Vertical Damping Research Articles

Effect of the axlebox arrangement of the bogie and the primary suspension parameters on the rail corrugation at the sharp curve metro track

Rail corrugation is a problem that have perplexed the researchers and administrators in railway engineering for many decades with complex formation mechanism and various affecting factors. In this paper, two finite element models includes the track system and the wheelset with an inner axlebox type bogie and with an outer axlebox type bogie are established to analyze the stability of the system using the complex modal analysis. The multibody dynamic analysis of the vehicle-track system is conducted to determine the relevant parameters that are the foundation of the finite element analysis. The effect of the axlebox arrangement of the bogie, the damping and stiffness of primary spring, the lateral spacing between the primary suspension points and the weight of the bogie and the carbody on corrugation are investigated. The results show: the inner axlebox type bogie is favorable for suppressing the rail corrugation. When the lateral spacing between the primary suspension points is 0.86 m, the effect to suppress the rail corrugation is best. The higher the vertical stiffness of the primary spring, the more easily the rail corrugation occurs. Too high or too low vertical damping of the primary spring can easily cause rail corrugation. The heavier the vehicle and the bogie, the greater the possibility of the rail corrugation occurrence.

Study on the mechanism for the wheel polygonal wear of high-speed trains in terms of the frictional self-excited vibration theory

In the paper, the frictional self-excited vibration of a wheelset-track system caused by the saturated wheel-rail creep force is proposed as a possible mechanism for wheel polygonal wear of high-speed trains. The wheelset-track system model is established, which consists of a wheelset, two rails, some sleepers and a slab. The stability of the wheelset-track system is studied through the complex eigenvalue method. Results show that the unstable vibration frequency of the wheelset-track system is f= 495.01 Hz, which can lead to the 18th-order wheel polygonal wear. This simulation result is approximately consistent with the field measurement result. Furthermore, the parameters sensitivity analysis shows that increasing the vertical damping of the fastener to a certain extent can suppress or eliminate wheel polygonal wear. In addition, a transient dynamic analysis of the wheelset-track system with the wheelset eccentricity is conducted. Results indicate that the wheelset eccentricity is an important factor affecting wheel polygonal wear.

Dynamic characteristics of a quasi-zero stiffness vibration isolator with nonlinear stiffness and damping

A quasi-zero stiffness (QZS) isolator is devised to acquire the feature of high-static-low-dynamic stiffness. Cam–roller–nonlinear spring mechanisms, where two horizontal dampers are installed symmetrically, are employed as a negative stiffness provider to connect in parallel with a vertical spring. From the static analysis, the piecewise restoring force in the vertical direction of the system is inferred considering possible separation between the cam and roller. The stiffness characteristics and parameters for offering zero stiffness at the equilibrium position are then determined. The dynamic equation is established and used for the deduction of the amplitude–frequency equation by means of the Harmonic Balance Method. The definitions of force and displacement transmissibility are introduced, and their expressions are derived for subsequent investigations of the effects of horizontal spring’s nonlinearity, excitation amplitude, horizontal damping, and vertical damping on the transmissibility performance. The comparative study is implemented on the isolation performance afforded by the QZS isolator and an equivalent linear counterpart, whose static bearing stiffness is same as the QZS isolator. Results indicate that the system with softening nonlinear horizontal spring can exhibit better performance than that with opposite stiffness spring. With the increase in horizontal damping ratio, the force transmissibility is further suppressed in resonance frequency range but increased in a small segment of higher frequencies and tends to unite in high frequency range. However, the horizontal damper deteriorates the ability to isolate the displacement excitation to a certain extent. Besides, the isolation capability of the QZS system depends on the magnitude of excitation amplitude. The quasi-zero stiffness system possesses lower initial isolation frequency and better isolation ability around resonance frequency compared with the linear system. Therefore, the quasi-zero stiffness isolator has superior low-frequency ability in isolating vibration over its linear counterpart.

Dynamic study of a roller bearing in a planetary application considering the hydrodynamic lubrication of the roller/cage contact

A new multi-body dynamics model for the simulation of roller bearings in planetary applications is presented. Analytical relations are used to model the lubricated contacts involved in the bearing. In particular, the vertical damping of the oil film in the roller/cage contact is taken into account, in order to get an accurate estimation of the forces endured by the cage. Results are presented for the case of a planet gear roller bearing in a turbofan planetary gearbox in terms of roller/ring and roller/cage forces and their influence on the instantaneous cage speed. The flexibility of the outer ring is also modelled using a finite element model; its influence on the results, i.e. on the maximum roller/ring force and on the bearing dynamics, is presented.

Key parameter selection of suspended monorail system based on vehicle–bridge dynamical interaction analysis

ABSTRACTThis study aims to select the proper key parameter values of suspended monorail system (SMS) by analysing the vehicle–bridge dynamical interaction. First, a coupled dynamical model of vehicle–bridge system is established by using ANSYS parameter design language (APDL). Further, the car-body accelerations obtained by the proposed model and field test are systematically analysed in frequency domain. A sensitive parameter influencing the vehicle ride comfort is identified. The key parameter value of the bridge is selected with the objective to improve the vehicle-bridge vibration level. Finally, accounting the out-of-round tyre, the dynamical performance of vehicle and bridge is investigated under periodic harmonic disturbance, and proper values of secondary suspension parameters of vehicle subsystem are selected. Results show that the space between bridge stiffeners is a sensitive parameter that can aggravate the car-body acceleration. This space is finally suggested to be 1.2–1.4 m in order to effectively reduce the vehicle-bridge dynamical interaction. Controlling the vertical stiffness of secondary suspension to be less than 0.2 MN/m, the periodic harmonic disturbance can be effectively isolated. To ensure a reasonable vibration level of vehicle–bridge system suffering from periodic harmonic disturbance, the vertical damping of secondary suspension is suggested to be about 27 kN·s/m.

Prediction of vertical damping property of lead rubber bearings for building based on finite element analysis

Prediction of vertical damping property of lead rubber bearings for building based on finite element analysis

Optimal Control for Torpedo Motion based on Fuzzy-PSO Advantage Technical

The torpedo is a nonlinear object which is very difficult to control. Via to manage the rudder angle yaw, the diving plane angle, and the fin shake reduction, the torpedo yaw horizontal, the depth vertical and roll damping of the system are controlled accurately and steadily. In this paper, the particle swarm optimization is used to correct the imprecision of architecture fuzzy parameters. The coverage width of membership function and the overlap degree influence of neighboring membership functions are considered in the method to adjust dynamically from the system errors. Thereby optimizing the control signal and enhancing the torpedo motion quality. The proposed method results in a better performance compared to the other control method such as adaptive fuzzy-neural that proved effective of the proposed controller.

Damping modification factor for the vertical seismic response spectrum: A study based on Japanese earthquake records

This paper aims to establish a regional (Japanese) damping modification model for scaling the 5%-damped vertical seismic response spectra to other damping ratios. In doing so, 3198 strong vertical ground motion (VGM) records are selected from the Japanese seismic database, and their linear elastic response spectra are computed by the Newmark-β algorithm. Taking the 5%-damped vertical response spectra as benchmarks, the vertical spectral damping modification factors (DMFV) for ζ (damping ratio) = 0.5%, 1%, 2%, 3%, 4%, 6%, 7%, 8%, 9%, 10%, 12.5%, 15%, 17.5%, 20%, 25%, 30%, 35% and 40% are calculated. For structural design purpose, the DMFVs of both the vertical pseudo acceleration response spectra and the vertical absolute acceleration response spectra are calculated. The DMFV spectra have their peaks (for ζ < 5%) or valleys (for ζ > 5%) at T = 0.12 s (here T indicates spectral period), and their values get farther away from unity as earthquake magnitude or VGM epicenter distance increases. The effect of earthquake hypocenter depth, local site condition (represented by Vs30) and peak ground acceleration on DMFV generally shows no pattern. For each ζ, the mean DMFV-lgT curves are simulated by highly accurate piecewise functions. Moreover, it is revealed that the normal distribution model is feasible for representing the probabilistic properties of DMFV, especially in the short-to-medium period region where the skewness of the DMFV distribution is not quite pronounced. The standard deviations of DMFV are modeled by piecewise functions as well, yet it is emphasized that the variation of a damping-scaled spectral ordinate is jointly controlled by the probabilistic properties of DMFV and the uncertainties of the 5%-damped spectral ordinates.

Seismic Analysis of a Cable-Stayed Bridge Using the Finite Element Method.

In this paper, a cable-stayed bridge is modelled and analysed using the finite element method on Ansys. The damping effect is studied in the vertical and inclined directions as an earthquake effect is applied on the cable-stayed bridge in the longitudinal and lateral directions with changes to the number, direction, and value of the damping coefficient (c) of the dampers. The results show that increments in the number of dampers and damping coefficient in inclined dampers were more effective than changes to vertical dampers in longitudinal and lateral earthquakes.

Semi-analytical solution for a problem of a uniformly moving oscillator on an infinite beam on a two-parameter visco-elastic foundation

In this paper a semi-analytical solution for transverse vibrations induced by a moving oscillator is derived and validated. It is assumed that the oscillator is moving uniformly on an infinite beam, which may be subjected to a normal force, and is supported by a two-parameter visco-elastic foundation. Full evolution of deflection shapes is derived with the help of integral transforms and methods of contour integration. Analytical solution of the problem is presented in the Laplace domain. In the time domain, vibrations are given by a sum of truly steady-state part, induced harmonic part and transient vibration that has generally low importance and rapidly decreasing tendency. Except for the transient vibration, solution is expressed as a finite sum of analytical expressions (sum of residues), of which each has at most one parameter that has to be obtained numerically. With the help of iterative techniques proposed in this paper, these parameters can be easily determined with any precision. These parameters are named as the induced frequencies and as such can identify the onset of unstable behaviour. Thus, derivations in this paper allow to predict not only the onset of instability, but also its severity, which is important for mitigation measures.Transverse vibrations obtained for infinite beams are validated by analyses on long finite beams, exploiting a program written in Matlab software, that was previously validated by finite element software LS-DYNA. The effects of the normal force, Pasternak modulus, harmonic component of the vertical force and foundation damping are discussed.

Control of Intra-Bunch Vertical Motion in the SPS with GHz Bandwidth Feedback

A GHz bandwidth vertical beam feedback system has been in development at the CERN SPS for control of unstable vertical beam motion in single bunch and bunch train configurations. We present measurements and recent studies of stable and unstable motion for intensities up to 2 × 1011 p/bunch[1]. The system has been operated at 3.2 GS/s with 16 samples across a 5-ns RF bucket (4.2 ns 3σ bunch at injection) and experimental results confirm damping of intra-bunch instabilities in Q20, Q22 and Q26 optics configurations. Instabilities with growth rates of 1/200 turns are well-controlled from injection, consistent with the achievable gains for the 2 installed stripline kickers with 1 kW broadband power.Measurements from multiple studies in single-bunch and bunch train configurations show achieved damping rates, control of multiple intra-bunch modes, behavior of the system at injection (including interaction with the existing vertical damper) and final damped noise floor. The work is motivated by anticipated intensity increases from the LIU and HL-LHC upgrade programs [2], and has included the development of a new 1 GHz bandwidth slotline kicker structure and associated amplifier system.

Oscillatory Motion of Microdroplets of a Droplet Cluster in a Linearly Nonuniform Electric Field

The forces acting on freely levitating water microdroplets in the structure found 15 years ago and called the droplet cluster (A. A. Fedorets, 2004) are considered. It is shown that lowfrequency vertical damping microdroplet oscillations can take place in such a cluster near the equilibrium position, which also exist in the case of instantaneous turn-on of an external electric field. These oscillations are considered from the viewpoint of the Fourier analysis.

Damping Oscillations of Microdroplets of a Droplet Cluster in an External Electric Field

The forces acting on levitating water microdroplets in the structure of a droplet cluster (A.A. Fedorets, 2004) have been analyzed. It is found that microdroplets in the cluster should undergo low-frequency vertical damping oscillations near the equilibrium position. Oscillations occur also when switching on an external electric field, which affects the oscillation frequency and equilibrium position. Microdroplets are shown to lose their stability in the critical range of parameters. The electric fields are calculated in the simplest experimental scheme for simulating the effect of electric field on a droplet cluster.

Analysis of Flexible Car Body of Straddle Monorail Vehicle

Based on the finite element model of straddle monorail vehicle, a rigid-flexible coupling dynamic model considering vehicle body’s flexibility is established. The influence of vertical stiffness and vertical damping of the running wheel on the modal parameters of the car body is analyzed. The effect of flexible car body on modal parameters and vehicle ride quality is also studied. The results show that when the vertical stiffness of running wheel is less than 1 MN / m, the car body bounce and pitch frequency increase with the increasing of the vertical stiffness of the running wheel, when the running wheel vertical stiffness is 1MN / m or more, car body bounce and pitch frequency remained unchanged; When the vertical stiffness of the running wheel is below 1.8 MN / m, the vehicle body bounce and pitch damping ratio increase with the increasing of the vertical stiffness of the running wheel; When the running wheel vertical stiffness is 1.8MN / m or more, the car body bounce and pitch damping ratio remained unchanged; The running wheel vertical damping on the car body bounce and pitch frequency has no effect; Car body bounce and pitch damping ratio increase with the increasing of the vertical damping of the running wheel. The flexibility of the car body has no effect on the modal parameters of the car, which will improve the vehicle ride quality index.

Seismic Response Analysis of an Isolated Structure with QZS under Near‐Fault Vertical Earthquakes

Seismic isolation devices are usually designed to protect structures from the strong horizontal component of earthquake ground shaking. However, the effect of near‐fault (NF) vertical ground motions on seismic responses of buildings has become an important consideration due to the observed building damage caused by vertical excitation. As the structure needs to maintain its load bearing capacity, using the horizontal isolation strategy in vertical seismic isolation will lead to the problem of larger static displacement. In particular, the bearings may generate large deformation responses of isolators for NF vertical ground motions. A seismic isolation system including quasi‐zero stiffness (QZS) and vertical damper (VD) is used to control NF vertical earthquakes. The characteristics of vertical seismic isolated structures incorporating QZS and VD are presented. The formula for the maximum bearing capacity of QZS isolation considering the stiffness of vertical spring components is obtained by theoretical derivation. From the static analysis, it is found that the static capacity of the QZS isolation system with vertical seismic isolation components increases when the configurative parameter reduces. Seismic response analyses of the seismic isolated structure model with QZS and VD subjected to NF vertical earthquakes are conducted. The results show that seismic responses of the structure can be controlled by setting the appropriate static equilibrium position, vertical isolation period, and vertical damping ratio. Adding a damping ratio is effective in controlling the vertical large deformation of the isolator.

Study on Influence of Diversified Parameters of Vehicle and Track on Wheel Hollow Wear

Wheel hollow wear of high‐speed train is one of the main damage types for the wheel. By optimizing the vehicle and track parameters and matching the wheel‐rail profile, the hollow wear of wheel can be reduced. In order to study the sensitivity of vehicle and track parameters to the wheel hollow wear, the sensitivity of suspension parameters and the track parameters of the CRH2Ctype high‐speed train wheel on the hollow wear of the wheel was studied by the parameter sensitivity analysis method. The concept of the cumulative wear power dissipation was put forward. The distribution characteristics of the wheel hollow wear under the different wheel/rail treads matching were forecasted. The results show that the damping of antihunting motion damper of the vehicle is the most sensitive to the maximum cumulative wear power dissipation of the wheel, followed by the longitudinal stiffness of tumbler journal box node, lateral stiffness of air‐spring suspension, vertical damping of primary suspension, vertical stiffness of track, and vertical damping of track. According to the analysis from the combination of sensitive parameters, the cumulative wear power dissipation is unevenly distributed in the lateral direction of the wheel tread and has the obvious peak area, which is basically the same as the actual wear distribution location in the field. The matching of the LMA wheel tread and the CN60N rail tread is a good choice to slow down the hollow wear and reduce the wheel wear rate. And the wheel reprofiling should be timely carried out, otherwise the wear rate would increase and the hollow wear would become more serious.

Ion Friction and Quantification of the Geomagnetic Influence on Gravity Wave Propagation and Dissipation in the Thermosphere‐Ionosphere

AbstractMotions of neutrals and ions in the thermosphere‐ionosphere (TI) do not, generally, coincide due to the presence of the geomagnetic field and associated electromagnetic forces affecting plasma. Collisions of ions with gravity wave (GW)‐induced motions of neutrals impose damping on the latter. We derive a practical formula for the vertical damping rate of GW harmonics that accounts for the geometry of the geomagnetic field and the direction of GW propagation. The formula can be used in parameterizations of GW effects developed for general circulation models extending from the lower atmosphere into the mesosphere and thermosphere. Vertical damping of GW harmonics by ion‐neutral interactions in the TI depends on the geometry of the geomagnetic field but not the strength of the latter. The ion damping of harmonics propagating in the meridional direction (in the geomagnetic coordinates) maximizes over the poles and reduces to zero over the equator. Waves propagating in the zonal direction are uniformly affected by ions at all latitudes. Accounting for the anisotropy produces changes in the GW drag in the F region of more than 100 m s−1 d−1, cooling/heating rates of more than 15 K d−1, and in GW temperature variance of disturbances by more than 5 K.

Analysis and suppression of a self-excitation vibration via internal stiffness and damping nonlinearity

This work concerns the usage of the internal stiffness and damping nonlinearity for vibration suppression in a van der Pol–type mechanical self-excitation system. Changing the vertical or horizontal damping could limit the growth of the flow-induced instability. Applying harmonic balance method, the energy transfer for the self-excitation vibration is investigated through the limit circle. The steady amplitude of the limit circle is a key parameter that could be used to evaluate the effectiveness of the self-excitation oscillation suppressing. Increasing horizontal damping could reduce the rate of roll on for the steady amplitude curve of the limit circle, but the critical flow velocity for the limit circle occurring is minimally affected. Increasing vertical damping could increase the critical flow velocity, but the rate of the roll on is virtually unaffected when the parameters are properly chosen.

Precast industrial buildings in Southern Europe: loss of support at frictional beam-to-column connections under seismic actions

This paper presents the evaluation of the loss-of-support conditions in frictional beam-to-column connections of industrial precast concrete buildings under seismic actions. This type of connection is widespread throughout Southern Europe in non-seismically designed industrial precast buildings. First, geometric properties of industrial precast buildings and of the frictional beam-to-column connections, together with reference values for the friction coefficient, are reviewed. Then, earthquake time histories taken from the European Strong-Motion sets and recordings of the two major shocks of the 2012 Emilia-Romagna events are presented and discussed showing the importance of the vertical component. Two dynamic models of increasing complexity are used to ascertain loss-of-support conditions under seismic action. The first model is an elastic one, representing a single frame of the industrial buildings. Results are obtained according to: (1) 2D analyses, disregarding the time correlation between the response peaks along the horizontal and vertical directions, (2) 2D analyses taking into account time correlation, and (3) 3D analyses to evaluate also directionality effects. The second model is a 2D non-linear planar frame developed within the OpenSees framework. Results show that simplified (linear) models are a good proxy to more refined (non-linear) ones. However, one must resort to non-linear models if differential displacements between beam and column are of interest. The non-linear numerical investigations show that friction coefficient, horizontal and vertical periods and damping, and column reinforcement ratio are the key variables in estimating the loss-of-support conditions.

Kineto-dynamic design optimisation for vehicle-specific seat-suspension systems

ABSTRACTDesigns and analyses of seat-suspension systems are invariably performed considering effective vertical spring rate and damping properties, while neglecting important contributions due to kinematics of the widely used cross-linkage mechanism. In this study, a kineto-dynamic model of a seat-suspension is formulated to obtain relations for effective vertical suspension stiffness and damping characteristics as functions of those of the air spring and the hydraulic damper, respectively. The proposed relations are verified through simulations of the multi-body dynamic model of the cross-linkage seat-suspension in the ADAMS platform. The validity of the kineto-dynamic model is also demonstrated through comparisons of its vibration transmission response with the experimental data. The model is used to identify optimal air spring coordinates to attain nearly constant natural frequency of the suspension, irrespective of the seated body mass and seated height. A methodology is further proposed to identify optimal damping requirements for vehicle-specific suspension designs to achieve minimal seat effective amplitude transmissibility (SEAT) and vibration dose value (VDV) considering vibration spectra of different classes of earthmoving vehicles. The shock and vibration isolation performance potentials of the optimal designs are evaluated under selected vehicle vibration superimposed with shock motions. Results show that the vehicle-specific optimal designs could provide substantial reductions in the SEAT and VDV values for the vehicle classes considered.