Friction Mode Research Articles

Improving the energy efficiency of power transmissions of a rolling stock on the basis of dynamic anisotropy of frictional contact

The analysis showed the following tendencies of development and energy efficiency of designs of gearboxes for track machines: provision of a maximum level of efficiency, removal of rupture of a stream of the passed capacity, provision of a high level of reliability, decrease of power input on gearbox work, provision of convenience, simplicity of service and steering, engine braking maintenance, and also maintenance of a relatively low cost. The above-mentioned tasks are performed by including clutch pinion gears with the built in frictional amplifier elements in an automatic gearbox, and also during the effect of dynamic anisotropy of frictional bonds. Besides a torque transfer, the clutch gear carries out a safety clutch function. That means that there is sliding at a high rotational power. Factor of strengthening of the given link is Кstr → ∞ due to occurence of dynamic anisotropy of frictional bonds. Physical and mechanical characteristics of contacting surfaces are formed in the course of dynamic interaction of roughnesses in friction units at modes of dry and boundary friction. Essential-nonlinear friction processes, interconnected with dynamic processes on the contact area, define values of target characteristics of frictional system. They can fluctuate in a very wide range. The friction factor fmp for the same friction units at preservation of constant conditions and friction parameters can vary from zero to infinity that is an essence of dynamic anisotropy of frictional bonds.

Transition between Modes of Adhesion and Sliding Friction in Contacts of Axially Symmetric Bodies

Transition between Modes of Adhesion and Sliding Friction in Contacts of Axially Symmetric Bodies

A research on magnetic properties of magnetic nanodispersed lubricants

The paper presents the results of theoretical and experimental studies of the magnetic properties of magnetic lubricating oils. It shows oil magnetization curves in the initial state and after tests in the boundary friction mode. Oil properties were measured by an original magnetometer with Hall sensors. It has been established that triboeffects change oil composition and structure and decrease its magnetization. The results will help determine the optimal operating conditions of magnetic oils while maintaining their magnetic and lubricating properties.

Thrust Slip Bearings in a Turbulent Friction Mode with the Rheological Properties of a Viscoelastic Lubricant

Based on the concept of the turbulent flow of a viscoelastic lubricant, a two-component lubrication system consisting of mineral oil and a viscoelastic lubricant that represents a melt of fusible metals is considered. The results of studies on the tribological characteristics such as friction forces and the bearing capacity of friction assemblies are presented taking into account the viscosity and shear modulus of the molten layer depending on the temperature. Ways to improve the properties of lubricants through the introduction of additives and fillers therein are considered.

Calculation of a Radial Slider Bearing with a Fusible Coating

A method for forming an exact self-similar solution to the problem of hydrodynamic calculation of a radial plain bearing that operates in a steady-state friction mode in the presence of a lubricant has been constructed. Based on the equation of motion for a viscous incompressible electrically conducting liquid in the case of a ???thin layer,??? the continuity equation, and expressions for the dissipation rate of mechanical energy, an analytical relationship for the molten surface profile of fusible coating on a bearing bush taking into account the viscosity and electrical conductivity of a liquid lubricant depending on pressure is obtained. The effect of the parameters characterizing the dependence of viscosity and electrical conductivity on pressure and the effect of a parameter caused by melting the fusible coating surface of the bearing bush exerted on the bearing capacity and friction force are demonstrated.

Features of concentration dependence of load-carrying performance of spheroidal carbonic nanoclusters ethanol solutions

Though having significant advantages, use of ethanol as motor fuel for internal combustion engines entails a number of drawbacks. Substantial disadvantages of ethanol as such are its low anti-wear properties due to low load-carrying performance. Low load-carrying performance of ethanol does not allow for hydrodynamic friction mode in frictional nodal points of the fuel-delivery equipment and thereby shortens their operational life. The essence of concept of load-carrying performance has been analyzed. It has been shown that load-carrying performance for liquid media is similar to the characteristic of hardness for solid bodies. Both of these properties characterize suitability of materials for operation in certain conditions. At the same time, results of studies on changes that occur in these properties depending on variation of material composition, external conditions and influences enable to determine mechanisms and consistent patterns of transformations in volume or in surface layers of the studied materials under the influence of different factors. To increase loadcarrying performance, we proposed to use nano-sized carbonic clusters of spheroidal structure as additives to ethanol fuels. The nonmonotone monomodal nature of dependence of load-carrying performance of ethanol solutions from the content of nano-sized (5–40 nm) spheroidal carbonic clusters has been established. It has been demonstrated that with increase in solution concentration of nanoparticles the load-carrying performance escalates and reaches a maximum with their mass fraction of 0.01 %. When concentration of nanoparticles exceeds this threshold value, the loadcarrying performance of the solution starts to decline and approaches a value that is characteristic of additive-free ethanol. The established extreme nature of dependence has been accounted for reorganization of liquid supramolecular structure under the influence of carbonic nanoparticles.

Повышение ресурса осевых газовых подшипников с антифрикционным покрытием на основе плазменного электролитического оксидирования: физический эксперимент

Повышение ресурса осевых газовых подшипников с антифрикционным покрытием на основе плазменного электролитического оксидирования: физический эксперимент

Formation of a carbonaceous film on the surface of Cu in a bovine serum albumin solution

The tribochemical reaction between metal ions and proteins can result in the formation of a carbonaceous tribo-layer on the surface of metal-on-metal (MOM) artificial joints. This carbonaceous film can lubricate the tribo-pair and reduce the corrosion of the metal. The purpose of this work is to investigate the catalysis efficiency of Cu and Co ions in the formation of carbonaceous films at the contact regions. A ball-on-disc (Al2O3-on-Cu and Al2O3-on-Co alloy) friction mode in bovine serum albumin (BSA) solution was chosen for the wear test experiments. After the wear test, the tribo-layer formed on the wear spot (on Al2O3 ball) and wear track (metal disc) were collected and characterized. The results show that the Cu ions released upon friction promoted the adsorption of BSA on the wear track of Cu to give a protein film which was further transformed into a carbonaceous tribo-layer under the shear force between the Al2O3-Cu tribo-pair. When the Al2O3 ball and Co alloy were chosen as the tribo-pair, however, a carbonaceous tribo-layer was not observed on the Co alloy after the wear testing. This means that the catalysis efficiency of the Cu ion for the formation of a carbonaceous tribo-layer is stronger than that of the Co ion.

Effect of Fluorination of Ultrahigh-Molecular-Weight Polyethylene and Its Composites on the Surface Structure and Properties

The fluorination of ultrahigh-molecular-weight polyethylene and its composites containing graphite nanoplates, montmorillonite, molybdenum disulfide, and schungite as fillers was studied. The degrees of fluorination of the composites achieved at equal intervals of time were found to depend on the type of the filler. SEM images were obtained, and an EMF analysis of the surface of the starting and fluorinated polymer samples was performed. Fluorination affected the surface morphology. The distribution of fluorine that reacted with the polymer in its surface layer was shown to depend on the introduced filler. The effect of fluorination on the sliding friction coefficient and the wear in the dry friction mode of ultrahigh-molecularweight polyethylene and its composites was determined. The surface fluorination led to a decrease in these characteristics.

Effect of rail dynamics on curve squeal under constant friction conditions

Curve squeal noise is a severe railway noise problem that can occur when a railway vehicle negotiates a sharp curve. It is usually characterised by a very loud tonal noise and can be very annoying for people in the vicinity. It is generally attributed to friction-induced instability, either due to a falling friction characteristic with increasing sliding velocity or to a mode coupling mechanism which can lead to instability even for a constant friction coefficient. The squeal frequency is usually associated with one or more wheel modes. However, the wheel is coupled dynamically to the track and insufficient attention has been paid in previous research to the role played by the rail dynamic behaviour. In this paper, the effect of the rail dynamics on curve squeal under constant friction conditions is investigated by means of different modelling approaches. The rail is firstly modelled using a waveguide finite element (WFE) model and it is found that the inclusion of the rail dynamics in the model can lead to squeal in some situations where it would otherwise not occur. Various effects are then considered that may introduce additional resonant behaviour into the rail dynamics. These include the effect of the rail cross mobility, rail cross-section deformation, the influence of the periodic support of the rail and reflections between multiple wheels on the rail. The effect of the rail pad stiffness is also explored. However, the results show that all these factors have little influence on the predicted curve squeal instabilities. By means of a reduced model, the main characteristics of the rail dynamics that can result in squeal are then assessed. It is shown that the mass and damping-like behaviour of the infinite rail are at the origin of the instabilities rather than any modal behaviour of the track. Curve squeal may occur for a single wheel mode even if the rail is represented by a damper, which is a close approximation to the vertical mobility of the track at high frequencies. This forms a third possible mechanism for curve squeal in addition to falling friction and wheel mode coupling.

Influence of geometric parameters of the rotary hook on interaction of its elements in high-speed modes sewing machine

PurposeThe purpose of this paper is to develop the analytical model of the rotary hook geometric parameters’ interconnections, which allows determining the characteristic modes of interaction of its elements. In this study, the interaction mechanism of the bobbin case, the rotary hook and the support finger was defined, which allows to reduce the unit vibro-impact activity.Design/methodology/approachAs practice shows, the bobbin case sometimes turns against the rotary hook movement. This phenomenon can be used for the free passage of the needle thread. The change in the geometric parameters of the rotary assemble will allow to decrease its vibro-impact activity.FindingsThe interrelations of rotary assemble geometric parameters are established, and it is possible to determine the characteristic modes of its elements interaction and to establish a mechanism for controlling them. This allows reducing the vibro-impact activity of joint, improving friction modes and sewing technology. Criteria and values of a gap formation between the right contacting face of bobbin case and support finger protuberance are found.Research limitations/implicationsIn the future, it is necessary to conduct research on the behavior of the rotary assemble elements in the frequency operating modes of the sewing machine. It is necessary to show the influence of the resonance modes of operation of the rotary hook drive on the interaction of elements.Practical implicationsThe practical use of the results of the work makes it possible to reduce the vibratory impact of the shuttle, and also to create conditions for the smooth operation of the rotary hook and the bobbin case, and ensure the formation of a gap between the contacting face of bobbin case and support finger protuberance for the free passage of the needle thread. The results of the work can be used in the design of a rotary assemble with specified characteristic parameters and modes of elements interaction.Originality/valueAn analytical model of interrelations of geometric parameters of a rotating hook is developed. The characteristic modes of interaction of the rotary assemble elements were studied. The reasons for the vibro-impact activity of the rotary hook are studied. Also, the conditions under which the bobbin case will move against the direction of rotary hook rotation are determined.

Nanoscratch of aluminum in dry, water and aqueous H2O2 conditions

Nanoscale deformation behavior of aluminum at sliding interface was investigated by nanoscratch experiment and X-ray photoelectron spec-troscopy (XPS) in variable conditions involving dry, water and aqueous H2O2, which has not been discussed previously. It was found that deformation of aluminum in the nanoscratch process could be divided into two regimes relying on the evolution of frictional coefficient. Similar results have been observed in dry and water conditions. However, the stick-slip behavior is integrated into deformation process with aqueous H2O2 compared with the results of that in dry and water conditions, resulting from the formation and breaking of chemical bonds interaction of OH and Al atom. In addition, this deformation behavior is described in the framework of a mathematical model based on Mo’s theory using the atomic contact concept instead of asperity contact, which relates the transition of friction from sub-linear to linear and deformation changing from elastic to changing elastic-plastic. Finally, a parameter of critical energy barrier is employed to reveal the atomic material removal mechanism in Al chemical mechanical planarization (CMP) process with the consideration of chemical actions and nanoscale deformation behavior.

EFFECT OF DIAMOND INTERLAYER ON THE TRIBOLOGICAL PROPERTIES OF TiAlN FILM SLIDING AGAINST CARBON STEEL

In this study, the effect of diamond interlayer on the tribological properties of titanium aluminum nitride (TiAlN) film sliding against medium carbon steel is investigated in dry rotary friction tests, by evaluating the coefficients of friction (COFs), wear rates, worn surfaces and element transitions of the contacted surfaces in the cemented carbide (WC-Co)-steel, TiAlN-steel, microcrystalline diamond (MCD)-steel, TiAlN/MCD-steel, micro- and nano-crystalline diamond (MNCD)-steel and TiAlN/MNCD-steel contacting pairs. It is found that compared with the TiAlN monolayer, the TiAlN/MCD bilayer film shows 57% higher COF, while the COF of TiAlN/MNCD multilayer inversely drops as much as 54%, due to the distinguished surface diamond grain morphologies of the MCD and MNCD interlayers as well as the copied effect of the TiAlN layer with relatively small thickness. Meanwhile, the diamond interlayer can provide robust load support for the top TiAlN layer, induce the wear mechanism transform from the abrasive wear to adhesive wear, and result in the mild wear of TiAlN/MCD and TiAlN/MNCD multilayers compared to the TiAlN monolayer. Moreover, the softer TiAlN top layer on MCD and MNCD interlayers can effectively improve the storage capacity of element oxygen and worn steel ball debris as well as accelerating the surface chemical reactions to form a smoother continuous ionic metal oxides tribofilm in the contacted zones due to its good self-lubricating property. Among all the hard coatings discussed when sliding against medium carbon steel, the TiAlN/MNCD coating shows the lowest COF and mild wear, due to the robust load support capacity of the beneath MNCD layer as well as the good self-lubricated and tribofilm formation capacity of the top TiAlN layer, which shows broad application potential in carbon steel machining.

Simulation, Experimental Testing and Optimization of Starting and Shifting Control Strategies of DCT Wet Dual Clutches with Respect to Sliding Friction

For starting and shifting processes of dual-clutch transmission vehicle, the combined starting control strategy for dual clutches is proposed to reduce temperature rise of clutch and the dynamics simulation model of starting and shifting is built. For the two different downshift modes during inertia phase, the work and power of sliding friction are comparatively analysed. The results can provide boundary conditions of heat source for thermal equilibrium analysis under two typical starting conditions. During the benchmark test, the extreme starting condition under full load and large gradient and the three typical shifting conditions are set. Then, the sliding friction test is executed. The transmitted torque of wet dual clutches and the speed of driving and driven plates of dual clutches are measured to calculate work and power of sliding friction, and the corresponding temperature rise of wet dual clutches is obtained. Furthermore, the heat generation and heat dissipation conditions under different sliding friction modes are analysed. The corresponding influences on clutch control and temperature rise of cooling oil are also discussed. Based on the simulation and test results, the thermal equilibrium of clutches is analysed. The evaluation indexes of sliding friction work are calculated, and then the starting and shift control strategies are optimized.

Influence of Physicochemical Characteristics of Tempering Medium and Friction Modes on the Structure and Kinetics of Strengthening and Destruction of Surface Layer of Nickel

The influence of the physicochemical characteristics of the tempering medium on the structure of nickel samples is studied. The micromechanisms of plastic hardening and fracture of the surface layer under friction are established. The temporal changes in strength characteristics of the metal surface layer at the initial stages of friction load are determined. These strength characteristics have a cyclic character. The duration of the cycle of strength characteristics strongly depends on the tempering medium.

The Wear Resistance of Composite Materials Based on Ultra-High-Molecular-Weight Polyethylene with Fillers of Various Types

The tribological properties and wear resistance under different action of composite materials based on of ultra-high-molecular-weight polyethylene (UHMWPE) and fillers of various types such as organomodified montmorillonite (MMT), graphite nanoplates (GNP), molybdenum disulfide, and shungite prepared via polymerization in situ are studied. According to the obtained results, the introduction of these fillers to UHMWPE in the amount of 0.4–7 wt % has almost no effect on the value of the coefficient of sliding friction on steel in the mode of dry friction. Composites with GNP, MoS2, and shungite are characterized by a significant (two- to threefold) increase in the wear resistance in the case of sliding friction on steel. The abrasive wear of composites in the case of friction on an abrasive paper is substantially affected by the type of filler, the use of MMT was the most effective for increasing the wear resistance of composites. In the case of a highspeed impact effect of water–sand suspensions all the studied composites are characterized by increased wear resistance in comparison with industrial UHMWPE at a low concentration of fillers and by an increase in the wear with the increase of the filler content.

Antifriction Properties of Plasma-Chemical Coatings Based on SiO2 with MoS2 Nanoparticles under Conditions of Spinning Friction on ShKh15 Steel

The antifriction properties of coatings in the form of a nanocomposite of a silica layer with molybdenum disulfide nanoparticles distributed in it, whose average sizes are 70, 64, 61, and 53 nm and concentrations are 80, 73, 68, and 62 wt %, respectively, grown via plasma-chemical deposition at atmospheric pressure on a 12Cr18Ni10Ti steel, are studied. The best tribotechnical properties are established for a SiO2 + 68% MoS2 coating (61 nm) which possesses the most stationary friction mode and a friction force two times lower as compared to a MoS2-free SiO2 coating.

Correlation between Lube Oil HTHS and Techno-Economic Performance and Service Life of a Reciprocating Engine

This paper discusses the effect of lube oil high-temperature viscosity on performance indices of high-powered automotive engines (e.g., power, fuel economy and wear rate of friction pairs). Such engines are generally prone to departure from hydrodynamic friction mode in friction pairs, caused by high mechanical load and high lube oil temperature. In this case friction horsepower will depend not only on oil viscosity parameters, but also on properties of anti-wear and anti-friction additives, if any. Moreover, spread in high-temperature viscosity of motor oils belonging to the same SAE group may be great enough. This paper furnishes evidence of existence of optimum high-temperature viscosity level, at which fuel economy reaches its maximum. Dependence of optimum viscosity on engine power conditions is revealed. One of the tasks of this work is examination of how high-temperature viscosity (HTHS) of modern all-synthetic motor oils, belonging to various viscosity classes, correlates with friction and wear characteristics of a high-speed motorcar engine.

Automatic Control System of an Oil Pressure Regulator for Hydraulic Press Assembly of Interference Fits

В статье рассматривается система автоматического управления регулятором давления масла на основе пропорционального регулятора, а также ее функциональная схема, составленная в соответствии с исходными данными об используемом технологическом оборудовании в исследуемом регуляторе давления и алгоритм управления данным регулятором. Приведены результаты тестовых испытаний регулятора давления с предлагаемым алгоритмом управления с целью определения оптимальных границ зоны нечувствительности (область, в которой изменения регулируемого давления не вызывают действия регулятора) исходя из стабильности работы системы с минимальной статической ошибкой. Предложенная система управления позволяет регулятору давления обеспечивать поддержание величины давления масла в требуемом диапазоне. Процесс автоматизированной гидропрессовой сборки гарантированно осуществляется в режиме жидкостного трения, реализуя достоинства технологии, а именно, сохранность сопрягаемых поверхностей и прочность соединения.

Self-Powered Wind Sensor System for Detecting Wind Speed and Direction Based on a Triboelectric Nanogenerator

The development of the Internet of Things has brought new challenges to the corresponding distributed sensor systems. Self-powered sensors that can perceive and respond to environmental stimuli without an external power supply are highly desirable. In this paper, a self-powered wind sensor system based on an anemometer triboelectric nanogenerator (a-TENG, free-standing mode) and a wind vane triboelectric nanogenerator (v-TENG, single-electrode mode) is proposed for simultaneously detecting wind speed and direction. A soft friction mode is adopted instead of a typical rigid friction for largely enhancing the output performance of the TENG. The design parameters including size, unit central angle, and applied materials are optimized to enhance sensitivity, resolution, and wide measurement scale. The optimized a-TENG could deliver an open-circuit voltage of 88 V and short-circuit current of 6.3 μA, corresponding to a maximum power output of 0.47 mW (wind speed of 6.0 m/s), which is capable of driving electronics for data transmission and storage. The current peak value of the a-TENG signal is used for analyzing wind speed for less energy consumption. Moreover, the output characteristics of a v-TENG are further explored, with six actual operation situations, and the v-TENG delivers fast response to the incoming wind and accurately outputs the wind direction data. As a wind sensor system, wind speed ranging from 2.7 to 8.0 m/s can be well detected (consistent with a commercial sensor) and eight regular directions can be monitored. Therefore, the fabricated wind sensor system has great potential in wireless environmental monitoring applications.