The influence of the abrasive particle size and modifiers (low molecular weight liquid ribbers (LMWR), sulfidosilane) on the rate of wear on abrasive paper of rubbers based on natural rubber (NR), carbon black (CB) and polyoxadiazole (POD) fiber is studied as a function of structure and mechanical properties of rub-bers. Model rubber blends were prepared in a closed-type mixer, the abrasive wear tests were conducted on a drum-type machine, the structure and the mechanical properties of rubbers were characterized by DMA, static tensile tests, hardness measurements and tear resistance. The wear surfaces were analyzed by SEM. Tests have shown that the addition of fiber does not affect the rate of abrasive wear of the original NR/CB rubber regardless of the grain size of the abrasive. Addition of modifiers that increase the tensile modulus M10, hardness H_Sh, tear resistance T_R, tensile strength A, degree of crosslinking γ reduces the wear rate at friction on coarse abrasive, which is characteristic of abrasive wear with a predominance of micro-cutting. The greatest influence, judging by the value of the correlation coefficient, is exerted by the value of M10, dependent on the bond strength between the matrix and the fiber, which allows to predict the wear rate of rubbers based on the results of mechanical tests. When worn on a fine abrasive paper, the increase in M10, H_Sh T_R, γ on the contrary, raises the wear rate of rubber, and the tensile toughness has practically no effect on it. This is attributed to the predominance of the fatigue wear mechanism, in which the wear rate increases with contact stresses, in proportion to the strength properties, with tear resistance exerting the greater effect on the wear rate.

The results of a study of the tribological properties and microstructure of rapidlysolidified Al — 12.2 wt. % Si — 0.2 wt. % Fe (AK12vp) and Al — 12.5 wt. % Si — 0.8 wt. % Mg — 0.4 wt. % Mn — 0.7 wt. % Fe — 0.9 wt. % Ni — 1.7 wt. %, Cu (Al–Si–M) alloys are presented. The effect of multicomponent alloying on the microstructure of near-eutectic silumin was studied using scanning electron microscopy and X-ray spectrometry. Multicomponent alloying of the Al—Si eutectic alloy with magnesium, manganese, iron, nickel and copper leads to a reduction in the size of the primary α-Al dendrites to 3—4 μm. Tribological tests carried out under conditions of dry friction with reciprocating motion of the indenter showed that alloying by metals of rapidly solidified eutectic silumin leads to a reduction in the coefficient of friction by 25 %. An analysis of the surface state of the track showed that, as a result of deformation heating, the oxidation of the α-Al phase occurs, the destruction of the oxide film, which represents the third body, and its removal beyond the track. The fragmentation of silicon plates in the track area into nano-sized particles was also obtained. The impact of the indenter also leads to a uniform distribution of equiaxed particles of intermetallic com-pounds while maintaining their phase composition.

In this work tribotechnical tests of antifriction hard-lubricating coatings in a friction pair “metal—polymer” are presented. The tests were carried out according to ASTMG99 standard on a friction machine working on the scheme “sphere—disk” at sliding velocity V = 0.8 m/s, load F = 23 H and rotational speed n = 310 min^–1. During the tests, the value of sliding friction force was continuously recorded and the value of friction coefficient was automatically calculated. The tests were carried out until the specified friction path was accumulated L = 2880 m. After the tests the linear wear of the spherical counter body was measured. Antifriction hard-lubricating coatings based on molybdenum disulfide and polytetrafluoroethylene applied on steel samples were tested. Polyoxymethylene spheres with a diameter of 10 mm were used as a counter body. The tests were carried out with the use of various greases based on mineral and synthetic oils with a complex of antifriction additives. It is established that the use of antifriction hard-lubricating coatings together with greases allows to reduce linear wear of counter bodies in 5,9—10,1 times, and friction coefficient in 1,5—2,3 times depending on the brand of the used coating. By selection of an optimum combination of antifriction hard-lubricating coatings and plastic grease it is possible to achieve reduction of linear wear of the counter bodies up to 14.2 times, and friction coefficient — up to 4.4 times.

This work investigated the hydrocarbon degradation and depletion of the anti-wear additive zinc dialkyldithiophosphate (ZDDP) in several used marine motor oils using high-resolution nuclear magnetic resonance (NMR). The article presents research results showing that during engine operation a number of characteristics of motor oil change: degree of aromaticity, ratio of methyl/methylene groups, and composition of phosphorus-containing additives. The possibility of determining oil using the NMR spectrum lines of antiwear additives has been demonstrated. For anti-wear additives containing phosphorus, such as ZDDP and molybdenum dialkyldithiophosphate (MoDDP), ³¹P NMR has been found to provide both depletion rates and insight into the wear mechanism of the additives. The high efficiency of using the high-field NMR spectroscopy method for studying fresh and destruction of used marine motor oils has been demonstrated. ¹H, ¹³C and ³¹P NMR studies show the presence of changes in motor oil caused by the accumulation of products of its decomposition, degradation and decomposition of additives during engine operation. The ability of the NMR radiospectroscopy method to monitor additive depletion is analyzed, which is apparently one of the most difficult problems in used oil analysis. A characteristic feature of the NMR spectra of all used oils is line broadening caused by the presence of metal wear particles. It is characteristic that the broadening of the 13C NMR lines for waste oils is significantly less than the lines broadening in the NMR spectra of protons. In the 13C NMR spectrum of used oil, an increase in the intensity of the line from aromatic hydrocarbons is observed, i.e. as the degree of oil degradation increases, the content of aromatic compounds increases. The results of the study of fresh and used motor oils obtained in this work are new. They can be used to create a system for monitoring the quality of motor oils and for diagnosing engine malfunctions using used oil.

Friction is often accompanied by local fracture at the boundary of the contacting bodies. The gap between the bodies usually contains moving particles of different origin (third body), a change in the effective friction conditions may be associated with some changes in the structure of the “third body”. This paper presents a new series of experiments in which the process of rearrangement of intermediate layer particles interacting with various elastic materials (glass-rubber and steel) is modeled at different scale levels. A technique for visualizing the effect of mutual influence that occurs when two balls are pressed into a layer of rubber is proposed. It is the mutual influence that causes the effect of convergence or separation of the balls or particles during reciprocating frictional loading. The velocity of these processes depends on humidity and, in case of contact with the rubber layer, on the thickness of the layer. At high humidity, the configuration of the particles changes faster, and the friction force decreases. Replacing sand with an abrasive leads to increase in the coefficient of friction and wear with a change in the microrelief of the surface. The minimum roughness is obtained for a humidity of 30 %.

The article presents the results of an experimental determination of the friction coefficient of various materials (steel 95Х18 and bronze BrAZh9-4, fluoroplastic F-4 and polyamide PA-6, graphite MPG-7) in a friction pair with single-crystalline aluminum oxide under low speeds and various loads conditions. Deter-mining the coefficient of friction of aluminum oxide at low sliding velocity made it possible to record and evaluate the static friction for various counterbody materials, to identify the mechanisms of interactions between rubbing bodies and their influence on friction processes. Studies of the tribological characteristics of single crystal aluminum oxide have shown that it does not have antifriction properties and when using it in friction units, it is necessary to take into account the mating material, the load on the friction contact and the sliding velocity. Aluminum oxide has a high affinity for metals, which causes strong adhesive interaction up to wear with cohesive destruction of metals. Polymer materials such as fluoroplastic and polyamide weakly adhesively interact with aluminum oxide, which ensures stable sliding without lubrication with low friction coefficients over a wide range of loads and velocity. Dry friction of the self-lubricating graphite material is determined by the tribological properties of the graphite. At low loads and sliding velocity, the adsorption component of friction is revealed. When forces are sufficient to destroy bonds in crystalline layers of graphite, the friction process is limited by the effect of self-lubricating of graphite.

To study the wear and friction force of a solid surface during friction with the ground, a carousel-type laboratory stand was created. The main task was to measure friction forces under various parameters of the model soil and speeds of relative movement close to real ones during field agricultural work. Traditional electronic dynamometers are designed for static or slowly varying loads. Laboratory stands with such sensors have a linear design, a limited friction path (up to 2 m) and very low relative movement speeds (up to 0.15 m/s). The short friction path complicates the running-in process at the beginning of the experiment. Integral friction forces depend on speed. The adhesion component depends entirely on the presence of soil water at the interface and, thus, on the time required for water to move to the friction surface. With a carousel design of the stand, the friction path is infinite and the speed can be increased by an order of magnitude (up to 1.5 m/s). Since studies usually compare the influence of different materials or soil compositions on the results of experiments, the systematic error due to the difference in the friction path from a straight line is insignificant. To measure rapidly changing loads, a force measuring station was developed based on a flat spring and a small displacement mechatronic sensor. The advantage of mechatronic linear displacement sensors is high sensitivity, ease of switching on and high reliability. Disadvantages include dependence on temperature conditions and consequently the need for calibration in each experiment.

The phasing of the friction process provides for the formation of the intersurface phase of the rubbing surfaces of the friction pair — the “third body”. In essence, the “third body” is a hinge of internal friction of a developed stage of joint plastic deformation of surfaces. Being a consequence of the self-organization of surface adaptation processes in the presence of environmental chemistry, the “third body” can have a wide range of tribological properties. These properties, in turn, are a consequence of the formation of a wide range of optimal (compatible) structures of the “third body”, which determines the controllability of friction. The relationship of structure and properties as the basic principle of tribomaterial science provokes the question of what are the limits of this relationship. For example, what are the minimum properties of friction and how are they reflected in the essence of the structural structure and behavior of the friction contact? The equation of a quasi-ideal solid “third body” under friction is obtained, which proves the existence of an elementary structural element of a solid body under friction (deformation) – a mechanical (nano) quantum. A mechanical quantum, as an ideal (theoretical) crystal of atomically rough and spherical shape, is an oscillator of dynamic dissipative friction structures. The potential energy accumulated initially during the evolution of contact is further dissipated in the area of compatibility into these formed mechanical quanta of the “third body” (elementary tribosystem) in the form of surface energy, creating prerequisites for their elastic reversals with an abnormally low coefficient of friction between them. The efficiency of the “third body” is proportional to the spectrum of elastic reversals of structural shapes.

The work sets the task of determining the conditions for tribological testing of coatings, in which the coating realizes its potential of physical, mechanical and tribological properties regardless of the substrate. A standard method of tribological testing was used on a friction machine according to the “pin-disk” scheme with a circular motion of a spherical indenter pin. Experimental data are presented on the study of the structure and properties of vacuum ion-plasma nitride coatings TiN, TiAlN, CrAlSiN. The coatings had a thickness of 0.8–4.0 microns and were applied to plate steel samples intended for testing in a friction machine. The wear process of coatings is considered from the perspective of contact fracture mechanics and fatigue theories. A calculation and analytical model is proposed for quantitative assessment of contact and wear parameters during friction tests: the size of the contact area; the depth of contact approach; the depth of the plastic zone; stresses in the coating; fatigue limit; critical thickness of the coating, which excludes its deflection. To assess the wear of coatings in this case, it is recommended to use fatigue failure models with the construction of a Woehler fatigue curve and determination of the fatigue limit based on the Murokami-Endo theory. The implementation of the recommended approach was carried out for the nitride coatings using a database of our own experimental data.