Explore the vast range of titles available.

A classic-type SPAR has a natural heave period in the range of 25–30 seconds, making it vulnerable to resonance when wave periods approach this range. To reduce resonance effects, this study investigates the influence of a spring-mass type Tuned Mass Damper (TMD) on the SPAR’s heave motion response. Simulations were performed using a frequency-domain numerical method with Nemoh software to obtain the heave Response Amplitude Operator (RAO). Key parameters evaluated include the TMD mass ratio to SPAR displacement, spring stiffness coefficient, and damping coefficient. Results indicate that TMD parameter variations significantly affect the RAO curve, altering the height of resonance peaks, generating new peaks, and shifting the resonance frequency. The most effective configuration reduced the maximum RAO from 2.216 m/m without TMD to 1.536 m/m. However, in spectral response analyses under 1-year and 100-year wave conditions at the West Seno site, the TMD showed limited effectiveness due to a mismatch between the structure’s critical RAO frequency and the dominant energy regions of the wave spectrum. This highlights the importance of aligning TMD design with site-specific wave characteristics for optimal performance.

In recent years, 3D printing technology has become very important in many fields of science, manufacturing, design, medicine, aviation, sports, etc. Furniture design and manufacturing are also not left out of this trend. In this study, the results of bending moments and stiffness of joints of thin structural elements connected by 3D printing with polylactic acid (PLA) connectors are given. The connectors are newly developed, and information on their strength characteristics is lacking in the literature. Ten joints were investigated, made with 9 and 12 mm plywood and 6 mm MDF. The tested joints constructed by 3D-printed connecting elements show a high strength under arm compression bending load, between 44.16 and 24.02 N·m. The stiffness coefficients of joints with 3D-printed connecting elements are between 348 and 145 N·m/rad and are higher than those of conventional detachable mitre joints but lower than those of glued ones. The type of filling of the hollow section of the connecting elements and the wall thickness influenced the joints’ strength and stiffness. Reducing the width of the connecting elements from 40 to 30 mm and the inner radius between the arms from 2 to 1 mm does not significantly affect the joints’ strength and stiffness coefficients.

Purpose To verify the relationship between muscle volume, lateral centre-edge angle (LCEA), alpha angle (AA), body mass index (BMI) and Beighton score with stiffness coefficient (SC). To analyse the difference of traction force at different physical states of hip joint capsule. Methods Thirty-six patients who underwent hip arthroscopy operation were included. The volumes of some related muscles were measured in MRI images by 3D Slicer. We recorded and tested differences in traction force of five joint capsule physical states, including before (State 1) and after joint capsule puncture (State 2), after the establishment of anterolateral and mid-anterior approaches (State 3) and after incision of the joint capsule through these two approaches (States 4, 5). The correlation between muscle volume, BMI, LCEA, AA and SC was verified by Spearman test. Poisson regression was used to explain confounding variables. Results The average force at State 1 was 531.8 N. There were significant differences in traction force between these five states ( p  < 0.001). There was a significant positive correlation between muscle volumes and SC ( p  < 0.001). BMI had no correlation with SC ( n.s. ). The preoperative LCEA of the affected side was correlated with SC ( p  = 0.043). AA and SC were not correlated ( n.s. ). Conclusion The physical states of the hip joint capsule affected traction force. Muscle volume rather than BMI is an ideal index to estimate preoperative traction force. LCEA affected traction force, whilst AA and Beighton score did not. Measuring the muscle volume can help estimate the most suitable traction force for the patient. Levels of evidence IV.

New technologies are being developed to elaborate cutting-edge electrical jet engines to replace classical constructions. These new concepts consider the possibility of using electrical machines both as starters and generators, as well as suspension systems for the turbine shafts of aircraft engines. The paper will present mathematical analysis regarding active magnetic bearing (AMB) implementation for rotor–shaft support. This technology allows the elimination of friction forces between cooperating kinematic pairs (stator and rotor), reduces the adverse effects of classic bearings, and increases operating speed range and an operational susceptibility. The mathematical and numerical analysis of active magnetic suspension systems are presented. Next, a comparison of the theoretical studies using Comsol Multiphysics software and its experimental verification are described. A discussion regarding the mathematical analysis and experimental effects is also provided. The conclusion summarizes the theoretical and experimental features of heteropolar radial active magnetic bearings in new electric aircraft engines.

This study presents a spectro-geometric vibration model for analyzing free as well as forced vibration properties for FGM cylindrical double-walled shells with internal structures. The boundary conditions and coupling effects are modeled using an artificial virtual spring approach, which allows for the simulation of arbitrary boundary and coupling conditions by varying the elastic spring stiffness coefficients. The spectral geometry method is employed to represent the displacement variables of the FGM substructure, overcoming the discontinuity phenomenon commonly observed when traditional Fourier series are used. The dynamic equations of the FGM cylindrical double-walled shell with an internal structure are derived using the first-order shear deformation assumption and the Rayleigh–Ritz method, and the corresponding vibration solutions are computed. The model’s reliability and prediction accuracy are confirmed through convergence checks and numerical comparisons. Additionally, parametric studies are conducted to examine the influence of material constants, position parameters, and geometric parameters on the shell’s inherent characteristics and steady-state response.

We obtain the through-thickness elastic stiffness coefficient (C33) in nominal 9 nm and 60 nm BaFe2As2 (Ba-122) thin films by using picosecond ultrasonics. Particularly, we reveal the increase in elastic stiffness as film thickness decreases from bulk value down to 9 nm, which we attribute to the increase in intrinsic strain near the film-substrate interface. Our density functional theory (DFT) calculations reproduce the observed acoustic oscillation frequencies well. In addition, temperature dependence of longitudinal acoustic (LA) phonon mode frequency for 9 nm Ba-122 thin film is reported. The frequency change is attributed to the change in Ba-122 orthorhombicity (a−b)/(a+b). This conclusion can be corroborated by our previous ultrafast ellipticity measurements in 9 nm Ba-122 thin film, which exhibit strong temperature dependence and indicate the structural phase transition temperature Ts.

To determine the appropriate stiffness coefficient k values for rubber belts used in dynamic testing of the elastic modulus and shear modulus of timber and solid wood composite materials, this study employed three different thicknesses of rubber belts. Dynamic tests were conducted on straw boards, Laminated Veneer Lumber (LVL), and Spruce-Pine-Fir (SPF) materials, and the results were validated and analyzed using static four-point bending tests. The conclusions drawn from this research indicate that the range of stiffness coefficient k values for the rubber belts obtained through dynamic testing fell between 0.05 and 0.28 N/m. The correctness of the dynamic testing method was verified through static four-point bending tests. The error levels for elastic modulus E and shear modulus G of the same type of board measured using the three different rubber belts were below 9.5% and 9.8%, respectively.

AbstractThe Discrete Element Method (DEM) is a numerical technique proposed for solving mechanics problems of non-continuous media. However, applications of DEM in continuous media structures are relatively limited. In this manuscript, a modification of the torsional spring stiffness coefficient of the simply supported boundary contact element is proposed based on our previous work. Then, the plate DEM based on modifying the torsional spring stiffness coefficient is adopted to solve the load-bearing problems of cylindrical shells. This study aims to investigate the validity of using the plate DEM based on modification of the torsional spring stiffness coefficient for nonlinear large deformation analysis of shell-type structures. Compared to traditional methods, continuity of displacement and deformation coordination are not required for the plate DEM, and there is no need to assemble a stiffness matrix, so matrix non-convergence problems are evitable. To evaluate accuracy of the developed plate DEM, several popular benchmark problems of geometric nonlinearity for shells are solved by adopting the plate DEM. The results demonstrate that the proposed numerical method can obtain highly accurate solutions in the nonlinear large deformation numerical calculations of shells, which further confirms the feasibility of the plate discrete element method in solving the geometric nonlinear problems of plate and shell structures.

Currently, the beam vibration equations established based on the nonlocal elasticity theory of Euler-Bernoulli beams not only do not take into account the effect of rotational inertia, but also ignore the length interactions between the atomic lattices, so they cannot reflect the real mechanical properties of the beams. Therefore, the main goal of this manuscript is to propose a novel computational method to accurately reveal the true mechanical behavior of beams with global coupling. Firstly, the method has successfully constructed a physical model of nonlocal Euler-Bernoulli beam vibration under the effect of rotational inertia on viscoelastic Pasternak foundations by considering the global coupling mechanism through the length interaction between atomic lattices, and a degradation validation method for the modeling process is given. Secondly, the physical model is converted from a time-domain problem to a frequency-domain problem by using the Fourier transform, and Hasselman’s complex modal synthesis method is introduced to successfully give the transfer function of the spatial state of the nonlocal Euler-Bernoulli beam vibration model under the effect of rotational inertia on a viscoelastic Pasternak foundation, as well as the analytical solution and the degradation validation method of the model. degenerate verification. Finally, the mechanism of global coupling is revealed intrinsically through the material point of the beam, and the effects of the nonlocal factor, foundation shear coefficient, foundation stiffness coefficient, and damping coefficient on the vibration frequency and amplitude of the nonlocal Euler-Bernoulli beam vibration under the action of rotational inertia on a viscoelastic Pasternak foundation are analyzed. The theoretical and technical gaps of non-local Euler-Bernoulli beam vibration under the action of rotational inertia on viscoelastic Pasternak foundations are bridged. The research results not only provide theoretical basis and practical guidance for adjusting the parameters of nanobeams to enhance their stability and performance. Moreover, it can play a more important role in guiding the application of nanobeams in the fields of biosensors, cell-material surface interaction studies, and disease diagnosis and treatment.

The design of shallow foundations for wind turbines is typically governed by serviceability and fatigue limit states. To estimate the deformations of shallow foundations under working loads, existing design standards generally employ analytical uncoupled isotropic elastic solutions based on idealized soil conditions. However, many natural soil deposits exhibit some degree of stiffness anisotropy due to their deposition and complex stress history. This study has investigated coupled elastic stiffness coefficients for circular shallow foundations founded on cross-anisotropic soils under combined VHMT loadings (vertical, horizontal, moment and torsional) using finite element analysis. A three-parameter anisotropic soil model was applied to the problem. The study extensively explores the effects of soil stiffness non-homogeneity (i.e. linear increase of elastic modulus with depth) and foundation embedment on the foundation stiffness coefficients. Fitted expressions of these stiffness coefficients were also derived. In addition, a practical application using the proposed stiffness coefficients was presented to demonstrate the effects of soil stiffness anisotropy on the responses of a typical large wind turbine shallow foundation.