THE USE OF A MONOMOLECULAR PROTECTIVE FILM ON THE SURFACE OF FRICTION UNITS TO INCREASE THE RELIABILITY OF AGRICULTURAL MACHINERY

One of the factors limiting the reliability of machines and mechanisms is the wear of the contacting surfaces of friction units, which affects their service life. To prevent it, the friction units are treated with lubricants. Surfactants containing fluorinated hydrocarbon radicals are of the greatest interest as an additive to lubricants. (Research purpose) The research purpose is in studying the effect of a protective monomolecular film of fluorinated surfactants on the processes of friction and wear occurring on the surfaces of friction units under conditions of boundary and hydrodynamic friction. (Materials and methods) The structure of the metal was studied before and after the application of a monomolecular protective film, the contact potential difference and the hardness of the samples were determined. The influence of surface energy on the oil absorption of materials was evaluated. (Results and discussion) It was revealed using the contact potential difference method, the process of applying a monomolecular protective film ends after 1.5-3.0 minutes and further exposure in the composition does not lead to a change in the contact potential difference. The values of the adhesion action and wetting energy for surfaces with this coating indicate that the surface energy does not depend on the material, but is determined by the coating of the monomolecular protective film of the test sample. The compositions of 0.05 percent of solutions of fluorinated surfactants form a more porous coating compared to the concentration of 0.5 percent. (Conclusions) Fluorinated surfactants have a high tribotechnical efficiency as antifriction and anti-wear nanomaterials. Their use makes it possible to protect the contact surfaces with a film 3-6 nm thick both under boundary and under hydrodynamic friction. The specified protective film performs the function of a "compensator" for various lubrication modes.

Effect of the Geometric Profile of Top Ring on the Tribological Characteristics of a Low-Displacement Diesel Engine

The present study aims to analyze the influence of the geometric profile of the compression ring on the tribological properties of the lubricant. Additionally, the influence of the rotation speed and the engine load on the state of the lubricant is evaluated. For this study, a single-cylinder diesel engine is taken as the basis, from which a CAD model of the combustion chamber-piston assembly was made. In addition, the conditions in the cylinder chamber were analyzed when the engine operates at a rotation speed of 3000, 3300, 3600, and 3900 rpm, and a load of 1.5, 3.0, 4.5, and 6.0 N. The calculations were developed using the OpenFOAM® simulation software. The results obtained show that changes in the geometric profile of the ring can contribute to reducing the hydrodynamic friction force by 13% and the friction force caused by roughness by 61%. This implies a decrease in the power lost by friction. In general, the modification of the geometric profile allowed a reduction of 21% in the lost power associated with friction. Additionally, it was observed that the shape of the profile allows to reduce the pressure in the lubricant by 65% and obtain a greater thickness of the lubrication film. On average, an increase of 300 rpm and 1.5 N in the speed and load of the engine causes the friction force and power losses to increase by 45% and 10%. The above results imply that the geometric profile of the compression ring can improve tribological performance in the engine, allowing a reduction in fuel and better lubricant performance.

POTENTIAL FOR EXPANDING THE RANGE OF FLUID FRICTION WHILE MINIMISING FRICTION RESISTANCES AND IMPROVING AN OIL FILM ’S LOAD BEARING CAPACITY

Traces of mechanical wear appear on co-working surfaces in the operation of precision fluid bearings. This should not be the case, since fluid friction and uninterrupted oil film should be present in a friction pair, which is a concept that this paper attempts to outline. The way friction forces, resistance, and oil film vary as unit pressure rises linearly is discussed. Three stages of the variations are distinguished. At the first stage, the oil film thickness and force of friction remain steady while the resistance declines. Stage two is temporary: Triboelectrical phenomena already escalate considerably and begin to decide effects of the friction process while a lubricant loses rheological properties of the Newtonian fluid. Hydrodynamic friction continues at the third stage, yet the triboelectrical effects are decided by stabilised triboelectrical phenomena. The third range can be identified as boundary friction where the layer separating surfaces is thicker than in the area of Newtonian rheology. This is very good in respect to wear, but higher-energy (not electrically neutral) particles cause increases in friction resistances. This range seems to exhibit a very high potential for being controlled with an adequate selection of oil based additions.

Incentives of Using the Hydrodynamic Invariant and Sedimentation Parameter for the Study of Naturally- and Synthetically-Based Macromolecules in Solution

The interrelation of experimental rotational and translational hydrodynamic friction data as a basis for the study of macromolecules in solution represents a useful attempt for the verification of hydrodynamic information. Such interrelation originates from the basic development of colloid and macromolecular science and has proven to be a powerful tool for the study of naturally- and synthetically-based, i.e., artificial, macromolecules. In this tutorial review, we introduce this very basic concept with a brief historical background, the governing physical principles, and guidelines for anyone making use of it. This is because very often data to determine such an interrelation are available and it only takes a set of simple equations for it to be established. We exemplify this with data collected over recent years, focused primarily on water-based macromolecular systems and with relevance for pharmaceutical applications. We conclude with future incentives and opportunities for verifying an advanced design and tailored properties of natural/synthetic macromolecular materials in a dispersed or dissolved manner, i.e., in solution. Particular importance for the here outlined concept emanates from the situation that the classical scaling relationships of Kuhn–Mark–Houwink–Sakurada, most frequently applied in macromolecular science, are fulfilled, once the hydrodynamic invariant and/or sedimentation parameter are established. However, the hydrodynamic invariant and sedimentation parameter concept do not require a series of molar masses for their establishment and can help in the verification of a sound estimation of molar mass values of macromolecules.

Lubricated steady sliding of a rigid sphere on a soft elastic substrate: hydrodynamic friction in the Hertz limit

Lubricated sliding on soft elastic substrates occurs in a variety of natural and technological settings.

Active nematics with anisotropic friction: the decisive role of the flow aligning parameter

We use continuum simulations to study the impact of anisotropic hydrodynamic friction on the emergent flows of active nematics.