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2024-03-01 | This study proposes a hybrid metaheuristic optimal design method for an impact damper system, which is attached to a flexible cantilever beam. A nonlinear damper consists of an embedded closed chamber where a ball can move and reduce the amplitude of the main system via motion transfer. Due to the complexity and large number of calculations required to analyze an impact damper behavior, the hybrid metaheuristic method has been used to determine the optimal parameters of the impact damper. First, the equations governing the nonlinear energy sink and the beam are obtained. Then by solving them numerically and using the genetic algorithm method, the damper parameters are optimized to achieve the minimum range of vibrations. The optimization considers the mass ratio of the nonlinear energy sink and the beam, the coefficient of restitution, and the position of the damper on the beam. It is for the first time that all the design parameters of the nonlinear energy sink are investigated for optimal design. In the hybrid imperialist competitive ant colony algorithm, the imperialist competitive algorithm is used as a tool for the exploration phase, while the ant colony algorithm is used as an amplifier for the extraction phase. In the following, each of the mentioned parameters is examined, and the optimal value for each of them is calculated. | Optimizing the performance of nonlinear impact damper connected to beam in forced vibrations with hybrid metaheuristic method | 10.1007/s41939-023-00197-2 |
2024-02-23 | In this study, we investigate the relativistic dynamics of vector bosons within the context of rotating frames of negative curvature wormholes. We seek exact solutions for the fully-covariant vector boson equation, derived as an excited state of zitterbewegung. This equation encompasses a symmetric rank-two spinor, enabling the derivation of a non-perturbative second-order wave equation for the system under consideration. Our findings present exact results in two distinct scenarios. Notably, we demonstrate the adaptability of our results to massless vector bosons without compromising generality. The evolution of this system is shown to correlate with the angular frequency of the uniformly rotating reference frame and the curvature radius of the wormholes. Moreover, our results highlight that the interplay between the spin of the vector boson and the angular frequency of the rotating frame can give rise to real oscillation modes, particularly evident in excited states for massless vector bosons. Intriguingly, we note that the energy spectra obtained remain the same whether the wormhole is of hyperbolic or elliptic nature. | Vector bosons in the rotating frame of negative curvature wormholes | 10.1007/s10714-024-03213-z |
2024-02-21 | In this work we present a multibody dynamics system composed of geometrically exact nonlinear beams with inelastic behavior, representing flexible system components. The main focus of the work is to introduce advanced energy dissipation models using hardening and softening plasticity into such beam models and to show how they can also recover a vibration amplitude decay typical of viscous damping. The damping model is represented by the constitutive behavior of the flexible beam element chosen as an elasto-viscoplastic response with linear isotropic hardening and subsequent softening plasticity. The formulation is cast within the mixed variational framework, where the strong embedded discontinuity is introduced into displacement/rotation fields in the softening phase leading to localized plastic deformation. We also aim to ensure model capabilities to deliver results for long-term loading simulations, which is of interest for quantifying the risk of fatigue failure for such flexible system component. The corresponding numerical implementation combines the space discretization based on the finite element method with the time discretization based upon energy-conserving or energy-decaying integration schemes. The results of several numerical simulations are presented in the dynamics of flexible-rigid multi-body systems to illustrate a very satisfying performance of the proposed model. | Multibody dynamics system with energy dissipation by hardening and softening plasticity | 10.1007/s11044-024-09972-6 |
2024-02-21 | This work deals with the solution and asymptotic analysis for a porous-elastic system with internal damping of the fractional derivative type. We consider an augmented model. The energy function is presented and establishes the dissipativity property of the system. We use the semigroup theory. The existence and uniqueness of the solution are obtained by applying the well-known Lumer-Phillips Theorem. We present two results for the asymptotic behavior: Strong stability of the $$C_0$$ C 0 -semigroup associated with the system using Arendt-Batty and Lyubich-Vũ’s general criterion and polynomial stability applying Borichev and Tomilov’s Theorem. | Asymptotic behavior for a porous-elastic system with fractional derivative-type internal dissipation | 10.1007/s13540-024-00250-y |
2024-02-21 | Input and command shaping are extensively utilized in point-to-point maneuvers to transfer objects in industry. Most of the research conducted on these techniques assumes dynamic systems with no damping and zero initial conditions. In some cases, the initial conditions cannot be assumed to be zero. For example, a crane trolley may not be exactly on top of the payload when it starts moving, which forces the system to start from an initial angle. Furthermore, when damping is relatively large, it can have an undesirable effect on the shaper’s performance. Not accounting for such conditions can create unwanted oscillations, unsafe maneuvers, and inaccurate positioning. In this work, a new closed-form command shaper controller based on trigonometric format for a single degree-of-freedom pendulum is proposed to eliminate the residual oscillations, considering both damping and nonzero initial angles. The equation of motion of a single DOF, damped pendulum with nonzero initial angles is derived, linearized, and then solved analytically to find the shaper constant parameters in a closed form. To utilize the full system capabilities, this shaper has a selectable maneuvering time and ensures maximum cruising velocity. To evaluate the performance of the shaper, it is compared to several different types of shapers, both numerically and experimentally. The results show that the proposed shaper can eliminate induced residual vibration at the end of motion more effectively, despite the damping and nonzero initial conditions. | A waveform command shaping control of a damped single degree-of-freedom crane system with nonzero initial conditions | 10.1007/s40435-024-01392-w |
2024-02-19 | This work investigates the well-posedness and stability outcomes of the one-dimensional Cauchy problem within a system involving swelling-porous elastic soils and thermal effects. The heat conduction in this system is described by the Lord–Shulman theory. By the energy method, we establish the existence of solutions and then prove an exponential stability result under suitable hypotheses. Our results were achieved without the need for the condition of equal velocities, and it is also considered a good improvement to our work in the paper (Choucha et al. in Mathematics 11(23):4785, 2023), completely dispensing with any damping term. | On a Lord–Shulman swelling porous thermo-elastic soils system with microtemperature effect: well-posedness and stability results | 10.1007/s13370-024-01170-z |
2024-02-19 | The stiffness (K) and slenderness factor (λ) of a steel plate-based damper has been studied on the basis of elastic-inelastic-plastic buckling (EIP) modes and flexural/shear/flexural-shear failure mechanisms (FSF-S), which has been designed for the improvement of the behavior of concentrically braced frames. Steel plate-based dampers offer significant benefits in terms of mode shapes and failure mechanisms, contributing to improved dynamic performance, enhanced structural resilience, and increased safety of civil engineering structures. Their effectiveness in mitigating dynamic loads makes them a valuable tool for engineers designing structures to withstand extreme environmental conditions and seismic events. This study was undertaken by using the learning abilities of the response surface methodology (RSM), artificial neural network (ANN) and the evolutionary polynomial regression (EPR). Steel plate dampers are special structural designs used to withstand the effect of special loading conditions especially seismic effects. Its design based on the prediction of its stiffness (K) and slenderness factor (λ) cannot be overlooked in the present-day artificial intelligence technology. In this research work, thirty-three entries based on the steel plate damper geometrical properties were recorded and deployed for the intelligent forecast of the fundamental properties (λ and K). Design ratios of the steel plate damper properties were considered and models behavior was recorded. From the outcome of the model, it can be observed that even though the EPR and ANN in that order outclassed the other techniques, the RSM produced model minimization and maximization features of the desirability levels, color factor scales and 3D surface observation, which shows the real model behaviors. Overall, the EPR with R^2 of 0.999 and 1.000 for the λ and K, respectively showed to be the decisive model but the RSM has features that can be beneficial to the structural design of the studied steel plate damper for a more robust and sustainable construction. With these performances recorded in this exercise, the techniques have shown their potential to be applied in the prediction of steel damper stiffness with optimized characteristic features to withstand structural stresses. | Prediction of steel plate-based damper for improving the behavior of concentrically braced frames based on RSM and ML approaches for sustainable structures | 10.1038/s41598-024-54845-9 |
2024-02-17 | In this paper, a Damping Impedance Method (DIM)-applied power Hardware-in-the-Loop Simulation (HILS) test-bed is proposed to test the stability of a Low Voltage DC (LVDC) grid composed of multiple converters. The impedance interaction between the source-side system and load-side system which consists of the LVDC grid is analyzed by the Extra Element Theorem. Furthermore, the stability of the LVDC Grid is assessed by using the Opposing Argument Criterion. Using those analyses, the power HILS test-bed is implemented using the DIM. This approach leverages the CPL characteristics of the load-side system to propose an offline design method for the damping impedance used in the DIM, which can reduce implementation complexity and can obtain an accurate power HILS test-bed. Finally, the accuracy and effectiveness of the proposed power HILS test-bed are verified using a 500-W Dual-Active-Bridge converter. | Development of Power Hardware-in-the-Loop Simulation Test-bed to Verify LVDC Grid Stability Using Offline Damping Impedance Design | 10.1007/s42835-024-01817-8 |
2024-02-17 | This paper proposes a new hybrid optimization technique that merges a differential evolution algorithm with a local strategy using the Nelder–Mead algorithm or simplex search algorithm and in Matlab software package, referred to as ( fminsearch ). To examine the variation in parameter estimation erros resulting from different optimization techniques. For a numerical model to exhibit good agreement with experimental values, it should prevent any clearances in the system and achieve an improved fit for the parameters of the Bouc–Wen-modified dynamic model. The study includes an experimental design to control the excitation current, frequency, and piston displacement. In this study, the model employed is the numerically parameterized model implemented by Wang, which utilizes experimental dynamic behavior of a commercial magnetorheological damper and applies a method to fit symmetric and asymmetric sigmoid functions using experimental data. These optimization algorithms are used to identify the sixteen parameters of the modified Bouc–Wen model. | Comparing optimization algorithms for parameter identification of sigmoid model for MR damper | 10.1007/s40430-024-04698-0 |
2024-02-16 | Prolonged exposure of vehicle vibrations can cause poor vehicle stability, driver tiredness, ride discomfort, impair focus, and even increase the chance of an accident. Automotive suspension systems are a common way to make a ride more comfortable, protect the rider and vehicle from the harmful effects of vibration. Along with variable damping, the stiffness variability is also another important aspects for the comfortable ride and vehicle stability. With this motivation, the present research focuses on developing a hybrid semi-active vibration isolator that combines a four-parametric visco-elastic model and the conventional Bouc-Wen model to demonstrate the variable damping and stiffness characteristics. The half-car model, including the suspension system, is modeled mathematically and simulated in MATLAB environment. Numerical simulations are conducted under circular, trapezoidal, sinusoidal, and random disturbances to test the performance of the vibration isolator. The peak value of displacement is reduced by 87.5%, 92%, 83.33% and 89.6% whereas the RMS acceleration value is decreased by 84.83%, 86%, 89.35% and 94.90% in comparison with the passive system for circular, trapezoidal, sinusoidal and random disturbances, respectively. Around 40% reduction in settling time is also observed for sinusoidal, circular and trapezoidal road profiles. The comparative results exhibit that the suggested isolator has superior performance compared to the passive system. | Development of a hybrid vibration isolator for better ride comfort and vehicle stability | 10.1007/s40430-024-04711-6 |
2024-02-15 | The problems of vibration and noise have seriously affected people’s production and life. Hydrogel can be used as damping material because of its good viscoelasticity, but the current damping material is difficult to meet the needs of actual production and life because of the lack of wide damping temperature and frequency range and high loss factor. In this work, ammonium persulfate was used as both initiator and oxidant to form a mixed double network hydrogel of polyacrylamide and oxidized sodium alginate. The double network hydrogel prepared by this method has good adhesion and mechanical properties. In addition, due to the adjustable viscoelasticity of the hydrogel, the hydrogel shows excellent damping properties. When the concentration of MBA is 0.02%, it can reach the temperature range of 0-125 ℃, and the damping factor is more than 0.3. The visualization experiment proves the practical application effect of the hydrogel, so it is expected to be used as a damping material in damping, noise reduction and other fields in the future. | Study on viscoelasticity and damping properties of OSA/PAAM hydrogel | 10.1007/s10965-024-03913-9 |
2024-02-14 | We propose a simple numerical procedure to approach the symbol of a self-adjoint linear operator $$\mathcal {A}$$ A by using trace estimates of a corresponding discretization matrix A , with numerical data. The Symbol Approximation Method (SAM) is based on an adaptation of the matrix trace estimator to successive distinct numerical spectral bands in order to build a piece-wise constant function as an approximation of the symbol $$\sigma $$ σ of $$\mathcal {A}$$ A . The decomposition of the spectral interval into band of frequencies is proposed with several approaches, from the formal spectral to the multi-grid one. We apply the new method to different operators when discretized in finite differences or in finite elements. The SAM is also proposed as a tool for the modeling of waves equations, and is presented a means to capture an additional linear damping term (hidden operator) in hydrodynamics models such as Korteweig–de Vries or Benjamin Ono equations. | The symbol approximation method: a numerical approach to the approximation of the symbol of self-adjoint operators | 10.1007/s40314-023-02586-2 |
2024-02-14 | The sustainability of today’s industry turned into a critical requirement on account of energy cost increases, environmental pollution, and carbon emissions. As an important segment in mechanical drive, the vibration and noise from gear transmission negatively impact the physical and psychological health of workers and interfere with the machine running. This paper proposes a new temperature-controlled vibration-damping lightening polymer composite gear model with a modified lightweight web structure. The characteristic of polymer (mechanical properties changed by structure temperature) was trying to be used for the gear damping variable control. The spur gear web was replaced with a spoke-like structure connected with a ring structure that adheres to the heating film. That was required to assure torsional rigidity and compliance meanwhile controlling the web structural damping performance. For experimental purposes, the gears were manufactured from three kinds of viscoelastic polymer using additive manufacturing technology. The gear frequency sweeping excitation testbed was built in the experiment. The vibration exciter and gear dynamic responses were measured through the force and torque sensor. In the tests, the modal frequency and damping of gears were measured at different temperatures by control heating films. The experimental result coincides with vibration analysis in the finite element (FE) method. Variable damping could be achieved by changing the viscoelastic polymer temperature and gear web structure. This research can provide guidance for the polymer material gear damping control in mechanical transmission applications. | Temperature control-based design of variable damping and lightweight gear bodies | 10.1007/s00170-024-13133-6 |
2024-02-13 | Traditional squeeze-film dampers are used in modern aircraft generators as vibration-suppressing devices. However, the conventional squeeze-film damper has the disadvantage of highly nonlinear oil film force. This study aims to improve the dynamic characteristics of the squeeze-film damper by changing its geometric structure, so a hybrid squeeze-film damper (HSFD) is proposed. Besides, the turbulent flow could also be found in lubrication analysis of high rotating speed turbo-machineries, and the ignorance of turbulent flow would lead to significant failure results. Accordingly, the study presents a nonlinear dynamic analysis of a turbulent bearing-rotor system under quadratic damping equipped with HSFD. The dimensionless speed ratio and dimensionless unbalance parameter are used to plot the bifurcation diagrams, and abundant harmonic, subharmonic, quasi-periodic, and even chaotic motions are found with dynamic trajectories, power spectrum, Poincaré maps, Lyapunov exponent, and fractal dimension, simultaneously. Finally, an active control method is applied to suppress the chaotic responses. The simulation results will provide valuable suggestions for designing and developing rotating machinery, such as rotor-bearing systems operating at high rotational speeds and nonlinearity. | Nonlinear dynamic of turbulent bearing-rotor system under quadratic damping with HSFD and active control | 10.1007/s40430-024-04691-7 |
2024-02-13 | The generalized fractional derivative is a useful tool for describing the mechanical property of viscoelastic dampers in vehicles. However, the complex integral form of the generalized fractional operator and the non-Markov property of fractional system make it challenging to perform stochastic dynamic analysis on multi-degree-of-freedom (MDOF) vehicle systems with generalized fractional damping. Thereby, the main purpose of this paper is to explore the stochastic dynamic characteristics of generalized fractional systems in the framework of the direct probability integral method (DPIM). To this end, a vehicle model with generalized fractional dampers is first constructed to simulate the driving process on uneven pavement, in which the random pavement roughness and discrete impulse excitation are described as continuous Gaussian white noise and discrete Poisson white noise, respectively. Then, the equivalent MDOF stochastic system of the model is derived, and the corresponding probability density integral equation (PDIE) is further established for uncertainty propagation. Benefiting from the historical memory of PDIE, a DPIM-based strategy is proposed to address the random vibration problem of the generalized fractional MDOF system. Finally, the stochastic bifurcation and dynamic reliability analyses of vehicle systems with generalized fractional damping are realized via the proposed strategy. The results indicate that the change of generalized fractional order, as a key design parameter, will cause stochastic bifurcation phenomenon and stochastic chaotic motion, which remarkably affects the vehicle ride comfort and driving safety. | Stochastic bifurcation and dynamic reliability analyses of nonlinear MDOF vehicle system with generalized fractional damping via DPIM | 10.1007/s11071-024-09313-4 |
2024-02-13 | In this study, a novel passive hybrid damper based on combinations of shape memory alloy (SMA), steel and glass fiber-reinforced polymer (GFRP) was introduced. The hysteretic properties of both SMA and steel and reversibility effect of both SMA and GFRP rods provide a superior passive damping device to dissipate large amounts of input excitation energy besides superior re-centering characteristics. A series of experiments to achieve material properties were carried out with the aim to incorporate accurate properties of triple materials utilized in analytical model. The non-dominated sorting genetic algorithm II was applied to evaluate the quantity of proportionality for each material used in the device, in terms of increasing energy absorption, improving reversibility and reducing manufacturing costs. Then, the optimal damper was constructed and tested based on results obtained from analytical modeling. The results showed the high efficiency of proposed hybrid damper to attain mentioned multi-objective goals. Subsequently, the application of damper in a prototype structure was investigated. The results of the analyses showed that the use of the damper has a significant effect on reducing seismic effects. Therefore, the damper can be used as a superior low-cost device in a retrofitting program for various types of structural systems in new and existing deficient buildings in earthquake-prone regions. | A Novel Passive Hybrid Triple-Material Damper | 10.1007/s13369-024-08734-y |
2024-02-10 | The damping efficiency of vertical porous baffles is investigated for a dynamically coupled fluid-vessel system. The system comprises of a two-dimensional vessel, with a rectangular cross-section, partially filled with fluid, undergoing rectilinear motions with porous baffles obstructing the fluid motion. The baffles pierce the surface of the fluid, thus the problem can be considered as separate fluid filled regions of the vessel, connected by infinitely thin porous baffles, at which transmission conditions based on Darcy’s law are applied. The fluid is assumed to be inviscid, incompressible and irrotational such that the flow in each region is governed by a velocity potential. The application of Darcy’s law at the baffles is significant as it makes the system non-conservative, and thus the resulting characteristic equation for the normal modes leads to damped modes coupled to the moving vessel. Numerical evaluations of the characteristic equation show that the lowest frequency mode typically has the smallest decay rate, and hence will persist longest in an experimental setup. The maximum decay rate of the lowest frequency mode occurs when the baffles split the vessel into identically sized regions. | Dynamic sloshing in a rectangular vessel with porous baffles | 10.1007/s10665-024-10333-7 |
2024-02-08 | We consider the total energy decay together with the $$L^{2}$$ L 2 -bound of the solution itself of the Cauchy problem for wave equations with a short-range potential and a localized damping, where we treat it in the one-dimensional Euclidean space $$\textbf{R}$$ R . To study these, we adopt a simple multiplier method. In this case, it is essential that compactness of the support of the initial data not be assumed. Since this problem is treated in the whole space, the Poincaré and Hardy inequalities are not available as have been developed for the exterior domain case with $$n \ge 1$$ n ≥ 1 . However, the potential is effective for compensating for this lack of useful tools. As an application, the global existence of a small data solution for a semilinear problem is demonstrated. | Energy decay for wave equations with a potential and a localized damping | 10.1007/s00030-023-00906-3 |
2024-02-08 | Concrete-filled steel tube (CFST) arch bridges have a high center of gravity and a substantial mass, resulting in a discernible seismic response. Consequently, long-span CFST arch bridges must retain exceptional seismic performance and appropriate seismic control design. In this study, the dynamic response and seismic performance of a unique swallow-type CFST arch bridge when subjected to longitudinal earthquake forces were analyzed using numerical simulation methods. The displacement and axial force response results and their laws of the key bridge components were obtained. Taking into account seismic checking calculations, two damping measures were proposed for the CFST arch bridge, as the relative displacement of the girder end exceeded the allowable value specified. The appropriate design parameters for viscous dampers and lead shear dampers were examined. Additionally, the seismic performance of these dampers was verified through a shaking table test using a 1:16 scale model. The findings indicated that when subjected to Wenchuan Wolong wave action, the relative displacement between the steel box girder and the concrete girder of the bridge was significantly larger, leading to girder end pounding. The limit values were surpassed by 32.5% and 50%, when subjected to the uniform and traveling wave excitations, respectively, thus indicating that the expansion joint was the most vulnerable component. Following the selection of optimal parameters for the dampers, the dampers exhibited the capability to mitigate seismic and pounding impacts. Long-span CFST arch bridges with dampers were found to effectively reduce the seismic response of the skewback strain and vault, as well as the relative displacement of the girder ends. Furthermore, the average maximum damping rates achieved by the viscous damper and the lead shear damper reached 44.9% and 44.6%, respectively. | Shaking table test study on the seismic control of concrete-filled steel tube arch bridges based on dampers | 10.1007/s43452-024-00864-2 |
2024-02-07 | This paper presents the effects of geology and local soil conditions on the intensity of ground agitation with a moderate earthquake of magnitude M _ w = 6.8 that struck Boumerdes, on May 21st 2003. The analysis of the earthquake response of the ground soil specific to the site of Zeralda, located west of Algiers was carried out. The first part consists in developing a database of the experimental site based on geophysical and geotechnical testing to estimate the local site conditions. In the second part, a numerical analysis is performed out using the FLAC^2D software to evaluate the dynamic characteristics of the sand and consolidated sand, in particular the determination of the evolution curves of the shear modulus (G) and the damping (D) versus the shear strain ( γ ). The nonlinear model developed by Ramberg–Osgood and limited by the Mohr–Coulomb criterion is used. In the third part, the earthquake response from the ground surface was analyzed using the FLAC^2D code, considering the nonlinear soil deposition behavior approach. The response spectrum resulting from this analysis of the nonlinear approach was compared with the response spectra of the Algerian seismic code (RPA 99, 2003) and Eurocode 8. A numerical evaluation of the G/G_max( γ ) and D( γ ) curves of soil deposits seems to be compatible and close to other experimental data in the literature. The model presented by Ramberg–Osgood is applicable to the surface layer composed mainly of sand and consolidated sand. It therefore appears that the response spectrum was relatively underestimated by the Algerian building code, particularly during the short periods where the maximum spectral accelerations occur. The obtained results also validate the ability of the Ramberg–Osgood model to simulate the seismic response of the overburden to ground motions. | Analysis of local site effects on seismic ground response under Boumerdes earthquake scenario: case study of Zeralda site of Algeria | 10.1007/s41062-024-01368-x |
2024-02-03 | In the last two decades, bottom ash has been widely used as an alternative to conventional granular fill in various construction activities, either by replacing the whole or a portion of the fill material. This study investigates the dynamic behaviour of bottom ash and compares its response with sand through strain-controlled constant volume cyclic simple shear tests. The effects of relative density, shear strain, vertical stress, and number of loading cycles on the dynamic behaviour of bottom ash and sand are discussed. The results of the study indicate that bottom ash is highly compressible than sand under one-dimensional anisotropic compression, attributed to the angular and vesicular texture of bottom ash particles. This texture results in associated particle breakage in dense bottom ash specimens. Further, the damping of bottom ash is lower than that of sand in most cases, and the shear modulus is found to be smaller or larger than that of sand depending on shear strain magnitude and the number of loading cycles. At medium shear strain magnitudes, bottom ash and sand exhibit almost the same initial shear modulus. However, the degradation of the shear modulus with the number of loading cycles is significant in sand compared to bottom ash, thereby indicating that bottom ash exhibits a better dynamic resistance than sand. The study highlights that specimen dimensions critically influence the results obtained from cyclic simple shear tests and that careful interpretation of results is necessary, especially when comparing materials with different particle sizes or admixtures. Furthermore, the influence of cyclic loading frequency on the overall dynamic response of tested materials is also discussed. The findings of the study contribute to the understanding of bottom ash behaviour and its potential use as a granular fill material in construction applications. | Investigating the Dynamic Behaviour of Bottom Ash Versus Sand Using Cyclic Simple Shear Tests | 10.1007/s10706-024-02743-2 |
2024-02-02 | Bolted joints play a more and more important role in the structure with lighter weight and heavier load. This paper aims to provide an overview of different experimental approaches for the dynamic behavior of structures in the presence of bolted joints, especially the energy dissipation or damping at frictional interfaces. The comprehension of energy dissipation mechanisms due to friction is provided first, while the key parameters and the measurement techniques, such as the excitation force, the preload of the bolt, or the pressure at the interfaces, are briefly introduced. Secondly, the round-robin systems aim to measure the hysteresis parameters of the frictional joints under tangential loads are reviewed, summarizing the basic theory and the strategies to apply the excitation force or acquire the response in different testing systems. Followed by parameter identification strategies for bolted structures, the test rigs with one or more simplified bolted joints are summarized to give an insight into the understanding of typical characteristics of bolted structures, which are affected by the presence of friction. More complex test rigs hosting real-like or actual engineering structures with bolted lap or flange joints are also introduced to show the identification process of the dynamic characteristics of bolted connections employed in specific applications. Based on the review paper, researchers can get the basic knowledge about the experimental systems of the bolted structures, especially several classical round robin systems, such as the Gaul resonator and widely used Brake-Reuß beam system. Readers can take advantage of this background for more creative and effective future studies, make more progress on the study of assembled structures and understand the influence of bolting frictional connections on the dynamic response better. | Experimental studies on the energy dissipation of bolted structures with frictional interfaces: A review | 10.1007/s40544-023-0809-8 |
2024-02-01 | The utilization of communication linkages generates delays that degrade system dynamic performance and cause fluctuations in the system frequency while the extensive integration of renewable energy sources may cause further increase in the frequency oscillations owing to low inertia. By considering the inclusion of the virtual inertia and damping (VID) control in load frequency control (LFC) systems with time delays, this article investigates the impacts of the VID control on the stability delay margins (SDMs) of two-area LFC systems. For this purpose, an exact method, which is based on recursively removing exponential terms from the characteristic equation, is first implemented to compute SDMs of the two-area LFC system enhanced by VID control for a wide range of controller gains. Secondly, the effect of the VID parameters on the SDMs is investigated by employing the exact method. Theoretical results clearly illustrate that SDMs significantly increase as VID parameters increase. Furthermore, simulation analysis elucidates that with the VID incorporation, the performance of the LFC system with low inertia is enhanced and the rate of change of the frequency and frequency nadir are remarkably decreased, improving the stability of time-delayed LFC systems. | Impact of virtual inertia and damping control on stability delay margins of load frequency control systems with renewable energy sources | 10.1007/s00202-023-01984-3 |
2024-02-01 | The aim of this study is to evaluate the performance of a recently proposed tuned mass damper (TMD) to control seismic demands of multi-degree of freedom (MDOF) structures. The TMD is composed of a mass, a viscous damper, a linear spring, and a shape memory alloy (SMA)-based nonlinear stiffness unit. The performance of the TMD is compared to that of a conventional linear TMD while both embedded on three different lumped mass shear models (6, 10, and 25 stories). The numerical analyses of the structural models are carried out subjected to broad-band excitations involving 50 far-field ground motions and a filtered Gaussian white noise. The results show that the nonlinear TMD, which benefits from gradually increasing hysteretic damping in addition to viscous damping, performs better than the linear TMD, especially for longer structural periods. However, the damper mass displacement in the nonlinear TMD is not significantly higher than that of the linear TMD. Furthermore, the height-wise distribution of structural responses obtained from various TMD tunings confirms that the different optimization objectives used for the nonlinear TMD tuning do not significantly affect its seismic performance. | Evaluation of a nonlinear TMD seismic performance for multi-degree of freedom structures | 10.1007/s42107-023-00850-8 |
2024-02-01 | The permanent magnet electrodynamic suspension (PMEDS) owns the promising application prospect, due to its simple structure, low cost and reliable load capacity. However, the underdamping of the PMEDS system is still a challenge in engineering applications of transportation. This paper proposes a passive damping method and its implementation structure to improve the underdamping characteristics. This method utilizes the inherent magnetic leakage of on-board magnets technically. The principle of passive damping and its implementation structure is introduced in detail. And the kinetic models of ordinary and improved structure are established based on the topology graph. Besides, the magnetic field and the electromagnetic force involved in the kinetic models are analyzed, and the numerical analysis method of the drag force is verified by the high-speed test rig. Furthermore, the performance of passive damping is verified by finite element method (FEM) and the time-domain response analysis. The results show that the improved damping structure can effectively suppress vibration and improve the dynamic stability of the PMEDS system. It is beneficial to the engineering application of the PMEDS in the future. | Damping characteristics improvement of permanent magnet electrodynamic suspension by utilizing the end-effect of onboard magnets | 10.1007/s00202-023-01959-4 |
2024-02-01 | Based on two-grid discretizations, this paper introduces a parallel finite element method for the 2D/3D Navier–Stokes equations with damping. In this method, we first solve a fully nonlinear problem on a global coarse grid, and then solve linearized residual subproblems in overlapping fine grid subdomains to update the coarse grid solution by some local and parallel procedures. With the help of local a priori estimate for the finite element solution, errors of the approximate solution from the proposed method are estimated. Performance of the proposed method is also illustrated by some numerical tests. | A parallel two-grid method based on finite element approximations for the 2D/3D Navier–Stokes equations with damping | 10.1007/s00366-023-01807-w |
2024-02-01 | A damper is a significant tool that can enhance a building’s seismic performance. When these dampers are integrated into a structure, they help to reduce seismic forces such as absolute acceleration, displacement, velocity, and base shear. By simulating earthquake scenarios with and without tuned mass dampers (TMDs), it has been demonstrated that this system can effectively decrease responses based on the structure’s sensitivity. The study involved creating analytical models for both the structure and TMD, treating the TMD as a passive energy device, to assess the dynamic absorber's efficiency. The analysis aimed to determine how the structure’s dynamic behavior is influenced when the absorber is installed on the top floor. A comparison between the structure with TMD and without revealed that TMDs also enhance the structural behavior by lessening displacement, drift ratio, and shear force, depending on the frequency content of the earthquake excitation. | Inelastic behavior of reinforced concrete structure with tuned mass damper | 10.1007/s42107-023-00881-1 |
2024-02-01 | Elastohydrodynamic lubrication (EHL) point contact occurs between two rough surfaces at the mesoscopic level, while the interaction of rough surfaces involves contact between asperities at the microscale level. In most cases, the contact between asperities within an interface takes the form of lateral contact rather than peak contact. Regions devoid of contact asperities are filled with lubricating oil. However, conventional models often oversimplify lateral contact forms as interactions between asperities and a smooth, rigid plane. These simplifications fail to accurately represent the true contact conditions and can lead to inaccuracies in the analysis of EHL’s contact performance. To address this issue, we have developed a novel EHL interface model comprising two rough surfaces. This model allows us to explore the influence of asperity height, contact angle, and contact azimuth angle on EHL interface performance. | Elastohydrodynamic Lubrication Interface Stiffness and Damping Considering Asperity Lateral Contact | 10.1007/s10338-023-00441-9 |
2024-02-01 | The study of a monopile offshore wind turbine with the soil–structure interaction effect is most challenging in structural design under multiple hazards, i.e., the combined wind, sea wave, and earthquake excitations. Different arrangements of passive tuned mass dampers (TMDs) were used to mitigate the service and seismic loads affecting an offshore wind turbine (OWT) including the pile–soil–structure interaction (PSSI) effect. Different schemes of passive TMDs, placed at the top of the OWT tower or also at the center of gravity (CG) of the OWT tower or at the connection between the OWT tower and monopile, were tested. Various arrangements of TMDs including the proposed herein top radial TMDs arrangements have been investigated to determine their validity in resisting vibrations resulting from service and earthquake loads. The lateral displacements, shear forces and bending moments in both horizontal directions and the axial forces all over the OWT tower and monopile heights were recorded to compare the performance of each mitigation scheme of TMDs. The comparison results showed that the TMDs placement should be at the top of the OWT tower and the top radial 6 TMDs arrangement was found to be the most effective mitigation scheme for all straining actions in the tower and the monopile of the OWT subjected to service and earthquake loads. | Assessing seismic mitigation schemes of tuned mass dampers for monopile offshore wind turbine including pile–soil–structure interaction | 10.1007/s42107-023-00877-x |
2024-02-01 | An autonomous system of ordinary differential equations describing nonlinear oscillations on the plane is considered. The influence of non-autonomous perturbations decaying at infinity in time is investigated. Such systems are usually called asymptotically autonomous and arise, in particular, as a result of the reduction of multidimensional autonomous and non-autonomous systems. In this paper, we consider a special class of oscillatory perturbations that satisfy the non-resonance condition and do not vanish at the equilibrium of the unperturbed system. We construct a near-identity transformation that averages the system in the first asymptotic terms at infinity in time, and study the structure of the simplified equations. Under some natural assumptions, we describe possible long-term asymptotic regimes for solutions and analyse their stability by constructing Lyapunov functions. In particular, we show how oscillatory terms of perturbations can break the stability of the system and discuss conditions under which the perturbed system behaves like the corresponding unperturbed autonomous system or has new stable regimes. The results obtained are applied to some examples of oscillatory systems with time-decaying oscillatory perturbations. | Asymptotic regimes in oscillatory systems with damped non-resonant perturbations | 10.1007/s11071-023-09195-y |
2024-02-01 | Curved bridges have seen widespread application in complex transportation networks, including interchanges and river crossings. If the displacements caused by an earthquake are too large, curved bridges have a greater risk of suffering serious damage due to the rotation of the superstructure. Since curved bridges are more susceptible to damage during earthquakes due to the effect of curvature, this factor also significantly influences the seismic behaviour of curved bridges. The present investigation has ascertained the impact of the radius of curvature on the seismic response of a bridge. The effect of ground motion characteristics and levels of shaking on the performance of bearings has also been studied. It has also been investigated how the bridge responds to seismic activity for both unidirectional and bidirectional effects. To determine the effect of the radius of curvature on the seismic response of the bridges, a non-isolated and isolated curved bridge with high damping rubber bearings has been considered. Bridges with varying radius of curvature ( R = ∞, 315m, 157m, and 105m) have been modelled in the finite element-based software SAP 2000, and their response to three different ground motions has been observed. Isolation bearings in a bridge have been found to be more effective against seismic loads. The performance of an isolated bridge is superior to that of a non-isolated bridge when isolation bearings are installed in all of the piers and abutments. It is observed that a lower radius of curvature increases the deck displacement. It is also observed that bidirectional loading increases the seismic response of the curved bridge significantly relative to unidirectional loading. | Efficacy of a curved bridge with isolation bearing under seismic loading | 10.1007/s42107-023-00900-1 |
2024-02-01 | Heave plate is one of the most commonly used plates for controlling the movement of floating structures that are used for offshore deep water operations. Heave plates, in fact, move in both directions simultaneously. Therefore, the primary goal of this work is to examine the coupling motion’s effects on hydrodynamic coefficients caused by the heave and pitch motion of a heave plate. Numerical simulations are used to first simulate coupling motion in phase, and then out of phase which varies from $$0^\circ$$ 0 ∘ to $$90^\circ$$ 90 ∘ . The effects of added mass and moment, as well as pitching and heaving damping are investigated. Based on the results of the coupling oscillation of the heaving plate at different Keulegan–Carpenter (KC), the results indicate that added mass and pitching damping have more influence than added moment and heave damping coefficient. | The effects of hydrodynamics load on the heave and pitch coupling oscillations of a plate | 10.1007/s00773-023-00983-0 |
2024-02-01 | Global existence and scattering are proved for some damped bi-inhomogeneous Schrödinger equation of Choquard type whenever the damping coefficient is large enough. For arbitrary damping, global existence of the solutions is claimed if the initial data belongs to some stable set. | Wellposedness and Scattering for Some Bi-inhomogeneous Schrödinger–Choquard Equation with Linear Damping | 10.1007/s12591-023-00675-6 |
2024-02-01 | The MR damper parameters used in the vehicle model correspond to a real-world damper and are chosen so that the MR damper model characteristics match those of the experimental damper. The control and response statistics of a non-linear vehicle model utilising an MR damper are produced iteratively using the equivalent linearization method, and the findings are validated using rider optimisation (RO) simulation modelling. The suggested technique is easy to use, robust and well-suited for solving highly non-linear situations. The optimal parameters-arrived performance measure is examined, including ride comfort, tyre force, and protentional power, as well as the optimal design specifications for the front and rear dampers. The optimal control using preview reduces a performance index, which is a collection of vehicle performance parameters such as mass acceleration, displacement and both front and rear suspension stiffness. The results reveal that the developed RO algorithm is capable of determining the optimal parameters of the MR dampers. | Parametric analysis of non-linear suspension system by optimal MR damper by rider model with sensor | 10.1007/s42107-023-00852-6 |
2024-02-01 | The architectural requirements imposed on the structural design of buildings sometimes necessitate vertical and horizontal irregularities with their possibly dangerous effects when these structures are subjected to earthquakes. One of the greatest challenges in structural engineering is the design of a steel high-rise building (HRB) with vertical and horizontal irregularities. In this research, two irregular steel high-rise buildings (HRBs) were seismically analyzed as 3D models considering soil–structure interaction (SSI) and tuned mass damper (TMD) systems were used to mitigate their seismic response under different earthquakes. The two studied HRBs were a vertically irregular (step-pyramid-shaped) steel HRB, and a both vertically and horizontally irregular (L-shaped in-plan, stadium-shaped) steel HRB. The SSI provides the actual response of the tall buildings subjected to earthquake, and mitigation schemes using TMDs were suggested with arrangements of the TMDs on the top plan and along the elevation of the steel high-rise buildings to achieve seismic control of these structures. The present study has shown that the best efficiency in the mitigation of the effect of earthquakes on vertically and horizontally irregular steel high-rise buildings is obtained by implementing TMDs at the corners of the HRB plan on the top of the HRB and also at different floor levels along the upper half-height of the HRB. | Seismic control of vertically and horizontally irregular steel high-rise buildings by tuned mass dampers including SSI | 10.1007/s42107-023-00890-0 |
2024-02-01 | The use of an electromagnetic-tuned liquid column inerter, known as ETLCDI, for mitigating the seismic response in a nuclear containment structure has been studied. The optimization of the structure incorporating the device has rarely been reported. The recently introduced enhanced version of the traditional liquid column inerter, called the ETLCDI, has been designed to meet the demanding requirements of engineering applications. This study explores the parameters and seismic analysis FPS-based structures that incorporates ETLCDI devices. Numerical method is used to optimize the parameters of the two components of the structure, which will minimize the variations in the seismic response. The results are based on the analysis of the stationary stochastic conditions under the influence of the FPS system’s nonlinear damping. This study thoroughly examines the effects of ETLCDI on a FPS-isolated framework. The numerical analysis of the structure is performed on a 2-DOF FPS-isolated framework that is equipped with an optimal ETLCDI. It has been found that the optimized ETLCDI can effectively address both the superstructure and base floor responses during severe seismic events. | Optimal design of earthquake-resistant containment for FPS-Isolated nuclear power plants with electromagnetic tuned liquid column damper inerter | 10.1007/s12206-024-0107-z |
2024-01-30 | In the present paper, we have analyzed the surface roughness influence on the dynamic performance of Rayleigh step bearing by taking the squeezing action. The non-Newtonian lubricant in the film region considered is a couplestress fluid. A stochastic random variable with a non-zero mean, variance and skewness characterizes the roughness. The improved averaged Reynolds type equation is obtained using constitutive Stoke’s equations for couple stress fluid and stochastic surface roughness theory. For volume flow rate, steady-state characteristics and dynamic characteristics are derived in closed-form expression and are solved numerically by Simpson rule using Mathematica software. The non-Newtonian couplestress fluid enhances (diminishes) the steady load carrying capacity, the dynamic stiffness, and the dynamic damping coefficients, also a decrease (increase) in the volume flow rate is required for negatively (positively) skewed surface roughness in accordance with the Newtonian case. The relative percentage increase in bearing characteristics is studied. The results are considered with that of the smooth case. | Surface Roughness Influence on the Dynamic Performance of Rayleigh Step Bearing Lubricated with Couplestress Fluid | 10.1007/s40010-023-00869-1 |
2024-01-30 | This paper proposes a method for the small signal stability analysis and correction of power system based on Light Gradient Boosting Machine (LightGBM). Taking the load power, branch power, and generator power as inputs, the minimum damping ratio is output to build the mapping relationship between input and output. A small signal stability analysis model is established to assess the minimum damping ratio of the system, and the influence of noise on the accuracy of assessment results is also considered. The damping ratio sensitivity of generator is estimated based on LightGBM method, and the approximate sensitivity optimization model of the generator damping ratio is established when the system is weakly damped. The outputs of generators are adjusted according to the optimization model to correct the minimum damping ratio to enhance the system’s stability and finally estimate the modified minimum damping ratio by LightGBM algorithm. Test results on 3-machine 9-node and 10-machine 39-node systems indicate that the proposed method is hardly prone to over-fitting under noise interference with better robustness and could maintain better performance in assessing and correcting the small signal stability of the power system. | Research on power system small signal stability analysis and correction based on LightGBM algorithm | 10.1007/s00202-023-02226-2 |
2024-01-29 | The sub-synchronous resonance (SSR) characteristics and countermeasures of grid-forming permanent magnet synchronous generators (PMSGs) controlled by DC voltage synchronization control (DVSC) are investigated in this paper. First, small-signal models of two PMSGs connected to a series-compensated network are established, where a recently developed grid-forming control, i.e., DVSC is applied. Then, a modal-analysis method is conducted to evaluate the impacts of the control parameters, series compensation level (SCL), and electrical distances on stability. It is interesting to see that PMSGs with DVSC exhibit unstable SSR like traditional synchronous generators. Moreover, the dominant wind turbine (WT) is investigated using participate factor analysis. Then, a simple but effective SSR damping controller (SSRDC) is designed using feedforward control signals, which is only activated when SSR occurs. It is shown that the designed controller can provide strong damping support for SSR suppression. Electromagnetic transient simulations are performed in different scenarios to find the unstable SSR conditions, as well as to verify the correctness of the SSR analysis and the effectiveness of the proposed SSR damping scheme. | Sub-synchronous resonance in grid-forming PMSGs connected to series-compensated networks | 10.1007/s43236-023-00748-3 |
2024-01-25 | It has been corroborated that thermoelastic damping (TED) is one of incontrovertible sources of energy dissipation and limiting the quality factor ( Q -factor) in micro/nanostructures. On the other hand, it has been clarified that the fitting description of heat transfer process in structures with such small dimensions should be carried out through non-Fourier models of heat conduction. This article strives for providing a size-dependent analytical framework for estimating the value of TED in circular cross-sectional micro/nanorings with the help of Moore–Gibson–Thompson (MGT) generalized thermoelasticity theory. To reach this objective, after deriving the equation of heat conduction according to MGT model, the fluctuation temperature in the ring is obtained. Then, by applying the existing definition of TED in the purview of entropy generation (EG) method, an analytical relationship in the form of infinite series is rendered to evaluate the amount of TED. In the results section, first, the precision of the developed formulation is examined by way of a validation study. Graphical data are then presented to illuminate how many terms of the extracted infinite series yield convergent results. The final stage is to conduct an all-embracing parametric analysis to make clear the role of various crucial factors in the alterations of TED. According to the obtained results, the impact of MGT model on TED sorely relies on the vibrational mode number of the ring. | Non-Fourier thermoelastic damping in small-sized ring resonators with circular cross section according to Moore–Gibson–Thompson generalized thermoelasticity theory | 10.1007/s00419-023-02529-7 |
2024-01-25 | Nowadays, vibration energy absorption devices are widely implemented in many buildings subjected to severe vibration due to natural hazards, such as earthquakes, strong winds, and typhoons. Recently, viscous dampers have been commonly used in many structures as the most conventional damper type. However, the high maintenance cost resulting from oil leakage from cylinder seals has prompted researchers to seek an alternative system to viscous damper systems. Therefore, the main aim of this research is to develop a new rubber bracing damper (RBD) system by implementing high damping rubber material as a viscoelastic material to be installed in framed structures as diagonal bracing members. This will help dissipate vibration effects on the structure. To achieve this, the initial design for the RBD device has been developed, and finite-element simulation has been conducted to evaluate the behavior of the proposed RBD under various dynamic loading conditions. To define the viscoelastic material properties in finite-element modeling, high damping rubber material has been produced and experimentally tested to determine the numerical model of the material. Subsequently, the test data were utilized to develop the analytical model of the RBD device, and its performance was evaluated by applying cyclic loads and conducting nonlinear analysis. Furthermore, a series of cyclic dynamic tests with various displacement amplitudes and frequencies have been conducted on the prototype of the RBD device based on the finite-element results. Finally, to analyze the dynamic behavior of the structure equipped with RBD, a finite-element model of a three-story reinforced concrete frame structure furnished with RBD dampers has been developed. The response of the structure has been evaluated under seismic loads, and a parametric study has been conducted to investigate the response of the structures with various rubber properties. The numerical analysis results indicated that the implementation of the RBD device leads to a reduction in the occurrence of plastic hinges and lateral displacements of the structure by up to 69%. This demonstrates the efficiency of the RBD device in diminishing the seismic load effect on the structure’s response. | Seismic performance of structure equipped with a new rubber bracing damper system | 10.1007/s43452-023-00845-x |
2024-01-24 | The dissipation behavior of granular balls in a quasi-2D closed container subjected to vertical vibration is studied by means of discrete element method in this paper. Four universal granular phases playing high damping effect are finalized by simulating the gravity environments of Earth, Mars and Moon, respectively. Based on the commonality of dense granular clusters in the four high damping granular phases, the ideal dissipation behavior of granular balls in the quasi-2D closed container is indicated. Moreover, the optimal damping mechanism of granular balls in the quasi-2D vibrated closed container is further revealed by analyzing the differences of kinetic energy and potential energy of vibrated granular balls in the three different gravity environments. This study lays a foundation for maximizing the damping effect of vibrated granular materials with constant mass by controlling their dissipation behavior, which provides a new idea for the universal design of granular damping structures in engineering practice. | Dissipation Behaviors of Vibrated Granular Balls in Different Gravity Environments | 10.1007/s12217-024-10097-w |
2024-01-18 | The damping ratio of reinforced concrete structure cannot be considered as a constant value, and some parameters such as increasing the age of the structure, the corrosion of the reinforcements, and the ground motion amplitude can significantly change the damping ratio. This study investigates the effect of the damping ratio on dynamic increase factor (DIF) against sudden column removal of structures in terms of progressive collapse. To this end, various reinforced concrete structures with moment-resisting frames and regular rectangular plans with different stories and span lengths were designed based on ASCE7 and ACI318-14 in SAP2000. Several column removal scenarios were examined in various locations of the structures by the alternate load path method, and several nonlinear dynamic and static analyses were performed to achieve the data points. Four different curves were fitted to the extracted data points using SPSS, and four modified empirical equations were derived for DIF at damping ratios of 1%, 5%, 10%, and 15%. The difference between the curves shows the impact of the damping ratio on the DIF. In order to integrate four equations, an empirical equation was derived to estimate DIF, including the damping ratio. Moreover, the effect of some other parameters such as the beam span lengths and the location of column removal in the stories and plan on the DIF was investigated and discussed. The equation proposed by the guidelines for DIF provides underestimated and upper estimated values for the DIF in the structures with damping ratios, respectively, less than 5% and higher than 5% because this equation does not include the effect of the damping ratio. Therefore, the derived equation in this research can be suggested as an alternative to the equation proposed by the guidelines. | A Study of Progressive Collapse in Moment-Resisting Reinforced Concrete Structures Considering Damping Ratio | 10.1007/s40996-023-01331-3 |
2024-01-18 | In the paper, in order to explore the influence of human-structure interaction (HSI) in the vertical direction on the dynamic response of floors due to human-induced excitation, the formula for the human-plate interaction system is deduced. The pedestrian is in turn modelled as moving force (MF), spring-mass-damper (SMD), and added mass-spring-mass-damper (MSMD). The floor is modelled using a formulation in modal coordinates. Aiming at the formula of human-plate interaction system, the state space method is used to get the instantaneous frequency and instantaneous damping ratio of the floor under walking excitation, and the acceleration responses can be obtained using the Runge-Kutta method. Furthermore, this work studies the influence of pedestrian mass and structural modal mass on structural vibration response. The results show that the floor frequency is observed to decrease and the damping ratio gives the opposite trend when the pedestrian enters the floor. The MF model overestimates the measured response, while the actual results can be well approximated by the results for SMD and MSMD models considering HIS. Accounting for increasing human mass and decreasing modal mass lead to significant increase in the dynamic properties and the structural response. | Study on Coupled Vibration of Human-plate System under Pedestrian Excitation | 10.1007/s12205-024-1446-0 |
2024-01-17 | The stick–slip friction observed in an atomic force microscope (AFM) experiment has been widely studied using the Prandtl-Tomlinson (PT) model or molecular dynamics (MD) simulations. However, the mechanisms of friction energy dissipation in AFM are still not well understood. Our detailed MD simulations of a benchmark system, a Pt metal tip sliding on the Au (111) surface, provide a method of computing the contact stiffness and damping between the tip apex and the metal surface. We revealed that the contact stiffness is largely dependent on the very first contact layer atoms of the tip apex, but essentially independent of the temperature and the atomic mass of the AFM tip, and is also less dependent on the normal load if the contact geometry remains unchanged in elastic contact. Furthermore, by connecting the atomic relaxation rate to the damping coefficient, an important parameter gauging the friction dissipation in the PT model but the choice of which is usually empirical, we demonstrate that this damping coefficient is dependent on the atomic structure of the tip apex and the intrinsic relaxation rate of the individual atoms in the contact layer. We use such mechanisms to calculate the two parameters and carry out Langevin dynamics simulation within the framework of the PT model for two friction systems: a small Pt tip consisting of 3956 Pt atoms and a large polycrystalline Pt tip consisting of 18,365 Pt atoms. Our simulation results show that both tip apexes are underdamped in a stick–slip friction. We also demonstrate that the results from the Langevin dynamics simulation using these two critical parameters compared remarkably well with the straightforward MD simulation results in a range of sliding velocity ( V = 0.01 – 1 m/s). | Contact Stiffness and Damping in Atomic-Scale Friction: An Approximate Estimation from Molecular Dynamics Simulations | 10.1007/s11249-023-01824-2 |
2024-01-09 | This paper deals with the long-time dynamics of a nonlinear system of coupled wave equations with fractional damping term and subjected to small perturbations of autonomous external forces. Inspired by the works of Chueshov and Lasiecka (J Dyn Differ Equ 16:469–512, 2004; Appl Math Optim Equ 58:195–241, 2008; Mem AMS 912:1–167, 2008; Von Karman evolution equations. Well-posedness and long time dynamics, Springer, New York, 2010) on the property of quasi-stability of dynamic systems, we show first the quasi-stability property holds for the problem considered here and then prove the existence of global and exponential attractors. We also prove the upper semicontinuity of global attractors with respect to the fractional exponent. Finally, we show the continuity of global attractors with respect to a pair of parameters in a residual dense set and their upper semicontinuities in a complete metric space. | Quasi-stability and Upper Semicontinuity for Coupled Wave Equations with Fractional Damping | 10.1007/s00245-023-10072-8 |
2024-01-07 | As the world increasingly turns to renewable energy sources, the integration of solar photovoltaic (PV) systems into the grid has emerged as a pivotal solution. Effective control methods are paramount to harnessing the full potential of these grid-connected PV systems. While existing control methods have laid a foundation, there persists a compelling need for innovative approaches capable of surpassing the limitations of conventional methods. This paper introduces a novel nonlinear control approach utilizing an enhanced Lyapunov function for a single-phase PV/grid electric power system. High-performance operation of the solar PV system, interfacing with a grid-connected single-stage inverter, is achieved through the control of maximum PV voltage using predictive voltage control for MPPT. The enhanced Lyapunov function maintains PV voltage stability at the dc-bus by treating the difference between PV voltage and its reference as a controlled state error. Notably, this approach ensures the stability of the closed-loop PV system even under varying solar irradiances. To achieve full active power injection into the grid with high quality, the proposed enhanced Lyapunov function is augmented by integrating an LCL filter with virtual resistance as an active damping circuit for grid current feedback control. This integration introduces an opposing current to the grid-side inductance current. This compensation mechanism corrects the q -axis grid current using the dq-SRF mathematical model of the global PV/grid system. The LCL parameters and virtual resistance design methods are provided. The effectiveness of the enhanced Lyapunov function is demonstrated through simulations using MATLAB/Simulink software. The results showcase outstanding performance when compared to conventional Lyapunov function and sliding mode control strategies in achieving key objectives, including zero state errors, global stability, and the generation of a sinusoidal grid current signal with low total harmonic distortion and the unit power factor at the point of common coupling. | Performance and Stability Analysis of Enhanced Lyapunov Function and Predictive Voltage Control with Active Damping for Single-Phase PV/Grid Electric Power System | 10.1007/s40998-023-00686-7 |
2024-01-05 | Objectives To study the effect of proportional damping on the dynamic response of centrifugally stiffened Timoshenko beam. Methods A novel method has been successfully developed to model and analyze the forced damped response of centrifugally stiffened Timoshenko beam. The method uses a single beam element with six physical nodal coordinates. The transverse displacement and rotation of the beam are described using a mixture of polynomial and enriching trigonometric shape functions. The damping matrix is incorporated into the equations of motion (EOM) according to Rayleigh assumption. The damped EOM are expressed in state space form. Results The dynamic characteristics for the rotating forced damped vibration of Timoshenko beam are analyzed by assuming modal damping ratios for the first two modes and then finding the constants for the proportional damping. The EOM are integrated numerically to evaluate the system’s dynamic time response under various rotating speeds, external loading conditions, and modal damping ratios. Notably, the study goes a step further, providing a comprehensive exploration of the frequency response function (FRF) across a spectrum of parameter changes. The validity and efficiency of the developed method are demonstrated through numerical examples across various cases. Conclusions Proportional damping is pivotal for controlling vibrations, stability, and energy dissipation in rotating beams, shaping their response characteristics. It affects the damping ratio, natural frequency, and amplitude of the beam’s response. Higher damping ratios lead to quicker vibration decay, lower natural frequencies, and diminished amplitudes. | Dynamic Modeling and Analysis of Centrifugally Stiffened Proportionally Damped Timoshenko Beam | 10.1007/s42417-023-01241-8 |
2024-01-04 | Introduction The study employed novel non-destructive testing techniques for coal sample such as resonant column testing, cyclic torsional technique, and ultra-sonic pulse velocity analysis. Methodology The study confirms the coal in the present study as bituminous coal by analyzing the microstructure and composition of coal using scanning electron microscope and energy-dispersive X-ray spectroscopy method. Objective The damping characteristics (resonant frequency, damping ratio) and dynamic shear modulus of the coal are determined using the resonant column test and the ultrasonic pulse velocity test. Further, numerical simulations using the finite-element method (FEM) in ABAQUS software are performed to obtain resonant frequencies for intact coal samples under torsional and flexural vibrations, and the results of the experimental and numerical studies are found to be in good agreement. Conclusion The study has established a critical damping factor range based on the input frequency that can help ensure sustainable design of underground and surface mines. | Evaluation of Material Damping Properties in Bituminous Coal: A Comparative Analysis of Numerical and Experimental Approaches | 10.1007/s42417-023-01247-2 |
2024-01-03 | In this paper, we investigate the viscoelastic wave equation with variable coefficients and a delay, which is subject to nonlinear and nonlocal boundary dissipation. The existence of strong and weak solutions is obtained by means of Faedo-Galerkin approximation and denseness argument. By introducing an equivalent energy functional and using the Riemannian geometry method, we show the general decay rate of energy when kernel function satisfies some sufficient small conditions that we provide the range accurately. | Stabilization of the Viscoelastic Wave Equation with Variable Coefficients and a Delay Term in Nonlocal Boundary Feedback | 10.1007/s10883-023-09673-x |
2024-01-01 | This chapter focuses on the response of a single degree of freedom (SDOF) system. It explains the basic procedure of vibration analysis which can be further extended for a system with a higher degree of freedom system. The chapter begins with the un-damped free response, damped free response and forced harmonic response of a SDOF. These are further extended for the response due to rotating unbalance and external motion, which form the basis of working principles of vibration isolator and vibration measuring instruments. This chapter also covers the response of a SDOF system due to transient force by using convolution integral and method of Laplace transform. Free and forced response of system having Coulomb and hysteretic damping are also explained. | Response of a Single Degree of Freedom System | 10.1007/978-981-99-3614-4_4 |
2024-01-01 | Purpose This work presents the comparative damping performance of conventional viscoelastic material (VEM), 0–3 viscoelastic composite (VEC), and viscoelastic particulate composite (VEPC) damping layers in the active/passive constrained layer damping mechanism for plate vibration. Methods In the present study, passive and active–passive damping mechanisms, namely constrained layer damping (CLD) and active constrained layer damping (ACLD) are analysed to control the plate vibration. The CLD mechanism is achieved in both symmetric and asymmetric sandwich plate configurations where damping material lies at the core. In contrast, for the ACLD mechanism, the top face layer in the asymmetric sandwich plate is replaced by an extensional-mode piezoelectric actuator. A closed-loop finite element (FE) model is first derived for the damping analysis of sandwich plates following the layer-wise first-order shear deformation theory and velocity-feedback control strategy for the ACLD mechanism. Subsequently, the utilization of the same FE model for damping analysis of the CLD mechanism of symmetric and asymmetric sandwich plates is demonstrated for each of the three kinds of damping layers. Results and Conclusions The modal loss factors and frequency responses for each of the three kinds of damping layers in CLD/ACLD treated plates are estimated for the comparative study. The results reveal that damping performance of 0–3 VEC or VEPC layer in CLD/ACLD mechanism is significantly more than that for the conventional VEM layer. The VEPC layer may be used for the CLD mechanism in a symmetric sandwich configuration, while 0–3 VEC is a suitable one for the same damping mechanism through an asymmetric sandwich configuration. Moreover, 0–3 VEC may also be more suitable for the ACLD mechanism due to the magnification in active–passive damping performance compared to VEPC. | Damping Capabilities of Viscoelastic Composites for Active/Passive Constrained Layer Damping of the Plate Vibration: A Comparative Study | 10.1007/s42417-023-00882-z |
2024-01-01 | This chapter focuses on the modeling of different components of vibrating systems. The procedure of determining potential energies and kinetic energies of different type of discrete and continuous systems, which are required to develop mathematical model of any vibrating system, is also explained. Different types of damping models as well as modeling of different types of external forces are also presented. | Modeling of Components of a Vibrating System | 10.1007/978-981-99-3614-4_2 |
2024-01-01 | The present study proposes a novel eddy-current-based tuned inerter damper (EC-TID) that integrates the tuned inerter damper (TID) with nonlinear eddy current damping. The inclusion of nonlinear eddy current damping is expected to improve the control performance of optimal TID. In particular, the mechanical model and configuration of proposed EC-TID are introduced in detail. A closed-form solution for EC-TID optimal design in both undamped and damped structures is established based on effective damping ratio enhancement (EDRE) effect. This closed-form solution ensures equivalence of nonlinear eddy current damping through employment of statistical linearization techniques (SLT) with both force-based and energy-based equivalent criteria. The EC-TID control effectiveness obtained through Monte Carlo simulation under white noise excitation, which include effective damping ratio and EDRE effect, verifies the accuracy of the closed-form solution established via SLT, and highlights the importance of a large critical velocity of EC-TID in achieving higher accuracy. Moreover, it has been found that the closed-form solution for EC-TID and eddy-current-based tuned viscous mass damper (EC-TVMD) optimal design exhibit significant similarities when their equivalent damping ratios are identical. Several numerical studies have been conducted to investigate the control performance of EC-TID under real seismic excitations. The results demonstrate that both TID and EC-TID exhibit superior EDRE effects in mitigating the seismic response of structures compared to viscous and eddy current dampers with the same damping parameters. Additionally, EC-TID offers improved performance over TID, including slightly higher effectiveness, pre-designed maximum damping force, and reduced deformation. Noted that EC-TID is more effective than EC-TVMD in reducing structural seismic responses when their equivalent damping ratio is set at 0.03. This finding contrasts with a recent study where TID and tuned viscous mass damper (TVMD) exhibited comparable effectiveness under the same conditions. | Improving the control performance of optimal tuned inerter damper via nonlinear eddy current damping | 10.1007/s11071-023-09054-w |
2024-01-01 | Most civil engineering structures exhibit a combination of viscous and Coulomb damping. It is known that the dominant mechanism of energy dissipation in the presence of structural defects such as cracks, defective connections etc. is due to dry Coulomb friction. Contrary to this, in the undamaged state of structures, the dissipation of energy is mostly due to material damping which is considered macroscopically viscous. Thus, identification of Coulomb friction in modal damping could reveal the presence of defects in a structure. Past research suggested that dry Coulomb friction damping is dependent on initial amplitude and normal force between contact surfaces. However, detailed investigations on this matter are scares. Thus, insight into the effect of these parameters on a combined dry Coulomb friction and viscous damped system could provide the basis for identifying and isolating the dominant energy dissipation mechanism. Therefore, this study investigates the influence of magnitude of Coulomb friction between contact surfaces and oscillation amplitude on the damping behavior of a system subjected to coexisting dry Coulomb friction and viscous damping. Experimental investigation was conducted using the free vibration decay of a cantilever beam under varying magnitudes of Coulomb friction and initial dis-placement amplitudes inside the laboratory. In the investigation, it was observed a strong correlation between increase in the Coulomb friction force and the nonlinear behavior of damping. Nonlinearity of damping behavior was seen increased when the Coulomb friction force was increasing. Nonlinearity of damping behavior is more pronounced at lower oscillation amplitude and magnitude of damping was observed become asymptotes to a constant damping value when oscillation amplitude is large irrespective of magnitude of applied Coulomb friction force. Increase in the magnitude of normal contact force always increased dry Coulomb damping. When both Coulomb friction and viscous damping were present, it was observed that dry Coulomb friction dominating the damping of oscillation at lower amplitudes and the viscous damping is dominating the damping behavior at higher oscillation amplitudes. Thus, it is evident that effect of dry Coulomb damping is most recognizable at lower oscillation amplitudes of free vibration. | Experimental Investigation on Characteristics of Combined Viscous and Coulomb Damped System | 10.1007/978-3-031-49723-0_20 |
2024-01-01 | In this study, we examined the applicability of a response surface approach in the experimental design, parametric optimization, and formulation of predictive models in the 3D printing of aluminium-7075/Ti_48Zr_20Hf_15Al_10Nb_7 shape memory high-entropy alloy (SMHEA) composite. The input variables consist of the SMHEA dosage (A), laser power (B), and powder flow rate (C), which vary from 2 to 8 wt%, 400 to 800 W, and 1.44 to 7.2 g/min, respectively. In the meantime, the yield strength, tensile ductility and modulus, hardness, damping capacity, and loss modulus were examined. The ANOVA results indicated that the input variables A, B, and C had significant effects on the responses, resulting in mathematical models with a high degree of fitness that adequately represented the experimental outcomes. Optimal parametric optimization was achieved at 6.4 wt%, 388 watts, and 3.6 g/min with a desirability of 0.916%. Comparing the predicted responses to the validation results under optimal conditions revealed a deviation < ± 5%, validating the models’ potency to predict the responses. Thus, optimal parametric conditions for the development of a 3D-printed aluminum-7075/Ti_48Zr_20Hf_15Al_10Nb_7 composite were confirmed to be adequate. | Enhancing mechanical and damping performance of 3D-printed aluminium-7075 with shape memory high-entropy alloy (SMHEA): parametric optimization and mathematical modeling | 10.1007/s00170-023-12651-z |
2024-01-01 | In the last decade, various promising nonlinear modal identification techniques have been developed based on the nonlinear normal mode (NNM) concept. Most of these techniques rely on the phase resonance testing approach where the identification of nonlinear modal damping is still an unresolved issue. The response-controlled stepped-sine testing (RCT) framework provides a convenient way of accurately quantifying nonlinear modal damping by applying standard linear modal analysis techniques to frequency response functions (FRFs) measured at constant displacement amplitude levels with standard modal test equipment. Various studies by the authors have shown that these constant-response FRFs come out in quasi-linear form even in the case of a high degree of nonlinearities. The RCT approach has been validated so far on several systems including a real missile structure with moderate damping nonlinearity mostly due to bolted connections and a micro-electromechanical device with a stack-type piezo-actuator. This study makes a step further by validating the method on a real control fin actuation mechanism that exhibits very high and nonlinear modal damping; the maximum value of viscous modal damping ratio goes up to 15% and the percentage change of the damping with respect to vibration amplitude is about 70%. | Experimental Modal Analysis of Structures with High Nonlinear Damping by Using Response-Controlled Stepped-Sine Testing | 10.1007/978-3-031-36999-5_17 |
2024-01-01 | Research on offshore wind technology has increased in the last two decades following progress and cost reduction in turbine design and operation, and the increased demand for renewable energy production. Coupled dynamic response of a floating offshore wind turbine under simultaneous wind and wave loading can be investigated by experimental and computational methods. In the scope of this paper, a numerical study is conducted on a floating offshore wind turbine. A standard baseline wind turbine supported by a Tension Leg Platform is investigated under simultaneous wind and wave loading. For comparison, cases with only wind loading and only wave loading were also simulated to identify the dominating contributions in different design situations. Larger platform surge response is observed due to the resonance triggered by the turbulent wind at the platform surge natural frequency. Pitch motions are large at the wave frequencies and at the resonant frequency, mainly due to first-order wave loads. Aerodynamic damping associated with the rotation of the rotor resulted in decreased platform fluctuating pitch response. Results of this study are the basis of a sensitivity study aiming at improving the MIT/NREL TLP wind turbine design. | Numerical Investigation of a TLP Wind Turbine Under Wind and Wave Loads | 10.1007/978-3-031-53059-3_20 |
2024-01-01 | This paper presents the development of a Moving Element Method (MEM) for analyzing the dynamic behavior of a functionally graded material (FGM) plate. The FGM plate is resting on a Pasternak foundation characterized by variable foundation parameters following a power-law distribution along the length of the FGM plate. Additionally, the plate is subjected to both thermal and moving loads. The governing equation of motion for the considered FGM plate is derived by applying the principle of virtual work. The determination of the total strains of the plate encompasses both temperature-induced strain and mechanical strain, achieved by employing the superposition principle. The governing equation of motion is discretized using the moving plate elements and subsequently assembled to generate the final system of equations. This system is then solved using the Newmark’s β numerical method. Prior to conducting the dynamic analysis of the FGM plates, accounting for the variable foundation parameters, two scenarios are investigated to verify the accuracy of the proposed model in comparison to previous studies. The findings of this study suggest that the elastic stiffness coefficient k _ wf exerts a notable influence on the displacement of the FGM plates, while the damping coefficient c _ f has a negligible impact on the plates’ behavior under the specified temperature conditions. | Moving Element Method in the Dynamic Analysis of Functionally Graded Material Plates Subjected to Thermal Loads and Resting on a Variable Stiffness Foundation | 10.1007/978-981-99-7434-4_155 |
2024-01-01 | Purpose Our primarily objective is to investigate the properties of the hair clipper with the fractional model damping and proposed a robust control method to keep this device in the relevant operation zone. First, an appropriate strategy is applied to study the amplitude-frequency response of the hair clipper system with the fractional derivative. Secondly, under the consideration of constraints such as uncertainties and unmolded dynamics, a robust stabilization method is proposed to control the motion of the mobile part of the magnetic circuit of the hair clipper with a time delay. Study design/methodology/approach With the help of fractional models, some technical specifications about the hair clipper parameters are proposed and cannot be obtained by the classical integer ones. The ultimate stabilized properties is used to derive the Ricatti equation which the solution ensures the convergence of the systems states. Findings The majors’ results obtained of this paper are threefold 1. Perfect knowledge of the dynamics behavior of the hair clippers with the effects of fractional damping. 2. Improvement of the design of the hair clippers devices from a technological point of view 3. Establishment of a robust controller for the air-gap position to avoid a collision. Originality/value This work is unique in the literature notably the control proposed. This analysis allows disclosing some novel and interesting nonlinear phenomena were disclosed. It’s important to note that the technic developed in this paper enable not only to overcome the disturbances and delays but also to achieve the objective with accuracy and faster. This strategy can be efficiently implemented for the hair clippers systems and also for different types of real physical systems such as mechanical systems, electrical systems and electromechanical systems. | Dynamic Responses of Electrical Hair Clippers with Fractional Damping and Its Robust Stabilization Design | 10.1007/s42417-023-00895-8 |
2024-01-01 | Vibration, in most cases, is an undesirable phenomenon in electro-mechanical systems. The adverse effects of vibration in a system are noise, loss of energy, compromise on comfort, and reduced life span of mechanical systems. The current study focuses on vibration damping of a Flexible Cantilever beam (FCB) by utilizing a differential type of electromagnetic actuator. The electromagnetic forces of both actuators are controlled by Pulse Width Modulation (PWM) using a current controller designed in the lab. The electromagnets are mounted above and below the FCB by maintaining a distance along the same vertical axis. The non-contact active vibration attenuation study is carried out by varying the PWM values of upper and lower electromagnets to produce different electromagnetic forces. The current research work compares different combinations of forces on upper and lower electromagnets experimentally and, based on the analysis, provides the best combination of forces on both actuators to damp the vibrations as swiftly as possible. The study is divided into three cases where case I study the vibration damping with the same PWM on both electromagnets; in case II and case III, one of the electromagnets has fixed PWM while the PWM on other electromagnet is varied. | Experimental Investigation of Pulse Width Modulation-Based Electromagnetic Vibration Attenuation of a Ferromagnetic Flexible Cantilever Beam (FCB) | 10.1007/s42417-022-00845-w |
2024-01-01 | This research study aimed to assess the impact of employing fluid viscous dampers (FVDs) on the seismic performance of ten-story, moment-resisting reinforced concrete (RC) buildings. The investigation involved the modeling and design of 17 RC structures, which were equipped with non-linear dampers arranged in 4 distinct configurations and subjected to 4 diverse damping coefficient distribution methods. The designs adhered to the guidelines outlined in IS456:2000. To analyze the seismic response of each system, non-linear time history analysis (fast non-linear analysis) was conducted employing 11 ground motion records within the ETABS software. The seismic responses of the frame were studied and compared in terms of the maximum roof displacement, interstory drift ratio, base shear, and dissipated energy through dampers. Moreover, a comprehensive cost analysis was undertaken to assess the economic implications of damper implementation. The outcomes elucidated that the RC structures adopting the scissor-jack configuration with the story shear strain energy method (SEM) distribution yielded optimal performance in terms of both cost-effectiveness and overall structural response attenuation. While scissor-jack performed much better than other damper configurations such as diagonal, chevron, and toggle configurations, the effect of change of damping coefficient distribution method was marginal. The higher mode effect was also observed in the efficient story shear strain energy method (ESEM) of damping coefficient distribution. This observation highlights the criticality of conducting modal analysis prior to damper implementation, underscoring the need to account for higher modes in order to achieve an accurate assessment of the system’s behavior. | A comprehensive study of viscous damper configurations and vertical damping coefficient distributions for enhanced performance in reinforced concrete structures | 10.1007/s42107-023-00831-x |
2024-01-01 | The paper presents full-scale observations and wind tunnel tests carried out to clarify the mechanisms driving the hanger vibrations observed in the final phases of completing the 1915 Çanakkale suspension bridge. It is found that high frequency low amplitude vibrations were caused by rhythmic vortex shedding whereas large amplitude low frequency vibrations were caused by rain wind galloping. Stockbridge dampers were introduced to mitigate the hanger vibrations but were found to fail due to fatigue of the messenger wire. Taut string theory is reviewed and combined with the wind tunnel test results and damper characteristics to explain the likely cause for damper failure. It is concluded that Stockbridge dampers are well suited for mitigation of vortex induced vibrations if properly designed but are insufficient for mitigation of rain wind vibrations of the hanger cables. Mitigation of rain wind vibrations requires hydraulic dampers connecting the hanger cables to the bridge deck structure. | Vibration Excitation and Damping of Suspension Bridge Hanger Cables | 10.1007/978-3-031-47152-0_19 |
2024-01-01 | Hysteresis is a memory-dependent and approximately rate-independent behavior seen in material damping. Some materials show asymmetric hysteresis loops that are pinched at the origin. In this paper, we propose a hysteresis model that captures pinched hysteresis loops with both symmetry and asymmetry. The model can capture a variety of hysteresis loop shapes. The versatility of the proposed hysteresis model is studied in this paper. We derive analytical expressions, for the hysteretic response and for the per cycle dissipation. We show a practical application of the hysteresis model to tuned mass damper systems. Numerical solutions are compared with results from a semi-analytical approximation. | A Versatile Asymmetric Hysteresis Model Motivated by a Study of Elastic Material with Microcracks | 10.1007/s42417-022-00843-y |
2024-01-01 | In this paper, based on monotone iterative method in the presence of the lower and upper solutions, a class of nonlocal problem of structural damped elastic systems with delay are studied in the case of noncompact semigroups in ordered Banach space. Firstly, we introduce the concept of lower S -asymptotically $$\omega $$ ω -periodic solution and upper S -asymptotically $$\omega $$ ω -periodic solution, on the premise of the existence of upper and lower S -asymptotically $$\omega $$ ω -periodic solutions, the existence of maximal and minimal S -asymptotically $$\omega $$ ω -periodic mild solutions for the elastic system are obtained. Then, an existence theorem of positive mild solutions for elastic system is obtained without assuming lower and upper S -asymptotically $$\omega $$ ω -periodic solutions. Finally, as the application of abstract results, the existence and uniqueness of S -asymptotically $$\omega $$ ω -periodic mild solutions and positive mild solutions for a classes of nonlocal damped elastic systems with delay are discussed. | Lower and upper solutions for damped elastic systems with delay in ordered Banach space | 10.1007/s13160-023-00615-5 |
2024-01-01 | We consider the damping problem for a nonstationary control system described by a system of differential-difference equations of neutral type with smooth matrix coefficients and several delays. This problem is equivalent to the boundary-value problem for a system of second-order differential-difference equations, which has a unique generalized solution. It is proved that the smoothness of this solution can be violated on the considered interval and is preserved only on some subintervals. Sufficient conditions for the initial function are obtained to ensure the smoothness of the generalized solution over the entire interval. | Smoothness of Solutions to the Damping Problem for Nonstationary Control System with Delay of Neutral Type on the Whole Interval | 10.1007/s10958-024-06940-5 |
2024-01-01 | Full Heusler alloys (FHA) offer excellent possibilities due to their high Curie temperature, spin polarization, and predicted half metallicity. Among various FHA, $${\text{Ni}}_{2} {\text{FeAl}}$$ Ni 2 FeAl is the least studied alloy that can offer vast possibilities in exploring spin-based devices. By keeping this aspect in mind, $${\text{ Ni}}_{2} {\text{FeAl}}$$ Ni 2 FeAl nanoparticles have been prepared by the cost-effective ball milling process. As-prepared dried samples were vacuum annealed at 900 °C in the presence of the mixture of H_2 and N_2 gas to avoid oxidation for different time durations. XRD pattern revealed the B2 type atomic ordering with a crystallite size of approximately $$21$$ 21 nm. Morphological properties were investigated using SEM which revealed the formation of uniform nanoparticle flakes. Nearly perfect stoichiometry was obtained in EDS elemental mapping. The ferromagnetic properties were investigated by static magnetic measurements conducted by vibrating sample magnetometry. The dynamic magnetic response was measured from Vector Network Analyzer ferromagnetic resonance (VNA-FMR) technique in a broad range of microwave frequencies (5–20 GHz). A broad FMR linewidth was obtained from the FMR experiment due to the presence of magnetic inhomogeneities in the bulk sample. The Gilbert damping parameter which describes the magnetization relaxation was obtained from the fitting of FMR data with the Landau-Lifshitz-Gilbert equation. We obtained the lowest value of the Gilbert damping for the sample annealed at 900 °C temperature for 4 h. These investigations can open a new pathway in designing and fabricating $${\text{Ni}}_{2} {\text{FeAl}}$$ Ni 2 FeAl based ultra-fast, energy efficient spintronics devices. | Investigation of Static and Dynamic Magnetization in Ni_2FeAl Full Heusler Alloy Nanomaterials | 10.1007/978-981-99-4878-9_77 |
2024-01-01 | Air springs have many advantages; besides, air spring dampers hold much promise for application in car suspension systems. A thermodynamic model of pneumatic elements is proposed in this study. Unlike the standard model generally accepted at present, this one does not imply that the rubber-cord membrane is absolutely flexible, and its middle surface is inextensible. The force and geometric characteristics of pneumatic elements not depending on the temperature are considered. Two examples of mathematical modeling of force and geometric characteristics of Firestone pneumatic springs with rubber-cord membranes of bellow and rolling-lobe types illustrate the proposed method. Compared to the standard model, the accuracy of coincidence with the experimental data has increased significantly. | The improvement of scientific foundations for the technical theory of pneumatic elements with rubber-cord membranes: thermo-dynamic model of force and geometric characteristics of air springs | 10.1007/s12206-023-1205-z |
2024-01-01 | This paper examines the influence of discrete mode controllers with optimum sampling frequency to enhance the stability of the grid-integrated AC microgrid. The damping of low-frequency electromechanical oscillation performance of distributed generators of AC microgrid is analyzed. The AC microgrid is comprised of two renewable energy resources a photovoltaic (PV) farm, a variable wind speed type DFIG wind farm, and another two distributed generators hydro and diesel are based on synchronous generators. The diesel generator is used as a backup source to provide the load demand when the grid is subjected to disturbance and the generation of renewable power is not as per demand. This research investigates the effect of the execution of different discrete type’s power system stabilizers with an optimum sampling frequency to enhance the stability of the AC microgrid. The discrete type time domain mode PSSs such as conventional PSS (Δω-PSS and ΔPa-PSS), MBPSS-4B, and LQG-based PSS controllers are executed on DGs of the AC microgrid for the damping of low-frequency electromechanical oscillation. The MATLAB/Simulink software gives a comparative analysis of the discrete mode controller's response to distributed generators of AC microgrid. The simulation result verified the system performance with an effective operational sampling frequency of discrete time domain mode controllers such as conventional PSSs, MBPSS-4B, and LQG controllers under fault conditions. | Stability Enhancement of AC Microgrid Using Discrete Mode Controllers with Optimum Sampling Frequency | 10.1007/978-981-99-6749-0_64 |
2024-01-01 | The damping system will oscillate during the operation of the adjusting camera, which is not conducive to the operation stability of the adjusting camera. Therefore, in order to suppress the oscillation, the corresponding controller can be designed with the help of particle swarm optimization algorithm, which will be studied in this paper. Firstly, the basic concept and application advantages of are introduced. Secondly, the controller design is carried out around the controller design idea. Finally, the optimize the control and the simulation. The simulation the controller optimized is more prominent in damping oscillation suppression effect. | Design of Oscillation Controller for Camera Damping System Based on Particle Swarm Optimization | 10.1007/978-981-99-9416-8_3 |
2024-01-01 | The main task of dynamic experiments in wind tunnels is to obtain model-scale stability information of an aircraft at realistic Reynolds and Mach numbers. The forced oscillation technique is the most widely used wind tunnel technique for stability derivatives measurements. The oscillatory motion is induced to a model in one (the primary) degree of freedom. The aerodynamic reaction measured in the primary degree of freedom determines direct damping derivatives. Stability derivatives are obtained from in-phase and out-of-phase components of the measured aerodynamic reactions. This paper describes the determination of the pitch-damping derivative in the T-38 wind tunnel. The T-38 pitch/yaw apparatus is a full-model forced oscillation apparatus with primary angular oscillation around the wind tunnel model transversal axis. The model is forced to oscillate at constant amplitude. Test results obtained in the T-38 wind tunnel are compared with published experimental data of one of the world’s leading wind tunnels: Arnold Engineering Development Center-von Karman (AEDC, USA). | Wind Tunnel Measurement of Pitch-Damping Derivative Using Forced Oscillation Technique | 10.1007/978-3-031-42041-2_5 |
2024-01-01 | The methods for improving the seismic performance of the structure are the increasing the strength or the ductility capacity of the structure. In order to increase the strength of the shear wall structure, there are methods to increase the cross section of the structural member as like the shear wall or beam, and increase the rebar amount, but these are unreasonable in terms of design and construction. Therefore, in order to improve the seismic performance of the shear wall structure, it is reasonable to improve the ductility capacity by using the damping device. In this study, the seismic performance of shear wall structures with the lintel type damping device was analyzed. It can be seen that the energy dissipation of the damping device is greatly increased after the nonlinear behavior of the shear wall structure, thereby reducing the damage of the main structural members. | Lintel Type Damping Device for Seismic Retrofit of Shear Wall Structure | 10.1007/978-981-99-6368-3_32 |
2024-01-01 | In this paper, we considered the plane problem of steady-state bending vibrations of a hinged-supported bimorph in an alternating magnetic field, considering damping. The bimorph under study consisted of a multilayer electromagnetoelastic composite modeled using the effective modulus approach. Within the framework of Kirchhoff's hypotheses, an applied theory was constructed, which considered the quadratic distributions of electric and magnetic potentials along the thickness of the bimorph and considered heterogeneity in the longitudinal direction. In addition, the theory introduced linear viscoelasticity. Using the resulting theory, distributions of electric, magnetic, and mechanical fields were constructed. Comparison of the obtained results, based on the theory, with the results of the finite element model in the COMSOL Multiphysics package showed a good convergence of the results. Next, based on the obtained theory, the behavior of plate de-flection in the vicinity of the first resonance was studied at various values of the damping coefficient, which showed that the obtained theory can be used to analyze the bandwidth of converters, based on constructing the amplitude-frequency characteristics of bimorphs made of an electromagnetoelastic composite. | Applied Theory of Vibrations of a Composite Electromagnetoelastic Bimorph with Damping | 10.1007/978-3-031-52239-0_34 |
2024-01-01 | Extensive research has significantly improved the vibration isolation performance of off-road vehicle seat suspensions, effectively addressing issues such as driver fatigue, and low-back pain. However, variations caused by road roughness, vehicle speed, and load can lead to stability switches and sudden events in seat vibration excitation. Ignoring these factors in semi-active and active seat suspensions can cause insufficient robustness and excessive costs. To address this, we propose an intelligent damping switching method that optimizes seat suspension damping mode by considering the stability and suddenness of excitation. Utilizing a long short-term memory (LSTM) network, we accurately identify stability, while the multi-input and multi-output optimization (MIMO) method labels the network input through system identification of the seat dynamics model. Event trigger (ET) handles suddenness effectively. By combining these techniques, our approach achieves effective vibration isolation while maintaining the desired suspension deflection. Comparative analysis validates our novel seat suspension control system design approach. | Improvement of vibration isolation performance of multi-mode control seat suspension system through road recognition using wavelet-LSTM approach | 10.1007/s12206-023-1210-2 |
2024-01-01 | The present study aims to investigate the effect of damping on the bifurcation characteristics of a pitch–plunge aeroelastic system subjected to dynamic stall-induced aerodynamic nonlinearities. It is observed that structural damping has a considerable impact on both the bifurcation boundaries and the response dynamics. To understand the physics behind the altered response dynamics, a synchronization study is undertaken next. The synchronization characteristics are identified through phase-locking value (PLV) under different values of plunge ( ζ _ ξ ) and pitch ( ζ _ α ) damping ratios. The phase locking of the plunge and pitch modes is demonstrated to be significantly affected by increasing the values of plunge and pitch damping. It is demonstrated that increasing the damping in pitch enhances synchronization by increasing the PLV. Additionally, stall flutter is delayed in the presence of pitch damping. The increase in plunge damping leads to the early onset of the synchronization regime leading to the early onset of stall flutter. The combined effect of the two damping leads to delayed onset of both aperiodic as well as stall flutter regimes. | Effect of Damping on Bifurcation and Synchronization Behavior of an Aeroelastic System Under Dynamic Stall | 10.1007/978-981-99-5755-2_12 |
2024-01-01 | A theoretical analysis of displacement pump capacity pulsation was carried out. In a hydraulic system, capacity pulsation contributes to pressure pulsation. It has been pointed out that increased pressure pulsation affects the surroundings, including human beings, causing an increase in the noise generated into the surroundings and increasing vibration levels. The values of the frequencies of the pressure pulsation thus created correspond to the frequencies of the capacity pulsation and are derived from the number of displacement elements in the pump and the speed on its drive shaft. A complex univariate was used to determine the frequency characteristics of the system with a hydraulic long line by subsequently determining the transmittance of the system. | Some Causes and Effects of Pressure Pulsation in a Hydraulic System Including the Impact on the Environment | 10.1007/978-3-031-53598-7_8 |
2024-01-01 | This article introduces a novel mechanical variable inertance-variable damping (VIVD) seat suspension based on an adaptive robust sliding-mode (ARSM) controller, including its characteristics validation and performance experiment. In this paper, a variable damping (VD) device and a flywheel are connected in series to form a variable inertance (VI) device with real-time controllable inertance, which is connected in parallel with another VD device to form a VIVD device. A two-layer control scheme is proposed where an upper desired controller is designed based on adaptive robust sliding-mode control and the desired control force is calculated; then a force tracking control strategy with energy priority storage (EPS) is designed as the lower layer controller. Under road random excitation, the VIVD seat suspension exhibits 21.89% and 9.56% lower RMS acceleration values compared to the passive seat suspension and a semi-active traditional sliding-mode control seat suspension. The new system demonstrates advantages in controllability and energy efficiency, with energy consumption falling within the milliwatt range. The proposed semi-active VIVD device shows potential in vehicle vibration control. | Adaptive Robust Sliding-Mode Control of a Semi-active Seat Suspension Featuring a Variable Inertance-Variable Damping Device | 10.1007/978-981-97-0554-2_10 |
2024-01-01 | The Sonic Black Holes (SBH) absorber consists a cylindrical cavity with a set of rigid thin rings. The inner diameters of the rings are gradually decreasing. The sound speed in SBH can be progressively slowed down, then the effective sound absorption performance can be obtained. In order to further improve the acoustic performance of the SBH, the sponges are used as sound-absorbing material in SBH. The sponges of 2 mm thickness are arranged at the bottom and the different ranges of the inner wall of the SBH. The absorption coefficients of the SBH before and after the sponge arrangement are experimentally investigated. The experimental results reveal that the SBH structure is different from the traditional vibration-based acoustic black hole (ABH) structure. The sound absorption performance cannot be improved effectively when the sponge is placed at the bottom of the SBH. However, when the sponge is placed on the inner wall around the bottom of the SBH, the sound absorption performance can be improved markedly. | Experimental Investigation of Sound Absorption Properties of the Damped Sonic Black Holes | 10.1007/978-981-99-8861-7_28 |
2024-01-01 | Urban development has recently got the attention of the supervisor and inspector of construction. The researcher must find a method to assess the structural situation. The cables of the cable-stayed bridge are simplistically modeled to evaluate the cable tension that have been defined in this report, through the Euler beam theory of the cables with viscous damping. Owing to simplified assumptions of boundary conditions, the tension of cables and viscous damping coefficient has been found through measured frequencies. The proposed method is experimented with by a cable of the Phu My cable-stayed bridge over the Saigon River in Vietnam. | Evaluating Damping Model Applied for Cable Tension of Cable-Stayed Bridge | 10.1007/978-981-99-2345-8_63 |
2024-01-01 | High damping rubber bearings (HDR) are made by combining natural rubber with carbon fillers. Because of its simple structure can be easily applied to seismic isolation design and is easy to manage. Also, high damping rubber bearings are seismic isolators with excellent damping ability against earthquakes. High damping rubber bearings have high horizontal flexibility against earthquake motion and can dampen seismic energy, but the mechanical dependence resulting from material properties cannot be ignored. This research aims to experimentally reveal the dependence and nonlinearity of high damping rubber based on dynamic loading tests and to propose an advanced accurate hysteresis model. First, a dynamic loading test was performed using a scaled-down high damping rubber specimen, and mechanical properties such as equivalent stiffness, equivalent damping constant, and strain energy were evaluated. Subsequently, based on the mechanical evaluation, a hysteresis curve was modeled considering the characteristics of high damping rubber. In this research, a hysteresis model considering these characteristics was proposed by focusing on the rate dependence due to the Mullins effect and the hardening phenomenon occurring in the region of large shear deformation, such as a large earthquake. Finally, the actual behavior of high damping rubber and the feasibility of the modeling procedure were evaluated by comparing the results of the dynamic loading test using seismic waves assuming real earthquakes and dynamic analysis. As a result, it was possible to propose a hysteresis model that can represent the nonlinear characteristics of high damping rubber. | Research on Hysteresis Model of High Damping Rubber Bearings Considering Mechanical Properties Based on Dynamic Loading Test | 10.1007/978-981-99-4049-3_82 |
2024-01-01 | The molten metal crane faced with high difficulty to control can be mainly attributed to the features as a typical underactuated system and liquid sloshing phenomenon is often ignored in the existing control methods. Consequently, this paper firstly establishes the multi-mass-spring-damping mechanics model of liquid sloshing, followed by deducing the dynamics equation of the molten metal crane system based on the model in detail, which verifies the correctness of the system model from the physical sense. Then, a low pass filter global sliding mode control (LPF-GSMC) is introduced to effectively eliminate the high frequency signals of the system and keep the system on the sliding mode surface. Lastly, a hardware experiment and three kinds of numerical simulations were designed for the molten metal crane system. The hardware experiment shows that compared with the traditional solid-load model, the proposed model is more consistent with the dynamic characteristics of liquid load during transportation. And the numerical simulations show that compared with the conventional sliding mode controller and low-pass filter sliding mode controller, the proposeed LPF-GSMC controller possesses higher response speed and better control performance. Also, under the interference of wind and the non-zero initial angular, the proposed controller can ensure that the maximum load swing angle is less than 2° degrees and converges within 7 seconds, which fully demonstrats favorable global robustness. | Research on LPF-GSMC Control of Molten Metal Crane Based on Multi-mass-spring-damping Model | 10.1007/s12555-021-0377-5 |
2024-01-01 | The robust control method is effective in suppressing the phenomenon of low frequency oscillations (LFOs) in power systems. Aiming at the problem of LFOs in AC/DC transmission system, a coupling robust damping controller design method based on multiple input multiple output (MIMO) system model is proposed to enhance the damping of specific oscillation modes by utilizing the interaction between different control loops instead of decoupling the control loops. Firstly, the global least squares—rotation invariant (TLS-ESPRIT) technique is used to identify the reduced order model of MIMO system and the oscillation modes of the system. Then a kind of hybrid H_2/H_∞ method is used to design coupling robust damping controller based on different control loops. The balanced truncation method is used to reduce the order of the controller, which has both robust performance and practical engineering application. Finally, a four-machine two-area AC/DC test system is built in PSCAD/EMTDC. The time domain simulation results show that the coupling robust controller can effectively suppress the LFOs under various disturbances and faults, and the system can quickly recover stable operation. At the same time, output feedback control is utilized, which is convenient for engineering practice. | Design of Coupling Robust Damping Controller for AC-DC Interconnection System | 10.1007/978-981-99-9251-5_5 |
2024-01-01 | Regenerative chatter is a common challenge in milling large and difficult-to-cut complex curved parts, which seriously affects the machining efficiency and quality. Variable pitch cutters (VPCs) and process damping are known to be effective in suppressing chatter. However, the complex multiple interactions between process damping and variable pitch bull-nose cutters (VPBNCs) have been rarely investigated due to unavoidable runout and multiple modes of the milling system. In addition, the simultaneous identification of shearing force coefficients and ploughing force coefficients presents a challenge when the dynamic characteristics of VPCs are considered. To this end, this paper first establishes the geometric parametric modeling of VPBNCs, and a mechanical model is proposed to uniformly handle shearing force and process damping force, which accounts for cutter runout. Secondly, the multiple interactions comprehensive dynamics model of VPBNCs milling system is developed. The milling system involves multiple regeneration delays, multiple modes and process damping effects. A modified hybrid multi-step method (MHMSM) is employed to analyze milling stability. Then, combined with the mechanical model considering cutter vibration, a multi-parameter synchronous calibration method (MPSCM) is proposed to identify ploughing force coefficients and runout parameters. Finally, experimental validation is performed to verify the proposed model and calibration method. The results show good agreement between simulation and experimental results. Furthermore, the joint influences of process damping and pitch angle variation on stability in different speed ranges are explored in detail. | Dynamics modeling and simultaneous identification of force coefficients for variable pitch bull-nose cutter milling considering process damping and cutter runout | 10.1007/s00170-023-12777-0 |
2024-01-01 | The frequency equation for a cable damped at a fraction location, generally being a transcendental equation, was reformulated into an algebraic form. Based on the fundamental theorem of algebra and the characteristics of logarithmic function in the complex domain, the solution structures were revealed and several examples with given damper positions were presented to study the variation of the solutions with the damping coefficient. The results show that: 1) All solutions of the frequency equation of the system could be classified into a finite number of solution branches. 2) The solutions of different orders in the same solution branch share an identical real part and any two adjacent solutions share an identical difference. 3) According to different variations in decay rate and frequency with damping coefficient, all the solution branches could be classified into four categories, each of which showed different trend of variation. | The Algebraic Frequency Equation of a Taut String Damped at a Fraction Location: Solution Structures and Properties | 10.1007/978-3-031-49723-0_21 |
2024-01-01 | The step responses of many systems to be controlled show an overshoot behavior. This is the case, for example, with active vibration damping with spring-mass systems. This document provides PID controller tables for overshooting systems. Such systems can be approximated with second-order systems. The parameters were calculated with the simulation and optimized with a search for the best values according to the minimum ITAE criterion. For this purpose, parameter sets were calculated using hill climbing, an approach from artificial intelligence. It minimizes the criterion in transient response over time. The publication provides tables for systems with different system damping. So that the sets can be used in general, a way of easily identifying such systems is also presented. The controller parameters are then verified using the position control of a weakly damped spring-mass system. | Artificial Intelligence Algorithm for Optimizing PID Parameters to Control Weakly Damped Systems | 10.1007/978-3-031-47721-8_49 |
2024-01-01 | The prediction of fatigue life and the assessment of resistance in welded structures are crucial aspects in the field of structural and mechanical engineering, especially in the design of vehicle structures. In this paper, a three-dimensional numerical model was developed using the ANSYS software to investigate the static and fatigue behavior of a simplified quarter vehicle model subjected to damped loads. Static load applied to the chassis, structure thickness, weld bead thickness, spring stiff-ness, and speed bump amplitude have a significant impact on the durability of our welded design, which represents the vehicle chassis. The objective of this study is to validate and compare the numerical results with experimental tests through parametric studies. We aim to evaluate the influence of various parameters on the reliability and durability of the welded structure. To achieve this, a scaled-down test bench was designed and constructed to measure the rigidity and durability of the structures under static and dynamic loads. The experimental results obtained align well with the developed models, exhibiting an error rate below 10%. | Experiment, simulation and investigation of the effect of different parameters on the durability of welded structure under damped loads for automobile utilization | 10.1007/s12008-023-01585-1 |
2024-01-01 | Milling cutters with runout, process dampening, and variable pitch did not solve milling difficulties because they did not address the regenerative chatter mechanism. When the phase difference between two waves varies from tooth to tooth, it throws off the regeneration process. The focus of this study is on devising a quick and accurate technique to quantify these influences during end milling. To enhance production quality and process stability while decreasing tool wear and machining costs, these methods may be included into an adaptive model for managing cutting force. The simulation results show that the cutting forces in end milling are small as compared to conventional scale cutting. In this study, an alternative process damping model has been presented for end milling based on an equivalent viscous damping approach. Furthermore, the technique is used to investigate how different tool geometries affect stability tendencies in variable pitch milling. Some novel phenomena are shown and discussed for certain parameter combinations. | Numerical Simulations of the Cutting Forces in an End Milling Process with Process Damping, Tool Runout and Variable Pitch Effects | 10.1007/978-981-99-6774-2_39 |
2024-01-01 | The objective of this study is to examine the nonlinear dynamic behavior of the rod-fastening combined rotor-bearing (RFCR) system with rub-impact, with a specific focus on the influence of internal damping. A dynamic model for the RFCR system is formulated using the finite element method based on the Lagrange equation. This model takes into account the system’s nonlinear characteristics, including rub-impact forces and oil-film forces. Through the analysis of bifurcation diagrams, Poincaré maps, time-domain plots, and frequency spectra, the effects of internal damping and stator stiffness on the system’s instability and nonlinear response are investigated. The findings reveal that both internal damping and stator stiffness have a significant impact on the vibration and instability of the RFCR system at varying speeds. Particularly, systems with rubbing faults exhibit pronounced nonlinearity and instability in high-speed regions. Furthermore, the presence of internal damping disrupts the stability of the P3 motion in the system, and the effect of divergence becomes more pronounced as the friction coefficient increases. In conclusion, considering internal damping is crucial when undertaking dynamic modeling and analysis of such complex rotors, as it plays a vital role in fault diagnosis and vibration control for practical RFCR systems. | Nonlinear Dynamic Analysis of Rub-Impact Rod-Fastening Combined Rotor Systems with Internal Damping | 10.1007/978-981-97-0554-2_7 |
2024-01-01 | In recent decades, the most impactful effects of thermal gradients on the shear modulus of compacted soils have been increasingly well documented. The thermal repercussions on the corresponding damping ratios, however, have not been as thoroughly investigated. In this work, a series of thermo-controlled resonant column tests was conducted on statically compacted samples of three distinct types of cohesive-frictional soils, namely low plasticity clay, non-plastic silt, and clayey sand, to assess the effect of elevated soil temperatures on their respective small-strain damping ratios. Damping ratio for each soil type and test condition was determined via both the frequency response curves ( bandwidth method ) and the underdamped free-vibration cycles ( logarithmic decrement ) in order to perform a comparative analysis of damping assessment methods. The corresponding stress–strain hysteresis loops were also evaluated for further qualitative insights into any possible thermal sensitivities of their material damping in the field. Results show a mostly detrimental effect of increasing soil temperature on the small-strain stiffness of cohesive-frictional soils, with their damping ratio remaining virtually unchanged (clays) or experiencing a gradual increase (silts and sands) with increasing soil temperature. | A Comparative Analysis of Damping Assessment Methods in Cohesive-frictional Soils via Thermo-controlled Resonant Column Testing | 10.1007/s10706-023-02578-3 |
2024-01-01 | Purpose The present investigation is devoted to providing two/three-dimensional (2D/3D) models for estimating the amount of thermoelastic damping (TED) in circular cross-sectional micro/nanorings by capturing the effects of size on thermal domain via dual-phase-lag (DPL) heat conduction model. Methods To achieve the goal of the article, first of all, the equation of heat conduction derived in the framework of DPL model is solved. In this way, for 2D and 3D models of heat propagation, the temperature field in the ring is obtained in the form of infinite series. Next, by exploiting the relation of quality factor in entropy generation (EG) approach, a formulation including the two phase lag parameters of DPL model is extracted to anticipate TED value in small-sized rings with circular cross section. Results By comparing the results of this investigation with those of studies in the literature that are based on simpler heat conduction models, a validation study is accomplished. An intensive numerical study is also performed to discern the influence of some of the most significant factors such as phase lag parameters of DPL model, vibration mode, the dimensions and ring material on TED. Conclusion The findings reveal the noticeable effect of phase lag parameters of DPL model on the magnitude of TED in miniaturized circular cross-sectional rings, especially in smaller dimensions and higher vibration modes. | Analytical Model for Thermoelastic Damping in In-Plane Vibrations of Circular Cross-Sectional Micro/Nanorings with Dual-Phase-Lag Heat Conduction | 10.1007/s42417-023-00876-x |
2024-01-01 | The need to measure complex mechanical structures has grown in importance for efficiency in the design process and for structural monitoring. Despite the convenience of using a 3D scanning laser Doppler vibrometer (LDV), fixed acceleration sensors are still widely used for industrial applications. However, the effects of sensor attachments cannot be disregarded for lightweight structures. This paper provides a thorough description of how various sensor attachment techniques affect vibration measurements over a wide frequency range (up to 16 kHz). Frequency response function (FRF) measurements were conducted on an aluminum plate using both the LDV and an accelerometer simultaneously, excited by a scalable automatic modal hammer (SAM). For particular frequency ranges of interest, recommendations for fixation methods are proposed. Recommendations for fixation techniques are proposed for certain frequency ranges. The study’s findings offer practical advice for industrial structure measurement evaluations. An important outcome of this study is how the fixation method influences the experimental results of the modal properties. The research reveals that the fixation, the contact area, the sensor, and the test specimen built a dynamic system that influences the results especially at higher frequencies and should be considered for precise measurements. | Parameter Investigation of Sensor Fixation Methods Compared with High-Quality Laser Measurement Using a Scalable Automatic Modal Hammer | 10.1007/978-3-031-37007-6_7 |
2024-01-01 | In power transmission lines, conductors and guard wires are subjected to different types of mechanical vibrations, such as galloping, aeolian vibrations, and in the case of conductor bundles, sub-span oscillations. In this paper, a calibrated finite element model (FEM) is developed to evaluate the dynamic response due to aeolian vibrations of a single OPGW (Optical Ground Wire) cable with Stockbridge dampers. The model included the geometric, material, and damping characteristics of the OPGW cable and dampers, calibrated in previous work. The wind power input was simulated using a stochastic wind model based on Wiener processes, which allowed for a more realistic representation than deterministic models available in the literature. In addition, a Polynomial Chaos-Kriging (PCK) metamodel of the FEM model was constructed to reduce the computational cost of the model evaluation. The uncertainty of the wind load was propagated through the metamodel to obtain the distributions of the variables regarding the dynamic response, including the antinode and bending amplitudes, as a function of the Von Karman vortex shedding frequency. This was achieved using a Monte Carlo simulation approach, in which a large number of random simulations based on the wind model probability distribution were generated. The results were aggregated to obtain the distributions of the variables of interest. Field measurements were recorded with specific equipment to validate the simulation results. The results obtained in this study provide valuable insights into the dynamic behavior of cable-damper systems under aeolian vibrations, which are of great importance in their robust design. | Propagation of the Uncertainty in the Dynamic Behavior of OPGW Cables Under Stochastic Wind Load | 10.1007/978-3-031-47152-0_11 |
2024-01-01 | This chapter focuses on the response of a two degree of freedom (TDOF) system. It begins with the undamped free response, damped free response and forced harmonic response of a TDOF system. These are further extended to explain working principles of vibration absorber. This chapter also covers the response of a TDOF system by using the method of Laplace transform and transfer function. Static and dynamic coupling of a TDOF system is also explained. | Response of a Two Degree of Freedom System | 10.1007/978-981-99-3614-4_5 |
2024-01-01 | In recent years, magnetorheological fluid dampers have been paid more attention because of their smart nature and properties. This paper presents the mathematical background of magnetorheological fluid dampers and their use in advanced technological applications. The main objective of this paper is to delineate how to find equations of motion for dynamics of MR dampers for different degrees of freedom and how to find their responses for various damping forces. In this paper, the performance of a MR damper are compared by MATLAB simulation. | Mathematical Modeling, Analysis and Simulation of MR Fluid Damper | 10.1007/978-3-031-34644-6_56 |
2024-01-01 | Purpose Elastic Ring Squeeze Film Damper (ERSFD) is normally incorporated into high-speed ball bearings to attenuate the vibration amplitude of the rotor system in aero-engines. At high rotor speeds, the bearing introduces considerable nonlinear excitation to the journal, causing it to exhibit distinct dynamic properties. As well, the deformation of the elastic ring in the ERSFD model significantly influences the hydrodynamic reaction force on the journal. This paper develops a high-speed ball-bearing excited ERSFD model with the deformation of the elastic ring analytically formulated. The effects of rotor operating speed and squirrel cage stiffness on the transient and steady-state dynamics of the journal were examined. Methods The journal is modeled under the excitation of ball-outer raceway interaction rather than rotor unbalance force, emphasizing heavy thrust-applied load. Ball-outer raceway interaction is calculated using a modified quasi-static model. Elastic ring deformation is derived analytically through a thin-walled ring and the oil film pressure is governed by the generalized Reynolds equation. Runge–Kutta approach was used to numerically integrate the differential equations of motion, and the journal center orbit and vibration acceleration were experimentally measured. Results The results show that as the squirrel cage stiffness increases by 1.23 times from 0.6855, the eccentricity and transmissibility for the ERSFD with bearings are increased by a factor of 1.8 and 3, respectively. Correspondingly, the values for the ERSFD without bearings are increased by a factor of 1.7 and 2.7. As the rotor operating speed increases by 1.75 times from 8000 r min^−1, the eccentricity and transmissibility for the ERSFD with bearings are decreased by 28.6% and 54.6%, respectively; for the ERSFD without bearings, the eccentricity remains unchanged and the transmissibility is decreased by 26.2%. Conclusion It was concluded that when the journal works at a steady state an increase in squirrel cage stiffness disadvantages attenuation in bearing excitation; adequately high rotor operating speeds benefit journal dynamics when bearing excitation is considered in ERSFD. At transient state, lower squirrel cage stiffness and higher rotor operating speed allow the journal to behave in stable periodic motion for the ERSFD with bearing excitation; however, for the ERSFD without bearing excitation, lower squirrel cage stiffness fails to make the journal whirl periodically, and the rotor operating speed has little effect on the transient dynamics of the journal. | Dynamic Characteristics of Elastic Ring Squeeze Film Damper Oscillated by Bearing Contact Force | 10.1007/s42417-023-00851-6 |
2024-01-01 | Purpose Gas turbine blades are subjected to fluctuating gas forces and centrifugal forces, which result into large resonant stresses and further lead to the failure of blades. Nowadays, dry friction damping is frequently applied in gas turbines, especially at hot locations, to reduce resonant stresses. The novelty of the paper lies in simulation of an assembly consists of two gas turbine blades and an under-platform damper through bond graph modelling technique. In this research work, dynamic behaviour of turbine blade and under-platform friction damper are obtained by evaluating their parameters. Method A lumped parameter model is developed for turbine blades and damper assembly. Further, the values of equivalent damping coefficient ( C _eq) for an under-platform friction damper are evaluated through Lazan’s law. For simulation, a discrete bond graph model of the turbine blades–damper assembly is created and simulated through Runge–Kutta method. Results and Conclusions The dynamic parameters viz. displacement, velocity and force on turbine blades, damper’s displacement, velocity and frictional force of under-platform damper for all varying values of equivalent damping coefficients ( C _eq) are obtained. These evaluated dynamic parameters of turbine blades and under-platform friction damper are further analysed for optimum designing of under platform friction damper to reduce resonant stresses and hence increase the fatigue life of turbine blades. | Parametric Evaluation and Dynamic Analysis of Turbine Blades–Damper Assembly Using Bond Graph Technique | 10.1007/s42417-023-00867-y |
2024-01-01 | Tuned Liquid Dampers (TLDs) are dissipative devices whose distinguished features like low cost in installation and maintenance or their multidirectional and multifrequency application to new and already existing structures make them an attractive damping option. Their working principle is similar to that of a Tuned Mass Damper but in this case the relative movement comes from a fluid that provides with mass, damping and stiffness. Moreover, TLDs can mitigate both horizontal and vertical vibrations. All these make TLDs worth deeply studying. TLD utilization in civil vibration control arose in the 1980s. From early years, different improvements have been implemented to achieve a better performance. Some of these modifications include passive variations in the geometry or the fluid. The use of smart materials applied on TLDs has also been of great interest since the 1990s and comprehends different configurations in which magnetic fields are used to passively or semi-actively improve the TLD performance. A lack of review is detected in this field. For this reason, a state-of-the-art review is presented in this paper. Its aim is to help researchers find a thorough, up-to-date classification of the different possibilities, configurations, numerical evaluation, materials used and also found limitations and future development in the application of magnetic fields on TLDs. | Magnetic Fields to Enhance Tuned Liquid Damper Performance for Vibration Control: A Review | 10.1007/s11831-023-09971-4 |
2024-01-01 | The paper reviews some recent results of the authors’ research group related to the modeling of the hysteretic behaviour of metallic stranded cables and applies them to the definition of a theoretical model for the self-damping of a widespread typology of overhead electrical line conductors, namely the ACSR conductors. Closed-form expressions of the dissipated power per unit of length of the conductor, previously derived by the authors, are cast in a new form that allows for a more effective comparison with available experimental data of the literature. | On the Modeling of Self-damping in Overhead Electrical Line Conductors Subject to Vortex-Induced Vibrations | 10.1007/978-3-031-53059-3_16 |
2024-01-01 | Cork composites, which are made from natural cork with other materials to increase their performance, have recently been considered for vibration damping applications. This chapter provides an overview of cork composites, emphasizing their structure, properties, manufacturing methods, and applications. We also present a case study on the vibration behavior of three distinct types of cork composites: fine-grained agglomerated cork, VC1001, and VCPAD5051. Fine-grained cork, with its unique cellular structure, exhibits greater stiffness, damping, and natural frequency characteristics than other composites. VC1001, a combination of cork and natural rubber, offers a balance between damping and stiffness, while VCPAD5051, a combination of cork and polymer matrix, shows intermediate properties. | Vibration Damping Applications with Cork Composites | 10.1007/978-3-031-51564-4_4 |
2024-01-01 | An estimate of MHD stability MHD stability is an important criterion when attempting to increase the aluminium reduction cell Aluminium reduction cell efficiency. The MHD stability MHD stability is achieved by optimizing the magnetic field Magnetic field and the electric current distribution Current distribution in the liquid metal. The magnetic field Magnetic field distribution is mostly determined by the external busbar network and the magnetized steel parts, while the electric current in the liquid metal is affected by the design elements of anode Anode and cathode Cathode block collector bar construction details. Theoretical studies of MHD stability MHD stability often rely on a simplified uniform current distribution Current distribution over the cathode Cathode bottom. Modelling Modelling of commercial cells Cell requires a detailed 3D representation of the cell Cell cathode Cathode , coupled to the liquid metal. The software MHD-VALDIS permits to account for current distribution Current distribution in the liquid metal and the cathode Cathode including variable material properties, contact resistances Contact resistance , temperature dependent collector conductivity, carbon block length and ledge Ledge profile along cell Cell perimeter. The software permits to compute full electric current and magnetic field Magnetic field 3D distribution change in time associated with the velocities and metal/electrolyte interface wave development leading to damping or growth in an unstable cell Cell . To quantify the instability the damping rate is determined using a new technique based on the consecutive wave peak heights comparison Comparison . Examples of application to a commercial Trimet cell Cell are presented. | MHD Stability of Aluminium Cells—Cathode Design Effects | 10.1007/978-3-031-50308-5_94 |
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