.

Droplet-based microfluidics have drawn much attention in recent years and have been successfully applied in biochemical analysis, material synthesis, and biomedical engineering. Precise and flexible manipulations of droplets are the basis of various applications. Numerous techniques have been introduced to achieve on-demand control of droplets, including electric, magnetic, acoustic, optical, and thermal methods. Among these, the combination of acoustics and microfluidics (termed acoustofluidics) has shown great potential and advantages in droplet manipulation as it is non-invasive, high-precision, low-cost, easily integrated, and biocompatible. Here, we summarize recent works on acoustofluidic manipulations of droplet-based microfluidics. This paper is structured into three main sections. First, the commonly used acoustic devices in acoustofluidics and their working principles are introduced. Such acoustic devices include interdigital transducers, Lamb wave resonators, and bulk acoustic resonators, and generate acoustic waves with frequencies ranging from kilohertz to gigahertz. Second, the forces and effects involved in droplet manipulations using acoustofluidics are analyzed. Third, the manipulation processes of droplet microfluidics using various acoustofluidic techniques are summarized and compared with other methods, including droplet generation, mixing, splitting, fusion, sorting, transportation, and internal particle patterning. Finally, current challenges and future prospects for acoustofluidic manipulation techniques for droplet-based microfluidics are discussed.

The ScAlN film has a large electromechanical coupling and low mechanical loss, enabling RF filters with wide bandwidth, low insertion loss, and a steep filter skirt. In order to meet the growing demand for RF filters operating above 5 GHz, the use of polarization inverted multilayers is continuously being proposed. This Perspective discusses the advantages of overtone mode operation in polarization inverted multilayers for high-frequency bulk acoustic wave (BAW) filter applications: high parallel resonance Qp, high series resonance Qs, high electromechanical coupling, high power capability, and better acoustic isolation from the electrode and supporting medium. Three potential approaches for ScAlN polarization inverted multilayers: film transfer technique, unusual N-polar growth, and external DC voltage application are overviewed. This Perspective includes an experimental demonstration of an acoustic isolation of polarization inverted 30-layer resonators as well as frequency switching between the fundamental mode and the third overtone mode in the currently commercial frequency range of 1.3–3.5 GHz. This article provides a metrics of Q and electromechanical coupling coefficient of recently reported BAW and Lamb wave resonators above 5 GHz, along with experimental data on the elastic tensor, dielectric constant, electromechanical coupling coefficient, temperature coefficient of frequency, and relative Q values in ScxAl1−xN films with varying Sc concentration.

A novel optimization method for transducer array in Lamb wave detection of variable cross-section structures.

Effective generation of shear horizontal waves from Lamb waves by meta-converters

Lamb wave based non-destructive evaluation of FSW lap joints

Effects of NbN superconducting electrodes on the cryogenic characteristics of lamb wave mode AlScN piezoelectric MEMS resonators

Mode-conversion between fundamental Lamb waves (A0-S0 mode) during scattering at a part-thickness notch

Damage location of concrete based on reference-free Lamb wave tomography

Abstract The massive eruption of the Hunga Tonga–Hunga Ha’apai volcano on January 15, 2022, triggered various phenomena, such as severe lightning from plume activities, atmospheric Lamb waves, conventional tsunamis, tsunamis caused by sea surface displacement due to Lamb waves, and total electron content variations in the ionosphere. We analyzed the observed magnetic field data at ’Atele, Tongatapu (Tonga), approximately 73 km south–southeast of the volcano, revealing two distinct timescales of variation after the eruption. The first variation, with periods of approximately 256 and 278 s, were predominantly observed in the horizontal magnetic components. Previous studies have reported variations during the same period in Apia (Samoa) and Honolulu (USA). Notably, the amplitude and dominant variation direction at ’Atele and Apia differed. The amplitude at ’Atele was approximately ten times larger than that at Apia, and the dominant variation was observed in the north–south direction at ’Atele but east–west at Apia. These variations were attributed to atmospheric acoustic resonance caused by the eruption, i.e., the electric currents induced by motion in the ionosphere and the electric field propagated along the field line of the geomagnetic main field. The second variation, with a timescale of approximately 2 h, primarily manifested in the vertical magnetic component at ’Atele. In addition, the eastward component shows similar variations at ’Atele and Apia. Simple electric current models of the ionosphere could not explain the magnetic field features at ’Atele and Apia if the variations were related to localized electric current induced in the ionosphere by the volcanic eruption. The variations in the vertical component at the two stations highlight the importance of considering electromagnetic induction within the Earth and discussing the electric currents responsible for these magnetic field variations. Graphical Abstract