Rolling Friction Force Research Articles

An Experiment on the Dwell Time Effect of Rubber Seal O-Rings: Friction Force in Intermittent Reciprocating Motion

The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring’s rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.

The effect of the track plan on the damage to rails by contact fatigue crambling

An analysis of foreign and domestic experience in improving traffic safety while extending the service life of rails and improving their interaction with the wheels of rolling stock shows that the working conditions of rails are much more difficult in curved sections of the track, especially in the outer thread, due to the intense impact of the ridges of the wheels of rolling stock on the lateral working One of the reasons for the formation of contact fatigue stains on the lateral working surface of the rail head is the presence of tangential stresses that occur in the absence of perpendicular pressure of the wheel on the rail head. In addition, the movement of the wheels on the rails is accompanied by slippage, which appears due to the taper of the wheels and the occurrence of the wheel crest on the rail head. A typical case of the wheel crest running over the rail head is the movement of the crew along curved sections of the track. In this case, the guide axle runs over one of the wheels on the rail head. As a result, there is a transverse slip of the wheel on the rolling surface and friction forces between the wheel and the rail are appropriately oriented to the axes. These processes, enhanced by an increase in dynamic action, cause more intense damage to the rail heads by defects 11 in the curves, while defects mostly appear on the outer rail thread.

Establishment of scratching force model for micro-removal of SiCp/Al composites by ultrasonic vibration

In the process of micro-removal machining SiCp/Al, the real-time prediction of cutting force is of great significance to ensure the surface quality of the workpiece and safe production. Based on the two major sources of cutting forces: the elastic-plastic deformation resistance of the machined material and the friction between the tool and the material, this paper established an ultrasonic vibration-assisted scratching force model by considering four aspects: chip formation force, SiC particle breaking force, tool and Al matrix friction force and rolling friction force. The model was experimentally validated by a self-built ultrasonic scratching device, and the effects of scratching speed, SiC particle volume fraction, and ultrasonic amplitude on the scratching force were investigated. The results showed that the scratching force is minimum when the scratching speed is 400 mm/min for both ordinary scratching (OS) and ultrasonic vibration-assisted scratching (UVAS). As the volume fraction of SiC particles increases, the scratching force gradually increases. Under the same experimental conditions, the force of UVAS is much smaller than OS. The maximum error between the experimental value and the predicted value of the model is 33% and gradually decreases with the increase of scratching speed and SiC volume fraction. The overall trend of the two is consistent, which proves the feasibility of the scratching force model. This study can provide some theoretical guidance for the force control when machining SiCp/Al. The ultrasonic vibration-assisted scratching force model was established by considering the chip formation force, SiC particle breaking force, tool matrix friction force, rolling friction force and ultrasonic vibration applied. And the model was verified by experiments. • A new machining process of ultrasonic vibration-assisted scratching was proposed. • An ultrasonic vibration-assisted scratching force model was established. • The experimental values were in good agreement with the model predicted value, which verified the feasibility of the established model.

Mechanical models for the adhesive friction of nano- and micro-particles

Friction is common in human’s daily life and production that may be either detrimental or beneficial. The friction law at microscale or even smaller scales nevertheless is lacking. In the present work, on the basis of JKR model for adhesive contact and by analogy with the emission of dislocations at a crack tip, the critical tangential force has been obtained for the onset of sliding. When the tangential force in adhesive contact induces a torque at the interface, a mechanical model for rolling adhesion has been presented on the basis of the assumption that it is governed by adhesion hysteresis. The critical torque and tangential force for rolling onset have been determined, which may be taken as measure for the rolling friction force. Comparisons with relevant experiments and models have been made to support the present concept. A kind of friction duality in small sized particles can thus be predicted.

Effects of Carriage Flexibility on Friction Force in Linear Ball Guides

Abstract This article presents the effects of carriage flexibility on the friction force in linear ball guides, which includes hydrodynamic rolling friction, elastic hysteresis friction, slip friction, and drag friction. To this end, we developed a computational model for the friction force in linear ball guides that accounts for the carriage flexibility. The model was validated through experiments, and the results prove that it provides more accurate friction-force estimates than the conventional model under the assumption of a rigid carriage. Subsequently, we examined the effects of external load, preload, and speed on the friction force. Among several friction components, hydrodynamic rolling friction makes a major contribution to the total friction force. Ball contact loads, which significantly vary with carriage flexibility, were found to influence the hydrodynamic rolling, elastic hysteresis, and slip friction forces. The proposed model considering carriage flexibility in linear ball guides is expected to find use in the design and operation of linear-ball-guide systems.

ESTIMATION OF ENERGY INDICATORS OF A MULTI MOTOR TRACTOR ELECTRIC DRIVE FOR PUBLIC TRANSPORT

The purpose of the work is to analyze the energy parameters of a multi-motor asynchronous traction electric drive in a city vehicle to ensure a reduction in electric energy losses when driving along the route. The research was carried out for a lightweight double-decker bus, the maximum number of passengers transported is set at 100 people. To achieve the goal, mathematical modeling was used in the MatLab package, in which energy losses were calculated in the multi-engine electric drive of a bus with a different number of traction asynchronous motors. The calculation was carried out for the most characteristic sections of the city cycle of the bus: constant modes of movement with different speeds and transient modes of acceleration. To control the speed of the engines, a proportional law was used to change the voltage on the stator winding and frequency, which correspond to the voltage frequency values at the stator winding of 25 Hz and 50 Hz and, respectively, the standard phase ratio of 110 V and 220 V. The change in the loading moment of the vehicle engines due to the change in the rolling friction force of the wheels for three cases of a complete, half-complete and empty bus is taken into account. The load change due to air resistance when the speed changes is taken into account. In operation it is shown that application of multi-motor asynchronous electric drive allows to reduce energy losses in traction asynchronous electric motors when vehicle is moving at constant speed and at acceleration at different number of carried passengers. Moreover, in order to achieve energy saving, the number of engines used in a multi-motor electric drive must vary depending on speed and acceleration, as well as on the total load moment of the multi-motor electric drive.

Vibration Characteristics of Rolling Mill System under Constraints of the Nonlinear Spring Force and Friction Force from Hydraulic Cylinder

Considering the two kinds of nonlinear constraints of rolling mill hydraulic cylinder, spring force and friction force, the vibration model of rolling mill system is established. The amplitude frequency response equations are obtained by using the average method. Comparing the time history curves of vertical vibration displacement of rolling mill system under the nonlinear spring force and friction force, the amplitude frequency characteristic curves are simulated. The external excitation amplitude is viewed as the bifurcation parameter, and the system bifurcation response changing with the external excitation amplitude is analyzed. The influence of the external excitation amplitude on the system stability is studied. The results indicate that the increase of the nonlinear spring force makes the rolling mill system’s unstable area to become wider, and the influence on the rolling mill system of nonlinear friction force behaves as the damping characteristics; the vibration of rolling mill system is alternating between the periodic, period-doubling, and the chaotic motion. The research results provide a theoretical support for restraining the vibration of the rolling mill system in the actual production process.

THE GRINDING MECHANISM ON A KNIFE CENTRIFUGAL GRINDING MACHINE

The article presents a methodology for calculating the force effect on a fibrous suspension of working bodies in a centrifugal grinding apparatus. The aim of the research is to calculate the force per tooth of an inertial body at different speeds of rotation of the rotor, to determine the effect of the circumferential speed of movement of inertial bodies on the grinding process of fibrous semi-finished products. The article discusses the mechanism of grinding on a centrifugal knife grinding apparatus, determines the tangential shear forces at the contact of the grinding satellite knives with the grinding bowl knives, determines the effect on the fiber of rolling friction forces and sliding friction forces when the grinding satellite knives come into contact with the grinding bowl knives, as well as the effect of specific pressure at the point of contact of the satellite knives with the grinding bowl knives under the influence of inertial forces. Based on the research results, it is scientifically substantiated that the forces arising at the minimum of the considered values of the rotation speed of inertial bodies are sufficient to break the fiber when using this installation for grinding fibrous semi-finished products. An increase in the speed of rotation of the satellites causes a positive change in the physical and mechanical characteristics of the finished castings.

Friction models for grease lubricated ball-race contacts

In this paper the authors theoretically investigated the influence of the hydrodynamic rolling friction forces in greased ball-race contacts at low loads. Two IVR-EHL transitions equations for hydrodynamic rolling friction forces have been applied to the ball-race contacts in a modified thrust ball bearing by using three types of greases having base oil viscosities between 40 mm2/s and 1000 mm2/s. Based on the total friction torque analytically estimated and experimentally determined has been evidenced the influence of the hydrodynamic rolling friction force on the total friction torque as the most important parameter for both proposed transition equations. The theoretical values of the total friction torque have been experimentally validated. The experiments was realized with a modified tree ball thrust bearing, without cage in a range of speed between 60 rpm and 400 rpm and for a normal load of 1.422 N for each ball.

Scaling law of contact time for particles settling in a quiescent fluid

Numerical simulations are conducted for the gravity–driven settling of two particles in a viscous quiescent fluid. A method is proposed to determine the scaling law of inter–particle contact time. The method is simple and general. The resulting scaling law explains the observations of literature and predicts the influences of particle–fluid density ratio, fluid viscosity, friction, rolling friction, and adhesion force.

Power loss in grease lubricated ball bearings

The authors theoretically investigated and then validated the power loss generated both by sliding and rolling in a modified thrust ball bearing with 3 balls operating at low axial load and grease lubrication. Based on ball forces and moment equilibrium, it has been determined the tangential forces on contact ellipses. The hydrodynamic rolling friction forces have been determined by using Biboulet & Houpert’s methodology considering base oil viscosity of the grease. Total power loss has been obtained as a sum of two components: power loss generated by sliding and power loss generated by rolling. Also, total friction torque has been theoretically determined and, as an alternative method, the total power loss has been calculated as a product between total friction torque and angular speed. Finally, based on previously experimental results, the power loss has been validated as the product between experimentally total friction torque and angular speed. A good correlation between the power losses determined by all three methods for 100, 200, 300 and 400 rpm have been obtained.

Elucidation of the role of cohesion in the macroscopic behaviour of coarse particulate systems using DEM

Ignoring the effect of cohesion between particles in Discrete Element Method (DEM) may incur in errors in the predictions of bulk properties. In this research work, we investigated the role of the cohesion force on macroscopic and microscopic characteristics of monodisperse and bidisperse iron ore granule systems, specifically on the angle of repose and coordination number of the assemblies. In order to simulate the cohesion between particles, a combination of the Hertz contact force and the pull-off force as predicted by the JKR model was employed. The monodisperse systems were made of particles whose sizes ranged between 3 and 10 mm. In order to analyse the effect of bidispersity on the characteristics of the particle assemblies, combinations of 10 mm particles with smaller particles (from 3 to 7 mm) were considered. The results showed that similarly to the rolling friction force, the cohesion force caused a considerable increase in the angle of repose, for the whole particle size range here studied. More importantly by increasing particle size, the rate at which the angle of repose increased as a result of the cohesion force, decreased significantly. This influence became more outstanding by increasing the value of the rolling friction coefficient, signifying the interplay between rolling friction force and cohesion force. In contrast to the case of non-cohesive particles, the effect of particle size on the angle of repose was independent of the rolling friction force in the presence of cohesion force and led to a decrease in the angle of repose for the entire range of rolling friction coefficient values. An empirical analysis of the obtained angles of repose confirmed the strong dependency of the angles on the Bond number and the rolling friction coefficient for cohesive particles. In addition, the coordination number of all studied systems was influenced by both parameters, as the value of coordination number increased by increasing cohesion force but decreased by increasing rolling friction force.

Fuzzy Sliding Mode Wheel Slip Ratio Control for Smart Vehicle Anti-Lock Braking System

With the development of in-wheel technology (IWT), the design of the electric vehicles (EV) is getting much improved. The anti-lock braking system (ABS), which is a safety benchmark for automotive braking, is particularly important. Installing the braking motor at each fixed position of the wheel improves the intelligent control of each wheel. The nonlinear ABS with robustness performance is highly needed during the vehicle’s braking. The anti-lock braking controller (CAB) designed in this paper considered the well-known adhesion force, the resistance force from air and the wheel rolling friction force, which bring the vehicle model closer to the real situation. A sliding mode wheel slip ratio controller (SMWSC) is proposed to yield anti-lock control of wheels with an adaptive sliding surface. The vehicle dynamics model is established and simulated with consideration of different initial braking velocities, different vehicle masses and different road conditions. By comparing the braking effects with various CAB parameters, including stop distance, braking torque and wheel slip ratio, the SMWSC proposed in this paper has superior fast convergence and stability characteristics. Moreover, this SMWSC also has an added road-detection module, which makes the proposed braking controller more intelligent. In addition, the important brain of this proposed ABS controller is the control algorithm, which can be used in all vehicles’ ABS controller design.

Studying the influence of structural-mode parameters on energy efficiency of the plough PLN-3-35

Current research addresses improving the effectiveness of the technological process of tilling the soil for agricultural crops. Based on the experimental study into the technological process of plowing, we have determined the efforts that act on the mechanism of a tractor’s attachment and a landside. It was found that universal casings for ploughs enhance plowing effectiveness by improving their stability. It was established that this leads to a decrease in the energy intensity of a plough casing during soil tilling, as well as provides for a uniform wear of the friction surface due to changes of its surface. It was determined that it is necessary to improve the components of tillage machinery in order to prolong the mean time between failures for working bodies and to reduce their traction resistance. It was established that the influence of a transverse pressure force that acts on a plough’s landsides has not been sufficiently studied. Not enough attention has been paid to determining the magnitude of a traction effort for each link in the mechanism of an attachment to a tractor’s assembly. One of the reserves for enhancing technological indicators and reducing energy intensity of a plowing assembly is the structural improvement of a standard plough’s landside. In the course of experimental study, we used a system for measuring the dynamics and energy efficiency of mobile machines, which refers to the tools for technical diagnosing and operational control. The strain gauges were placed on a plough’s landside, at the middle, left, and right links in the mechanism of a tractor’s attachment. It was determined that the mean value for a shear force of pressure acting on a landside installed at the bearer of a first plough’s casing is 1,610–1,668 N. At the bearer of a second casing, it is 1,525–1,630; at the bearer of a third casing, it is 1,848–1,870 N. It has been proposed to use, instead of a standard landside for the mounted ploughshare PLN-3-35, a flat-rounded element in the form of a disk with a hub that has a horizontal axis of rotation. The disk transforms the sliding friction forces into rolling friction forces. The application of disk reduces energy intensity of the plough by 13–15 %. That leads to a decrease in the traction effort of the plough’s casings, improves their stability, and lowers consumption of petrol, oil, and lubricants.

Modeling of cutting force prediction in machining high-volume SiCp/Al composites

Variations in cutting forces significantly influence the tool wear and part quality in machining high-volume SiC-particle-reinforced aluminum matrix (SiCp/Al) composites. Properties of the reinforcement SiC particles, such as size and volume fraction, contribute to the change in the cutting forces. This paper presents a cutting force model based on the geometrical and mechanical nature of the tool and workpiece, considering the effect of the SiC reinforcement particles. The cutting force is predicted as three components (Fz, Fx, and Fy) and the resultant cutting force Fτs. The cutting force was considered to generate three deformed zones: (a) shear deformed zone, (b) friction deformed zone on the chip–tool interface, (c) plow deformed zone. The effect of SiC reinforcement particles on friction deformed zone is analyzed emphatically. The friction force from friction deformed zone was obtained by calculating the sliding friction force and rolling friction force. To verify the feasibility and validity of the predicted model of cutting force, cutting experiments were performed with different combinations of cutting speed, feed rate, depth of cut, and tool nose radius. The predicted cutting force values demonstrate good agreement with the measured experimental cutting force values in most cutting conditions. The average percentages of the prediction error were 1.93%, 6.20%, and 10.48% for the Fz, Fx, and Fy components, respectively, thus proving the validity and accuracy of the predicted model of cutting forces.

Analytical substantiation of constructive parameters of rotating field board of plow’s body

The article shows importance of use of dump plowing for formation and maintenance of soil structure and pest control and diseases of cultivated plants. A significant drawback of plowing process is indicated, which is its high energy intensity. To reduce energy consumption, it is proposed to use rotating field boards, which allow replacing sliding friction forces with rolling friction forces. The article presents a description of design of plow’s body with rotating field board and notes that without a preliminary analytical study and justification of initial parameters, their use may not be effective. Analytical relations connecting value of radius of rotating field of board, rate of collapse of soil, allowable value of indentation of field board into soil and specific force of cutting resistance of soil that ability to use it for baseline technical parameters. To analyze obtained dependence, the article presents its graphical solution. The authors obtained an expression for determining the value of arm’s force of reference reaction from soil to balance a plow’s body, in addition, this indicator can be used to adjust a body when working on soils with different physical and mechanical parameters and at different depths.

Rolling Dynamics of Nanoscale Elastic Shells Driven by Active Particles.

Self-propelled elastic shells capable of transducing energy to rolling motion could have potential applications as drug delivery vehicles. To understand the dynamics of the nanoscale size elastic shells, we performed molecular dynamics simulations of shells filled with a mixture of active and passive beads placed in contact with an elastic substrate. The shell skin is made of cross-linked polymer chains. The energy transduction from active beads to elastic shell results in stationary, steady rolling, and accelerating states depending on the strength of the shell–substrate adhesion and the magnitude of a force applied to the active beads. In the stationary state, the torque produced by a friction (rolling resistance) force in the contact area balances that due to the external force generated by the active beads, and the shell sticks to the substrate. In the steady rolling state, a rolling friction force balances the driving force, and the shell maintains a constant rolling velocity. The scaling relationship between the magnitude of the driving force and the shell velocity reflects a viscoelastic nature of the shell skin deformation dynamics. In the accelerating state, the energy supplied to a system by active beads exceeds the energy dissipation due to viscoelastic shell deformation in the contact area. Furthermore, the contact area of the shell with a substrate decreases with increasing shell instantaneous velocity.

Design of Three New Cam-Based Constant-Force Mechanisms

Constant-force mechanisms are designed to keep a constant or nearly constant input force along a prescribed stroke of the mechanism. The implementation of this kind of mechanisms has been approached in literature using compliant mechanisms or through a certain combination of springs and nonlinear transmissions. In this work, three new constant-force mechanisms based on the use of springs, rollers, and cams are presented and analyzed. The rolling friction forces between the rollers and the cam are included in the force equilibrium equations and considered in the integration of the cam profile. The influence of the friction force on the input force as well as the design parameters involved is studied based on numerical techniques and simulations. In fact, the results evidence that to obtain a precise constant-force mechanism, rolling friction forces must be considered in the cam profile definition. The main design guidelines for the three constant-force mechanisms proposed are described.

Influence of Rolling Contact Surface and Contact Load on Fluctuation of Rolling Friction Force

This paper presents the experimental analysis for the fluctuation of rolling friction force, which deteriorates high precision motion in linear ball guideways. A simple drive with four tracks and four balls was used to investigate the influence of contact surface and contact load on the friction force fluctuation. To provide different surface integrity, ground, polished, and shot-peened surfaces were prepared. Experimental results showed that the friction force fluctuation was dependent on position change and influenced by the inclination angle of the rolling contact surface. The fluctuation of friction coefficient was inversely proportional to the cube root of the contact load. The wavelength analysis on the friction coefficient showed that friction coefficient was suppressed as the contact load increased. An empirical formula for estimating the friction force fluctuation was proposed based on these experimental results and a single ball friction model proposed by Ishikawa and Suda.

Badanie zależności tarcia tocznego od promienia kulki łożyskowej

There are two alternative historical laws of rolling resistance formulated by French scientist Coulomb and Dupuit. It has been decided to verify experimentally again, which of these laws describes freely rolling ball bearings on a hard surface better. An inducement to carrying out the measurements was the idea of the constant thickness of roadbed, which is consistent with Dupuit's theory. Measurements have been done using the damped oscillations in the pendulum bearings. Results have shown better consistency with the Coulomb's theory with small, but measurable deviations. These deviations were successfully explained by the so called "Cobblestones model". Parameters designated by this model have been successfully verified by the surface roughness's profile measurement. An additional theoretical aspect of this work is distinguishing two types of rolling friction force: dynamical and kinematical in an analogy to two types of specific heat capacity in the thermodynamics of gases.