Dynamic Friction Model Research Articles

Modelling the bitumen scour effect: Enhancement of a dynamic friction model to predict the skid resistance of rubber upon asphalt pavement surfaces subjected to wear by traffic polishing

This paper explores the prediction of whole-life cycle skid resistance for asphalt. When asphalt surfaces are newly laid, the microtexture of the aggregates is masked by a film of bitumen binder that tends to lower skid resistance during the early life of a pavement, typically the first two year dependent on traffic volume. However, as it is subjected to traffic polishing, the skid resistance of a newly laid pavement starts increasing as a consequence of the scouring of the bitumen binder film, which gradually reveals the microtexture. Once fully exposed, the microtexture is progressively polished by the traffic tending to cause a decrease in skid resistance and leading to pavements becoming more slippery again in the long term.To take into account the early life masking of the microtexture of an asphalt surface, a coefficient or “weight factor” is introduced to a Dynamic Friction Model (DFM) previously developed to predict the skid resistance of rubber moving upon a rough surface. To validate the modified model, mosaic and asphalt samples are prepared utilizing different aggregates and submitted to controlled laboratory polishing, to simulate both the wear of surface texture and scour of the bitumen film under traffic. The specimens’ surface textures are recorded at different stages of polishing, and contact friction measurements taken using a Wehner-Schulze machine. These experimentally obtained values are compared with the fiction coefficients calculated with the modified model. The results illustrate comparable friction coefficients (More than 85% of the model simulations produced results with accurate at ± 2% of the experimental measures), and accordingly demonstrate the robustness of the enhanced model to account for the initial presence of the bitumen binder film, in the evaluation of skid resistance for asphalt pavement surfaces.

Modelling the temperature in joint friction of industrial manipulators

SummaryIn this paper, a new model for joint dynamic friction of industrial robot manipulators is presented. In particular, the effects of the temperature in the joints are considered. A polynomial-based model is proposed and the parameter estimation is performed without the need of a joint temperature sensor. The use of an observer is then proposed to compensate for the uncertainty in the initial estimation of the temperature value. A large experimental campaign show that the model, in spite of the simplifying assumptions made, is effective in estimating the joint temperature and therefore the friction torque during the robot operations, even for values of velocities that have not been previously employed.

Analysis of Physical Friction Characteristics about Handwrite Feeling—Rough and Smooth

Writing was an important factor in human society since long time ago. And previous studies indicate many consumers evaluate pens in handwriting feeling above all other factors when they select recently pens. The fact they work always grabbed in hands considered, the emotional design of writing tools is essential. However, the feeling such as handwriting feelings is gradually disappearing due to the development of mobile devices. So we thought that the need for an engineering approach. The technology of the sense of touch belongs to the technology of the sensibility field, but it is positively necessary to objectify the sense of touch in order to develop new technologies or products by expressing this numerically and applying it to engineering. In order to objectify the sense of touch, the variables (the pressure, temperature, texture of material, etc.) of the friction when the stylus pen first touches the surface of the object should be digitized. And static and dynamic friction models should be established and the variables that affect the friction behavior should be organized. This study investigated the handwriting feeling of various writing tools and attempted to use it for the development of new mobile devices in the future through physical friction test. This study investigated the handwriting feeling of various writing tools and attempted to use it for the development of future mobile devices through physical friction test. Using developed model which can explain how the experimental parameters and emotional user experience, developer can design their product which can give user expected emotional sensibility.

Validation of a constitutive law for friction-induced vibration under different wear conditions

Recent work (Cabboi et al. [1]) has shown promising agreement between measurements and theoretical modelling of high-frequency dynamic sliding friction. This paper confirms and extends this agreement by presenting results for a wide selection of contacting materials. Additional measurement techniques are also introduced, to give independent confirmation of parameter identification and improve the robustness of the identification process. The results show that virtually every individual measurement can be fitted accurately by the proposed theoretical model, and that in all cases where rapid wear of the contacting materials was not an issue it was possible to achieve a good global fit to sets of tests at different normal loads and sliding speeds. The evidence suggests that this measurement procedure is able to characterise the dynamic behaviour at a frictional interface up to kiloHertz frequencies, and consequently provide the means to discriminate among, and calibrate, proposed dynamic friction models. Identifying a reliable model could significantly improve the prediction accuracy for friction-induced vibration such as vehicle brake squeal.

New Insights into the Short Pitch Corrugation Enigma Based on 3D-FE Coupled Dynamic Vehicle-Track Modeling of Frictional Rolling Contact

A three-dimensional (3D) finite element (FE) dynamic frictional rolling contact model is presented for the study of short pitch corrugation that considers direct and instantaneous coupling between the contact mechanics and the structural dynamics in a vehicle-track system. In this study, we examine the system responses in terms of vibration modes, contact forces and the resulting wear with smooth rail and corrugated rail with progressively increasing amplitude to infer the conditions for consistent corrugation initiation and growth. Wear is assumed to be the damage mechanism, and short pitch corrugation is modeled using wavelengths from field observations of a Dutch railway. The contribution of this paper is a global perspective of the consistency conditions that govern the evolution of short pitch corrugation. The main insights are as follows: (1) the longitudinal vibration modes are probably dominant for short pitch corrugation initiation; (2) during short pitch corrugation evolution, the interaction and consistency between longitudinal and vertical modes should determine the development of short pitch corrugation, and once a certain severity is reached, vertical modes become dominant; and (3) in the case simulated in this paper, corrugation does not grow probably due to not only the different resulting main frequencies of the vertical and longitudinal contact forces, but also the inconsistency between the frequencies of the vertical and longitudinal vibration modes and the resulting wear. It is inferred that in the continuous process of initiation and growth of the corrugation, there should be a consistency between them, and this could be done by the control of certain track parameters.

A Mindlin derived Dahl friction model

Friction modeling is essential in a vast amount of engineering applications. In this paper Mindlin contact friction model, a Masing rule compliant model, is manipulated in order to find a correlation with Dahl dynamic friction model, a Masing rule not compliant model. The resulting equations are then numerically compared and the correlation demonstrated with several loading functions. The result is a modified Dahl model that captures the partial slip behavior following the contact theory. The Dahl model, classically used in control engineering as an empirical model due to its implementation facility, finds in this new formulation a physical meaning to its parameters and finally identified physical parameters (according from Mindlin model) for the Dahl model.

Experimental evidence for dynamic friction on rock fractures from frequency‐dependent nonlinear hysteresis and harmonic generation

AbstractFrictional properties affect the propagation of high‐amplitude seismic waves across rock fractures and faults. Laboratory evidence suggests that these properties can be measured in active seismic surveys, potentially offering a route to characterizing friction in situ. We present experimental results from a subresonance torsional modulus and attenuation apparatus that utilizes micron‐scale sinusoidal oscillations to probe the nonlinear stress‐strain relation at a range of strain amplitudes and rates. Nonlinear effects are further quantified using harmonic distortion; however, time series data best illuminate underlying physical processes. The low‐frequency stress‐strain hysteretic loops show stiffening at the sinusoid's static ends, but stiffening is reduced above a threshold frequency. This shape is determined by harmonic generation in the strain; the stress signal has no harmonics, confirming that the fractured sample is the source of the nonlinearity. These qualitative observations suggest the presence of rate‐dependent friction and are consistent between fractures in three different rock types. We propose that static friction at the low strain rate part of the cycle, when given sufficient “healing” time at low oscillation frequencies, causes this stiffening cusp shape in the hysteresis loop. While rate‐and‐state friction is commonly used to represent dynamic friction, it cannot capture static friction or negative slip velocities. So we implement another dynamic friction model, based on the work of Dahl, which describes this process and produces similar results. Since the two models have a similar form, parameterizations of field data could constraint fault model inputs, such as specific location velocity strengthening or weakening properties.

Experimental and numerical analysis of the dynamic behaviour of a foil bearing structure affected by metal shims

This paper gives a detailed overview of a shimmed first generation gas foil bearing (GFB). Three metal shims are inserted inside the elastic GFB structure between the bumps and the bearing sleeve. Dynamic shaker tests with a harmonic excitation are used for evaluating dynamic stiffness and damping of the elastic structure. In addition, a numerical structural bump model, based on a link-spring model, is applied to confirm the experimental results, where a dynamic friction model with pure Coulomb friction is used. It neglects Stribeck’s effects and avoids numerical problems in time domain analysis. Good agreement between experiments and simulations is observed.

A fully coupled air foil bearing model considering friction – Theory & experiment

The dynamics of air foil bearings (AFBs) are not yet fully captured by any model. The recent years have, however, seen promising results from nonlinear time domain models, and simultaneously coupled formulations are now available, avoiding the previous requirements for undesirably small time steps and temporal convergence studies.In the present work, an alternative foil structure model is substituted for the simple elastic foundation model to avoid its inherent limitations. The new foil model is based on a truss representation from the literature, but incorporates the foil mass and a dynamic friction model. As a consequence of the friction model's velocity dependency, the foil mass is included to obtain a set of differential equations that can be coupled to the rotor and fluid domains while allowing a simultaneous solution.Considerations leading to a practically applicable implementation are discussed and numerical results are compared with experimental data. The model predicts natural frequencies and mode shapes well, but it is not yet capturing the unbalance response when friction is considered. Possible causes for this discrepancy are discussed and it is suggested that sticking is a more prevalent state than previously assumed.

The effect of longitudinal high-frequency in-plane vibrations on a 1-DoF friction oscillator with compliant contact

The effect of vibrational smoothing of dry friction has been studied intensively in the past. High-frequency vibrations have been shown to reduce average friction forces and thus smooth the effective characteristics of dry friction. Consequently, undesired friction-induced phenomena, such as friction-induced vibrations or stick-slip motion, can be avoided. While most publications focus on rigid contacts using classical Coulomb friction models, a class of dynamic friction models, namely the Dahl, LuGre and the elasto-plastic model proposed by Dupont et al., is considered here in order to account for contact compliance. Based on a simple 1-DoF friction oscillator, the effect of longitudinal high-frequency vibrations is investigated. An averaging procedure is applied in order to derive the effective friction–velocity characteristics of the system. Using a Galerkin procedure, analytical approximations can be derived for the Dahl and the LuGre friction model, while numerical calculations have to be performed for the elasto-plastic model. In order to validate the results, full timescale numerical simulations are performed. When accounting for contact compliance, the smoothing effect can still be observed. However, the calculated friction forces are higher compared to the classical results using Coulomb friction. Hence, the assumption of a rigid contact leads to overestimation of the smoothing effect.

Modeling and experimental investigations on the drag reduction performance of an axial oscillation tool

The high friction of a drill string against a wellbore is a concern during directional and horizontal drilling. An axial oscillation tool (AOT) is typically used to reduce drag and torque. This study examined the axial oscillation drag reduction mechanism using a specially designed laboratory test rig. An indoor simulation experiment was conducted, followed by model recognition and identification of the friction model parameters based on the experimental data. A torque/drag model and drilling string axial vibration model were used to establish the numerical model. Additionally, the boundary condition between the drill pipe and wellbore was based on a nonlinear dynamic friction model. Finally, the model was solved using a numerical method to gain an understanding of the drag reduction mechanism of the axial oscillation tool. The indoor experiment of the nonlinear friction model revealed that the Coulomb friction model appeared to disagree with the measured data of the experiment. The nonlinear dynamic friction model, however, which was based on the acquired parameters using particle swarm optimization (PSO), yielded results that were in good agreement with the experimental results. Comparisons with experimental setups, data and models from the literature were conducted. The simulation results clearly demonstrated that the friction reduction was effective when the amplitudes of the vibration velocities exceeded the drive velocity. Decreasing the slip velocity of drill strings and increasing the amplitude of the axial oscillation tool vibration force effectively lengthened the drilling-string vibration range. Furthermore, the optimal position of the axial oscillation tool corresponded to a highly deviated well section that was characterized by the existence of high friction resistance. Therefore, the oscillation motion of the drill pipe at a highly deviated well section could significantly decrease the total friction force of the entire drill string.

Influence of Friction Models on the Dynamics of 2-DOF Friction Oscillator

The dynamics of two Degrees of Freedom (DOF) mass-spring-damper system, resting on a moving belt are investigated. Due to friction force generated between the moving belt and the masses, the friction model plays a significant role on the energy transfer between the contacting surfaces. Therefore, in this study a steady-state and a dynamic friction models are implemented. The influence of these friction models on the system response is investigated. Additionally, the both systems where subjected to a number of initial conditions, to address the system dependency on the initial conditions. Finally, using the provided governing equations and the systems jacobain matrices Lyapunov exponent spectra were calculated.

Haptic Feedback in Needle Insertion Modeling and Simulation.

Needle insertion is the most basic skill in medical care, and training has to be imparted not only for physicians but also for nurses and paramedics. In most needle insertion procedures, haptic feedback from the needle is the main stimulus in which novices need training. For better patient safety, the classical methods of training the haptic skills have to be replaced with simulators based on new robotic and graphics technologies. This paper reviews the current advances in needle insertion modeling, classified into three sections: needle insertion models, tissue deformation models, and needle-tissue interaction models. Although understated in the literature, the classical and dynamic friction models, which are critical for needle insertion modeling, are also discussed. The experimental setup or the needle simulators that have been developed to validate the models are described. The need of psychophysics for needle simulators and psychophysical parameter analysis of human perception in needle insertion are discussed, which are completely ignored in the literature.

Modeling Friction Performance of Drill String Torsional Oscillation Using Dynamic Friction Model

Drill string torsional and longitudinal oscillation can significantly reduce axial drag in horizontal drilling. An improved theoretical model for the analysis of the frictional force was proposed based on microscopic contact deformation theory and a bristle model. The established model, an improved dynamic friction model established for drill strings in a wellbore, was used to determine the relationship of friction force changes and the drill string torsional vibration. The model results were in good agreement with the experimental data, verifying the accuracy of the established model. The analysis of the influence of drilling mud properties indicated that there is an approximately linear relationship between the axial friction force and dynamic shear and viscosity. The influence of drill string torsional oscillation on the axial friction force is discussed. The results indicated that the drill string transverse velocity is a prerequisite for reducing axial friction. In addition, low amplitude of torsional vibration speed can significantly reduce axial friction. Then, increasing the amplitude of transverse vibration speed, the effect of axial reduction is not significant. In addition, by involving general field drilling parameters, this model can accurately describe the friction behavior and quantitatively predict the frictional resistance in horizontal drilling.

Friction characteristics of piston rings in a free-piston engine generator

Free-piston engine generator is a new alternative to traditional reciprocating engine, which moves without mechanical restriction of crankshaft system. This article investigated numerically the friction characteristics of piston rings in a free-piston diesel engine generator by adopting coupled models of dynamic and friction. The development of the dynamic model and friction model was described, and an iterative calculation method was presented, giving insight into the coupled parameters of these two models. The detailed effects of the dynamic on friction and lubrication were investigated compared with a corresponding traditional crank engine. The friction characteristics of the free-piston engine generator were found to differ clearly from those of the traditional engine due to its special piston motion. Compared with the traditional engine, the minimum lubricant film thickness of piston rings in the free-piston engine generator is thicker and lasts shorter at the dead center regions, but it is generally thinner at other positions. The average friction force, friction power, and friction work of the piston rings in the free-piston engine generator are less than the traditional engine due to the better lubrication in endpoints region. Meanwhile, the friction power of the free-piston engine generator increases with the increase in fuel mass or decrease in load. The friction efficiency varies in correlation with the generator load; the optimum friction efficiency can be obtained by either increasing or decreasing from a certain generator load.

Scaling laws of gelatin hydrogels for steady dynamic friction

In this article, we use population balance based dynamic friction model for steady sliding to develop scaling laws in the terms of mesh size of gelatin hydrogels. First of all, it is observed in the sliding experiments that shear modulus of gelatin hydrogels depends on sliding velocity. This dependence is more evident in the case of low sliding velocity. Moreover, relaxation time constant of a dangling chain at the sliding interface scales with the same exponent as its stiffness. The scaling law is also developed for chain density and viscous retardation at the sliding interface. It is also established that the Hookean-based dynamic friction model is sufficient to study frictional behaviour of hydrogels. The reason for this observation is attributed to the weak bonding between a gelatin hydrogel and glass interface.

A new method for the identification of the parameters of the Dahl model

Friction is a nonlinear phenomenon that is present in many areas of science and engineering. It has static and dynamic characteristics. This paper deals with a dynamic model of friction, namely the Dahl model. More precisely, this paper proposes a new methodology for the identification of the parameters of the Dahl model. It is shown that, in the absence of noise, the identified parameters are equal to the real ones. Numerical simulations are carried out to illustrate the identification methodology.

A semi-analytic dynamical friction model for cored galaxies

We present a dynamical friction model based on Chandrasekhar's formula that reproduces the fast inspiral and stalling experienced by satellites orbiting galaxies with a large constant density core. We show that the fast inspiral phase does not owe to resonance. Rather, it owes to the background velocity distribution function for the constant density cores being dissimilar from the usually-assumed Maxwellian distribution. Using the correct background velocity distribution function and the semi-analytic model from Petts et al. (2015), we are able to correctly reproduce the infall rate in both cored and cusped potentials. However, in the case of large cores, our model is no longer able to correctly capture core-stalling. We show that this stalling owes to the tidal radius of the satellite approaching the size of the core. By switching off dynamical friction when rt(r) = r (where rt is the tidal radius at the satellite's position) we arrive at a model which reproduces the N-body results remarkably well. Since the tidal radius can be very large for constant density background distributions, our model recovers the result that stalling can occur for Ms/Menc << 1, where Ms and Menc are the mass of the satellite and the enclosed galaxy mass, respectively. Finally, we include the contribution to dynamical friction that comes from stars moving faster than the satellite. This next-to-leading order effect becomes the dominant driver of inspiral near the core region, prior to stalling.

A survey and comparison of several friction force models for dynamic analysis of multibody mechanical systems

This study is aimed at examining and comparing several friction force models dealing with different friction phenomena in the context of multibody system dynamics. For this purpose, a comprehensive review of present literature in this field of investigation is first presented. In this process, the main aspects related to friction are discussed, with particular emphasis on the pure dry sliding friction, stick–slip effect, viscous friction and Stribeck effect. In a simple and general way, the friction force models can be classified into two main groups, namely the static friction approaches and the dynamic friction models. The former group mainly describes the steady-state behavior of friction force, while the latter allows capturing more properties by using extra state variables. In the present study, a total of 21 different friction force models are described and their fundamental physical and computational characteristics are discussed and compared in details. The application of those friction models in multibody system dynamic modeling and simulation is then investigated. Two multibody mechanical systems are utilized as demonstrative application examples with the purpose of illustrating the influence of the various frictional approaches on the dynamic response of the systems. From the results obtained, it can be stated that both the choice of the friction force model and friction parameters involved can significantly affect the simulated/modeled dynamic response of mechanical systems with friction.

Modelling the Belt – Envelope Interactions during the Postal Mail Conveying by a Sorting Machine

The purpose of this study is to predict the trajectory of an envelope when conveyed between two flat belts in a mail sorting machine. Each of the two sides of the envelope is in contact with one belt. The friction coefficient can vary between the two sides, e.g. for the cases of a postcard or a plastic windowed envelope. The two belts are assumed to travel horizontally with the same velocities, but in real world small velocity differences can occur. Also, some deviation from the horizontality of the belts can be observed. These phenomena can lead to unexpected situations where the relative position of the envelope to the belt changes during transportation. The work focuses on the belt-envelope mechanical interactions in order to predict the envelope position during its conveying. A 2D model is developed which considers the dynamic equilibrium of the envelope and simulates the transient behavior at different locations in the sorting machine. In the dynamic friction model, the contact surfaces between the envelope sides and the belts have to be determined at each time step. The belt/envelope friction forces are applied at the centers of these contact surfaces One side of the envelope is considered stuck (in adhesion) to the belt while the other is considered slipping. The position of the envelope center of gravity and the angle with the horizontal axis are calculated. For evaluation of the proposed dynamic model, several cases of operation are simulated.