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Keywords = torsional elastic waves

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18 pages, 8367 KiB  
Article
Passive Seismic Surveys for a Simplified Experimental Dynamic Characterization of the Messina Bell Tower (Sicily, Italy)
by Sabrina Grassi, Sebastiano Imposa and Gabriele Morreale
Appl. Sci. 2025, 15(9), 4973; https://doi.org/10.3390/app15094973 - 30 Apr 2025
Viewed by 399
Abstract
This study proposes a simplified approach for the experimental dynamic characterization of the historic Messina Bell Tower (northeastern Sicily) using passive seismic single-station surveys. The Horizontal-to-Vertical Spectral Ratio (HVSR) analysis identified a site resonance frequency of approximately 1.06 Hz, while the Multichannel Analysis [...] Read more.
This study proposes a simplified approach for the experimental dynamic characterization of the historic Messina Bell Tower (northeastern Sicily) using passive seismic single-station surveys. The Horizontal-to-Vertical Spectral Ratio (HVSR) analysis identified a site resonance frequency of approximately 1.06 Hz, while the Multichannel Analysis of Surface Waves (MASW) survey contributed to the characterization of the shear wave velocity profile, providing a coherent geophysical framework useful for structural dynamic analysis. Spectral ratios analysis revealed four distinct vibration modes, including a fundamental rocking mode (~1.4 Hz), a torsional mode (3.5 Hz), and two higher-frequencies flexural modes. The structure’s dynamic behavior, notably its sensitivity to torsion and rocking, is attributed to the deformable subsoil. Damping ratios estimated via the Random Decrement Method (RDM) were below 1%, consistent with the expected linear elastic response under ambient vibrations. The results show strong agreement with previous long-term monitoring, validating the effectiveness of passive seismic techniques for rapid, non-invasive assessment. This study demonstrates that streamlined, time-efficient methodologies are capable of delivering modal parameters consistent with those obtained from more extensive and resource-intensive monitoring campaigns, thereby providing a reliable and practical approach for the seismic vulnerability assessment of heritage structures. Full article
(This article belongs to the Special Issue Simplified Seismic Analysis of Complex Civil Structures)
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15 pages, 1459 KiB  
Article
New Torsional Surface Elastic Waves in Cylindrical Metamaterial Waveguides for Sensing Applications
by Piotr Kiełczyński, Krzysztof Wieja and Andrzej Balcerzak
Sensors 2025, 25(1), 143; https://doi.org/10.3390/s25010143 - 29 Dec 2024
Viewed by 778
Abstract
In this paper, we demonstrate that torsional surface elastic waves can propagate along the curved surface of a metamaterial elastic rod (cylinder) embedded in a conventional elastic medium. The crucial parameter of the metamaterial rod is its elastic compliance [...] Read more.
In this paper, we demonstrate that torsional surface elastic waves can propagate along the curved surface of a metamaterial elastic rod (cylinder) embedded in a conventional elastic medium. The crucial parameter of the metamaterial rod is its elastic compliance s44(1)ω, which varies as a function of frequency ω analogously to the dielectric function εω in Drude’s model of metals. As a consequence, the elastic compliance s44(1)ω can take negative values s44(1)ω<0 as a function of frequency ω. Negative elastic compliance (s44(1)ω<0) enables the emergence of new surface states, i.e., new types of surface elastic waves. In fact, the proposed torsional elastic surface waves can be considered as an elastic analog of Surface Plasmon Polariton (SPP) electromagnetic (optical) waves propagating along a metallic rod (cylinder) embedded in a dielectric medium. Consequently, we developed the corresponding analytical equations, for the dispersion relation and group velocity of the new torsional elastic surface wave. The newly discovered torsional elastic surface waves exhibit virtually all extraordinary properties of their electromagnetic SPP counterparts, such as strong subwavelength concentration of the wave energy in the vicinity of the cylindrical surface (r=a) of the guiding rod, very low phase and group velocities, etc. Therefore, the new torsional elastic surface waves can be used in: (a) near-field subwavelength acoustic imaging (super-resolution), (b) acoustic wave trapping (zero group and phase velocity), etc. Importantly, the newly discovered torsional elastic surface waves can form a basis for the development of a new generation of ultrasonic sensors (e.g., viscosity sensors), biosensors, and chemosensors with a very high mass sensitivity. Full article
(This article belongs to the Collection Ultrasound Transducers)
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12 pages, 3029 KiB  
Article
Influence of Halides on Elastic and Vibrational Properties of Mixed-Halide Perovskite Systems Studied by Brillouin and Raman Scattering
by Furqanul Hassan Naqvi, Syed Bilal Junaid and Jae-Hyeon Ko
Materials 2023, 16(11), 3986; https://doi.org/10.3390/ma16113986 - 26 May 2023
Cited by 9 | Viewed by 1848
Abstract
The relationship between halogen content and the elastic/vibrational properties of MAPbBr3−xClx mixed crystals (x = 1.5, 2, 2.5, and 3) with MA = CH3NH3+ has been studied using Brillouin and Raman spectroscopy at room [...] Read more.
The relationship between halogen content and the elastic/vibrational properties of MAPbBr3−xClx mixed crystals (x = 1.5, 2, 2.5, and 3) with MA = CH3NH3+ has been studied using Brillouin and Raman spectroscopy at room temperature. The longitudinal and transverse sound velocities, the absorption coefficients and the two elastic constants C11 and C44 could be obtained and compared for the four mixed-halide perovskites. In particular, the elastic constants of the mixed crystals have been determined for the first time. A quasi-linear increase in the sound velocity and the elastic constant C11 with increasing chlorine content was observed for the longitudinal acoustic waves. C44 was insensitive to the Cl content and very low, indicating a low elasticity to shear stress in mixed perovskites regardless of the Cl content. The acoustic absorption of the LA mode increased with increasing heterogeneity in the mixed system, especially for the intermediate composition where the Br and Cl ratio was 1:1. In addition, a significant decrease in the Raman-mode frequency of the low-frequency lattice modes and the rotational and torsional modes of the MA cations was observed with decreasing Cl content. It clearly showed that the changes in the elastic properties as the halide composition changes were correlated with the lattice vibrations. The present findings may facilitate a deeper understanding of the complex interplay between halogen substitution, vibrational spectra and elastic properties, and may also pave the way for optimizing the operation of perovskite-based photovoltaic and optoelectronic devices by tailoring their chemical composition. Full article
(This article belongs to the Special Issue 100th Anniversary of Brillouin Scattering)
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28 pages, 13000 KiB  
Article
Thrust Enhancement of DTMB 5415 with Elastic Flapping Foil in Regular Head Waves
by Lei Mei, Wenhui Yan, Junwei Zhou and Weichao Shi
J. Mar. Sci. Eng. 2023, 11(3), 632; https://doi.org/10.3390/jmse11030632 - 17 Mar 2023
Cited by 4 | Viewed by 2809
Abstract
Recent studies indicate that bow foil biomimetic systems can significantly improve ship propulsion in waves. In this paper, the DTMB 5415 ship model is taken as the object and a semi-active elastic flapping foil is proposed to install at its bow underwater position. [...] Read more.
Recent studies indicate that bow foil biomimetic systems can significantly improve ship propulsion in waves. In this paper, the DTMB 5415 ship model is taken as the object and a semi-active elastic flapping foil is proposed to install at its bow underwater position. When a ship sails in head wave, heave and pitch motion will occur, which will drive the bow foil to form heave motion. According to the working characteristics of elastic foil, bow foil can generate forward thrust under drive of given heave motion. At first, co-simulation of the ship with self-pitching bow foil in head waves is realized by ISIS-CFD solver and preliminarily realizes drag reduction and thrust increase effect of the bow foil. At the same time, it is found that the effect of bow foil on hull drag reduction is reflected in two aspects, one is the additional thrust generated by the bow foil and the other is that suppression of the bow foil on hull motion also reduces hull resistance in waves. Then, in order to optimize the working characteristics of elastic bow foil, the influence of spring stiffness and span length of the bow foil on drag reduction and thrust increase effect is discussed. A preliminary spring optimization result is obtained, as well as the influence of the span length of the bow foil on the system. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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22 pages, 313 KiB  
Viewpoint
Energy Mechanisms of Free Vibrations and Resonance in Elastic Bodies
by Yury A. Alyushin
Physics 2021, 3(4), 1133-1154; https://doi.org/10.3390/physics3040072 - 25 Nov 2021
Viewed by 2592
Abstract
The scientific novelty of this work is determined by the rationale for the participation in transformations, along with the kinetic energy of particles, of four types of elastic energy, identified by the peculiarities of their phase changes in the oscillation process. Two types [...] Read more.
The scientific novelty of this work is determined by the rationale for the participation in transformations, along with the kinetic energy of particles, of four types of elastic energy, identified by the peculiarities of their phase changes in the oscillation process. Two types are converted into kinetic energy, while the other two types change the deformed state of particles in accordance with the equations of motion due to internal sources. The result is obtained based on the use of the superposition principle in the space of Lagrange variables with the imposition of forced and free oscillations, as well as a new model of mechanics based on the concepts of space, time, and energy with a new scale of average stresses that takes into account the energy of particles in the initial state. In such a model of mechanics, a generalized measure of the elastic energy of particles is a quadratic invariant of asymmetric tensor whose components are partial derivatives of Euler variables with respect to Lagrange variables. The concept of kinematic energy parameters is introduced, which differ from the corresponding volumetric energy densities by a multiplier equal to the modulus of elasticity, which is directly proportional to the density and heat capacity of the material, and inversely proportional to the volumetric compression coefficient. Comparison of the values of kinematic parameters shows that most of the energy required for oscillations is associated with the deformation of particles and comes from internal sources. The mechanisms of transformation of forced vibrations into their own for transverse, torsional, and longitudinal vibrations are considered, as well as the occurrence of resonance when free and forced vibrations are superimposed with the same or a similar frequency. The formation of a new free wave after each cycle of external influences with an increase in amplitude, which occurs mainly due to internal, and not external, energy sources is justified. Full article
(This article belongs to the Section Applied Physics)
12 pages, 3095 KiB  
Article
Structural-and-Phase Transformations in Fe-4.10 and 7.25 at.% Mn Alloys under Intensity External Actions
by Vladimir V. Ovchinnikov, Efrem V. Makarov and Natalia V. Gushchina
Metals 2021, 11(11), 1667; https://doi.org/10.3390/met11111667 - 20 Oct 2021
Cited by 1 | Viewed by 1702
Abstract
The effect of high-pressure torsion (HPT) (P = 8 GPa, e = 5.9) and irradiation with continuous beams of Ar+ ions with energy E = 15 keV on the atomic structure and phase composition of initially quenched iron alloys with 4.10 [...] Read more.
The effect of high-pressure torsion (HPT) (P = 8 GPa, e = 5.9) and irradiation with continuous beams of Ar+ ions with energy E = 15 keV on the atomic structure and phase composition of initially quenched iron alloys with 4.10 and 7.25 at.% Mn was studied by the method of Mössbauer spectroscopy. The supersaturated α-solid solution of Fe-7.25 at.% Mn, in contrast to the stable Fe-4.10 at.% Mn, which passes into a highly nonequilibrium metastable state as a result of HPT deformation, is transformed under the influence of ion irradiation at an abnormally low temperature of 280 °C into a two-phase α + γ-state with a highly enriched γ-phase (austenite) (38.4 at.% Mn) and a depleted α-solid solution with 5.76 at.% Mn. The rapid processes with the formation of the γ-phase with a concentration of Mn close to the extrapolation estimate using the equilibrium phase diagram are explained by the cascade radiation shaking of the material by post-cascade powerful elastic and shock waves. Cascade radiation shaking plays the role of temperature and opens up the possibility of achieving states close to equilibrium in the absence of thermally activated processes at record low temperatures. Full article
(This article belongs to the Special Issue Radiation Effects in Steels and Alloys)
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18 pages, 16179 KiB  
Article
Viscoelastic Biomarkers of Ex Vivo Liver Samples via Torsional Wave Elastography
by Inas H. Faris, Juan Melchor, Antonio Callejas, Jorge Torres and Guillermo Rus
Diagnostics 2020, 10(2), 111; https://doi.org/10.3390/diagnostics10020111 - 19 Feb 2020
Cited by 9 | Viewed by 4251
Abstract
The clinical ultrasound community demands mechanisms to obtain the viscoelastic biomarkers of soft tissue in order to quantify the tissue condition and to be able to track its consistency. Torsional Wave Elastography (TWE) is an emerging technique proposed for interrogating soft tissue mechanical [...] Read more.
The clinical ultrasound community demands mechanisms to obtain the viscoelastic biomarkers of soft tissue in order to quantify the tissue condition and to be able to track its consistency. Torsional Wave Elastography (TWE) is an emerging technique proposed for interrogating soft tissue mechanical viscoelastic constants. Torsional waves are a particular configuration of shear waves, which propagate asymmetrically in-depth and are radially transmitted by a disc and received by a ring. This configuration is shown to be particularly efficient in minimizing spurious p-waves components and is sensitive to mechanical constants, especially in cylinder-shaped organs. The objective of this work was to validate (TWE) technique against Shear Wave Elasticity Imaging (SWEI) technique through the determination of shear wave velocity, shear moduli, and viscosity of ex vivo chicken liver samples and tissue mimicking hydrogel phantoms. The results of shear moduli for ex vivo liver tissue vary 1.69–4.0kPa using TWE technique and 1.32–4.48kPa using SWEI technique for a range of frequencies from 200 to 800Hz. Kelvin–Voigt viscoelastic parameters reported values of μ = 1.51kPa and η = 0.54Pa·s using TWE and μ = 1.02kPa and η = 0.63Pa·s using SWEI. Preliminary results show that the proposed technique successfully allows reconstructing shear wave velocity, shear moduli, and viscosity mechanical biomarkers from the propagated torsional wave, establishing a proof of principle and warranting further studies. Full article
(This article belongs to the Special Issue Elastography)
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13 pages, 2761 KiB  
Article
In Vivo Measurement of Cervical Elasticity on Pregnant Women by Torsional Wave Technique: A Preliminary Study
by Paloma Massó, Antonio Callejas, Juan Melchor, Francisca S. Molina and Guillermo Rus
Sensors 2019, 19(15), 3249; https://doi.org/10.3390/s19153249 - 24 Jul 2019
Cited by 16 | Viewed by 4288
Abstract
A torsional wave (TW) sensor prototype was employed to quantify stiffness of the cervix in pregnant women. A cross-sectional study in a total of 18 women between 16 weeks and 35 weeks + 5 days of gestation was performed. The potential of TW [...] Read more.
A torsional wave (TW) sensor prototype was employed to quantify stiffness of the cervix in pregnant women. A cross-sectional study in a total of 18 women between 16 weeks and 35 weeks + 5 days of gestation was performed. The potential of TW technique to assess cervical ripening was evaluated by the measurement of stiffness related to gestational age and cervical length. Statistically significant correlations were found between cervical stiffness and gestational age ( R 2 = 0.370 , p = 0.0074 , using 1 kHz waves and R 2 = 0.445 , p = 0.0250 , using 1.5 kHz waves). A uniform decrease in stiffness of the cervical tissue was confirmed to happen during the complete gestation. There was no significant correlation between stiffness and cervical length. A stronger association between gestational age and cervical stiffness was found compared to gestational age and cervical length correlation. As a conclusion, TW technique is a feasible approach to objectively quantify the decrease of cervical stiffness related to gestational age. Further research is required to evaluate the application of TW technique in obstetric evaluations, such as prediction of preterm delivery and labor induction failure. Full article
(This article belongs to the Special Issue Smart Sensors for Healthcare and Medical Applications)
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