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Based on the inverse piezoelectric effect and other characteristics of piezoelectric ceramics, a new type of piezoelectric variable friction damper is developed, and the output performance test of piezoelectric ceramic actuator and piezoelectric variable friction damper is carried out, and the parametric mechanical model of the damper is established by using Simulink to carry out numerical simulation, and compared and analyzed with the test results. The results of the study show that the simulation and the test present a good regular agreement. With the increment of loading voltage, the displacement deformation and zero-displacement thrust of piezoelectric ceramic actuator are approximately linear with the loading voltage; when the loading voltage is increased by 15V every time, the test value of the output damping force of the damper increases by 259.66N on average step by step, and the simulated value increases by 256.14N step by step, and the damping force has a linearly incremental relationship with the voltage and the slope of the linear increase is 16.434. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of viscous effects on the added mass and damping forces during free heave decay of a cylinder with a hemispherical bottom. Results from unsteady Reynolds-averaged Navier–Stokes (URANS) simulations and linear potential-flow solutions are compared. Expressions for the cycle-averaged viscous added mass and damping coefficients are derived based on first-order Fourier analysis of the URANS results. Viscous effects are extracted by comparing the URANS results and linear potential-flow solutions, as nonlinear potential-flow effects in this case are demonstrated to be negligible. It is observed that viscous effects on the added mass coefficient are minor during heave decay, such that the linear potential-flow model can predict the value of the added mass coefficient to within 5% deviations. In contrast, the viscous damping coefficient exhibits strong cycle-dependent variations. A parametric study of the effects of initial displacement, cylinder diameter and draft shows that viscous damping forces can play an important role when the cylinder has a relatively small diameter and large draft. Further, the damping coefficient is transformed to the nondimensional drag force coefficient, and its dependence on the Reynolds number R e is investigated, for Keulegan–Carpenter numbers in the range K C = 1.5–2.5. It is found that the drag force coefficient is likely to be unrelated to R e and K C during the first cycle. From the second cycle to the fourth cycle, the drag force coefficient rapidly decreases with increasing R e , up to R e ≈ 3 × 1 0 5 . [ABSTRACT FROM AUTHOR]

This work presents and discusses a method for evaluating a dynamic eddy-current damping (ECD) force that is automatically generated in response to eddy currents induced within a conductive plate while moving across a magnetic field in relative motion to a nearby stationary magnet. In the experiment, a Doppler shift frequency signal between the optical interference fringe frequencies was used to calculate the velocity of the moving conductive plate. The other relevant mechanical quantities acting on the plate, such as the displacement, acceleration, and resultant force, were then evaluated by performing numerical calculations of the velocity. Finally, the evaluation of the ECD force could be achieved by performing a calculation to remove the frictional force component from the resultant force. Furthermore, an approximation analysis used to calculate the value of the ECD force was proposed and compared with the measured value as well. From the experimental results, the combined standard uncertainty for evaluating the ECD force was approximately 3.57 mN, corresponding to 3.13% of the maximum eddy-current force of approximately 114.0 mN. [ABSTRACT FROM AUTHOR]

In order to solve the problems of high power consumption and low output damping force of magnetorheological dampers, the relationship model between the structural parameters and the optimization objectives of dampers is established with the low power consumption and lightweight of magnetorheological dampers. The key structural parameters of the magnetorheological damper are optimized by the multi‐objective genetic algorithm, and the optimal solution is obtained, and the optimized magnetorheological damper is tested and studied. The rationality of the selected parameters is verified by experimental study. The results show that the power consumption of magnetorheological dampers is reduced by 43 % and the damping force is increased by 30 % after optimization. There is a balance relationship between the power consumption optimization and the damping force optimization of the damper. Therefore, when finding the optimal solution, we should consider the needs of the actual situation and select the most reasonable parameters. [ABSTRACT FROM AUTHOR]

• A novel twin-tube MR damper with meandering channel is proposed. • The maximum dynamic range of the proposed MR damper is 10.76 when I = 0.5 A. • Temperature characteristics and damping characteristics of the proposed MR damper are experimental studied. • The damping force of the proposed MR damper reaches 4523 N when I = 0.5 A, f = 2.0 Hz, and A = 8 mm. A twin-tube magnetorheological (MR) damper with meandering channel is proposed in this paper. The proposed MR damper has a longer damping channel than conventional MR dampers due to the structure of twin-tube and the design of meandering channel. The magnetic circuit model and the damping force model of the proposed MR damper are established and finite element analysis is conducted. In addition, experimental research is conducted on the temperature characteristics and damping characteristics of the proposed MR damper. Results demonstrate that the theoretical and experimental maximum damping forces of the proposed MR damper are in good agreement. The temperature of the coil surface changes very little under a current of 0.5 A. The maximum damping force of the proposed MR damper can reach 4523 N and the maximum dynamic range is 10.76 at the current of 0.5A. Furthermore, the maximum dynamic range of the proposed MR damper is larger than that of other conventional MR dampers in references. [ABSTRACT FROM AUTHOR]

The principle of centrifugal force produced by flowing fluid through the semicircular section of a pipe line is not sufficient to explain the characteristic of the centrifugal force type flow transducer developed from this principle. In this study, a modified form of this flow transducer is developed using a modified force sensing technique. This modified force principle explains the characteristic of the flow transducer to a very good extent. The modified force produced in the modified transducer system is composed of four components namely, centrifugal force, momentum force, damping force and restoring force. These forces produce the identical downward and upward movements of the lever ends of a common balance which is initially made horizontal at zero flow by using similar sensing U‐tube and dummy U‐tube. These movements are sensed by two identical inductive sensors. The static characteristic equation of the prototype unit of the transducer using the modified force sensing technique is derived mathematically in the study. The equation coefficients are calculated from the design parameters and are found to be matched with the same obtained from the average characteristic of repeated experiments performed under the same laboratory environment. Thus the proposed modified model appears to be established. [ABSTRACT FROM AUTHOR]

A hybrid type magneto-rheological (MR) fluid damper based on electromagnet and two permanent magnets apart from electromagnet was designed and its characteristics were analyzed numerically. In the proposed MR damper, the magnetic field is generated by the permanent magnet and raised by the additional electromagnet. This combination provides a larger amount of damping force with lower consumption of electric energy. The proposed model has an additional advantage of providing a moderate damping force in case of electromagnet failure. The magnetic circuit of a hybrid MR valve was analyzed by applying Kirchhoff's law and magnetic flux conservation rule. A 2D axisymmetric model of the proposed hybrid MR damper was developed in commercial software where magnetic field properties are analyzed by finite element method. The optimization process was developed to optimize the geometric parameters and generated damping force using design of experiment (DoE) technique. The damping force of the MR damper was selected as an objective function. The optimal solution to the optimization problem of the hybrid MR valve structure was evaluated and compared with the solution obtained from the initial parameters. It is demonstrated that the novel hybrid type provides higher damping force than the previous model. [ABSTRACT FROM AUTHOR]

The intensive impact load will generate a huge acceleration in the primary part of the Electromagnetic buffers (EMBs), resulting in an instantaneous increase in the eddy current loss of the permanent magnet (PM). In this paper, the PM eddy current loss is taken into account in the electromagnetic buffering under intensive impact load. The reason why the eddy current damping force differs between two different buffer stages is analyzed. The experimental results signify that the model considering the PM eddy current loss is more accurate. [ABSTRACT FROM AUTHOR]

In this work we consider the Riemannian geometry associated with the differential equations of one dimensional simple and damped linear harmonic oscillators. We show that the sectional curvatures are completely determined by the oscillation frequency and the friction coefficient and these physical constants can be thought as obstructions for the manifold to be flat. Moreover, equations of simple and damped harmonic oscillators describe nonisomorphic solvable Lie groups with nonpositive scalar curvature. [ABSTRACT FROM AUTHOR]

Tiny piezoelectric transducers transform a very small fraction of ambient energy into electrical power. Power losses and breakdown voltages unfortunately limit how much of this power reaches the microsystem. The piezoelectric harvester presented here operates at the maximum power point (MPP) without the separate MPP stage that typical piezoelectric harvesters need. As a result, the system loses less power and occupies less space. In addition, with only four transistors, the charger increases the voltage with which the piezoelectric current generates power. This way, the harvester draws more power from vibrations. By precharging the transducer between half cycles, the 0.81–1.2-μm CMOS system outputs 0.7–49 μW of the 1.2–55 μW that a vibrating 16.8-nF transducer avails at 120 Hz. This is up to ${\text{6.8}}\times $ more power than a lossless diode bridge can harness and as much as the best recycling bridge can output, but with four fewer power switches and without a separate maximum power-point stage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The dynamic performance of twin tube shock absorber is tested. • The failure characteristics are presented and analyzed. • Virtual prototype is utilized to simulate and analyze the failure details. Abstract Shock absorber is widely utilized in different engineering fields, such as automotive engineering, civil engineering and aerospace engineering, etc. In this paper, the dynamic performance of a twin-tube shock absorber is investigated by experiment and simulation. Force-velocity and Force-displacement curves are tested; results indicate damping force decreases abruptly at the end of compression stroke, when piston speed is between 0.31 and 0.75 m/s. Besides, damping force may also decrease at the end of rebound stroke when velocity continues increase. Furthermore, the virtual prototyping technology is proposed to further investigate dynamic properties of shock absorber. Effects of frequencies and vibration amplitudes on dynamics of shock absorber are comprehensively investigated. Dynamic stiffness and damping coefficients are investigated under multiply conditions. These results show the virtual prototype is an effective approach to characterize the dynamic performance of shock absorber; which can be further optimized under multiple conditions by such simulation. Design charts are also presented, to decide the operation domain of shock absorber. [ABSTRACT FROM AUTHOR]

The transient horizontal vibration of top loading washing machine with large capacity has been more important because of the radius of the inner tub in the washing machine increases proportionally. In this paper, we introduce a new vibration reduction technology, namely, a quad horizontal damper system for reduction of the transient horizontal vibration of top loading washing machine. And analyzes the vibration characteristics of a top loading washing machine with a quad horizontal damper system using Newtonian mechanics. For verification and validation of the established dynamic model, the displacement of an actual top loading washing machine are obtained from six laser sensors attached at the upper part and the lower part of outer tub respectively. Optimal design was carried out to ensure sufficient strength and reliability for each component of the horizontal damper. The damping force of the horizontal damper was also optimized so that the horizontal vibration in the transient state of top loading washing machine was reduced by about 35~45 % more than the conventional top loading washing machine and no abnormal noise was generated at high spin speed. [ABSTRACT FROM AUTHOR]

This paper focuses on the thrust ripple reduction in permanent magnet synchronous linear motors (PMSLMs), which are applied to laser cutting machines. To meet the high-precision performance requirements of laser cutting machines, a novel auxiliary suppression device, tuned viscoelastic damper (TVD), is designed to reduce the thrust ripple of PMSLM. First, TVD is designed with the structure and motion characteristics of PMSLM. The PMSLM with TVD is an integrated structure. Then, the equivalent magnetization method is used to analyze the PMSLM thrust, which is the excitation of TVD. Under the excitation of the PMSLM thrust, the damping force of TVD is expressed by the Kelvin model and validated by finite-element analysis (FEA). Subsequently, the thrust of PMSLM with TVD is obtained by adding the PMSLM thrust and TVD damping force. Finally, the thrust ripple rate is selected as a performance index of TVD in reducing the thrust ripple. Simulation is performed to confirm the theoretical analysis. A prototype of PMSLM with TVD is manufactured and experiments are conducted to validate the effectiveness of the proposed auxiliary suppression device. [ABSTRACT FROM AUTHOR]

Abstract Impact of adhesive particles with a wall occurs in many applications, over a wide range of impact speeds. Prediction of whether or not an impacting particle will stick to the wall, and if not prediction of the rebound velocity of the particle, is critical for estimating particle deposition rate and for simulation of particle transport using approaches such as the hard-sphere discrete element method (DEM). The problem is complicated by the fact that several different damping mechanisms act to inhibit particle rebound from the wall, even for the relatively simple case of normal particle impact. While comparisons of theoretical expressions for different damping mechanisms (e.g., viscoelastic damping, squeeze-film damping, plastic damping, van der Waals adhesion, etc.) are typically conducted with consideration of only one damping mechanism, in practice all of these mechanisms must be accounted for to make appropriate comparison of predictions with experimental data. The current paper presents a simplified model that integrates previous theoretical expressions for these different damping mechanisms. The integrated analytical expression yields predictions for particle normal restitution coefficient that are in excellent agreement with experimental data over a wide range of impact velocities. A sensitivity analysis was conducted using the method of variances to examine the influence of different parameters and different damping forces on measures of the restitution coefficient output. Graphical abstract Unlabelled Image Highlights • An analytical model integrating different damping mechanisms was proposed. • Integrated predictions model are in excellent agreement with experimental data. • Integrated model predictions apply over a wide range of impact velocities. • Sensitivity analysis used to assess sensitivity of model output to input variables. [ABSTRACT FROM AUTHOR]

• Improvement in fault ride-through (FRT) capability of the hybrid offshore wind-wave energy conversion systems. • A new scheme is proposed to enhance the FRT capability by controlling the damping forces of the integrated wave energy converters. • With the propose scheme, the DFIG can be kept within the safe operating limits without any additional DC chopper circuit or crowbar control. • The performance of the system is tested under symmetrical voltage drops and asymmetrical fault conditions. The hybrid offshore wind-wave energy conversion systems (HOW-WECS) have a huge potential for clean electricity production. However, many of the technical challenges associated with HOW-WECS need to be addressed before its full-scale commercialization. One of the main challenges is the fault ride-through (FRT) capability of the HOW-WECS, which is the focus of this study, as this issue has not been addressed in any of the previous studies. In this study, multiple linear generator-based wave energy converters (WECs) are integrated with a single doubly-fed induction generator (DFIG)-based wind energy conversion system to form the HOW-WECS. A new scheme is proposed to enhance the FRT capability by controlling the damping forces of the integrated WECs. During fault conditions, the excess kinetic energy of the wind turbine can be absorbed by the linear generator-based WECs through damping control. In this way, the dc-link voltage of the back-to-back power electronic converters of the DFIG can be kept within the safe operating limits without any additional DC chopper circuit or crowbar control to dissipate the power. Other characteristics of the DFIG including the stator voltage, rotor voltage, stator current, and rotor current, are also monitored and compared with and without the proposed scheme. The results prove the effectiveness of the implemented scheme, as the HOW-WECS can operate safely under normal and fault conditions. [ABSTRACT FROM AUTHOR]

Anovel adjustable magnetic fluid damper is designed in this paper that dissipates the vibration energy by viscous flow of magnetic fluid with movement of inertia mass. First, considering the viscosity of magnetic fluid and the size of the damper, the theoretical model of the magnetic mechanical coupling system is established, and the flow velocity of the damper can be obtained from this model. Second, based on the magneto-viscous characteristic of magnetic fluid, the numerical simulation model of the cantilever and damper system is established. The distribution of magnetic field in the damper is studied. Finally, the displacement response and frequency response of the freely supported beam are calculated, and the flow distribution of the magnetic fluid in the damper is analyzed. This damper can finely adjust the damping parameters, and has good damping effect on the vibration of low frequencies and small damping. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) fluid damper has been designed, fabricated and tested to find the stiffness and damping characteristics. Experimentally the MR damper has been tested to analyse the behaviour of MR fluid as well as to obtain the stiffness for varying magnetic field. MR damper mathematical model has been developed for evaluating dynamic response for experimentally obtained parameters. The experimental results show that the increase of applied electric current in the MR damper, the damping force will increase remarkably up to the saturation value of current. The numerical simulation results that stiffness of the MR damper can be varied with the current value and increase the damping forces with the reduced amplitude of excitation. Experimental and theoretical results of the MR damper characteristics demonstrate that the developed MR damper can be used for vibration isolation and suppression. [ABSTRACT FROM AUTHOR]

The paper mainly investigates the effect of different materials on metal foam magnetorheological (MR) fluid damper by simulation and experiment. The damper, with MR fluid stored in the metal foam, has the advantages of low cost and long lifetime. First the software ANSYS FEM is used to simulate the magnetic field in the different metal foams, and the magnetic flux density in the working gap and magnetic field distribution are obtained in the different excited current. Besides, a testing system, including the metal foam MR fluid damper, DC motor with speed controller, force sensor with amplifier, DAQ card and PC with LabVIEW software, is built to investigate its performance. Next the relationship between damping force and current is also obtained by changing the excited currents. As the applied samples, metal foam Ni (nickel) and metal foam Cu (cuprum) are selected to store MR fluid. The results show that, compared to metal foam Cu, metal foam Ni can provide a larger magnetic flux density. And the experimental results show that metal foam Cu MR fluid damper has a larger damping force, which implies that, for the metal foam MR dampers, the extracted volume of magnetorheological fluid (MR fluid) has a greater influence than the magnetic flux density. [ABSTRACT FROM AUTHOR]

In this study, an magnetorheological (MR) damper has been designed based on its energy harvesting capability which combines the key benefits of energy generation (reusing lost energy) and magnetorheological damping (controllable damping force). The energy harvesting part has a magnet and coil arrangement to generate energy. A two-dimensional axisymmetric model of the proposed magnetorheological damper is developed in COMSOL Multiphysics where different magnetic field properties are analysed generally by finite element method. Finally, the energy harvesting capability of the proposed magnetorheological damper model is tested by a universal testing machine and observed through an oscilloscope. The maximum induced output voltage was around 0.7 V. [ABSTRACT FROM AUTHOR]

Flexible risers are used in the oil industry to transport liquids and gas from the seafloor to extraction and production equipment at the sea suiface. Ongoing research aims at using composite materials instead of steel, in order to reduce weight and increase stiffness, Ensuring an optimal load transfer between the composite and metal components is very important. This paper presents an improved method for anchoring a flat fiberreinforced tendon using a double grip system with self-locking grips. The novelty is the combination of new experimental results and finite element (FE) analysis to develop a superior dry friction grip. Experimental results are carried using a dedicated test setup, through which the test parameters can be accurately controlled. The efficiency of the grip system during pullout is superior to results obtained with flat grips. Numerical results offer an in-depth understanding of the influence between friction, geometrical parameters, and performance, making it possible to optimize the design. Results show that this grip system offers immediate technical applications, in a variety of conditions. [ABSTRACT FROM AUTHOR]

The liquid flow through orifices produces larger damping, whereas the cushioning effect comes from the fluid’s compressibility. The hydraulic damper design is subjected to constant high pressure necessary to achieve the required forces, which drastically increases during the dynamic operation. Damper has different orifices or piston valves that lead to different flow losses. The main objective behind this work is to investigate the effect of number of orifices on the damping force at different velocities for rear side two-wheeler automobile mono tube damper. Three different orifice opening cases are considered for simulations and experiments such as two-orifice opening, six-orifice opening and ten-orifice opening. [ABSTRACT FROM AUTHOR]

The Lysekil wave energy converter (WEC), developed by the wave energy research group of Uppsala University, has evolved through a variety of mechanical designs since the first prototype was installed in 2006. The hundreds of engineering decisions made throughout the design processes have been based on a combination of theory, know-how from previous experiments, and educated guesses. One key parameter in the design of the WECs linear generator is the stroke length. A long stroke requires a taller WEC with associated economical and mechanical challenges, but a short stroke limits the power production. The 2-m stroke of the current WECs has been an educated guess for the Swedish wave climate, though the consequences of this choice on energy absorption have not been studied. When the WEC technology is considered for international waters, with larger waves and challenges of energy absorption and survivability, the subject of stroke length becomes even more relevant. This paper studies the impact of generator stroke length on energy absorption for three sites off the coasts of Sweden, Chile and Scotland. 2-m, 4-m, and unlimited stroke are considered. Power matrices for the studied WEC prototype are presented for each of the studied stroke lengths. Presented results quantify the losses incurred by a limited stroke. The results indicate that a 2-m stroke length is likely to be a good choice for Sweden, but 4-m is likely to be necessary in more energetic international waters. [ABSTRACT FROM AUTHOR]

Magnetorheological fluids containing nanometer size needle-like nonmagnetic particles whose long axis is 194 nm and aspect ratio is 8.3 are prepared as new magnetic functional fluids. Viscous properties of the fluids are investigated experimentally. Shear stress and viscosity coefficient are measured by using the rheometer which has the additional equipment for measurement in the presence of magnetic field. When the total volume fraction of the particles in the fluid is constant (0.30), larger amount of needle-like particles in the fluid gives larger viscosity in the absence of magnetic field. In the contrast, the viscosity and shear stress of the fluid containing 4% needle-like nonmagnetic particles and 26% micrometer sphere magnetic particles take large value than those of other fluids in the presence of magnetic field. [ABSTRACT FROM AUTHOR]

• B-spline curve is used to form the shape of a magnetorheological damper piston. • The optimal piston shape is obtained by tuning the parameters of B-spline curves. • The Quasi-Newton algorithm is used to optimize the piston shape. • The working conditions of the optimized magnetorheological damper are analyzed. Taking advantage of the magnetically controllable rheological properties of magnetorheological (MR) fluid, MR dampers are widely used in many engineering fields. Much effort has been made to improve the performance of MR dampers. Structural optimization is one of the popular methods to effectively improve the performance parameters of MR dampers. Most MR damper optimizations are focused on parts with regular shape, but shapes governed by equations can bring out more possibilities and further optimal results. Therefore, in this paper, a new MR damper is designed and optimized based on B-spline curves in order to maximize the controllable output damping force while saving the input power for the prosthetic knee. First, design principle of dividing the parts of the MR damper into two categories is introduced. Then, B-spline curves are used to form the piston shape, which is one of the crucial parts inside the magnetic circuit. Later, the optimal B-spline curve and other geometric parameters inside the magnetic circuit are obtained through simulation and optimization. Furthermore, the optimized MR damper is fabricated, assembled and tested. Finally, the proposed MR damper is compared with the ones in our previous work. Experimental results match well with the simulation ones. When working at the frequency of 1.0 Hz and the amplitude of 10 mm, the proposed MR damper has large maximum damping force and dynamic ratio, with acceptable equivalent damping. The proposed MR damper also performs better than the prototypes in our previous work in terms of maximum damping force, field dependent force, equivalent damping, dynamic range, and force-to-power ratio. [ABSTRACT FROM AUTHOR]

• A heavy load energy harvesting shock absorber is proposed with its precise model. • Sensitivity analysis is conducted to investigate its damping quantificationally. • Resistance and gear ratio affect equivalent damping coefficient significantly. • The optimal resistance range under different parameter matching is determined. • Excitation frequency and amplitude impact damping and absorbing energy drastically. In this paper, a mechatronic shock absorber based on ball screw pair is designed, which can produce large damping force under the same working conditions, the dynamic model of mechatronic shock absorber is established, in which the damping force is divided into inertial damping force, electromagnetic damping force, and mechanical damping force, respectively. The global sensitivity analysis methodology, named Sobol based on variance, is employed to carry out parameter sensitivity analysis, the parameters of excitation amplitude, frequency, load resistance, motor back electromotive force constant, motor electromagnetic torque constant, lead screw, motor reducer transmission ratio are investigated comprehensively. Results indicate that for the operational conditions, the load resistance has the greatest impact on equivalent damping coefficient; while for the structural parameters, the transmission ratio has the greatest impact on equivalent damping coefficient. Based on the results of parameter sensitivity analysis, aiming at vehicle ride comfort, take a certain type of light truck as an example, the optimal approach of load resistance range under different structural parameters are proposed. Finally, the experimental tests are conducted, and validates the established dynamic model. This work provides a theoretical basis for guiding the future design of the mechatronic shock absorber. [Display omitted] [ABSTRACT FROM AUTHOR]

In this article, an alternative to the classical dynamic equation formulation is presented. To achieve this goal, we need to derive the reciprocal theorem in rates and the principle of virtual work in rates, in a small deformation regime, with which we will be able to obtain an expression for damping force. In this new formulation, some terms that are not commonly considered in the classical formulation appear, e.g., the term that is function of jerk (the rate of change of acceleration). Moreover, in this formulation the term that characterizes material nonlinearity, in dynamic analysis, appears naturally. [ABSTRACT FROM AUTHOR]

In the paper a theoretical analysis of the monotube and twin-tube shock absorbers' suitability for sports cars, based on the thermodynamic processes occurring in them, is done. Investigation is carried out by modelling the transfer of heat, which forms in the shock absorbers of different constructions, to the atmosphere and the distribution of temperature in their bodies under different conditions. The thermodynamic processes that happen in the shock absorbers are represented by dependency graphs according to the linear heat flux density and the heat transfer to the atmosphere coefficient. In the article theoretically and by experiments the way the thermodynamic processes change the shock absorbers oil viscosity and density characteristics as well as the damping force is also analysed. [ABSTRACT FROM AUTHOR]

Aiming at the restricted application range of magnetorheological damper (MRD) with external power supply, based on the working characteristics of MRD and the investigation about harvesting energy from the vibration, a new type of Energy-regenerative MRD (called selfpowered MRD) was proposed. According to the analysis on function modules of Energy-regenerative MRD, the design methods of MRD integrated Energy-regenerative device was investigated to confirm their structure parameters, the electrical circuit was designed in accordance with Energy-regenerative device. Particularly, at the vibration condition of 1 Hz to 3 Hz frequencies and 10 mm amplitude, by utilizing the finite element software Ansoft, the simulation about power output of Energy-regenerative was performed, then the capacity of damping force produced by MRD under power output of Energy-regenerative was simulated. The simulation results show that the Energy-regenerative MRD can produce 1 072 N ~ 2 028 N, at the vibration condition of low frequency and small amplitude, the energy-regenerative MRD is able to change its damping characteristics without external power supply. [ABSTRACT FROM AUTHOR]

The damping force of elastomer buffer in shock environment is the research object of this paper. The impact experiment and data simulation are used to understand the whole mechanical system. Equation with velocity and damping force is used for modeling according to the specific type of the elastomer buffer. The data of velocity and damping force is obtained by experimental data collection and pretreatment. Genetic algorithm is used to identify parameters according to the time invariant feature of traditional model. Through the results of parameter identification by genetic algorithm it seems that the parameters have the time-varying characteristics. Therefore, time-varying method is used for parameter identification. Limited memory method, which is obtained by the improvement of traditional least square method, is used for time-varying parameter identification. And the fitting accuracy of the identification results is better than that of genetic algorithm. The numerical results prove that the model is effective and parameters are time-varying. [ABSTRACT FROM AUTHOR]

Viscous, magnetization and damping properties of magnetic compound fluids containing fibrous material such as alpha-cellulose were investigated experimentally. It is shown that adding fibrous material to magnetic functional fluids is effective on increasing viscosity on the fluid while the amplification ratio of damping force in the presence of magnetic field against damping force in the absence of magnetic field decrease with increase of volume fraction of the fibrous material. [ABSTRACT FROM AUTHOR]

In the nanopositioning system, a damping force is generated by eddy current in the cooling plate and it is a disturbing force for this system. In this paper, a new method is introduced to suppress eddy current by offsetting back EMF. In order to offset back EMF, several slits have been incorporated in the cooling plate, which can help with regulating the series order in every region. Based on the electromagnetic theory, the analytical model of new cooling plate is established. The analytical model and eddy current suppression effect of the new cooling plate are proven by experiment: 17% reduction in the damping force significantly help with reducing the thrust fluctuation, with less than 4% analytical error. [ABSTRACT FROM AUTHOR]

Damping properties of a damper utilizing magnetic particles are investigated experimentally. A group of magnetic particles is treated as the working fluid in a damper instead of oil. In the presence of magnetic field, the damping force of the particles damper drastically increases. The maximum damping force appears near the dead center of vibration and higher frequency produces stronger maximum damping force, when the vibration frequency is in the range of low frequency below 5 Hz. [ABSTRACT FROM AUTHOR]

Article deals with measurement and modelling of damping force of polyurethane foam specimen being compressed. The specimens were taken from car seats and differ by material density. For modelling of damping force during harmonical kinematical excitation the explicit formula is used. Its parameters are found by means of method based on evaluation of energy dissipated during one loading cycle and also on evaluation of position of damping force extreme. [ABSTRACT FROM AUTHOR]

Abstract: Dynamical behavior of particles in a Paul trap in the presence of damping force has been investigated. Position of trapped ions as a function of time, ion trajectories and the phase space curves considering the effect of the damping force were obtained. Four regions of stability for r and z components with the damping force as well as the maximum value of q when U =0 for the first region, namely q max, versus damping factor k were computed using the fourth-order Runge–Kutta method. Comparisons were made with the corresponding stability diagrams without the damping force effect recently published in the literature. The third and fourth stability regions in the presence of the damping force, the curve of q max as a function of k and the related equation are reported for the first time. [Copyright &y& Elsevier]

A quartz tuning fork-based atomic force microscopy for investigating the tip–sample interactions at the nanoscale in the shear-force mode is described. Results of force interactions (damping and elastic forces) can be obtained from the amplitude-phase-distance spectroscopy measurements made with a tuning fork with a tungsten tip and a sample surface. The influence of the interaction between tip and sample using the quality factor as an indicator is investigated. Furthermore, a simple model shows that the extension of a tuning fork-based AFM can be applied to quantitative analysis of the properties of the sample surface. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a new mathematical dynamic model of shock absorber is proposed to predict the dynamic characteristics of an automotive system. The performance of shock absorber is directly related to the car behaviours and performance, both for handling and ride comfort. Damping characteristics of automotive can be analysed by considering the performance of displacement-sensitive shock absorber (DSSA) for the ride comfort. The proposed model of the DSSA is considered as two modes of damping force (i.e. soft and hard) according to the position of piston. For the simulation validation of vehicle-dynamic characteristics, the DSSA is mathematically modelled by considering the fluid flow in chamber and valve in accordance with the hard, transient and soft zone. And the vehicle dynamic characteristic of the DSSA is analysed using quarter car model. To show the effectiveness of the proposed damper, the analysed results of damping characteristics were compared with the experimental results, which showed similar behaviour with the corresponding experimental one. The simulation results of frequency response are compared with the ones of passive shock absorber. From the simulation results of the DSSA, it can be concluded that the ride comfort of the DSSA increased at the low-amplitude road condition and the driving safety was increased partially at the high-amplitude road condition. The results reported herein will provide a better understanding of the shock absorber. Moreover, it is believed that those properties of the results can be utilised in the dynamic design of the automotive system. [Copyright &y& Elsevier]

Abstract: In this Letter, the determination of the damping force between the atomic force microscope (AFM) tips and sample is regarded as an inverse vibration problem. The inverse solution methodology based on the conjugate gradient method is presented for estimating the interaction force and the damping force. The method is required to treat the inverse problem using available displacement measurements of AFM cantilever. Numerical results show that the method can accurately estimate the interaction force and the damping force even for problems with error of displacement measurement. In addition, the initial guesses for the interaction force can be arbitrarily chosen and the computing time required for the inverse calculations takes less than one second using a Pentium III-450 MHz PC. [Copyright &y& Elsevier]

The pinch mode behavior and its pressure profile. • A mathematical model of a magnetorheological fluid in pinch mode is suggested. • The model proves incline of a pressure variation is altered by magnetic intensity. • The hardware test validates the effectiveness of the mathematical model. The flow behaviors of a magnetorheological fluid (MR fluid) can be divided into four operating modes: flow, shear, squeeze and pinch mode. Despite many research works on the first three modes, the study on the pinch mode is relatively few. This study proposes a new mathematical model of the pinch mode flow motion of MR fluid and its fidelity is verified through a comparison with experimental results. In order to achieve this goal, the flow configuration of the pinch mode is provided followed by the magnetic analysis to design an appropriate magnetic circuit and to obtain the relationship between the magnetic intensity and applied current. Then, a mathematical model for predicting the pinch mode flow motion is formulated based on the quasi-static flow associated with several different conditions of the flow velocity. It is shown from a comparative work between the simulation results from the proposed mathematical model and experimental test results of the pinch mode MR damper that the proposed model fairly well predicts the field-dependent damping force in a low flow volume domain. [ABSTRACT FROM AUTHOR]

Summary: Sliding isolation system is one of the widely used base isolation systems. Traditional pure sliding base isolation systems, however, lack restoring force and possess low damping energy‐dissipation capacity. To overcome these disadvantages, a novel low‐friction sliding isolation system with adaptive behavior using sliding implant‐magnetic bearing (IMB) has been proposed in this paper. The isolation system consists of an upper block and a base block, both having polyurethane elastomer fillings and circumferentially implanted permanent magnets. This configuration allows an alterable damping force related to the eddy currents associated with bearing movement. Meanwhile, the interactions between magnets deployed in the upper and base blocks provide a capitalized repulsive force. A quasistatic test is performed to appraise the performance of the IMB system. Theoretical analysis and numerical simulation are carried out for quantification of the repulsive force, damping force, and Coulomb friction, which facilitates the modeling of the isolator. In order to verify the mitigation performance of the IMB deployed in seismic structures, a comparative study against the sliding hydromagnetic bearing (HMB) is carried out. It is revealed that the IMB exhibits reliable frictional performance and excellent damping energy‐dissipation capacity, which commits the adaptability of the IMB in protecting the structures from severe vibration induced by high‐frequency earthquake ground motions. Although exhibiting similar mitigation effectiveness to the HMB, the IMB has the capacity of fulfilling a more effective deformation constraint when subjected to pulse‐type ground motions. [ABSTRACT FROM AUTHOR]

Detection of the pulse signal at low signal‐to‐noise ratio (SNR) is difficult but meaningful. Some documents have already used coupled Duffing oscillators to detect non‐periodic pulse signal, but those oscillators have a few defects. This Letter presents a type of strong coupled Duffing oscillators system, and by using the generalised time scale transformation, the system can detect signal with any sampling frequency. The system is coupled by damping force and restoring force of the oscillators and has characteristics of high synchronisation speed and high coupling degree. The simulation results show that the system can detect large amplitude signal, large time‐width pulse, and plus–minus signal, and the detection SNR is lower than −27 dB. [ABSTRACT FROM AUTHOR]

We established the vibration governing equation for a magnetoelastic (ME) biosensor with target loading in liquid. Based on the equation, a numerical simulation approach was used to determine the effect of the target loading position and viscous damping coefficient on the node ("blind points") and mass sensitivity (Sm) of an ME biosensor under different order resonances. The results indicate that viscous damping force causes the specific nodes shift but does not affect the overall variation trend of Sm as the change of target loading position and the effect on Sm gradually reduces when the target approaches to the node. In addition, Sm decreases with the increase of viscous damping coefficient but the tendency becomes weak at high-order resonance. Moreover, the effect of target loading position on Sm decreases with the increase of viscous damping coefficient. Finally, the results provide certain guidance on improving the mass sensitivity of an ME biosensor in liquid by controlling the target loading position. [ABSTRACT FROM AUTHOR]