Shipboard tests of tribochemical lubrication mode

The article is devoted to the tests of the main marine engine 8CHRN 32/48 (8NVD-48A-2U) SRT "Captain Rogozin" of the Murmansk SPCRK, operated in the tribochemical lubrication mode in the Barents Sea. The satisfactory condition of the cylinder-piston group parts is shown. Analysis of changes in the physical-chemical parameters of engine oil showed that the tribochemical lubrication mode with the TVM-S device stabilizes the physical-chemical properties of the oil when refilling fresh oil "on the fumes" and ensures continuous operation (up to 10 thousand hours) in a long-term mode equal to two of its resources.

Influence of aldol condensation processes on the formation of surface films during friction in ester lubricants

The boundary lubrication mode is usually implemented in conditions of low sliding speeds and high loads. The formation of strong boundary lubricating films under this friction mode determines the operability and durability of the friction units. It is believed that the formation of surface boundary films during friction includes the stages of the lubricant oxidation, and the aldol condensation reaction of oxidized molecules. As a result, high-molecular substances called “friction polymers” are formed. The paper studies the formation of surface films in the presence of substances with different reactivity in the aldol condensation and Claisen condensation reactions. Sunflower oil, bis (2-ethylhexyl) sebacate (DEHS), triisodecyl benzene-1,2,4-tricarboxylate (TC) were used as lubricants. It is shown by ATR IR-spectroscopy of that the common thing for the studied oils is that the C=O and C-O groups participate in the formation of boundary films in these oils. The addition of substances, active in aldol condensation reactions, into lubricants does not accelerate the formation of boundary films. Additives that can chemically interact with iron contribute to the dissolution of the surface oxide film and accelerate the formation of boundary layers. The formation of “friction polymers” occurs when the lubricant molecules interact with the metal surface.

Monitoring and Control System for Heat Experimental Equipment of High-Speed Vertical Spindle Bearings

High speed of spindle for high-speed machining is the mission and development trend of today's machine tools. However, improper lubrication can cause a large temperature difference on the bearings, causing thermal deformation that affects the accuracy of the spindle. Heat experimental equipment for high-speed vertical spindle bearing is necessary. This paper presents a design and manufacture of control and monitoring system of heat experimental equipment for high-speed vertical spindle bearing based on PLC, WinCC and Webserver. This experimental device with supervisory control solution allows easy implementation of the test mode and data collection to plan out the appropriate lubrication mode. The system includes motor control and monitoring, observing of sensors, alarm and reporting at local and on site remotely. This solution can be applied to other industrial equipment to meet the needs of Industry 4.0.

INFLUENCE OF WORKING FLUID VISCOSITY ON LUBRICATION MODE OF HYDRAULIC UNITS OF CONSTRUCTION MACHINES

The influence of dynamic viscosity of working liquids И-20А, МГЕ-46В, ВМГЗ on the lubrication of plunger pairs of axial-piston pumps of construction equipment is considered in the article. Based on the existing classification of lubricant types, a mathematical model is obtained to determine the effective viscosity, which corresponds to the transition of the plunger pair from the boundary lubrication regime to the semi-liquid mode. The obtained model takes into account the geometric parameters, the speed of rotation of the pump shaft and the size of the dimensionless criterion — the relative thickness of the lubricating film. The calculation of the change in the effective viscosity from the angle of rotation of the shaft for a plunger pair of an axial-piston pump with an inclined disk.

THE RESULTS OF THE STUDY OF THE INFLUENCE OF THE OPERATING CONDITIONS OF THE TURBOCHARGER ON ITS PERFORMANCE

The operability of the bearing assembly, which ensures the operation of the turbocharger at different speeds of its rotor, determines the reliability of the turbocharger as a whole. In this regard, the condition of the turbocharger bearing assembly determines the performance of the entire turbocharger. The purpose of the research is to justify the parameter that determines the performance of the turbocharger and a comparative assessment of changes in the state of turbochargers with a standard lubrication system and when using individual bearing assembly lubrication systems. The main factors affecting the state of the turbocharger bearing assembly, and hence the length of the rotor rotation by inertia after the engine stops, are considered to be: the increase in the clearance in the bearing assembly, the speed of rotation of the turbocharger rotor before the engine stops, and the time of pressure drop in the bearing assembly to zero after the engine stops. To obtain dependences describing the effect of the gap in the turbocharger bearing, the time of pressure drop in its lubrication system after the engine stops, and the change in the duration of rotation of the turbocharger rotor by inertia in dynamics, we conducted experimental studies. The experiment involved vehicles with a standard lubrication system and with an individual lubrication system for the turbocharger bearing assembly. The data was sample along the main diagonal of the matrix of experimental indicators. The dependences of the effect of the gap and the time of pressure drop in the bearing assembly on the duration of rotation of the rotor of the turbocharger by inertia after stopping the engine, at the speed of rotation of the rotor before stopping the engine 10000, 25000 and 40000 min-1 are obtained. A comparative analysis of this indicator is given for turbochargers with a standard and individual lubrication system of the bearing assembly, which shows that the duration of rotation of the rotor by inertia increases from 45 s (standard lubrication mode) to 90 s (with an individual lubrication system). This gives us reason to believe that the wear rate of the bearing will decrease by half during operation

Evaluation of operational properties of aviation oils by tribological parameters

The quality of aviation oils was evaluated online on the basis of their lubricating, antifriction, rheological and antiwear properties in the friction contact. The use of the software and hardware complex for evaluation of operational characteristics of triboelements is offered. Approbation of the proposed methodology was performed on aviation oils SM-9. The increase in antifriction properties of the “Bora B” SM-9 oil was established to be due to the formation of limiting adsorption layers of lubricant on friction-activated contact surfaces, which are characterized by low shear stresses of the lubricant, and their structuring provides high effective viscosity in the contact at a level of 5142 Pa.s. It was revealed that at start-up the lubricant temperature is 20 0С and the mixed lubrication mode prevails, but with increasing the lubricant temperature to 100 0С the elastic-hydrodynamic (contact-hydrodynamic) lubrication mode dominates, then at maximum rotation speed of friction pairs the hydrodynamic lubrication mode dominates, regardless of oil temperature, which indicates the effective separation of the contact surfaces due to the formation of a lubricating layer between them. Analysis of the specific work of friction in the friction contact showed that the instability of this parameter evidences to intensification of destructive processes in the near-surface layers of metal and reduction in its wear resistance. The decrease in wear resistance of the lagging surface in the conditions of rolling with sliding for all types of investigated oils is due to the different directions of the friction force vector in the contact. In the course of operation of friction pairs in nonstationary conditions, the softening of the surface metal layers occurs, which has a positive effect on the tribological processes in the contact. The practical significance of the work consists in developing a methodology of analysis of lubricants, which makes it possible to more accurately evaluate their performance and provide recommendations for the choice of lubricant for specific friction units.

Hydrodynamic calculation of wedge-shaped system «slider-guide» operating on compressible lubricant in presence of melt on surface of guide

In the article on the basis of the equation of motion of the compressible lubricant for the «thin layer», continuity, state, and the equation describing the profile of the molten contour taking into account the formula of mechanical energy dissipation the asymptotic and self-similar solution is found for the extreme (when the speed tends to infinity) and non-extreme case. As a result of solving the problem, a refined mathematical calculation model of a wedgeshaped sliding support with a low-melting metal coating on a movable contact surface is obtained, which compensates for an emergency lack of lubricant and provides a stable hydrodynamic lubrication mode

Boundary lubrication of friction contacts steel/steel with Cr—DLC-coatings

The results of an experimental study of the tribological characteristics of inactive, surface-active, and chemically active lubricants in the boundary lubrication mode when steel is rubbed against steel with a carbon diamond-like (Cr—DLC)-coating. For comparison, also tested friction in these friction contacts under similar conditions, but without lubricant. The maximum coefficient of friction and maximum wear was obtained by tribological testing of steel on steel. The minimum coefficient of friction was obtained when steel was rubbed against Сr—DLC-coated steel in a surface-active lubricant medium.

TEST RESULTS FOR BALL-BEARINGS IN THE DRIVES OF SYSTEMS AND SCIENTIFIC EQUIPMENT OF A SPACECRAFT IN OSCILLATORY OPERATIONAL MODE

This paper aims at elucidating some special operational aspects of instrument ball bearings used in systems and scientific equipment of a spacecraft in oscillatory mode in vacuum with the lubricant VNII NP-274n. The service life of such bearings is mostly determined by the lubrication mode, as well as anti-torque moment, which is an indicator of internal energy losses. To observe these parameters in the course of bearings operation in oscillatory mode in vacuum an electromechanical test rig was set up. The test data obtained in oscillatory mode were compared with data obtained during continuous rotation of the same bearings. Based on the results of the tests, a lubricating mode was determined, an empirical formula was proposed for the relationship between the anti-torque moment and oscillatory motion parameters, as well as recommendations on extending the service life were provided. The paper may be of use to developers of systems and scientific instrumentation of a SC with oscillating shaft, which uses as supports ball bearings with predominantly axial load. Key words: spacecraft life, oscillatory motion, rotational resistance, lubrication mode, inertial slippage