Damping Effect Research Articles

Experimental and numerical study on dynamic responses of a TLP-type modular floating structure system

This paper explores a proposed TLP-type modular floating structure system, incorporating both central TLP modules and peripheral floating artificial reef modules. The outermost floating artificial reef module can function as a floating breakwater, and also serving as a habitat for surrounding marine organisms. To assess the system's multi-body coupling dynamics under various wave conditions, both scale model tests (1:80) and time-domain numerical simulations were performed. The simulations accounted for hydrodynamic interactions among the bodies and the mechanical coupling effects. During the scale model test, a survival strategy has been proposed to prevent collision risks between reef modules and adjacent TLP modules, which involving a hinge connector with additional linear spring. A preliminary stiffness recommendation was suggested by a trade-off between the pitch of the reef module and the spring force. Numerical and experimental results have been widely compared and discussed, including the multi-body motion responses and the tension leg loads. A good agreement has been achieved, although responses are slightly overestimated by numerical simulation due to the neglect of the viscous damping effect. In addition, the responses of the proposed system, connected with and without the outermost floating artificial reef module, have been compared and analyzed. The results suggest that the connection of the reef module can significantly reduce the system's surge response and enhance its survivability under severe sea conditions. The validated numerical model can serve as a valuable reference for subsequent system optimization and further engineering applications.

Comparison of active and passive vibration control techniques for electric drive power electronic subsystem: Experimental validation

Reducing vibration and noise from power electronics components is vital for enhancing the performance and acceptance of electric vehicles, emphasizing the need for effective mitigation strategies in sustainable transportation. This paper compares passive and active vibration techniques, with a specific focus on utilizing particle damping for passive vibration control. The method achieves vibration reduction through viscoelastic deformation and friction resulting from the movement and collisions of granular material within the cavity. This contribution outlines diverse design strategies for integrating particle dampers into power electronic components. The active control approach, operating typically in the 50 Hz to 1200 Hz frequency range, can concurrently support passive noise treatments. Piezoelectric ceramics serve as both actuators and sensors in active noise reduction. Following the identification of dominant mode shapes, appropriate actuator and sensor positions are chosen. The control problem of the smart system is then addressed, opting for a velocity feedback control algorithm in a real collocated design. This algorithm computes input signals for actuators bonded to the outer surface, achieving significant active damping effects. Lab-tested techniques are validated in real-world conditions with a full-scale electric-drive toolkit, affirming their efficacy in reducing vibration and noise and underscoring their potential for implementation in electric vehicles.

A selective frequency damping and Janus adhesive hydrogel as bioelectronic interfaces for clinical trials

Maintaining stillness is essential for accurate bioelectrical signal acquisition, but dynamic noise from breathing remains unavoidable. Isotropic adhesives are often used as bioelectronic interfaces to ensure signal fidelity, but they can leave irreversible residues, compromising device accuracy. We propose a hydrogel with selective frequency damping and asymmetric adhesion as a bioelectronic interface. This hydrogel mitigates dynamic noise from breathing, with a damping effect in the breathing frequency range 60 times greater than at other frequencies. It also exhibits an asymmetric adhesion difference of up to 537 times, preventing residues. By homogenizing ion distribution, extending Debye length, and densifying the electric field, the hydrogel ensures stable signal transmission over 10,000 cycles. Additionally, it can non-invasively diagnose otitis media with higher sensitivity than invasive probes and has been effective in clinical polysomnography monitoring, aiding in the diagnosis of obstructive sleep apnea.

Experimental investigation on vortex-induced vibration characteristics of the dual parallel suspenders

This study investigates vortex-induced vibrations (VIVs) on dual parallel suspenders using wind tunnel experiments and employs a two-degree-of-freedom setup for each circular cylinder to closely simulate actual structural conditions. The VIV responses of dual cylinders exhibit notable deviations and complexity due to aerodynamic interaction. Results indicate a significant shift in the VIV lock-in range towards higher values for dual cylinders, compared to single ones. Both upstream and downstream cylinders demonstrate lower maximum VIV amplitudes than the single-cylinder. The cylinders exhibit effects of negative aerodynamic damping within the VIV process, with the aerodynamic damping becoming more pronounced as amplitude increases. Additionally, the time-dependent phase relationship between the cylinders contributes to these variations in response. Further analysis of surface wind pressure distribution reveals that aerodynamic interference in dual-cylinder systems leads to intricate pressure patterns and modal behaviors.

Developing a virtual physical system for vortex-induced vibration studies of a bluff body

A virtual physical system (VPS) for VIV studies of a bluff body is developed to replace the actual physical systems. It can arbitrarily and accurately control and edit the physical parameters, including mass, damping ratio and spring stiffness, specifically for the mass-spring-damper system. The recursive Duhamel integral method (DIM) with unconditional stability was used for the VPS control system, addressing real-time noise filtering problem and simplifying the system as a single input and single output (SISO) one. Delay compensation and inertial force elimination methods were investigated and proposed to overcome the crucial unwanted damping effects. An experimental facility for VIV model tests by VPS was manufactured, and the bluff body model with a measurement system was specially designed to accurately sense the hydrodynamic force during VPS operation. Systematic verification experiments for parameter editing and control of an actual physical target system were conducted, showing that the VPS can reproduce the equivalent spring-damper-mass system in high fidelity with an accuracy error of less than 5 %. VIV model tests for a bluff body at Reynolds numbers (Re= UD/υ, where U is the flow velocity, D represents the diameter of cylinder model, and υ is the kinematic viscosity coefficient) of 5.7E4 and 2.3E5 were performed using the VPS experimental facility, presenting well-Repeated VIV responses at low Re and unexpected VIV response with a large amplitude of 2.4 D at high Re, which can cause severe fatigue damage for relevant structures. The present VPS will provide promising and powerful experimental tools for VIV studies of a bluff body to reveal the related sensitive parameter effects.

Vibration Control of Corrugated Steel Web Box Girder Bridge with Friction Pendulum Isolation

In order to investigate the feasibility and applicability of friction pendulum bearings for vibration control of large-span space beam-arch bridges with corrugated steel web box girders, taking the Huian Yellow River Bridge in Guide County, Qinghai Province, China, as an example. A three-dimensional calculation model of the friction pendulum isolation space beam-arch composite bridge with a corrugated steel web was established by MIDAS, the modal analysis was carried out, and the damping effect of the friction pendulum isolation bridge was investigated using the response spectrum and the time history analysis methods; the influence of the design parameters of the friction pendulum isolation on the reduction effect was further analyzed. The results show that the friction pendulum isolation improves the stress conditions of both the girder and the pier and reduces the displacement and acceleration of the pier top, as well as reduces the acceleration of the girder, and the damping ratio is more than 50%. The optimal dynamic coefficient of friction and the radius of curvature for the corrugated steel web composite bridge are 0.04 and 3.0 m, respectively. Friction pendulum isolation has a good seismic absorption effect and provides an effective way for the seismic control of the corrugated steel web composite bridge. Doi: 10.28991/CEJ-2024-010-10-01 Full Text: PDF

Determination of Submerged Breakwater Efficiency Using Computational Fluid Dynamics

Wind-induced waves can lead to the partial or complete wash-over of beaches, causing erosion that impacts both the landscape and tourist infrastructure. In some regions of the world, e.g., Croatia, this process, which usually occurs during a harsh winter, has a major impact on the environment and the economy, and preventing or reducing this process is highly desirable. One of the simplest methods to reduce or prevent beach erosion is the use of innovative underwater structures designed to decrease wave energy by reducing wave height. In this study, submerged breakwaters are numerically investigated using various topologies, positions, and angles relative to the free surface. Not only is the optimal topology determined, but the most efficient arrangement of multiple breakwaters is also determined. The advantage of newly developed submerged breakwaters over traditional ones (rock-fixed piers) is that they do not require complex construction, massive foundations, or high investment costs. Instead, they comprise simple floating bodies connected to the seabed by mooring lines. This design makes them not only cheap, adaptable, and easy to install but also environmentally friendly, as they have little impact on the seabed and the environment. To evaluate wave damping effectiveness, the incompressible computational fluid dynamics (ICFD) method is used, which enables the use of a turbulence model and the possibility of accurate wave modelling.

Development of vibration protection system with quasi-zero stiffness and adjustable parameters

Relevance. While performing the operation processes, the technological equipment emits vibration. Vibration is a consequence of increased dynamic loads in structural elements and interfaces between systems and their elements. The development of fatigue damage can significantly accelerate. Therefore, the solution of the problems related to reducing vibration levels is always relevant. Each type of protective system has a linear law of changing the stiffness. This does not allow the effective damping of low-frequency vibrations. Thus, the information review demonstrates the future of the research according to the creation of the vibration protection systems, constantly improving their parameters in the following aspects: minimizing overall dimensions and number of parts; increasing reliability, especially in resonant mode; providing the ability to operate in modes with low stiffness. The last factor determines the good damping of vibration emitted by the source. Aim. To study the possibility of the vibration protection system development with quasi-zero stiffness with the ability to effectively dampen low-frequency vibrations. Methods. Information and analytical review in the field of the research, search for the constructive solutions, preliminary design calculations and 3D modeling, description of the device being developed and its operating principles. Results. The research presents the results of development of the vibration protection system with quasi-zero stiffness and a fragment of an information review of existing vibration protection systems. The authors indicated the main shortcomings specific to all vibration protection systems: relatively large sizes, large number of elements, insufficient operating frequency range. The authors proposed a constructive solution for creating a vibration damping system with a nonlinear law of change in stiffness. This solution allows eliminating the above shortcomings and providing the possibility of effective damping of low-frequency vibrations. The authors created the method for calculating the constructive parameters of a vibration damping system. An example of calculation is given in the paper. This system differs from existing vibration protection devices in its low stiffness and small dimensions, and a wide operating frequency range of vibration damping. The efficiency of the system operating with nonlinear and quasi-zero stiffness is proved.

Study on the mechanical properties, thermal properties, and microstructure of phase change concrete (PCC): The application of active frost resistance of concrete in frozen soil areas

This paper addresses the issue of freezing damage to concrete structures in regions with frozen soil and overcomes the limitations of traditional frost resistance enhancement methods by integrating both active and passive frost resistance strategies. A novel low-temperature phase change concrete (PCC) is developed using specially designed phase change aggregates and fly ash to replace gravel and cement, respectively. Macroscopic mechanical tests are employed to investigate the evolution of the mechanical properties of PCC. The temperature control capabilities of PCC are quantitatively assessed through thermal physical parameters, heat storage and release curves, and infrared thermal imaging, alongside the introduction of a temperature damping indicator to elucidate the mechanisms underlying active frost resistance enhancement. Furthermore, XRD NMR, and SEM are utilized to further explore the influence of fly ash and phase change aggregates on the microstructural characteristics of PCC. The results show that the addition of phase change aggregates can reduce the strength, porosity, and ductility of concrete. The PCC prepared by mixing phase change aggregates with fly ash demonstrates effective temperature control performance while maintaining satisfactory mechanical properties. The noticeable temperature plateau around 0 °C in the heat storage and release curve, along with the multi-layered annular flare distribution observed in infrared thermal imaging, suggests that the temperature damping effect significantly mitigates the freeze-thaw impact experienced by PCC. Overall, the A-8 sample, with 20 % phase change aggregate and 30 % fly ash added, exhibits the most favorable comprehensive performance, showing reductions of 2.63 %, 39.57 %, and 33.04 % in uniaxial compressive strength, porosity, and maximum temperature difference, respectively, compared to the control group, along with a 75.62 % increase in relative temperature damping.

The effect of small internal and dashpot damping on a trapped mode of a semi-infinite string

The effect of small internal and dashpot damping on a trapped mode of a 1D-waveguide, that is, a semi-infinite string on a Winkler elastic foundation, has been investigated. At the edge of the string a mass–spring–damper system is attached. The string is assumed to have an internal damping. Four models for the internal damping are considered: air damping, Kelvin–Voigt damping, local Kelvin–Voigt damping, and damping related to time hysteresis. Depending on the internal damping and the parameters in the formulated problem, it will be shown that the amplitude of a trapped mode of the string can decrease or increase with time.

Linear equivalence for motion amplification devices in earthquake engineering

AbstractMotion amplification devices utilized to amplify the motion of dampers can effectively improve the energy dissipation performance of dampers to reduce seismic responses of engineering structures. This study systematically develops a linear equivalence theory for motion amplification devices based on the proposed equivalent Maxwell model. This equivalent model accurately predicts the supplemental damping effect provided by motion amplification devices without approximation. Also, the equivalent model is capable of quantifying the amplification effect of motion amplification devices by means of deriving the analytical expressions of the equivalent damping and stiffness coefficients, which reveal that motion amplification devices simultaneously enhance the original damping and stiffness coefficients by , where is the proposed rigidity motion amplification factor. The representative value of member stiffness is developed to comprehensively evaluate the supporting stiffness of motion amplification devices. All the achieved results strongly support that the proposed linear equivalence theory provides a generic paradigm to explain, measure and compare different types of motion amplification devices in terms of their supplemental damping effects, and hence helps researchers and engineers gain valuable insight into the dynamic properties of motion amplification devices.

A memory-type thermoelastic laminated beam with structural damping and microtemperature effects: Well-posedness and general decay

Abstract In previous work, Fayssal considered a thermoelastic laminated beam with structural damping, where the heat conduction is given by the classical Fourier’s law and acting on both the rotation angle and the transverse displacements established an exponential stability result for the considered problem in case of equal wave speeds and a polynomial stability for the opposite case. This article deals with a laminated beam system along with structural damping, past history, and the presence of both temperatures and microtemperature effects. Employing the semigroup approach, we establish the existence and uniqueness of the solution. With the help of convenient assumptions on the kernel, we demonstrate a general decay result for the solution of the considered system, with no constraints regarding the speeds of wave propagations. The result obtained is new and substantially improves earlier results in the literature.

Nonlinear damping effects for the 2D Mindlin–Timoshenko system

AbstractIn this article, we investigate the asymptotic behavior of the Mindlin–Timoshenko system under the influence of nonlinear dissipation affecting the rotation angle equations. Initially, we provide a concise review of the system’s solution existence. Subsequently, we demonstrate that the energy associated with the solution of the Mindlin–Timoshenko setup follows a dissipation. Furthermore, under the condition of equal wave speeds, we establish a comprehensive decay theorem for the energy, offering explicit insights into its general behavior.

Secondary Resonances of Asymmetric Gyroscopic Spinning Composite Box Beams

A comprehensive theoretical investigation on the occurrence of secondary resonances in parametrically excited unbalanced spinning composite beams under the stretching effects is conducted numerically and analytically. Based on an optimal stacking sequence and Rayleigh’s beam theory, the governing equations of the system are derived using extended Hamilton’s principle. The system’s partial differential equations are then discretized using the Galerkin method. Numerical (Runge–Kutta technique) and analytical (multiple scales method) approaches are exploited to solve the reduced-order equations, and their results are compared and verified accordingly. Comparison and convergence investigations are performed to guarantee the validity of the outcomes. Stability and bifurcation analyses are accomplished, and resonance effects are thoroughly studied utilizing frequency-response diagrams, phase portraits, Poincaré maps and time-history responses. It is observed that among the various types of secondary resonance, only a combination resonance can be observed in the system dynamics. The outputs reveal that, in this resonance, the gyroscopic coupling results in the steady-state time response consisting of three main frequencies. By examining the effects of damping, eccentricity, and beam length, it is exhibited that this resonance does not occur in the system’s dynamics for any combination of these parameters. Therefore, these parameters can be adjusted in the design of asymmetric beams to prevent this type of resonance.

Effect of static magnetic field on the chemical short-range order of CoCrFeMnNi high-entropy alloy prepared by laser powder bed fusion

Recently, laser powder bed fusion (LPBF) has emerged as a potential technique for manipulating chemical short-range order (CSRO) in high-entropy alloys (HEAs), eliminating the need for homogenization treatment. The application of the magnetic field in LPBF has shown promise in refining the microstructure and optimizing the mechanical properties. However, the precise influence of magnetic field on the CSRO of LPBF-processed HEAs remains inadequately understood. Therefore, in this study, we investigate the impact of the static magnetic field on the CSRO of LPBF-processed HEAs. The findings reveal that the presence of the static magnetic field results in a reduction in CSRO, including the size and area fraction. This behavior can be attributed to the influence of the static magnetic field on the melt flow, which is perturbed by the electromagnetic damping effect and thermos-electromagnetic forces, thereby impeding the free diffusion of atoms and ultimately leading to a decrease in CSRO.

Largely enhanced damping performance of nitrile rubber/ethylene–vinyl acetate blends via phenolic resin-induced phase separation

The low glass transition temperature (Tg) and narrow effective damping temperature range (EDTR) greatly restrict the application of common vulcanized rubbers in fields relating to high temperature environmental condition due to the greatly reduced damping performances. In this work, phenolic resin (PR) was incorporated into nitrile rubber/ethylene–vinyl acetate (NBR/EVM) blends through melt-compounding processing, and the microstructure and damping performance changes induced by PR were comparatively investigated. The results show that PR induces the phase separation of the blends and most of PR particles selectively locate in the NBR component. Molecular dynamics simulation confirms that more hydrogen bonds form in the ternary blends, and reduced free volume fraction is also achieved. The ternary blends show good high-temperature damping performances, and apparently enhanced Tg (up to 17.7 °C) and EDTR (82.6 °C, from −2.6 to 80 °C) are also achieved. Additionally, the ternary blends exhibit good mechanical properties, including higher ductility and larger fracture energy, and better energy dissipation ability. This work provides an alternative resolution way to enhance the damping performances of the common vulcanized rubbers at high temperatures.

Analytical Solution for Dynamic Response of a Reinforced Concrete Beam with Viscoelastic Bearings Subjected to Moving Loads.

To provide a theoretical basis for eliminating resonance and optimizing the design of viscoelastically supported bridges, this paper investigates the analytical solutions of train-induced vibrations in railway bridges with low-stiffness and high-damping rubber bearings. First, the shape function of the viscoelastic bearing reinforced concrete (RC) beam is derived for the dynamic response of the viscoelastic bearing RC beam subjected to a single moving load. Furthermore, based on the simplified shape function, the dynamic response of the viscoelastic bearing RC beam under equidistant moving loads is studied. The results show that the stiffness and damping effect on the dynamic response of the supports cannot be neglected. The support stiffness might adversely increase the dynamic response. Further, due to the effect of support damping, the free vibration response of RC beams in resonance may be significantly suppressed. Finally, when the moving loads leave the bridge, the displacement amplitude of the viscoelastic support beam in free vibration is significantly larger than that of the rigid support beam.

Motion and Mooring Load Responses of a Novel 12-MW Semi-Submersible Floating Wind Turbine: An Experimental Study

Abstract Due to the complexity of the integrated Floating Wind Turbine (FWT) system, obtaining reliable results necessitates extensive experiments. This paper conducts a comprehensive study on the motion performance and mooring load responses of a novel 12-MW semi-submersible FWT through model tests carried out in a wave basin. A multi-blade large-scale wind-generation system, equipped with a rectifier network, was enhanced and constructed to provide a dependable wind field. And a flexible tower was designed and fabricated, achieving an accurate simulation of the tower's stiffness characteristic and its impact on the overall dynamic response. The marine environmental conditions encompass various combinations of wind, waves, and currents. Rigorous calibration and identification tests were undertaken to validate the environmental conditions and the model system. The findings reveal that, under mild wave parameters, the mooring load is primarily influenced by the resonance response with platform motions, particularly surge resonance. The load effect of wind and current induces mean surge and pitch motions, while their damping effect reduces the standard deviation of responses, notably suppressing the pitch response peak at its natural motion frequency. Wave loads predominantly dictate the vibration range of motion responses. When the current velocity reaches a sufficient magnitude, the coupling effect between current and wave in the wave–frequency region significantly amplifies the mooring response. Notably, motions and mooring loads in the 60-deg and 90-deg directions surpass those in the 0-deg direction, with the maximum responses occurring at 60 deg.

Modelling of air springs for metro vehicles and studies on the effect of orifice damping

With the metro vehicle as the subject, a mathematical model of the main chamber, the auxiliary chamber and the orifice of the air spring were established based on the thermodynamic theory. The lateral nonlinear model is obtained based on the analytical geometry. Establish the four-point levelling valve and differential valve models through theoretical analysis. A complete three-dimensional air spring model is established. The correctness of the model is verified by comparing it with the actual data. The impact of orifice diameters and secondary vertical dampers on the dynamic performance of the metro vehicle is investigated. The results show that the secondary vertical damping configuration has a greater effect on vertical stability and acceleration but a minor impact on operational stability. Metro vehicles equipped only with air springs in the smaller diameter orifice do not need to be configured with a vertical damper, resulting in excellent dynamic performance and savings in production costs.

Surface Currents and Relative-Wind Stress in Coupled Ocean–Atmosphere Simulations of the Northern California Current System

Abstract The dependence of surface-current damping on the definition of surface current for the relative wind is examined in coupled ocean–atmosphere numerical simulations of the northern California Current System (nCCS) during March–October 2009. The model response is analyzed for wind stress computed from relative wind for six different choices of effective model surface velocity. Simulations without surface-current coupling are also considered. As a function of the geographically varying uppermost grid-level depth, the model uppermost grid-level velocity is found to have a wind-drift component with a log-layer structure. Mean geostrophic wind work is concentrated in the shelf and slope regions during March–May (MAM) and in the deep offshore region in June–September (JJAS). The surface-current damping effect on ocean kinetic energy depends more strongly on the parameterization of atmospheric planetary boundary layer (PBL) turbulence than on the surface-current coupling formulation: weaker PBL mixing gives stronger surface-current damping. The damping effect is stronger in the less energetic offshore region than in the more energetic region closer to the coast. During MAM, the changes in kinetic energy and geostrophic wind work in the shelf and slope regions are spatially correlated, while during JJAS, the changes in geostrophic wind work are strongly modulated by SST–stress coupling. The wind-drift-corrected surface-current formulations result in large changes in the effective wind work based on the product of stress and relative-wind surface current but result in only small changes in the kinetic energy of the circulation. Significance Statement Ocean currents and atmospheric winds are coupled by the exchange of momentum across the air–sea interface, the strength of which depends on the relative wind, the difference between the surface wind and surface current. The purpose of this work was to examine the dependence of a coupled ocean–atmosphere model of the northern California Current System (nCCS) on the representations of the relative-wind surface current and turbulent mixing in the lower atmosphere. The model surface current was found to have a shallow wind-drift response. The model ocean circulation was driven primarily by near-coast winds during the spring and by offshore winds during the summer. The ocean response depended more strongly on the atmospheric turbulent mixing than on the surface current representation.