Elastic Wave Propagation Research Articles

This study investigates the mechanical, elastic wave, AC conductivity, and dielectric properties of (ZnSn)₁₋ₓMₓO nanocomposites (NCs), where M is Co or Cu (0.00 < x < 0.50), and compares them to those of ZnO and SnO nanosheets. Both Co and Cu series NCs showed minor changes in mechanical and elastic wave propagation up to x = 0.30. ZnSnO NCs exhibited higher AC conductivity and dielectric constants than ZnO or SnO nanosheets, which were subsequently reduced by incorporating Co or Cu ions. While ZnSnO NCs displayed high dielectric loss (tan δ), Co incorporation led to lower tan δ without affecting the quality factor (Qfactor); conversely, Cu significantly decreased tan δ and strongly improved the Qfactor. The conduction mechanism shifted from polaron in ZnO or SnO nanosheets to hole-dominated in ZnSnO and Co-doped ZnSnO NCs, whereas the Cu-doped ZnSnO NCs exhibited a mixed polaron and hole conduction depending on the incorporated Cu content. ZnSnO NCs demonstrated lower bulk impedance and electronic polarizability than binary ZnO and SnO nanosheets; however, doped ZnSnO NCs with high Co concentration dramatically increased both, a trend opposite to that observed with Cu. Effective capacitance (Ceff) was significantly enhanced in ZnSnO NCs relative to binary ZnO and SnO nanosheets, followed by Ceff decrease with the addition of Co or Cu ions. Conversely, the electric modulus of ZnSnO NCs was considerably reduced compared to SnO or ZnO nanosheets, and this reduction was further amplified by Co or Cu incorporation. Parameters such as polaron binding energy and hopping distance were estimated using the correlated barrier polaron hopping modelVariations in properties between nanosheets and NCs are primarily attributed to differences in internal structures. Notably, these (ZnSn)1-xMₓO NCs, both undoped and doped with Co or Cu, show promise for energy storage applications.

Abstract Phononic crystals (PnCs) can inhibit the propagation of elastic waves within specific frequency ranges, known as band gaps. They can also introduce localized defect bands that enable functionalities such as filtering, sensing, and energy harvesting. However, conventional approaches that use piezoelectric defects combined with external circuits have limitations. While odd-symmetric defect bands can be tuned with synthetic negative capacitors, even-symmetric defect bands remain insensitive due to voltage cancellation. This study introduces a segmented piezoelectric defect concept to overcome this limitation. In this concept, each segment is connected to an synthetic negative capacitor, which eliminates voltage cancellation and enables the simultaneous control of multiple defect bands. An electromechanically coupled transfer-matrix framework is developed in MATLAB to predict defect-band frequencies, defect-mode shapes, and transmittance spectra. Numerical validations performed in the one-dimensional finite element method demonstrate close agreement with the analytical results. The proposed configuration shifts both defect-band frequencies across the band-gap region, tailors the localization patterns of defect modes, and regulates the number and existence of transmission peaks. These results confirm that segmentation expands the design space of defective PnCs and provides a foundation for multifunctional phononic devices.

Elastic wave propagation and attenuation through deformable porous media containing two immiscible fluids taking into account gravity effect

Metamodeling elastic wave propagation using a mixed factorized Fourier encoder–decoder for online laser-ultrasound testing in additive manufacturing

The stabilimentum, or structural decoration, in spider orb webs is a fascinating structure. While the species that construct stabilimenta and their building techniques are well-documented, the precise functions of these structures remain unclear. This knowledge gap arises from conflicting reports in the literature and the significant behavioral flexibility spiders exhibit when incorporating stabilimenta into their webs. Notably, spiders can build stabilimenta in various geometries, which may influence the dynamical properties of orb webs—a relationship that has yet to be quantitatively explored. In this study, we combined extensive field observations with computational simulations to address this gap. The fieldwork focused on documenting the range of stabilimentum geometries in Argiope bruennichi, while the simulations examined how these variations influence the propagation of elastic waves across the web. Our results suggest that the stabilimentum, acting as an additional inertial mass, does not significantly slow down the propagation of elastic waves generated by prey impact in the transverse and normal directions relative to the radial threads. However, when prey impact induces vibrations tangential to the spiral threads of the web, the presence of the stabilimentum enhances the spider’s ability to detect prey location by allowing vibrations to reach a greater number of output points compared to webs without a stabilimentum. These findings deepen our understanding of the mechanical role of stabilimenta and provide new insights for the development of bio-inspired metamaterials, particularly those with tunable dynamic elastic properties.

The stabilimentum, or structural decoration, in spider orb webs is a fascinating structure. While the species that construct stabilimenta and their building techniques are well-documented, the precise functions of these structures remain unclear. This knowledge gap arises from conflicting reports in the literature and the significant behavioral flexibility spiders exhibit when incorporating stabilimenta into their webs. Notably, spiders can build stabilimenta in various geometries, which may influence the dynamical properties of orb webs-a relationship that has yet to be quantitatively explored. In this study, we combined extensive field observations with computational simulations to address this gap. The fieldwork focused on documenting the range of stabilimentum geometries in Argiope bruennichi, while the simulations examined how these variations influence the propagation of elastic waves across the web. Our results suggest that the stabilimentum, acting as an additional inertial mass, does not significantly slow down the propagation of elastic waves generated by prey impact in the transverse and normal directions relative to the radial threads. However, when prey impact induces vibrations tangential to the spiral threads of the web, the presence of the stabilimentum enhances the spider's ability to detect prey location by allowing vibrations to reach a greater number of output points compared to webs without a stabilimentum. These findings deepen our understanding of the mechanical role of stabilimenta and provide new insights for the development of bio-inspired metamaterials, particularly those with tunable dynamic elastic properties.

A numerical investigation of the anisotropy occurring in geological structures with porous and fractured heterogeneity is presented. The grid-characteristic method was used as the solution method. Numerical models of the medium and cracks are constructed taking into account their opening. Numerical calculations of elastic wave propagation are performed and the anisotropy parameter is calculated. The data obtained are compared with the results of a laboratory experiment.

Tectonic faults in coal-bearing rock formations are one of the most common geological factors that hamper the mining process. One of the most promising methods to localize tectonic faults below the Quaternary deposits is a complex that comprises geophysical methods (electrical tomography and seismic surveys using the correlation refraction method), geomorphological features of the terrain, and the hypsometry of the coal seams. The research was carried out at the Verkhne-Taluminskoye deposit in the South Yakutsk Basin. The principles of localizing tectonic faults in complex geological and geophysical interpretation included identification of significant anomalies by comparing geoelectric and velocity sections within a single profile and detection of the anomalous points; comparison of geophysical sections made using selected methods between the profiles (two different types of comparison based on the number of geophysical methods), correlation of the anomalous points' position on the geophysical sections. The main factors in identifying anomalous points included low values of elastic wave propagation, low values of specific electrical resistivity, and morphological similarity of anomalies on geophysical sections. These points were plotted on a topographic map of the investigated area and used for further interpretation. The next stage was interpretation of several adjacent profiles. These were used to correlate anomalies associated with the predicted tectonic faults. Correlation of anomalies between the profiles was made based on the similarity of the following parameters: the intensity of anomalies, the morphology of anomalous manifestations according to the methods, and the mutual arrangement of anomalies. The correlation was corrected on a topographic map with account of the geomorphological features. A tectonic diagram with lines of the predicted tectonic structures for mine takes of the Verkhne-Taluminskoye deposit was built based on the results of geological and geophysical interpretation of the profile groups, morphostructural features of the deposit terrain, and hypsometry of the coal seams.

Compliant walls made from homogeneous viscoelastic materials may attenuate the amplification of Tollmien–Schlichting waves (TSWs) in a two-dimensional boundary-layer flow, but they also amplify travelling-wave flutter (TWF) instabilities at the interface between the fluid and the solid, which may lead to a premature laminar-to-turbulent transition. To mitigate the detrimental amplification of TWF, we propose to design compliant surfaces using phononic structures that aim at avoiding the propagation of elastic waves in the solid in the frequency range corresponding to the TWF. Thus, stiff inserts are periodically incorporated into the viscoelastic wall in order to create a band gap in the frequency spectrum of the purely solid modes. Fluid–structural resolvent analysis shows that a significant reduction in the amplification peak related to TWF is achieved while only marginal deterioration in the control of TSWs is observed. This observation suggests that the control of TSWs is still achieved by the overall compliance of the wall, while the periodic inserts inhibit the amplification of TWF. Bloch analysis is employed to discuss the propagation of elastic waves in the phononic surface to deduce design principles, accounting for the interaction with the flow.

Abstract This study investigates different approaches to locate defects in composite structures. This instigation is performed using finite element simulations of 3D propagation of elastic waves in a multi-layer carbon fiber reinforced polymer (CFRP) composite plate. The simulations are analyzed using a well-known 3D Fourier-based technique applied on the calculated wavefields. The wavefields are here the out-of-plan velocity component at the top layer of the composite. These wavefields contain detailed information about the guided waves and the state of the composite structure. A novel Sliding Spectrum Extraction (SSE) algorithm applied on the wavefields is capable of the detecting areas where large changes in the frequency-time Fourier content are observed. These large changes are normally seen in areas with a defect such as delamination. The new Sliding Spectrum Extraction technique is used on wavefields from elastic wave propagation simulations performed on an 8-layer CFRP plate with a delamination defect.

Fast and power efficient GPU-based explicit elastic wave propagation analysis by low-ordered orthogonal voxel finite element with INT8 Tensor Cores

Abstract This paper analyses the sensitivity of piezoelectric (PZT) and fibre Bragg grating (FBG) sensors to propagating elastic wave modes. Elastic waves were excited by PZT actuator and sensed by PZT and FBG sensors. Elastic wave measurements with FBG sensors utilize the edge filtration method. This research conducted a detailed study of the propagation of elastic waves with the modes identification and separation in an aluminium panel. Both numerical simulations as well as experiments were utilized to study the wave propagation and investigate the differences in the sensitivity as well as the opportunity offered by both sensors for mode identification and separation. The numerical simulations were performed using the spectral element method (SEM) in the time domain to capture the spatial and temporal scales involved in the simulation of elastic wave propagation and sensing, especially using FBG sensors. Results showed that the investigated PZT sensor was sensitive to S0 and A0 modes, while the FBG sensor was sensitive to S0, A0, and SH0. The FBG senses the SH0 mode effectively when its propagation is perpendicular to the sensor line. On the other hand, the FBG senses the S0 mode effectively when its propagation is parallel to the sensor line. This sensitivity feature makes the FBG sensor interesting from the point of view of elastic wave sensing. A novel mode separation method based on the mode indicator was proposed and validated for aluminum samples. The proposed indicator was validated for a GFRP panel with unknown material properties and dispersion characteristics. It was shown that the proposed methodology could be utilized to distinguish between the symmetric and antisymmetric modes.

Groundwater seepage plays a critical role in the long-term safety of high-level radioactive waste (HLW) disposal, yet its characterization remains challenging due to the complexity of fractured rock media. This study introduces the Double-Layered Seismo-Electric Method (DSEM) for imaging groundwater seepage fields with enhanced sensitivity and spatial resolution. By integrating elastic wave propagation with electrokinetic coupling in a stratified framework, DSEM improves the detection of hydraulic gradients and preferential flow pathways. Application at a representative disposal site demonstrates that the method effectively delineates seepage channels and estimates hydraulic conductivity, providing reliable input parameters for groundwater flow modeling. These results highlight the potential of DSEM as a non-invasive geophysical technique to support safety assessments and long-term monitoring in deep geological disposal of high-level radioactive waste.

The concepts of twistronics and magic angle have been widely applied beyond electrons, powering up new advancements in optics, acoustics, and heat transport. However, achieving a unidirectional or all-direction "magic angle" remains an established yet unresolved challenge in twisted bilayer metasurfaces across various disciplines. Our work proposes and validates a "twist-on-twist" paradigm to realizing unidirectional propagation and robust magic angle at arbitrary directions of the elastic out-of-plane wave. Our elastic metasurface not only exhibits a twisted configuration between the stacked bilayer but also significantly enhances out-of-plane symmetry breaking by further twisting meta-atoms in one constituent layer. Our twist-on-twist method unleashes versatile potentials of twisted thin composite materials to control the extreme propagation of topological elastic waves and even opens up new possibilities for photonic, phononic, and thermal moiré metamaterials.

Buried polyethylene (PE) gas pipelines are widely used in urban construction. Precise localization of these pipelines is essential for regular maintenance. To address the issue of insufficient accuracy in existing localization techniques, this paper proposes a localization method based on compressional wave migration stacking imaging. The pipeline excitation approach is utilized to avoid interference from reflected waves, and the wavelet decomposition method is employed to suppress environmental noise and improve the signal-to-noise ratio. A pipe–soil coupling model was established using COMSOL6.3 Multiphysics to analyze elastic wave propagation induced by pipeline excitation. The results revealed a distinct velocity disparity between compressional wave and shear wave, with compressional wave velocity exhibiting significant superiority. Leveraging this propagation characteristic, we propose a novel pipeline localization method based on compressional wave migration stacking imaging. The method’s accuracy was validated through simulations and field experiments. Experimental results showed that the horizontal localization error was below 0.5%, and the depth error was below 4.25%, demonstrating a reliable localization accuracy. Furthermore, the pipeline direction was intuitively identified using 3D imaging technology, effectively distinguishing it from other foreign objects in the soil. This study provides a high-precision, low-interference solution for the trenchless detection of buried PE pipelines in complex soil environments.

Elastic wave propagation in metamaterials with non-orthogonal penny-shaped crack lattices

Controlling the propagation of flexural elastic waves with ceramic metatiles

Abstract Exploiting elastic wave propagation isolation mechanism-based support tethers is one of the commonly key techniques to enhance the quality factor (Q) of microelectromechanical systems (MEMS) resonators. Phononic crystals (PnCs) can generate bandgaps (BGs) to act as an elastic wave barrier when embedded into these tethers of the resonators. This paper proposes a four-circle-holed PnC (4CH_PnC) strip-shaped support tether to improve the Q in terms of anchor quality factor (QANC) of the designed resonator. The length extensional mode resonator vibrates at 110 MHz. The BG generated by the 4CH PnC has a width of 9.81 MHz and covers this resonant frequency. The QANC of the resonator is investigated according to the variation of the unit cell number (UCN) of the 4CH_PnC. Furthermore, this QANC is also compared to three benchmark support tethers to verify its effectiveness in suppressing/eliminating the anchor dissipation. In addition, the change of the BG formation of the 4CH_PnC with its dimension parameters is also evaluated. The finite element simulation results show that the QANC of the resonator with 4CH_PnC is considerably higher boosted than three other benchmarks. Specifically, this QANC equals 1.99 x 1015 compared to 3485.18, 802.06, and 6540.80 of three benchmarks circle-shaped stub PnC (C_PnC), square-shaped stub PnC (S_PnC), and ring-shaped stub PnC (CH_PnC), respectively. Only the 4CH PnC completely eliminates the anchor energy dissipation flow as its UCN reaches 19 cells. Therefore, the anchor loss suppression of the proposed PnC is superior to that of three benchmark tethers.

Numerical modeling of elastic wave propagation in the subsurface requires applicability to heterogeneous, anisotropic and discontinuous media, as well as support of free surface boundary conditions. Here we study the cell-centered finite volume method Multi-Point Stress Approximation with weak symmetry (MPSA-W) for solving the elastic wave equation. Finite volume methods are geometrically flexible, locally conserving and they are suitable for handling material discontinuities and anisotropies. For discretization in time we have utilized the Newmark method, thereby developing an MPSA-Newmark discretization for the elastic wave equation. An important aspect of this work is the integration of absorbing boundary conditions into the MPSA-Newmark method to limit possible boundary reflections. We verify the MPSA-Newmark discretization numerically for model problems. Convergence analysis of MPSA-Newmark is performed using a known solution in a medium with homogeneous Dirichlet boundary conditions. The analysis demonstrates the expected convergence rates of second order for primary variables (displacements) and between first and second order for secondary variables (tractions). Further verification is conducted through convergence analysis with the inclusion of absorbing boundary conditions. The stability of the scheme is shown through numerical energy decay analyses for waves travelling with various incidence angles onto the absorbing boundaries. Lastly, we present simulation examples of wave propagation in fractured, heterogeneous and transversely isotropic media to demonstrate the versatility of the MPSA-Newmark discretization.

The fluid solid coupling effect in the flow microchannel system can easily induce severe vibration and noise, which seriously affects the performance and safety of the equipment. By its bandgap characteristics, the phononic crystal provides a new way to suppress the propagation of elastic waves in specific frequency bands. In this study, the vibration suppression of fluid-solid coupled phononic crystal microchannels under shock excitation is addressed. Compared with the inadequacy of the existing bandgap calculation methods in fluid computation, this study innovatively combines the transfer matrix method with the wave-finite element method to establish a fluid-solid coupled dynamics model and perform a systematic analysis. The significant effects of fluid filling on the bandgap characteristics are revealed: the unfilled microchannels show two bandgaps (70–90 Hz, 280–690 Hz) in 0–800 Hz; the bandgaps evolve to three (40–65 Hz, 180–340 Hz, 485–735 Hz) after fluid filling. At the same time, the transient vibration propagation and attenuation mechanisms of the system under different fluid shock excitations are deeply investigated. It is shown that the flow velocity is the key parameter affecting the shock vibration suppression effect: at 0 m/s flow velocity, the phonon crystal bandgap can effectively attenuate the shock response; as the flow velocity increases to 10 m/s, the fluid-solid coupling effect is enhanced, and the attenuation intensity is weakened. This study elucidates the quantitative relationship between key parameters such as flow velocity, structural periodicity, and resonant unit characteristics and shock vibration attenuation performance. It is expected to provide an important theoretical foundation and design basis for the design of flow microchannel systems with excellent shock resistance.