Effects Of Rolling Friction Research Articles

A comprehensive comparison of Two-Fluid Model, Discrete Element Method and experiments for the simulation of single- and multiple-spout fluidized beds

We employ a two-fluid model (TFM) as well as a computational fluid dynamics coupled to discrete element method (CFD-DEM) approach to study the time averaged hydrodynamics of single- and multiple-spout fluidized beds. Simulations are validated against the experimental data of (van Buijtenen et al., Numerical and experimental study on multiple-spout fluidized beds, Chemical Engineering Science 66 (2011) 2368–2376) with four different interphase drag correlations. The kinetic theory of granular flow used for solving the motion of the solid phase in TFM, includes realistic particle–wall boundary conditions for momentum transfer and the flux of pseudo-thermal energy. Frictional stresses in TFM are modelled based on a μ(I)-rheology. We propose a new ad hoc modification of the μ(I)-rheology to account for the effect of rolling friction in TFM. In contrast, in CFD-DEM rolling friction is accounted by an additional torque. Our results show that there is a good agreement between both approaches with respect to time averaged volume fraction, solids velocities, solids fluxes and granular temperature.

DEM Parameter Calibration of Maize Seeds and the Effect of Rolling Friction

A set of suitable parameter values is crucial in discrete element method (DEM) simulations. As a non-spherical particle, the coefficients of rolling friction between maize seed particles and between the seed particles and the boundary are hard to measure directly and must be obtained by calibration. In this paper, taking three representative maize varieties as research objects, the necessity for the accurate calibration of the coefficients of rolling friction between seed particles and between seed particles and boundaries is investigated. Subsequently, by studying the sensitivity of the coefficients of rolling friction between seed particles and between seed particles and the boundary to the angle of repose test, the methods used to calibrate the coefficients of rolling friction between seed particles and between the particles and the boundary are determined. It can be seen from the results that the coefficients of rolling friction between the seed particles and between the seed particles and the boundary have a significant influence on the test results, so these two parameters must be accurately calibrated. Additionally, the coefficient of rolling friction between seed particles and the boundary has no effect on the piling angle, but the piling angle is highly sensitive to the coefficient of rolling friction between seed particles. By comparing the simulation results and the experimental results in the lifting cylinder and “self-flow screening” tests, the calibrated seed parameters were found to be accurate and valid.

Understanding the effect of rolling friction in the inclined track experiment

In general, undergraduate experimental physics laboratories do not usually have experiments designed to address rolling friction and to measure the value of the rolling friction coefficient. This work explores an experiment, which has the potential to arouse students’ curiosity about rolling friction by addressing a counterintuitive aspect of the behavior of a sphere that rolls up, stops and then rolls down on an inclined track. In fact, due to the difference in the net static friction in the upward and downward movements caused by the rolling friction term, the sphere’s acceleration when rolling upward is higher than when rolling downward. This difference, which had been predicted theoretically, was easily demonstrated graphically by video analysis, using both rubber and mouse balls. For two steel balls, this difference was more subtle, but it was still possible to detect it numerically. The experimental setup employed typical laboratory equipment and the free video analysis software Tracker to collect position and velocity data. The rolling friction coefficient was calculated with good precision by means of an angular coefficient of a fitted first-degree function involving appropriate variables.

An improved technique of finding the coefficient of rolling friction by inclined plane method

During the design process the mechanical engineer faces a challenge: the choice of the tribological parameters. Even most influential technical references offer ranges for the frictional characteristics. An emblematic example is the coefficient of rolling friction (CRF). The handiest solution in establishing the correct value of the CRF for a certain contact is to find it experimentally. One of the methods is the inclined plane manner. The weak point of the method consists in the particularly small values of the slope required to evidence the effect of rolling friction. The present work shows a technique for finding the CRF. The principle of the method consists in considering both the slope of the inclined plane and the torque of rolling friction as unknowns. The two parameters can be established by experimental finding of the acceleration of an axi-symmetric body, both for ascending and descending motions.

Effects of rolling friction on a spinning coin or disk

Experimental and theoretical results are presented concerning the motion of a spinning disk on a horizontal surface. The disk precesses about a vertical axis while falling either quickly or slowly onto the surface depending on the coefficient of rolling friction. The rate of fall also depends on the offset distance, in the rolling direction, between the centre of mass and the line of action of the normal reaction force. Euler’s angular momentum equations are solved to obtain estimates of both the coefficient of friction and the offset distance for a 50.6 mm diameter brass disk spinning on three different surfaces. The fall times varied from about 3 s on P800 emery paper to about 30 s on glass.

The influence of rolling resistance on the stress-dilatancy and fabric anisotropy of granular materials

The effects of rolling resistance on the stress-dilatancy behavior and fabric anisotropy of granular materials were investigated through a three-dimensional discrete element method (DEM). A rolling resistance model was incorporated into the DEM code PFC3D and triaxial DEM simulations under simulated drained and undrained conditions were carried out. The results show that there existed a threshold value of the rolling friction. When the rolling friction was smaller than this value, the mechanical behavior of granular materials under both drained and undrained conditions were substantially influenced by the rolling friction, but the influence diminished when it was larger than the threshold value. A linear relationship has been observed between the dilatancy coefficient and the natural logarithm of the rolling-friction coefficient when it was smaller than the threshold value. An increase in the rolling friction led to an increase in the fabric anisotropy of all strong contacts under both testing conditions until the threshold value was attained. The investigation on the effect of rolling friction on the microstructure of granular materials revealed that the rolling friction enhanced the stability of force chains, which resulted in the difference in the stress-dilatancy behavior. Finally, the relationship between the stress ratio q/p $$^{\prime }$$ and the fabric measure at strong contacts $$\hbox {H}_{\mathrm{d}}^{\mathrm{s}} /\hbox {H}_{\mathrm{m}}^{\mathrm{s}}$$ was found independent of the inter-particle friction, rolling friction and testing conditions.

Modeling a powered wheelchair with slipping and gravitational disturbances on inclined and non-inclined surfaces

Wheelchairs are broadly accepted and are widespread because of the assistance they provide to people with limited mobility. The design of a good controller generally involves the formulation of a comprehensive wheelchair model. Most dynamic models in the literature presume non-inclined planer surfaces within-doors, and therefore fail to take the combined effects of both gravitational forces and rolling friction on the usable-traction into consideration. Wheel-slip situations are also commonly neglected. This paper contributes to wheelchair modeling by proposing and formulating a dynamic model that considers the effects of rolling friction and gravitational potential on the wheelchair’s road-load force, on both inclined and non-inclined surfaces. The dynamic model is derived through the Euler Lagrange procedure, and wheel slip is determined by an approach that reduces the convectional number of slip-detection encoders. In the closed-loop model, the input-output feedback controller is proposed for tracking the user inputs by torque compensation. The optimality of the resulting minimum-phase closed-loop system is then ensured through the performance index of the non-linear continuous-time generalized predictive control with good simulation results.

METHOD OF THE DRIVE POWER DETERMINATION OF THE MECHANISMS OF THE BRIDGE CRANE MOVEMENT CONSIDERING THE ROLLING FRICTION

Purpose. The value of drive resistance to its movement is the main parameter at calculating the drive power of bridge crane. The value of the wheel rolling friction on the rails is one of the important parts of the resistance to movement. It is necessary to determine the dependence of static (dynamic) quantities of resistance to the bridge crane movement on a straight section of the track from the position of the bogie in the span, and explore the influence of the wheel flanges resistance for wear. Methodology. Using the analytical dependences for determining the rolling friction coefficient, that depends on the size of the half-width of the contact between the wheel and rail, the improved method for calculating the required drive power of the crane was proposed. Findings. With the proposed method of power calculation the characteristic curve of the crane wheel loads, the coefficient of rolling friction of the wheels and the crane resistance to movement from the position of the bogie on span were built. In the result of graphs analysis it was found that the engine power, obtained by the proposed method is higher than the recommended by the existing standards. The more precise formula for determining the total coefficient of sliding friction that takes into account the friction of wheel flanges on the rail is given. The characteristic curves of such coefficient of friction and the total resistance to movement of the position of the crane bogie were built. Originality. The scientists proposed an improved method of determining the required engine power of bridge crane, which takes into account the effect of rolling friction of the wheels on the rails and the bogie in the span. The improved formula for determining the coefficient of friction that takes into account the friction wheel flanges of the rail was given. The characteristic curve of this coefficient of friction and the total resistance movement of crane from the position of the crane bogie were built. Practical value. The application of the proposed method of determining the driving power of the crane allows determining its value more precisely, taking into account the impedance of the rolling friction of the wheels on the rails with a flanged on the rails. This approach enables better selection of elements of the mechanism of the bridge crane movement.

Effect of rolling friction on wall pressure, discharge velocity and outflow of granular material from a flat-bottomed bin

The present paper provides both experimental and DEM analyses of the filling and discharge of pea grains from a 3D flat-bottomed bin. In the DEM model, the fixed mean values of the experimentally determined single particle data, such as the particle density, Young's modulus, Poisson's ratio as well as the sliding and rolling friction coefficients were incorporated to analyse their effects on the macroscale indicators, such as the wall pressure, discharge velocities and material outflow parameters. The effect of rolling friction was studied based on the experimentally measured single particle rolling friction coefficient. This analysis is aimed at the quantitative prediction of flow parameters as related to the identification of material parameters.

Influence of rolling friction on single spout fluidized bed simulation

In this paper we study the effect of rolling friction on the dynamics in a single spout fluidized bed using Discrete Element Method (DEM) coupled to Computational Fluid Dynamics (CFD). In a first step we neglect rolling friction and show that the results delivered by the open source CFD–DEM framework applied in this study agree with previous simulations documented in literature. In a second step we include a rolling friction sub-model in order to investigate the effect of particle non-sphericity. The influence of particle–particle as well as particle–wall rolling friction on the flow in single spout fluidized bed is studied separately. Adequate rolling friction model parameters are obtained using first principle DEM simulations and data from literature. Finally, we demonstrate the importance of correct modelling of rolling friction for coupled CFD–DEM simulations of spout fluidized beds. We show that simulation results can be improved significantly when applying a rolling friction model, and that experimental data from literature obtained with Positron Emission Particle Tracking (PEPT) technique can be satisfactorily reproduced.

Modeling of the dynamic behavior of systems with rolling elements

Bearings, friction wheels, cams, etc. are widely employed elements in machine construction. The modeling of the dynamics of rolling friction plays therefore a crucial role in the simulation and optimization of such systems. This paper describes a recently developed transient-rolling-friction model with its application to different generic dynamical systems, to simulate the effects of rolling friction or traction on the dynamics of mechanical systems. The results, which are expressed in terms of the complex stiffness arising in the rolling-contact patches, show that the behavior depends on both the amplitude and the frequency of oscillation. For low amplitudes and frequencies, the behavior is quasi-linear. For increasing amplitudes and frequencies, however, strong non-linearities appear, leading to complex behavior.

Effect of rolling friction on binary collisions of spheres

Foerster et al. [Phys. Fluids 6, 1108 (1994)] proposed a binary collision model for spheres and a way to measure the constant impact parameters in the model. These three parameters were necessary to describe the translational momentum exchange during a collision. An extensive data set for a variety of materials was made possible using these measurements. In recent years many studies have shown that rolling friction between particles has strong effects on the bulk behavior of granular materials. In the present paper, an expansion of the previous collision model is studied to include rolling friction. It is shown that rolling friction does not affect the postcollision linear relative velocities for the conditions used in the impact experiments. Furthermore, it is suggested that the same impact experiment could potentially be used to measure the coefficient of rolling friction.

転がり摩擦モデルに基づく外乱オブザーバの始動時摩擦補償

This paper presents a rolling friction model-based initial friction compensation (IFC) by a disturbance observer for the fast and precise positioning of ball-screw-driven table systems. The effects of rolling friction in mechanisms should be suppressed in order to the achieve required control performance. In this study, therefore, a rolling friction model is adopted to compensate for the initial friction, so that delay-free friction estimation becomes possible. The proposed initial friction compensation method has been verified experimentally by using a prototype of industrial positioning devices.

Effect of vibration condition and inter-particle frictions on the packing of uniform spheres

We present a numerical study of the packing of uniform spheres under three-dimensional vibration using the discrete element method (DEM), focusing on the effects of vibration condition (amplitude and frequency) and inter-particle frictions (sliding and rolling frictions). The results are analysed in terms of packing density, coordination number (CN), radial distribution function (RDF) and pore structure. It is shown that increasing either the vibration amplitude or frequency causes packing density to increase initially to a maximum and then decrease. Both vibration frequency and amplitude should be considered to characterize the effect of vibration process on packing structure. The sliding and rolling frictions between particles can decrease packing density since they dissipate energy, although the effect of rolling friction is less significant. In line with the change of packing density, microstructural properties such as CN, RDF and pore distribution also change: a looser packing often corresponds to smaller CN, less peaked RDF and larger but more widely distributed pores.

Effect of Rolling Friction on the Development of {111} Texture in A1050 Aluminium Sheets

Commercially pure aluminum (A1050) sheets have been cold- rolled in vacuum, to obtain high friction between rolls and sheet. This cold-rolling in vacuum successfully introduced large shear deformation near the sheet surface. The shear strain is the highest at the sheet surface, and rapidly decreased to zero at the quarter thickness. These high shear strains are sufficient enough to produce {111} and {001} cold- rolling, or shear texture. Conventional cold-rolling texture such as (001) [100], is naturally observed at the mid-thickness. It is confirmed that a high shear strain and probably steep strain gradient through thickness have a sufficient effect on the increase in {111} cold-rolling texture near the sheet surface. {111} cold-rolling texture is proved to be effective in the evolution of {111} recrystallization texture. This development will be discussed based on the cold-rolling texture change.

Effects of Rolling Friction of the Balancing Balls on the Automatic Ball Balancer for Optical Disk Drives

This study is devoted to evaluating the performance of an automatic ball-type balance system (ABB) installed in optical disk drives (ODDs) with consideration of the rolling friction between the balancing balls and the ball-containing race of the ABB. Research has been conducted to study the performance of the ABB by investigating the nonlinear dynamics of the system; however, the model adopted to describe the rolling friction between the balancing balls and their race was a simple stick-slip type, which does not reflect the realistic contact dynamics, leading to an inaccuracy in predicting ABB performance. In this study, a complete dynamic model of the ABB including a detailed rolling friction model for the balls based on Hertzian contact mechanics and hysteresis loss is established. The method of multiple scales is then applied to formulate a scaled model to find all possible steady-state ball positions and analyze stabilities. It is found that possible steady-state residing positions of the ball inside the race are multiple and form continuous ranges. Numerical simulations and experiments are conducted to verify the theoretical findings, especially for the rolling friction model. The obtained results are used to predict the level of residual vibration, with which the guidelines on dimension design and material choices of the ABB are distilled to achieve desired performance.

Perturbation analysis of rolling friction on a turntable

The effect of rolling friction on the motion of a ball rolling on a uniformly spinning horizontal turntable is evaluated by a first-order perturbation approach, in which the unperturbed trajectories are the circular gyrations of the rolling ball in the absence of rolling friction. The analysis provides qualitative and quantitative understanding of the effect of rolling friction by itself and in combination with other ‘‘perturbations,’’ such as a tilt of the turntable.