Search Results (197)

In mechanical material evaluation and biomechanical studies, Young’s modulus is commonly used to describe the elastic response of materials. Existing measurement approaches are mainly based on contact loading or large-scale experimental instruments, which may limit excitation controllability and system integration in practical applications. In this work, a Young’s modulus measurement system based on electromagnetic excitation and capacitive sensing is designed and experimentally implemented. The system is composed of an electromagnetic driving unit and a capacitive sensing unit. In the driving unit, a coaxial copper wire coil is arranged with a ring-shaped neodymium–iron–boron permanent magnet assembly. When a square-wave electrical signal is applied, the coil generates a Lorentz force, which produces transient mechanical excitation on the tested sample. The resulting micro-scale deformation of the material surface is monitored using a coaxial passive capacitive sensor. The sensor records the relative capacitance variation (ΔC/C₀) induced by deformation during excitation. Based on the measured capacitance response, a force–capacitance coupling model is established to relate the electrical signal to the mechanical behavior of the material, enabling the inverse calculation of Young’s modulus. Commercial standard hardness blocks were used for system calibration and performance verification. The experimentally obtained Young’s modulus values are consistent with reference data within an acceptable deviation range, indicating that the proposed system can be used for quantitative evaluation of elastic properties. Due to its compact configuration and controllable excitation, the system is suitable for non-invasive surface mechanical characterization of soft materials, including biological tissues. Full article

Aiming at the problems of cumbersome parameter tuning and low computational efficiency in traditional methods for the bandgap optimization of periodic thin-walled stiffened coupled structures, this paper integrates the null-space method with the Kirchhoff thin-plate theory to establish an efficient model for bandgap analysis. The proposed method realizes matrix-based construction of coupled and periodic boundary conditions, decouples boundary constraints from displacement shape functions, avoids the limitations of virtual spring stiffness, and requires no remeshing during parameter variation. Comparisons with the finite element method verify its convergence and accuracy: the average deviation of bandgap widths in the 0–250 Hz range is 0.37 Hz, and the computational efficiency is about 2.5 times that of FEM(Finite Element Method). This paper also systematically analyzes the effects of four key parameters, including thin-wall thickness, stiffener thickness, stiffener height and stiffener spacing, on the number and width of bandgaps and proposes targeted optimization strategies for different engineering scenarios. The results provide a new method for vibration and noise reduction design of such structures and lay a foundation for future bandgap modeling and optimization of advanced lightweight periodic structures. Full article

Photovoltaic systems deployed on large floating platforms in nearshore waters are strongly influenced by hydroelastic effects, nonlinear shallow-water waves, and variable bathymetry. This study develops a time-domain hydroelastic framework that couples the fully nonlinear non-hydrostatic wave model NHWAVE with a Rankine-source potential-flow solver and a discrete-module Cummins formulation. The wave model provides incident pressures and kinematics over uneven seabeds, while the potential-flow solver evaluates radiation and diffraction effects and transfers the resulting hydrodynamic coefficients into the time domain. Numerical simulations are carried out for a 600 m modular floating structure under regular waves over flat and sloped bathymetries with $tan\alpha =0.0133$, wave periods of 4–6 s, and wave heights of 0.3–1.0 m. The results show that bathymetric variation intensifies shoaling-induced excitation, modifies added-mass and damping distributions, increases the spatial non-uniformity of hydroelastic motions, and amplifies bending-moment RMS responses relative to the flat-bottom case. Additional comparisons between rigid-body and hydroelastic models show clear period-dependent redistribution of motions and bending demand. These results demonstrate that both local bathymetry and structural elasticity must be considered for the reliable analysis and design of nearshore floating photovoltaic systems and other large floating structures. Full article

In order to study the noise reduction performance of Porous Elastic Road Surface (PERS), the vibration noise and air pumping noise has been separated from the tire–road noise through the finite element numerical simulation method. The tire–road noise model among the tire, road and surface air has been constructed by coupling of acoustic waves. The characteristics of tire–road noise under the PERS, Porous Asphalt Concrete (PAC), and Asphalt Concrete (AC) pavements have been analyzed through the modelling. The tire–road noise has also been investigated through the noise field tests. The generating process, coupling characteristics, and noise reduction performance of the vibration noise and the pumping noise of PERS pavements has been revealed. The results show that the tire–road noise was mainly generated by the vibration noise under the vehicle speed below 80 km/h. The proportion of pumping noise gradually exceeds that of vibration noise under the vehicle speed greater than 90 km/h. And the pumping noise gradually played the major role in the tire–road noise, which also increased with the increasing of vehicle speed. Comparing with AC and PAC pavements, PERS pavement exhibited the obvious advantages in noise reduction. Additionally, the reliability of the tire–road noise model has been verified through the field noise tests. It is expected that this work will serve as a reference for future research on the mechanics of the generation of tire–road noise, and try to provided theoretical support for the application of PERS. Full article

To address severe mine pressure disasters induced by the coupling of mining-induced dynamic stress and impact disturbance during close-distance coal seam mining, this paper takes the No. 8 and No. 9 close-distance coal seams in the 119 mining area of a coal mine in Ningxia, China, as the engineering background. Theoretical analysis and FLAC^3D numerical simulation methods were adopted to systematically study the evolution of overburden structure, the manifestation law of mine pressure caused by mining disturbance, and the dynamic response mechanism of roadway surrounding rock under impact load. The findings demonstrate: ① Based on key block theory and elasticity mechanics theory, the stress transfer mechanism of the complete bearing type overburden rock in close-range coal seams was clarified. The calculation model of floor plastic zone depth and additional stress was derived, and the influence mechanism of the bearing state of interlayer rock strata on the stability of underlying coal seam roadways was revealed. ② Comparative numerical simulations of mining schemes revealed that both schemes formed a “goaf pressure relief-workface-coal pillar” load-bearing configuration with “upward subsidence and downward bulging” basin-shaped settlement. Scheme A exhibited significantly increased stress peaks and interlayer plastic zones due to repeated mining-induced stress, substantially elevating the risk of strong mine pressure manifestation and surrounding rock instability. ③ Under 8 MPa cosine impact load with a vibration frequency of 50 Hz (peak particle vibration velocity of 9.57 m/s), compared with the unsupported roadway, the bolt–cable collaborative support system reduced the peak displacement of surrounding rock by over 35% and decreased the shock wave propagation velocity by more than 40%, effectively suppressing the expansion of plastic zones and the transfer of impact energy, while significantly enhancing the impact resistance of the roadway. This study not only provides a systematic theoretical basis for close-distance coal seam mining and rock burst prevention but also offers scientific guidance and technical reference for surrounding rock control and dynamic disaster prevention of roadways in similar close-distance coal seam mining projects, which is of important engineering value for ensuring the safe and efficient mining of underground coal resources. Full article

This paper studies the dynamic behavior of a catamaran hovercraft wind farm service vessel (CHWFSV) during the berthing coupling process with a wind turbine tower, aiming to enhance its safety and reliability in engineering applications. By constructing an arc-shaped elastic fender and employing computational fluid dynamics (CFD), it investigates the motion response under transverse waves considering the effects of thrust, air-cushion flow and the elasticity coefficient of the fender. A finite element analysis (FEA) model of the arc-shaped fender, accounting for elastic stress and strain, is developed to study its coupled mechanical behavior under different thrust conditions. The research in this paper is based on numerical CFD simulation with experimental validation. The motion modeling under transverse waves is further verified through uncertainty analysis. The series of research results indicate the following: vessel rolling resonance occurs at λ/L = 1.667 (λ/L denotes the dimensionless wavelength-to-length ratio); increasing air-cushion flow extends the roll period and reduces roll amplitude at λ/L = 0.667, while applying thrust at λ/L = 1.667~3 lowers roll but reduces pitch and heave stability; relatively good berthing performance is achieved when F_CM/∆ = 0.054 and the elastic coefficient is 1.25 × 10⁷ Pa/m (Δ represents the vessel weight). Full article

A growing global demand for wood, coupled with the role of this material in low-carbon strategies, is fuelling interest in fast-growing plantations, including short-rotation forestry (SRF) and agroforestry systems. However, evidence of the physical–mechanical properties and possible uses of non-native hardwoods in the Mediterranean environment remains limited. This study aimed to address this current knowledge gap by evaluating the main physical and mechanical properties of six fast-growing non-native tree species cultivated in experimental plots in Calabria, southern Italy. The wood of Eucalyptus occidentalis Endl., E. × trabutii (M. Vilm. ex Trab.) A. Chev., E. camaldulensis Dehnh., E. bridgesiana R.T.Baker, Melia azedarach L., and Paulownia tomentosa (Thunb.) Steud., were evaluated. The dynamic elastic modulus (MOE_d) was estimated on standing trees using stress waves (TreeSonic™). In the laboratory, swelling and shrinkage (ISO 13061-14 and 16), static modulus of elasticity (MOE_s) and modulus of rupture (MOR) (EN 408), and compressive strength (ISO 13061-16) were determined. The data were analysed using one-way ANOVA, followed by Tukey’s HSD test where appropriate. Swelling and shrinkage showed no significant differences (p > 0.05). One-way ANOVA revealed a significant effect of species on MOE_s (p < 0.001). Both standing-tree stress-wave measurements (MOE_d) and laboratory tests (MOE_s, MOR, and compression strength) revealed significant variability in stiffness and resistance among the species examined. The positive relationship observed between MOE_d and MOE_s indicates that stress-wave testing can serve as a practical, rapid tool for ranking plantation material at an early stage, thereby supporting early decision-making in SRF and agroforestry systems. These results provide comparative evidence for species and clonal selection, and to optimise the allocation of plantation resources to targeted value chains in Mediterranean environments. Full article

Stable wind resources in far-reaching sea areas are important direction for the development of renewable energy, making floating offshore wind turbine (FOWT) a focus of current research. However, the working environment of FOWT is severe. Under the condition of changeable wind and waves, the floating platform exhibits various motion responses, which may reduce power generation efficiency and even lead to structural damage with unpredictable consequences. In this paper, the National Renewable Energy Laboratory (NREL) 5 MW OC4-DeepCwind semi-submersible wind turbine is considered, and a multi-degree-of-freedom (M-DOF) tuned mass damper (TMD) system is designed to simultaneously suppress its roll and pitch motion responses. A multi-objective optimization problem is formulated to unify the frequency tuning accuracy, damping ratio constraints, and mass ratio limits through penalty functions. Then an improved Particle Swarm Optimization algorithm with time-varying acceleration coefficients (TVAC-PSO) is employed to determine the optimal TMD parameters, which dynamically adjusts exploration and exploitation capabilities to overcome the limitations of standard PSO in handling the strongly coupled parameter space. A high-fidelity aero-hydro-servo-elastic simulation model is established using OpenFAST to verify the vibration suppression performance under various sea state conditions. Simulation results demonstrate that the proposed M-DOF TMD system can effectively reduce the roll and pitch motion responses and significantly suppress the resonant peak energy, substantially improving the dynamic performance of FOWT. Full article

Multi-purpose platforms, which combine renewable energy generation devices and diverse functionalities, are a smart way to expand the applications of offshore platforms. An environmentally friendly multi-purpose offshore platform is proposed by the ‘Blue Growth Farm’ project, which includes a wind turbine, a set of wave energy converters, and an aquaculture system. To assess its feasibility and performance, a field experiment is conducted at an offshore site in Italy using a 1:15 scaled outdoor platform prototype. To provide comprehensive insights into the platform’s behavior, in the present work, aero–hydro–servo–elastic coupled numerical models based on the blade element method and potential flow theory are developed for various experimentally tested configurations of this multi-purpose platform. Time domain analyses are conducted to investigate the performance of the outdoor prototype platform under the recorded realistic environmental loads from the field experiment. The numerical results, including platform motion, mooring line tension forces, and wind turbine responses, agree with the corresponding experimental records. For example, the absolute mean value errors for platform roll and pitch motions are approximately 1 degree, validating the developed numerical model. Meanwhile, the present comparative study demonstrates the feasibility of the proposed multi-purpose concept and can provide a reference for similar projects in the future. Full article

An inhomogeneous thin internal stratum sometimes exists between two dissimilar materials, which is usually caused by non-uniform thermal distribution, interaction of different media, diffusion impurity or material degeneration and damage. In this paper, it is considered as a functional graded (FG) piezoelectric material in surface acoustic wave devices, and we investigate its effect on Love wave propagation within the framework of the linear piezoelectric theory. Correspondingly, the power series technique is presented and applied to solve the dynamic governing equations, i.e., two-dimensional partial differential equations with variable coefficients, with the convergence and correctness being proved. In this method, the material coefficients can change in random functions along the thickness direction, which reveals the generality of this method to some extent. As the numerical case, the elastic coefficient, piezoelectric coefficient, dielectric permittivity, and mass density change in the linear form but with different graded parameters, and the influence of material inhomogeneity on the Love wave propagation is systematically investigated, including the phase velocity, electromechanical coupling factor, and displacement distribution. In addition, the FG piezoelectric material caused by piezoelectric damage and material bonding is discussed. Numerical results demonstrated that both piezoelectric damaged and material bonding can make the higher modes appear earlier for the electrically open case, decrease the initial phase velocity, and limit the existing region of the fundamental Love mode for the electrically shorted case. The qualitative conclusions and quantitative results can provide a theoretical guide for the structural design of surface wave devices and sensors. Full article

Tuned liquid dampers (TLDs) are widely used in structural vibration mitigation, but they are limited by their damping frequency to use as passive damping equipment. To enhance the damping performance of the conventional TLD, a unique layered tuned liquid damper (LTLD) filled with water and diesel is proposed. The interfacial wave coupling mechanism for broadband energy dissipation has not been previously explored in sloshing-type dampers. A series of frequency-sweeping tests were carried out in the laboratory to compare the vibration suppression performance of the proposed LTLD against conventional TLD. The dampers were installed on an elastic supporting structural platform (SSP) with a height of one meter, and the bottom was horizontally excited with different amplitudes and frequencies using a hexapod motion simulator. The results indicate that the LTLD showed a better damping performance than the TLD under small-amplitude excitation and achieved optimization at two peaks. The separation surface movement dissipated the liquid motion’s energy and enhanced the hydrodynamic force in the horizontal direction. However, the damping effect of the LTLD weakened when the two liquids were no longer immiscible under large-amplitude excitation. Therefore, we recommend utilizing the LTLD to improve structural damping performance when $d_{max}/L$< 0.04984. In addition, the LTLD reduced the maximum wall pressure by about 25% in the transient state under large-amplitude excitation. This study presents experimental evidence that a water–diesel LTLD achieves broadband damping through interfacial wave coupling. The stable interfacial waves enhance energy dissipation and excite new vibration mitigation frequencies, offering a novel approach to overcoming the narrow-band limitation of conventional TLD. Full article

Blade pitch control is one of the most important control systems for a wind turbine: blade pitch controller malfunction can lead to increased vertical bending moment at the tower base, which may result in structural failure. This study investigated the collapse behavior mechanism at the tower root due to an extreme event of blade pitch malfunction for onshore and spar-floating wind turbines. An aero-hydro-elastoplastic coupled analysis tool previously developed and validated by one of the authors was utilized to capture the structural response at the tower root in elastic and plastic regions. Three strength models—(i) SM-01, (ii) SM-02, and (iii) SM-03—were selected to demonstrate the collapse behavior mechanism of onshore and spar-floating 5 MW wind turbines in a time-series simulation. The damage in the plastic region, termed the collapse extent, was evaluated at the collapsing section. Moment–rotational angle relationships are discussed under the same wind conditions. The tower vibrations were found to dominate the structural response of the onshore wind turbine, whereas the tower vibrations and floater response dominate the spar-floating wind turbine response during the failure event. The collapse extent of the spar-floating wind turbine was found to be 8 times larger than the onshore wind turbine under the same wind conditions. Furthermore, simulations were carried out for the spar-floating wind turbine to understand the effect of incoming waves on the collapse behavior: the collapse extent increases as the wave amplitude and period increase under the same wind conditions. Full article

This study introduces a unified analytical framework for investigating the transient thermoelastic vibration of a micro-scale beam resting on dual-parameter foundations. We apply the fractional three-phase-lag (FTPL) generalized thermoelastic model to accurately characterize scale-dependent coupled thermal and elastic responses by incorporating complex thermal relaxation effects through the fractional derivative order. By employing the Laplace transform technique and its numerical inversion, we derive the coupled distributions of temperature, displacement, bending moment, and deflection within the beams. A comprehensive parametric analysis is conducted to quantify the distinct influence of the fractional factor and the foundation’s shear and stiffness parameters on the beam’s dynamic stability and propagation characteristics. The calculated results are systematically compared with established classical theories to validate the model’s robustness while simultaneously demonstrating the enhanced predictive capacity of the (FTPL) approach, particularly for characterizing thermal wave dispersion at the micro-scale. This research provides critical design criteria for advanced micro-electromechanical systems (MEMSs) where foundation stiffness and thermal inertial effects are intrinsically linked, offering novel insights into the tailored design of microstructural components. Full article

Ventricular–arterial coupling (VAC) describes the dynamic interaction between left ventricular (LV) systolic elastance and the time-varying elastance/impedance of the arterial tree, a relationship that governs the instantaneous generation of aortic flow and ultimately cardiac output. VAC, typically expressed as the ratio of effective arterial elastance (Ea) to LV end-systolic elastance (Ees), has provided valuable mechanistic and prognostic insights, but is limited by its lumped, largely steady-state nature and by the need for pressure–volume modeling or complex surrogate formulas. Contemporary time-domain and wave-intensity approaches have underscored that the shape of proximal aortic pressure–flow waveforms encodes rich beat-by-beat information about ventricular–arterial interaction and energy transfer. Doppler echocardiography of the ascending aorta provides a readily available, high-temporal resolution measure of proximal aortic flow that is already used to quantify stroke volume, cardiac output and valvular lesions. We propose that proximal aortic flow, as recorded by Doppler echocardiography, may serve as a clinically practical proxy for beat-by-beat VAC, reflecting the instantaneous matching of ventricular and aortic elastances, which regulates the ejected flow towards peripheral tissues according to metabolic needs. Full article

This paper presents a dynamic analysis of ultrasonic motors (USMs) used in camera lens systems, which achieve high-precision motion via piezoelectric stators rather than electromagnetic components. The study focuses on the coupling of radial and tangential vibrations that create elliptical particle trajectories, driving the rotor through friction. The methodology is divided into two stages: Stage I: A discrete mass-spring model simplifies the coupled motion to a single degree of freedom. This analytical approach approximates natural frequencies and identifies modal degeneracy and the upper limits of representable modes via the Nyquist–Shannon criterion. Stage II: Based on continuous ring elasticity theory, the research establishes the actual coupled modal shapes. This stage demonstrates the manner in which kinematically linked displacements result in an elliptical trajectory on the stator surface. The analytical findings are validated using Finite Element Analysis (FEA) in CATIA. The simulations confirm the degeneracy of natural modes, proving that biphasic excitation is strictly necessary to maintain the progressive waves required for USM operation. Full article