Effect of mechanical factors on rubber wear in aggressive media

The effect of mechanical factors on rubber wear in aggressive slurries has been investigated. As the mechanical action becomes more intense, the effect of the aggressive medium increases. Rubber wear in an abrasive flow is a two-stage process: the aggressive medium modifies the surface layer, which is then worn away by the abrasive.Mekhanika Polimerov, Vol. 4, No. 3, pp. 499–503, 1968     

Cold flow and melting of plastics under severe friction conditions

Dry friction of a series of crystalline polymers (polypropylene, nylon, PTFE) against steel over a wide range of sliding velocities (4.4–4.4×10^–4 cm/sec) and loads (P=7.5–360 kg) with almost complete mutual overlap of the friction surfaces is studied. It is shown that friction of polymer materials against steel may be accompanied by melting of the crystalline polymer (at high velocities) or cold flow (at low velocities) in the surface layers associated with an orientation effect and the appearance of anisotropy.Mekhanika Polimerov, Vol. 1, No. 5, pp. 95–100, 1965     

Hysteretic Friction of a Sliding Rubber Element

Friction, especially friction of elastomers, can cause acoustic problems like noise, squeal and comfort drawbacks like vibrations and wear. Therefore, rubber friction affects the function of many products in technical applications, e.g. seals, belts and tires. It can be classified according to different physical phenomena like adhesion, hysteresis, cohesion and viscous friction, see [3]. The topic of this paper is hysteresis friction of rubber that is caused by the energy dissipation due to internal material damping during the process of deformation. The deformation itself occurs during the sliding of a rubber element across the micro‐scaled asperities of a rough surface. In this paper, the sliding process of a rubber element over real surfaces is simulated in time domain and compared to experiments. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Friction and wear of polymer-based composites

Polymeric materials containing different fillers and/or reinforcements are frequently used for applications in which friction and wear are critical issues. This overview describes how to design high temperature-resistant thermoplastics, e.g., filled with carbon fibers and internal lubricants, for operation under low friction and wear at elevated temperatures as sliding elements in, e.g., textile drying machines. Further information will be given on the systematic development of continuous fiber/polymer composites with high wear resistance, and on attempts for the prediction of their load-bearing capacity using a finite element approach. Finally, the application of such composites in thermoplastic filament-wound journal-bearings is discussed.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Institute of Composite Materials (IVW), University of Kaiserslautern, D-67663 Kaiserslautern, Germany. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 6, pp. 717–732, November–December, 1998.     

Investigation of polytetrafluorethylene surface texture

Results are given of an X-ray investigation of the formation of a textured surface layer on polytetrafluorethylene (PTFE) film and its dependence on external mechanical factors — unit load and sliding speed. It is established that the thickness of the surface texture of PTFE is determined by the relation between the processes of texture formation under the influence of frictional forces and its destruction by wear. These processes, in turn, are determined by the working parameters of the moving joint. Data on the kinetics of polymer surface texture formation in the presence of friction are extremely useful in relation to the design of efficient antifriction materials.Mekhanika Polimerov, Vol. 1, No. 2, pp. 129–132, 1965     

Effect of temperature and concentration of aggressive media on rubber wear in an abrasive flow

The effect of the temperature and concentration of the aggressive media on wear in an abrasive flow has been investigated. It is found that at small angle of attack the elasticity of the rubber has an important influence on wear resistance. As the temperature rises, the rate of wear of chemically resistant rubbers in aggressive media decreases owing to the improved elasticity, whereas that of relatively unstable rubbers increases as a result of chemical interaction with the medium. As the concentration of the aggressive medium increases, the wear rate of rubbers that are relatively stable under these conditions decreases owing to the growth in elasticity associated with swelling. It is possible to distinguish a special type of wear, namely, wear "in an abrasive flow."Mekhanika Polimerov, Vol. 4, No. 1, pp. 95–101, 1968     

Friction properties of highly elastic materials at high contact pressures

A newly designed high-pressure tribometer has been employed to investigate the pressure dependence of the friction force of SKN-40 crosslinked butadiene-nitrile rubber in contact with a steel surface on the pressure range to 1200 kgf/cm² (20°C). Over the entire range of contact pressures the friction process is molecular-kinetic in nature and characterized by a linear dependence of the friction force on the logarithm of the sliding velocity. In the region of normal pressures up to 200 kgf/cm², where the effect of pressure on the friction force reduces to the formation of the actual contact area, the friction constant (proportionality factor relating the friction force and the actual contact area) is practically independent of the pressure. At pressures above 200–300 kgf/cm² the increase in the friction force at fixed actual contact area is attributable to the effect of pressure on the friction constant. The nature of this effect is related not with an increase in the chain-surface interaction energy (the activation energy does not increase), but with an increase in the forces of adhesion owing to the greater number of polymer chain-steel surface contacts on the actual contact area (increase in contact density).Lenin Moscow State Pedagogical Institute, Laboratory for Problems of Polymer Physics. Translated from Mekhanika Polimerov, No. 1, pp. 140–146, January–February, 1971.     

Influence of ultradisperse additives on interaction of incompatible polymers

The influence of ultradisperse additives of -sialon and molybdenum disulfide on the interfacial boundary conditions of nitrile rubber containing 17–20% of acrylonitrile (SKN-18) and ultrahigh molecular-weight polyethylene (UHMWPE) is studied. The additives were introduced into the nonpolar UHMWPE, and then the modified composition was introduced into a crude rubber stock based on SKN-18. X-ray diffractometry, electron microscopy, and dynamic testing methods were used for studying the phase and supramolecular structure of the composition. A complex of physical and mechanical tests including the study of the wear and oil and cold resistance characteristics of the elastomeric compositions were carried out. It is shown that the use of ultradisperse additives allows us to improve the interaction at the SKN-18/UHMWPE interface and the operating properties of the materials.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Institute of Nonmetal Materials, Siberian Branch, Russian Academy of Sciences, Yakutsk, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 6, pp. 803–810, 1998.     

Effect of wear on the contact stress distribution in sliding bearings with plastic bushes

The contact problem is considered for a thin elastic annular layer compressed by a rigid cylinder with initial contact over a considerable area. Relations for calculating the maximum contact stresses in sliding bearings with plastic bushes are obtained with allowance for the wear of the bush. From an analysis of these relations it follows that, as the bush wear increases, the maximum contact stresses fall appreciably. This offers a partial explanation of the fall in wear rate as the bearing is run in.Bryansk Machine-Building Plant. Translated from Mekhanika Polimerov, No. 6, pp. 1046–1051, November-December, 1969.     

Effect of loading on the roughness set in run-in metal - rubber surfaces

A study has been made on the effect of loading on the roughness set of a metal surface run-in with rubber containing an SKN-18 + SKN-26 nitrile rubber blend in conditions of friction without lubrication. The experimental results are compared with those calculated.State Scientific-Research Institute of Mechanical Engineering, Moscow. Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 737–740, July–August, 1972.     

Friction and rheological properties of resin-impregnated glass tape

The dependence of the dynamic coefficient of friction of resin-impregnated glass tape on the sliding speed over the mandrel surface and the viscosity of the resin is derived. The formulas obtained are confirmed by the results of experiments which indicate a linear dependence of the coefficient of friction on the sliding speed of the tape over a metal mandrel. Graphically, this dependence is expressed by straight lines with a common origin and a slope that increases with the viscosity of the resin. The coefficient of friction of glass tape sliding over a prewound layer at low speeds also has a linear dependence. At high speeds the dependence takes the form of a damped curve.Translated from Mekhanika Polimoerov, No. 1, pp. 166–170, January–February, 1976.     

Wear of glass-reinforced plastics in aggressive media

The effect of certain aggressive media on the wear of glass-reinforced plastics has been investigated. It is shown that as the angle of inclination of the glass reinforcing fibers relative to the friction surface increases, the wear of the material is sharply reduced.Ukrainian Agricultural Academy, Kiev. Translated from Mekhanika Polimerov, No. 2, pp. 364–366, March–April, 1974.     

Temperature dependence of the actual contact area and friction force of high-elasticity materials

An investigation of the temperature dependence of the actual contact area (under static conditions and during friction at a given sliding speed) of materials based on butadienenitrile rubber in a wide temperature interval is described. Measurements of the friction force were also made. It was established that the temperature dependence of the contact area is associated with corresponding changes in the elasticity modulus (nonequilibrium static modulus for contacts at rest and dynamic modulus for nonstationary contacts). The friction constant c decreases linearly with rising temperature and does not depend on the applied load.Mekhanika Polimerov, Vol. 3, No. 4, pp. 726–729, 1967     

Effect of liquid media on the deformation of the surface layers of a polymer-metal pair in sliding friction

The relation between the high-elastic component of polyurethane deformation and the deformation of the surface layers of metals has been investigated for sliding friction in various media. The surface layers of polymer and metal are plastically deformed. There is a certain correlation between the coefficient of friction and the amount of deformation.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 1, pp. 147–149, January–February, 1970.     

Effect of loading rate on polymer wear

The effect of loading rate on polymer wear in metal-polymer friction pairs is considered. Investigations show that at low loading rates the wear resistance of the polymer specimens increases, evidently owing to orientation of the elements of the molecular structure in the surface layer. This finding applies both to dry friction and friction with lubricants.Mekhanika Polimerov, Vol. 2, No. 6, pp. 862–866, 1966     

Multifactor investigation of the process of polymer wear in the thermally stressed state

Conclusions 1. The temperature regime and stress in the surface layers of polymers exert the most significant effect on wear intensity.2. The effect of these factors is displayed via a change in contacting conditions and the complex of mechanical properties of the polymeric materials.3. The effectiveness of using statistical methods of experiment planning has been revealed in studying the wear process, and also in studying the change in mechanical properties from the action of temperature factors: Reliable mathematical models have been obtained which connect up hardness and wear intensity with temperature regimes.A report presented at the Third All-Union Conference on Polymer Mechanics, Riga, 1976.Rostov-on-Don Institute of Railroad Transport Engineers. Rostov Agricultural Engineering Institute. Translated from Mekhanika Polimerov, No. 1, pp. 67–72, January–February, 1978.     

Wear resistance of steel and brass in friction against filled polyethylene

The wear resistance of a shaft in friction against polyethylene filled with abrasive filler particles (fiberglass, SiO₂) has been investigated. Compositions containing fiberglass can be successfully employed in combination with steel, but are not recommended in combination with brass. Compositions containing SiO₂ cause considerable wear of the steel shaft.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 940–942, September–October, 1969.     

On the wear of brake pads

Within measurements of brake pads on the IDS high load Tribometer, the wear of pads was investigated by a new non-contact wear measurement under low normal pressures and low temperatures. The first results show that the wear of the pad in the sliding friction is nearly proportional to the friction work, and inversely proportional to the shear strength. The results are also interpreted by the adhesion theory of friction and Archard's equation. On the basis of further interpretations of shear strength and extension of adhesion theory of friction, the wear is derived as a piecewise linear function, which can evaluate explicitly the effect factors of wear and relative correlations at different pressures and different temperatures. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Control uncertain Genesio–Tesi chaotic system: Adaptive sliding mode approach

An adaptive sliding mode control (ASMC) technique is introduced in this paper for a chaotic dynamical system (Genesio–Tesi system). Using the sliding mode control technique, a sliding surface is determined and the control law is established. An adaptive sliding mode control law is derived to make the states of the Genesio–Tesi system asymptotically track and regulate the desired state. The designed control scheme can control the uncertain chaotic behaviors to a desired state without oscillating very fast and guarantee the property of asymptotical stability. An illustrative simulation result is given to demonstrate the effectiveness of the proposed adaptive sliding mode control design.     

The design of low-wear friction materials

The relation between the elastoplastic characteristics of the friction surface and contact pressure is analyzed on the basis of the molecular-mechanical theory of friction. A criterion for predicting certain physico-mechanical properties necessary to ensure high wear resistance over a broad temperature interval is proposed.State Scientific-Research Institute of Machine Science, Moscow. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 298–302, March–April, 1969.