Damping Forces Research Articles

Experimental study and rheology of magneto-rheological fluid for a suspension system

The formulation and synthesis of magneto-rheological (MR) fluids formed by submerging iron particles in carrier fluids are the key points of this work. To reduce the corrosion, agglomeration, and sedimentation constraints of the MR fluid (MRF), iron particles are coated with natural gums like guar and xanthan. Various MR fluid samples were prepared using combinations of carrier fluids (paraffin oil and synthetic oil), magnetic particles (carbonyl iron and atomized iron dust), and additives. The magnetic particles were characterized using scanning electron microscopy (SEM). Carbonyl iron has a fiber-like structure, whereas atomized iron dust has a granular structure. The MR fluid containing xanthan gum-coated iron particles showed improved sedimentation properties. Furthermore, the magnetic field of the magnetic piston was tested by supplying power, and it was observed that the magnetic flux density increased with an increase in the current in amperes. By conducting a visual inspection, the sedimentation analysis of the prepared MR fluids demonstrated that MRF 2 and MRF 1 improved the sedimentation rate more significantly than the others. The rheological properties of the MR fluids were determined by measuring their yield stress with respect to the applied magnetic flux density. Paraffin oil-based MR fluid mixed with xanthan gum-coated carbonyl iron (MRF 2) showed higher yield stress than other fluids. The higher value of yield strength will boost the damping force of the MR damper to effectively suppress vibrations in the system.

Modeling and performance analysis of open-loop remotely operated vehicles ORCA

<p>ORCA is a low cost remotely operated vehicle which was indigenously developed for underwater inspection and survey. As the underwater environment is quite unpredictable, dynamic modeling and simulation of the remotely operated vehicle are essential to understand the behavior of the vehicle and accomplish stabilized navigation. This paper discusses a detailed approach to the mathematical modeling of ORCA based on Newtonian dynamics and simulating the position and velocity responses in Simulink. The open loop nonlinear model of the remotely operated vehicle was used to study the navigation challenges due to the various perturbations present underwater namely Coriolis and centripetal force, added mass, hydrodynamic damping force, and restoring forces. The six-thruster open loop ORCA model was subjected to various thrust inputs (25%, 50%, and 75%) to achieve six degrees of freedom (DoF) respectively and it was observed that there was significant instability in the other DOFs along with the principal direction of motion. Further, the authors will incorporate the various control systems in ORCA and analyze the stability in navigation induced due to each of them.</p>

Stability of nonlinear vibrations induced by rolling force in a precise cold mill system

This paper investigates the stability of horizontal nonlinear vibration of four-high cold mill under the effects of gyro-precession and eccentricity between rolls. The threshold value of chaos about Smale horseshoe commutation is given from Melnikov method, and the correctness of the result is verified by the fractal process of the attraction basin. Through the analyzes of bifurcation, maximum Lyapunov exponents and bi-parameter bifurcation, it is revealed for the effect of different parameters variation on the nonlinear dynamic behavior of horizontal vibration in rolling system. The results show, the fluctuation amplitude of horizontal force increases, the stable domain decreases, and once its value ≥3.5, it is necessary to prefer to the adjustment of parameter-exciting stiffness; meanwhile, it is noticeable that the critical points of damping and average force of the system with bifurcation or chaos appear hysteresis. The evolutions of system dynamics with four pairs of parameter changes confirm the quantitative optimal couple of one structural plus one process parameter in the system. Based on this, we can also find a balance between the average horizontal force and eccentricity, so as to optimize the structural design so that there is a proper and reliable eccentricity between the rolls. The results provide a theoretical reference for service stability and dynamic reliability of the rolling mill system.

Development and experimental validation of finite element models for a prestressed lead extrusion damper

The emerging trend in earthquake-resistant structural design is to dissipate some part of the seismic input energy through energy-dissipating devices (EDDs). A prominent candidate to serve this purpose is the lead extrusion damper (LED), which dissipates seismic energy by the extrusion of lead through the displacement of a bulged shaft. The LEDs should be designed as they meet the demands of the host structural system. Hence, predicting the force–displacement relation and energy dissipation characteristics of the LED is essential. To serve this purpose, comprehensive three-dimensional finite element models (FEMs) were developed in this study to simulate the cyclic behavior of a prestressed LED. The methodology consisted of performing coupon tests, the development of FEMs, and experimental verification. Coupon tests were performed for lead and steel to simulate the nonlinear material behaviors better. The models were validated against the experimental results of the LED and a steel beam-to-column connection. In general, the adapted model satisfactorily captured the experimental results. The maximum differences in the maximum force and dissipated energy predictions were about 7.5% for the generated FEMs. In addition, the mean relative difference in predicting damper forces for eight LEDs selected from the literature was about 6%. The low relative differences between the models and experiments demonstrated that the adapted FEM could reliably estimate the cyclic response of the LEDs. It can be stated that the adapted three-dimensional finite element modeling strategy can be utilized robustly for design purposes.

DEVELOPMENT OF CAPPED VISCOUS DAMPING MODEL BASED ON RESTORING-FORCE AMPLITUDE

Stiffness proportional or Rayleigh damping are well-known typical viscous damping, but since it depends on the frequency, it becomes a problem when the damping coefficient is to be kept constant over a wide period band. As a countermeasure, mode damping is sometimes used, but it is a problem that it lacks practicality in large-scale analysis because the computer load is generally large. In this study, we focus on the capped damping model that gives an upper limit to the damping force of the initial stiffness proportional damping, which is expected to have a certain degree of frequency insensitiveness.

Experimental study on the dynamic performance of a winding rope fluid viscous damper

This study proposed a winding rope fluid viscous damper (WRFVD) using the winding ropes to amplify the damping force of a fluid viscous damper. To investigate the dynamic performance of the WRFVD, four different prototypes were fabricated and tested under a series of sinusoidal loading protocols. Experimental results demonstrated that the WRFVD is a velocity-dependent damping device with significant and stable energy dissipation capacity. The winding rope amplification mechanism can effectively amplify the damping force of the fluid viscous damper by 3 to 6 times, and amplify the energy dissipation of the fluid viscous damper by 3.5 to 6.9 times. After 30 cycles of fatigue loading, the maximum damping force and the energy dissipation capacity of the WRFVD almost not decayed. The damping force of the WRFVD had a linear relationship with the damping force of fluid viscous damper with the coefficient of β, and β was only related to the construction of the WRFVD itself. The theoretical model of damping force based on the Maxwell-β nonlinear model could reflect the mechanical properties of the WRFVD well, and the theoretical and experimental hysteresis curves are in good agreement.

Shock Vibration Control of SDOF Systems with Tubular Linear Eddy Current Dampers

The nonlinear dynamic characteristic of a tubular linear eddy current damper (TLECD) and the transient responses to shock excitations of a single-degree-of-freedom (SDOF) system with the TLECD are studied. First, the nonlinear force-velocity relationship of the TLECD is discussed using the finite element simulation and mathematical model fitting. Next, the influences of three forms of shock excitation and various mechanical parameters of the TLECD on shock vibration control of an SDOF system with the TLECD are investigated. Moreover, for the SDOF systems with the TLECD or the nonlinear fluid viscous dampers (FVD) at the same maximum displacement and maximum damper force, the time to reach the maximum displacement, the time to reach one-third of the maximum displacement, the energy input of the external loading, and the energy dissipation of dampers are analyzed and compared. Finally, the shock response spectrums (SRSs) of the SDOF system and the design flowchart for the TLECD are presented to provide a reference for shock vibration control of the SDOF system with the nonlinear TLECD and the design of TLECDs. The results show that there is an optimal dimensionless critical relative velocity that minimizes the dimensionless maximum damping force for reaching the target maximum displacement, and compared to the FVD, the TLECD greatly shortens the time to reach one-third of the maximum displacement.

On a thermo‐visco‐elastic model with nonlinear damping forces and L1 temperature data

The aim of this paper is to prove the existence of weak solutions to thermo‐visco‐elastic system of equations. In considered problem, the temperature term is included in the elastic constitutive equations (generalized Hooke's law) as well as in describing the evolution of visco‐elastic strain. The main idea of presented proof is to analyze reformulated model, in which visco‐elastic strain (internal variable) is eliminated. For such system of equations, we propose a two‐level Galerkin approximation, which allows us to show a non‐negativity of temperature during the entire deformation process. In order to characterize the weak limits in the nonlinearities occurring in the system at different levels of approximation, the following tools are used: Truncation methods for heat equation proposed in the paper of D. Blanchard [Nonlinear Analysis, 21(10):725‐743, 1993], modified Boccardo‐Gallouët's approach, and Minty‐Browder trick.

Full Multiphysics Electro-Vibroacoustic Analysis of a Balanced Armature Transducer

A balanced armature transducer, also known as a receiver in some industries, is a high-performance miniature loudspeaker that is often used in hearing aids but also in other in-ear audio products like earbuds. The electrical and vibroacoustic performance of a balanced armature transducer is analyzed using a full multiphysics analysis. The model includes acoustics and associated thermoviscous losses, structural components such as diaphragm and armature (made of magnetic steel), and as the electromagnetic components including permanent magnet and coil. The vibrating armature enters a magnetic circuit with alternating magnetic flux, generated by an AC coil, which has a strong interaction with the DC magnetic field of a magnet. The electromagnetic forces are included through volumetric and surface contributions of the Maxwell stress. The analysis is performed in a commercial finite element analysis software and predicts the linear response modeled in the frequency domain and nonlinear effects modeled in the time domain. The latter include nonlinear thin-film damping and nonlinear magnetic force contributions captured using a moving mesh.

Design optimization and experimental evaluation of a large capacity magnetorheological damper with annular and radial fluid gaps.

This paper presents an optimal design of a large-capacity Magnetorheological (MR) damper suitable for off-road vehicle applications. The damper includes an MR fluid bypass valve with both annular and radial gaps to generate a large damping force and dynamic range. An analytical model of the proposed damper is formulated based on the Bingham plastic model of MR fluids. To establish a relationship between the applied current and magnetic flux density in the MR fluid active regions, an analytical magnetic circuit is formulated and further compared with a magnetic finite element model. The MR valve geometrical parameters are subsequently optimized to maximize the damper dynamic range under specific volume and magnetic field constraints. The optimized MR valve can theoretically generate off-state and on-state damping forces of 1.1 and 7.41 kN, respectively at 12.5 mm/s damper piston velocity. The proposed damper has been also designed to allow a large piston stroke of 180 mm. The proof-of-concept of the optimally designed MR damper was subsequently fabricated and experimentally characterized to investigate its performance and validate the models. The results show that the proposed MR damper is able to provide large damping forces with a high dynamic range under different excitation conditions.

Theoretical and experimental study on performance of compound-driven MR valve-controlled damper

A compound-driven magnetorheological (MR) valve is designed to cope with the low reliability and high energy consumption of traditional MR valves. The operating magnetic field of the valve is applied by both the excitation coil and ring magnet, maintaining excellent pressure drop performance even at zero current. To analyze the performance and obtain the variation law of the magnetic flux density and pressure drop, a pressure drop mathematical model and a magnetic field simulation model are established. The key parameters of the MR valve are also optimized using non-dominated sorting genetic algorithms-II. A dynamic performance test system is built, and the influence of the load on the pressure drop and hysteresis characteristics of the MR valve is studied. The results show that the optimized pressure drop and adjustable coefficient are improved by 4.7% and 8.6% respectively. The pressure drop grows nonlinearly with the electric current and reaches saturation at a current of 1.5 A, and a pressure drop of 1485 kPa is still generated at zero current. The output damping force of the compound-driven MR valve-controlled damper can be continuously adjustable, indicating that the dynamic performance of the damper can be controlled by adjusting the input current.

Power Performance and Response Analysis of a Semi-Submersible Wind Turbine Combined With Flap-Type and Torus Wave Energy Converters

Abstract An integrated offshore wind and wave energy system is an attractive concept in areas with abundant wind and wave energy resources. The sharing of supporting platform and facilities, e.g., mooring systems, offers significant cost savings. This will effectively lower the levelized cost of energy (LCOE). In the present study, a conceptual design consisting of a braceless semi-submersible floating horizontal axis wind turbine (FHAWT), three flap-type wave energy converters (WECs), as well as a torus (donut-shaped) point absorber-type WEC is proposed. The flap-type WECs harvest wave energy through the flap motion caused by oscillating wave surge, while the torus WEC absorbs wave energy generated from its heaving motion. The absorbed mechanical power of the power take-off (PTO) systems is calculated based on linear damping forces and the motions of the WECs relative to the supporting platform. Hydrodynamic interaction between the WECs and the supporting platform is considered by including the coupling terms in the added mass and potential damping coefficient matrices. A fully coupled aero-servo-hydro-elastic numerical model of the concept is constructed. The feasibility study of the concept is carried out using time-domain simulations. Only operational environmental conditions are simulated based on simultaneous wind and wave hindcast data of a selected offshore site. The effects of the WECs on the wind turbine, platform motions, and WEC power take-off are examined. Based on the power performance of WECs, recommendations are also provided for optimum power absorption.

Performance analysis of magnetorheological plastomer dampers with different annular shear gaps

Magnetorheological plastomer (MRP) dampers are controllable semi-active smart devices, which are commonly used in the field of vehicle suspension systems, structural engineering, aerospace engineering and military equipment. This study was conducted to numerically investigate the performance of MRP dampers with different annular shear gap sizes. The MRP used in the analysis consisted of 60% Carbonyl Iron Powder (CIP) and 40% Polyurethane Matrix (MRP60). The focus of the analysis was on the MRP60 flow behaviour in the annular shear gap region, where the induced magnetic field generated a range of dynamic damping forces depending on the size of the annular shear gap. The numerical simulation involved an integration of the finite element analysis (FEA) to examine the magnetic field in the annular shear gap region as well as the computational fluid dynamics (CFD) analysis to simulate the damping characteristics of the MRP damper. The relationship between the yield stress and the magnetic flux density for MRP60 was used for the analysis. The results of the FEA showed that as the size of the annular shear gap increased, the magnetic flux density and the yield stress decreased. From the CFD results, it was observed that the damping force decreased as a result of increasing the size of annular shear gap.

Design and experimental research of stepped bypass magnetorheological damper

In order to meet the damper performance requirements of heavy vehicles, a stepped-bypass magnetorheological damper is proposed. The mathematical model of damping force is deduced, and its mechanical properties are numerically simulated. Then the damper is manufactured, and the mechanical properties of the stepped bypass magnetorheological damper are experimentally studied. The simulation are consistent with the experimental results. The damper is optimized by orthogonal optimization design test. Finally, it is concluded that the maximum output damping force of the stepped bypass magnetorheological damper is about 4500 N, and the adjustable coefficient K is about 5.4. After optimization, the damping force of the stepped bypass magnetorheological damper is increased by at least 5.3%, and the adjustable coefficient K is at least 1.37 times that before optimization, which is 13% wider than that before optimization.

Cartesian vector solutions for $ N $-dimensional non-isentropic Euler equations with Coriolis force and linear damping

<abstract><p>In this paper, we construct and prove the existence of theoretical solutions to non-isentropic Euler equations with a time-dependent linear damping and Coriolis force in Cartesian form. New exact solutions can be acquired based on this form with examples presented in this paper. By constructing appropriate matrices $ A(t) $, and vectors $ {\mathbf{b} }(t) $, special cases of exact solutions, where entropy $ s = \ln\rho $, are obtained. This is the first matrix form solution of non-isentropic Euler equations to the best of the authors' knowledge.</p></abstract>

진동감소 및 감쇠력 확보를 위한 와전류형 EM댐퍼 구조 설계

In this paper, we propose an eddy current type EM damper that can have the simple structure of an existing mechanical damper and the effective damping force of a magnetic fluid fluid damper at the same time. The proposed eddy current type EM damper has a structure similar to that of a mechanical damper, in which a permanent magnet is attached to a plunger and a conductor (copper) is provided on the outer wall of the cylinder to generate and generate an eddy current cutoff. Damping force. When the permanent magnet attached to the plunger vibrates up and down, an eddy current is generated, and a magnetic field having the opposite polarity to the magnetic field acting by the circulation of the eddy current is generated. In order to verify the reliability of the damping force of the eddy current type EM damper, analysis is performed using a finite element analysis method that applies axial symmetry analysis technology, and the direction in which the damping force is generated acts in the opposite direction to the vibration characteristics to generate external vibration. The damping ability to suppress was verified.

Seismic behavior of unbonded post-tension wall with replaceable energy dissipator

Unbonded post-tension (UPT) precast concrete shear walls achieve better recentering capacity with little residual drift but less energy dissipation capability. To improve the situation, a steel-reinforced UPT precast concrete wall with replaceable low-yield-point steel plates as energy dissipators (PEWs) is developed. The proposed wall is a load bearing-energy dissipation dual function system with two seismic lines of defense. A design approach is proposed to determine the damper force under a certain energy-dissipation moment ratios. The wall behavior is analyzed concerning four performance states under combined gravitational and lateral loads using an elaborate fiber model developed in OpenSsees. Lateral bearing yield strength and peak resistance increased under monotonic and cyclic loading respectively. All the relative energy-dissipation ratios of the PEW at different cycles are greater than 0.125, as recommended by ACI ITG T5.1. The performances of two eight-story frame shear wall structures with and without energy dissipators devices subjected to 22 the maximum considered earthquake records are compared. The base shear forces, roof displacement response and story drift of the PEW reduced significantly. The PEW specimens exhibited superior behavior in terms of lateral resistance and energy dissipation.

Coordinated Control of ESP-SAS System Considering Roll

To improve the antiroll ability of the vehicle, considering the coupling characteristics of vehicle dynamics and tire force, this paper proposes a vehicle active antiroll strategy based on an electronic stability program and semiactive suspension (ESP-SAS) coordinated control. According to the motion characteristics of the electronic stability program (ESP) and semiactive suspension (SAS), the fuzzy controller based on the ESP module and the proportion integration differentiation (PID) controller based on the SAS module are designed, respectively. Through the adjustment of ESP yaw moment and the timely matching of SAS damping force, the antiroll performance of the vehicle is optimized. At the same time, due to the coupling characteristics between the two, a coordinated controller is designed to minimize the transfer of tire dynamic load. The proposed strategy is simulated and verified by Fishhook test conditions. As is shown from the results, with a good effect on the control of vehicle roll risk, the proposed coordinated control strategy can not only effectively reduce the body roll angle but also improve the operation stability of the vehicle.

A New Modeling Approach for Viscous Dampers Using an Extended Kelvin–Voigt Rheological Model Based on the Identification of the Constitutive Law’s Parameters

In addition to elastomeric devices, viscous fluid dampers can reduce the vibration transmitted to dynamic systems. Usually, these fluid dampers are rate-independent and used in conjunction with elastomeric isolators to insulate the base of buildings (buildings, bridges, etc.) to reduce the shocks caused by earthquakes by increasing the damping capability. According to the EN 15129 standard, the velocity-dependent anti-seismic devices are Fluid Viscous Dampers (FVDs) and Fluid Spring Dampers (FSDs). Based on experimental data from a dynamic regime of a fluid viscous damper of small dimensions, for which not all the design details are known, to determine the law of behavior for the viscous damper, the characteristics of the damper are identified, including the nonlinear parameter α (exponent of velocity V) of the constitutive law. Note that the magnitude of the fluid damper force depends on both velocity (where the maximum value is 0.52 m/s) and amplitude displacement (±25 mm). Using the Kelvin–Voigt rheological models, the dynamic response of a structure fixed with a fluid viscous device is analyzed, presenting the reaction force and displacement during the parameterized application of an external shock. This new approach for FVDs/FSDs was validated using the standard deviation between the experimental data and the numerical results of the extended Kelvin–Voigt model offering researchers in the field of seismic devices a reliable method to obtain a constitutive law for such devices.

Approximate Solutions of the Jet Engine Vibration Equation by the Homotopy Perturbation Method

In this paper, we consider the jet engine vibration system. With the help of the homotopy perturbation method (HPM), we solve the jet engine vibration (JEV) equation, which is a second-order nonlinear differential equation in the presence of damping and external forces. We compare the results with the corresponding numerical method to show the efficiency and reliability of this method. The findings demonstrate how well HPM works as a solution to these concerns, and it is anticipated that HPM will be used in a variety of new problems.