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This paper describes research aimed at the experimental determination of the influence of rubber hysteresis on the friction coefficient between rubber samples for making soles and granite tiles. In the experiments, four types of shoe rubber with similar hardness and different hysteresis properties and two granite tiles with different roughnesses (smooth and anti-slip) were used. The determination of rubber hysteresis was carried out experimentally on a uniaxial testing machine. The friction coefficient was measured using a device specially developed for this type of test, which was based on the pulling force method, while the measurement conditions were based on the EN 13893:2011 standard. The friction coefficient was measured at two different speeds, 50 mm/s and 300 mm/s, with different surface conditions. Using regression analysis and the Taguchi method, the data obtained from the experiments were analyzed to determine the influence of parameters on the friction coefficient. The experimental research shows that different rubber mixtures with the same or similar hardness could have different hysteresis properties but also different friction properties. [ABSTRACT FROM AUTHOR]

The friction performance of tread rubber is related to the safety of the vehicle during driving, especially in terms of shifting speeds, cornering, and changing environmental factors. The experimental design used in this paper employed a self-developed automatic multi-working-condition friction tester to investigate the correlation between the friction coefficient of three tread formulations and various factors, including speed, pressure, temperature, side deflection angle, and lateral camber. This experimental study demonstrates that the coefficient of friction decreases with increasing load and increases with increasing sliding velocities due to changes in adhesion friction. Due to the increasing and decreasing changes in rubber adhesion and hysteresis friction caused by temperature, the coefficient of friction shows a tendency to increase and then decrease with the increase in temperature; thus, temperature has an important effect on the coefficient of friction. Based on the basic theory of friction and experimental research, the Dorsch friction model was modified in terms of temperature, and the analytical relationship between the rubber friction coefficient and the combined variables of contact pressure, slip velocity, and temperature was established, which is more in line with the actual situation of rubber friction. The model predictions were compared with the experimental results, and the error accuracy was controlled within 5%. This verifies the accuracy of the model and provides a theoretical basis for the study of rubber friction. [ABSTRACT FROM AUTHOR]

The British pendulum tester (BPT) provides a method to measure the skid resistance of pavement, which possesses both theoretical and practical engineering significance. This article aims to establish a numerical hysteresis friction model for BPT to reproduce the dynamic motion of the slider and estimate the pavement friction based on surface texture roughness, rubber viscoelasticity property and contact characteristics. The analytical hysteresis friction model was introduced based on one of the modern rubber friction theories. As an input parameter of this model, the average penetration depth of rubber was calculated based on the interfacial separation assumption. A numerical model was established by combining the geometric and motion characteristics of BPT. To validate the model, the self-affine characteristics of texture from four types of asphalt pavement were analysed; simultaneously, the storage and the loss modulus of rubber slider at various frequencies were obtained using the Zener constitutive model. As a result, the velocity of the slider decreases gradually with the dynamic fluctuation of the friction coefficient. A significant linear correlation was found between the predicted values and the measured data. This numerical friction model performs some potential for friction estimation. However, more conditions need considering for the improvement and practicability of the model. [ABSTRACT FROM AUTHOR]

Tribological behavior of Styrene-Butadiene Rubber (SBR) compound reinforced by silica and carbon-black fillers on two different asphalt-like surfaces is studied using theoretical and experimental approaches. Linear sliding friction and wear tests were performed on two different roofing asphalt papers. The surface roughness power spectra of asphalts and the master curves of the large-strain viscoelastic modulus of SBR compound were used to model the contact area and friction coefficient theoretically. The theoretical results are in good agreement with experiment providing the tribochemical degradation is not the dominant wear mechanism. When the formation of a tribo-modified layer prevails the mechanical abrasion, the wear rate, in terms of mass loss, does not necessarily increase with the increase of frictional work as expected theoretically. • Tribological behavior of Styrene-Butadiene Rubber on asphalt papers is studied. • Theoretical approaches are used to calculate the contact area and rubber friction. • Rubber friction and wear rate are obtained experimentally and compared with theory. • A tribo-modified layer is formed on the rubber surface at high sliding velocities. • The tribo-modified layer significantly affects the tribological behavior of rubber. [ABSTRACT FROM AUTHOR]

Machine elements and mechanical components have often surfaces with anisotropic roughness, which may result from the machining processes, e.g. grinding, or from wear. Hence, it is important to understand how surface roughness anisotropy affects the contact mechanics properties, such as friction and the interface separation, which is important for lubricated contacts. Here we extend a multiscale mean-field model to the lubricated contact between a soft (e.g. rubber) elastic solid and a rigid countersurface. We consider surfaces with anisotropic surface roughness, and discuss how the fluid flow factors and friction factors depend on the roughness power spectral density, as well as on the location of roughness on the interacting solids. Finally, we present an experimental study of the lubricated sliding contact between a nitrile butadiene rubber O-ring and steel surfaces with different kinds of isotropic and anisotropic surface roughness. The good quantitative comparison between the experimental results and the theory predictions suggests that the multiscale lubrication mechanisms are accurately captured by the theory. [ABSTRACT FROM AUTHOR]

We discuss on the rough contact mechanics in presence of a graded viscoelastic solid. In particular, we derive the effective surface admittance of a stepwise or continuously-graded half-space, which is then embedded in a Fourier-based residuals molecular dynamics formulation of the contact mechanics. The viscoelastic multilayer theory, which is of general applicability, is then applied to discuss on the role of small-scale wavelengths on polymer friction and contact area. We demonstrate that the rough contact mechanics exhibits effective interface properties which converge to asymptotes upon increase of the small-scale roughness content, when a more realistic rheology of the confinement is taken into account. [ABSTRACT FROM AUTHOR]

We discuss the influence of geometrical and rheological non-linearities on the prediction of rubber friction and true contact area for rough sliding interactions. In particular, we compare the results of a linearly-viscoelastic linear-contact model, formulated in the Fourier space, with those obtained from non-linear finite element calculations. A sinusoidal rigid profile indenting a rubber block is here considered for simplicity, whereas the effects of non-linearity are evaluated by varying the aspect ratio, loading conditions and sliding speed of the contact interface. It is found that accurate friction predictions can be obtained through the linear viscoelastic model, provided that the roughness under investigation features moderate values of root mean square slopes, whereas non-linear finite element computations should be adopted for large root mean square slopes. [ABSTRACT FROM AUTHOR]

This paper presents a new contribution to model tire/road friction. It proposes a calculation of hysteretic component of the rubber friction based on a simplified viscoelastic-rough contact model. The mechanical behavior of rubber elements is represented through “Kelvin–Voigt” model. The hysteretic friction force is calculated from the dissymmetry of the contact pressure due to the rubber viscoelastic behavior in given operating conditions. To validate the model, a series of texture and friction data are measured using two machines respectively, the Circular Track Meter and the Dynamic Friction Tester, through various test surfaces and compared to model results. The Circular Track Meter is a complementary measurement device to the Dynamic Friction Tester as texture measurements can be done on the exact same physical surface tracks where the Dynamic Friction Tester measuring pads have been in contact with the test surface. The obtained results show a very encouraging correlation between the model predictions to the experiment results, thus opening a promising and attractive way to predict tire–road friction. Some indications are given at the end to improve the modeling and to extend to it to a whole tire/road friction model. [ABSTRACT FROM AUTHOR]

The onset mechanism of frictional sliding is essential in understanding frictional strength between materials. In particular, the static friction coefficient is a very important but often overlooked indicator for the emergency braking performance of tyres. In ABS braking a significant area of the tyre contact patch is locally stuck to the road and becomes detached to frictional sliding when the local shear stresses exceed the local friction potential. The detachment phenomena were studied for rubber–ice contact by means of a high-speed camera and image processing. The image sequences of the contact were combined with friction force data. It was observed that for a smooth rubber sample a horseshoe-shaped detachment front was produced. The last contact point was always at the trailing edge or side of the sample. The textured sample had a ring-like detachment front that located the last contact point in the centre of the contact area. The dwell time had a logarithmic dependency on the static friction of the rubber–ice contact. Two different types of precursors were found. The first precursor occurred when the first signs of detachment were observed visually. The second precursor was found when the static friction rose so high that the movement of the sample was nucleated by the breaking of the ice rather than the detachment of the contact. [ABSTRACT FROM AUTHOR]

The energy dissipation in the contact regions between solids in sliding contact can result in high local temperatures which may strongly affect the friction. This is the case for rubber sliding on road surfaces at speeds above 1 mm/s. I derive equations which describe the frictional heating for arbitrary (non-uniform) motion, taking into account that some of the frictional energy is produced inside the rubber due to the internal friction in rubber. Numerical results are presented for one limiting case for steady sliding. [ABSTRACT FROM AUTHOR]

Abstract: We study the lubricated (wet) contact mechanics of a smooth hard cylinder sliding on a randomly rough nominally flat surface of a linear viscoelastic solid. We calculate the rolling and sliding friction, and study the transition from the boundary lubrication to the elasto-hydrodynamic lubrication regime. For the viscoelastic contact the minimum (average) separation does not monotonically increase with the sliding velocity, and the Stribeck curve exhibits new structures not shown for elastic solids. [Copyright &y& Elsevier]

Abstract: The paper presents an analytical multi-scale approach for the modelling of rough surfaces in regard to rubber friction properties. In addition to a fractal description of the micrometer range within the length-scale interval [5–100μm], the macrotexture is considered via the introduction of a second scaling regime for the contact interval [300–1000μm]. As a result, the hysteresis friction coefficient is decomposed in two distinct contributions. The macrotexture mostly contributes to hysteresis friction, while the microtexture is found to be determining for the amount of contact patches, e.g. the real area of contact. Experimental friction tests carried out for carbon black and silica filled S-SBR 5025 on rough surfaces and road pavement under wet conditions point out the relevance of a two-scaling-ranges approach for the modelling of hysteresis friction. Finally, predictions of the load dependent hysteresis friction coefficient are formulated for rough surfaces and give a deeper insight into the physical mechanisms involved in rubber friction properties. [Copyright &y& Elsevier]

Rubber friction has received much attention because of its practical importance for modelling, for example, tyre-road friction. Many experiments were carried out and a number of theories were proposed to investigate and explain its behaviour and dependency on external conditions such as temperature and velocity. However, only a few published articles describe the observed dynamic friction behaviour using compact analytical models. Models for dry friction, such as the Dahl and LuGre models and their several variations, have been proposed to describe rubber friction. Unfortunately, they cannot reproduce many important and specific phenomena observed in experiments focused on rubber friction. In this paper, we propose a simple analytical friction model suitable to simulate the dynamic friction behaviour of rubber-like materials on rigid surface. Phenomena such as pre-sliding, sticking/sliding transitions, relaxation of the friction force at standstill and stick-slip effects can be accurately modelled. We validated the model with several experiments, obtaining a good agreement between simulation and measurements. In addition, we propose a two-dimensions (2D) extension of the model, to broaden the field of cases, in which it can be used. The capability of the model to simulate 2D anisotropic friction behaviour was validated with measurements of a vehicle tyre. • Compact analytical model for dynamic friction behaviour. • Model captures pre-sliding, sticking/sliding transition, relaxation, stick-slip. • Extension to 2D for friction behaviour with combined motion on the surface. • Excellent predictive qualities and agreement with experiments. • Significant improvement over established models such as Coulomb, Dahl and LuGre. [ABSTRACT FROM AUTHOR]

Rubber-like materials are widely used in mechanical systems. Schallamach waves appear in friction process due to their small elastic modulus and relatively large surface adhesion energy, which may cause some negative influences, such as additional vibration and singular wear. In-depth researches into the characteristics and mechanism of Schallamach waves are of great significance to development and application of rubber-like materials. Therefore, the nucleation and propagation law of Schallamach waves are investigated by using in-situ experiments and 3D finite element simulation method. Results indicate that small wrinkles appear firstly at the edges of contact regions. Here, the small wrinkles propagate towards the centers of the contact regions in a spiral manner, which is analyzed by using elastic theory. The first Schallamch wave forms on the sides of the contact region, while the subsequent waves nucleate at the front of the contact region. Then, In-situ experiments are carried out to study the influences of materials ratios and sliding velocity on the behaviors of Schallamach waves. Based on the finite element model, analysis results reveal the law of propagation speed, wave length and wave amplitude of Schallamach waves, and the relationship between contact area and force (frictional and vertical force). There is basically no sliding exiting in the contact interface during friction process, and in some extent the Schallamach waves play a lubricating role. • A three-dimensional finite element model is built to simulate both the nucleation and progression of Schallamach waves for the first time. • The evolution process of small wrinkles on the edge of the contact area is analyzed in detail. • The first Schallamach wave is different from that of steady-state slip, the former is formed on both sides of the contact area, and the latter is formed in front of the contact area. • The wavelength, amplitude and velocity of Schallamach wave are analyzed by in situ experiment and 3D simulation. • The corresponding relationships among friction force, vertical force, contact area and surface deformation are obtained by 3D FEA. [ABSTRACT FROM AUTHOR]

A mathematical model developed previously for predicting adhesive sliding friction of rubber on a hard surface in the presence of Schallamach waves is extended here to include global effects of viscoelasticity, besides the previously included viscoelastic effects in the neighborhood of the debond (shear crack) tips; the crack tip model is unchanged. We find that global viscoelasticity limits the maximum sliding speed and minimum wavelength for which a wave train can exist and, as expected, increases the friction force. The model is shown to improve upon the agreement with experimental data on wave speed and wavelength in the previous paper. • This paper extends a previously developed model to include global viscoelastic effects. • It is shown there is a critical sliding speed above which Schallamach waves cannot exist because of global viscoelasticity. • There is also a lower limit on wave length. • The model and available experimental data are in very good agreement. [ABSTRACT FROM AUTHOR]

A mathematical model is developed for predicting adhesive sliding friction of rubber on a hard surface in the presence of propagating detachments or buckles known as Schallamach waves. The rubber is assumed to be elastic apart from a small zone at the leading edge of each detachment where viscoelasticity is significant. We assume the rubber is in a state of plane strain, and both contact surfaces are flat. Linear elasticity is used, together with the Fast Fourier Transform, for the wave analysis. Nonlinear elasticity is used with the finite element method to illustrate the detachment initiation. The model is shown to agree quite well with experimental data from three sources, despite the use of hemispherical sliders. • An analyical model is developed for predicting rubber friction due to adhesion. • The model and available experimental data are in reasonable agreement. • Criteria for existence of Schallamach waves are established. • A finite element model shows how these waves develop. • An experimental program is proposed for a more complete comparison with theory. [ABSTRACT FROM AUTHOR]