Lubrication and Friction

One of the major costs incurred by railway companies is the maintenance of turnouts.This situation occurs because the large dynamic forces between the wheels of a train and the rails of a turnout cause excessive wear, rolling contact fatigue and rapid degradation of other components. A thorough understanding of the dynamic interaction between a train and a turnout could lead to a better design of the corresponding vehicle/track or of the damage mechanisms and subsequently to a smarter maintenance planning. Such an insight can be obtained through a detailed model of the train-turnout interaction. Such models exist in the literature for vehicle-track interaction, but they have some shortcomings when it comes to train-turnout interaction. This leads to the following research questions: 1. How to model the wheel rail contact? In this thesis different models are presented for the search of the contact location as well as for the normal and the tangential contact problem. Especially the r...

Engine downsizing is desired for modern heavy-duty vehicles to enhance fuel economy and reduce emissions. However, the smaller engines usually cannot overcome the parasitic loads during engine start-up. A new clutch system is designed to disconnect the downsized engine from the parasitic losses prior to the idling speed. A multi-scale, multi-physics model is developed to study the clutch system. Multi-body dynamics is used to study the combined translational-rotational motions of the clutch components. A micro-scale contact model is incorporated to represent the frictional characteristics of the sliding surfaces. Although the clutch is designed for dry contact operation, leakage of actuating hydraulic fluid can affect the interfacial frictional characteristics. These are integrated into the multi-body dynamic analysis through tribometric studies of partially wetted surfaces using fresh and shear-degraded lubricants. Multi-scale simulations include sensitivity analysis of key operating parameters, such as contact pressure. This multi-physics approach is not hitherto reported in the literature. The study shows the importance of adhesion in dry clutch engagement, enabling full torque capacity. The same is also noted for any leakage of significantly shear-degraded lubricant into the clutch interfaces. However, the ingression of fresh lubricant into the contact is found to reduce the clutch torque capacity.

Organic friction modifiers (FMs) are commonly utilized in lubricants. FM molecules possess a polar head group that interacts with metallic surfaces and aliphatic chains that cohesively interact with neighboring molecules. Under boundary lubrication conditions, as experienced in engine valve trains and cylinders, fluid films are unable to form between metallic surfaces. This results in metal-metal contact. Thus, organic friction modifiers are commonly utilized to reduce friction under these conditions. While efficacious, these molecules are consumed over time owing to engine environments, reducing their effectiveness. To replenish organic friction modifier stocks in base oil lubricants, tertiary ester derivatives of fatty acid-containing dicarboxylic acids were investigated. A series of fatty acid-containing dicarboxylic acids were first developed based on a tartaric acid backbone and their friction modifying capabilities assessed. Coefficient of friction studies illustrated that friction-modifying capabilities were heavily influenced by polar head group type (i.e., carboxylic acid, ester) and chemical bond to tartaric acid (i.e., ester, ether). Thermogravimetric analysis coupled gas-phase Fourier transform infrared spectroscopy revealed that fatty acid-containing dicarboxylic acids degraded into their respective fatty acids at elevated temperatures. Controlled release studies were conducted on a compound modified with thermocleavable esters, and showed sustained friction modifying activity through the course of the entire study. These systems are ideal candidates for the controlled delivery of friction modifiers, which can increase engine efficiency and reduce fuel consumption, effectively reducing vehicle emissions.

Accurate descriptions of strength evolution are required in predictive models of fault zone behavior during earthquakes. At low sliding rates, frictional resistance between fault rocks is much higher than the shear stress that is typically inferred to be present during earthquakes. Laboratory experiments confirm that the friction coefficient drops at high sliding rates, and it is suggested that strengthening, possibly related to an increase in the area of viscous melt patches, may occur after this initial weakening stage. Most existing weakening mechanisms do not predict such strengthening, which may exert an important control on the thickness of the shear zone. We propose a micromechanical model of flash heating that describes how shear resistance evolves at the asperity scale as a result of distributed deformation over a weak layer that grows during the brief lifetime of each asperity contact. Beyond a threshold weakening velocity, our model predicts that friction should decrease with slip rate since higher sliding speeds cause the weak layer to thicken more rapidly. A comparison with published experimental data from a range of mineral systems shows good agreement with the model predictions. The parameter choices that ensure good model fits to the laboratory friction data are consistent with a priori estimates for the onset of asperity melting at high contact normal stresses. At higher sliding rates and/or elevated temperatures, our model predicts that the frictional rate dependence should transition from velocity weakening to become velocity strengthening because decreases in the contact lifetime with slip rate cause the average asperity strength to increase.

There are increasing pressures upon the automotive industry to reduce harmful emissions as well as meeting the key objective of enhanced fuel efficiency, while improving or retaining the engine output power. The losses in an internal combustion (IC) engine can be divided into thermal and parasitic as well as due to gas leakage because of untoward compression ring motions. Frictional losses are particularly of concern at low engine speeds, assuming a greater share of the overall losses. Piston–cylinder system accounts for nearly half of all the frictional losses. Loss of sealing functionality of the ring pack can also contribute significantly to power losses as well as exacerbating harmful emissions. The dynamics of compression ring is inexorably linked to its tribological performance, a link which has not been made in many reported analyses. A fundamental understanding of the interplay between the top compression ring three-dimensional elastodynamic behavior, its sealing function an...

The increasing attention to the environmental and health impacts of industrial activities by governmental regulations and by the growing awareness level in the society is forcing industrialists to reduce the use of mineral oil-based metalworking fluids as cutting fluid. Cutting fluids have been used extensively in metal cutting operations for the last 200 years. In the beginning, cutting fluids consisted of simple oils applied with brushes to lubricate and cool the machine tool. As cutting operations became more severe, cutting fluid formulations became more complex. There are now several types of cutting fluids in the market and the most common types can be broadly categorized as cutting oils or water-miscible fluids. In this review, the applicability of vegetable oil-based metalworking fluids in machining of ferrous metals has been undertaken. The advantages of metalworking fluids and its performances with respect to the cutting force, surface finish of work piece, tool wear and temperature at the cutting zone have been investigated. It has been reported in various literature that metalworking fluids, which are vegetable oil-based, could be an environmentally friendly mode of machining with similar performance obtained using mineral oil-based metalworking fluids. © 2011 Elsevier Ltd. Allrightsreserved.

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http://www.sciencedirect.com/science/article/pii/S0890695511001726

Engine downsizing is desired for modern heavy-duty vehicles to enhance fuel economy and reduce emissions. However, the smaller engines usually cannot overcome the parasitic loads during engine start-up. A new clutch system is designed to disconnect the downsized engine from the parasitic losses prior to the idling speed. A multi-scale, multi-physics model is developed to study the clutch system. Multi-body dynamics is used to study the combined translational-rotational motions of the clutch components. A micro-scale contact model is incorporated to represent the frictional characteristics of the sliding surfaces. Although the clutch is designed for dry contact operation, leakage of actuating hydraulic fluid can affect the interfacial frictional characteristics. These are integrated into the multi-body dynamic analysis through tri-bometric studies of partially wetted surfaces using fresh and shear-degraded lubricants. Multi-scale simulations include sensitivity analysis of key operating parameters, such as contact pressure. This multi-physics approach is not hitherto reported in the literature. The study shows the importance of adhesion in dry clutch engagement, enabling full torque capacity. The same is also noted for any leakage of significantly shear-degraded lubricant into the clutch interfaces. However, the ingression of fresh lubricant into the contact is found to reduce the clutch torque capacity.

In the past there has been considerable interest in the possibility of using liquid lubricants containing dispersed, solid particles in the 1-50 micron size range to reduce friction and wear. These particles are used in greases and some industrial oils. Researchers are now directing their attention to the behavior of much smaller colloidal particles in the range of 5 nm to 200 nm diameter. Such systems are formally known as ''colloidal sols'' and have been claimed to influence friction and wear. Further reasons for studying such colloidal particles is that they are present in soot-contaminated engine lubricating oils, as wear debris and as partially-soluble additives. Thus, the objective of the work derived in this paper was to investigate the mechanism of action of colloidal solid particles in the range of 5 to 200 nm diameter in lubricating oils. Of particular interest was the effect of slide-roll ratio on particle entrainment and the influence of the ratio of particle diameter to elastohydrodynamic lubricant film thickness on particles' behavior. This study has shown that in thin film contacts, colloid nanoparticles penetrate EHD contacts mainly by a mechanism of mechanical entrapment. It is found also that in rolling contacts at slow speeds, colloids formed a boundary film of at least 1 or 2 times the particle size. This film influence friction and wear. However, this film is lost at high speed and the film thickness reverts to the colloid-free fluid. The results of this study have enabled a mechanism of lubricating action by colloid sols to be derived.

The 2D crystal structure of MoS2 gives rise to interesting properties for applications such as solid lubricants, optoelectronics, sensors and catalysis. Transition-metal doping has been shown to enhance performance in solid lubrication and catalysis. However, the mechanism for improvement, especially in coefficient of friction and reduction in wear for lubrication is unclear, which we address in this paper with theoretical calculations. Our previous work investigated Ni-doped MoS2 in the bulk 2H phase with structure, elasticity, thermodynamics, and Raman/IR spectroscopy. This work now explores other polytypes (1H and 1T monolayer, and 3R bulk) to determine favorable sites for Ni, the doping effect on crystal structure, electronic properties and the layer dissociation energy. The doping formation energy for Mo and S substitution or intercalation/adsorption shows the most favorable are tetrahedral intercalation, Mo-atop and hollow site in bulk phases, 1H and 1T respectively and suggests a possibility of phase change from 2H to 3R under substitution. In-plane change in lattice parameters were small but lattice parameters out of plane change notably. We find metallic behavior in 3R and 2H under Mo substitution, and in-gap states for Mo and S substitution in 1H, which could have interesting optoelectronic applications. Doping the 1T phase resulted in reconstructions leading to a metal-semiconductor transition. We find that Ni doping strengthens the layer binding which can explain the mechanism of low wear. Our systematic study shows the effect of doping concentration. This work gives insight into the previously unclear structure of Ni-doped MoS2, the relation of energy and structures of doped monolayers and bulk systems, the electronic properties under doping, and the effect of doping on interlayer interactions.

In this study, a review of the available literature on lubrication techniques during machining processes was conducted. Factors such as workpiece material, tool material and machining conditions were observed to be vital to the performance of any of the techniques. The performance and drawback of each technique were highlighted based on the machining conditions. It concludes by making a case forminimum quantity lubrication (MQL) method using vegetable oil-based lubricant in different machining processes, as a way of addressing the environmental health issues and cost associated with the application of lubricant in machining processes. © 2012 Elsevier Ltd. All rights reserved.

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http://www.sciencedirect.com/science/article/pii/S0959652612005483

This article presents the experimental findings for the contact pressure, anti-wear, and extreme pressure properties of engine oils fortified with 2% of Lupromax EA Sulfurized Ester using Portable Timken Load Machine adopting a compound leverage ratio of 1:25.89

The purpose of the project is to fabricate a Personal Transporter (PT).This vehicle is designed to overcome the cost of the actual Segway Vehicle and to provide zero pollution within the campus or industries and this transporter doesn’t use the gyroscope unit and sensors to keep the vehicle in the flat position, Instead this is achieved by the supporting wheels. The project aims at fabricating a vehicle which can reach a maximum speed of 20kmph (can be programmed up to 50kmph) and travel a distance of approximately 8- 10 kms. The time for which the vehicle runs is roughly 2 hours and vary depending on the speed at which the vehicle travels. The torque and power of the motor and are selected from the various configurations available in the market and which satisfies our requirements also. The wheels used are hub motor type wheels in which the motor is situated inside the hub of the wheel at the center. These wheels are not generally available in India and need to be imported. These wheels require less torque and power when compared to motor driving the wheel. The input to the wheel is given through an accelerator and is controlled using an electronic controller. Brakes can be applied to any wheel and turning the vehicle can be done by applying brakes on any of the side required depending on the direction of turn to be taken. For the vehicle to stop completely both the brakes need to be applied.

In this paper are presented the power losses and sources of their occurrence in worm gear boxes. These are the losses that occur in the coupling of worm teeth and worm gear, losses in bearings, seals and oil churning power losses in the transmission. When the operation of worm gearing is characterized by line contact of coupled elements which is accompanied by significant sliding, the highest value have the power losses in the worm and worm gear coupling compared to other losses in gearing. Among other things, in the paper also presents the expressions that are used for calculation of individual power losses and efficiency of the gearing. The size of the losses primarily depends on the type of coupled material and geometry of worm pair, circumferential velocity (input rotational speed), the type and viscosity of lubricating oil, load, worm shape, and temperature and so on. The paper also deals with the influence of different factors on power losses and efficiency. As the efficiency of the worm pair is significantly lower compared to other types of gear pairs, the appropriate combination of geometric parameters and materials of worm and worm gear, lubrication and working conditions can significantly affect its increase.

A B S T R A C T Textured surfaces have been shown to provide enhanced tribological performance in a variety of contacts. Numerical analysis and optimisation methods are combined for application-oriented texture optimisation. However, an analytical approach is advantageous in providing more generic in-depth understanding of the nature of the relationships between texture parameters and objective functions, such as enhanced load carrying capacity and reduced friction. The paper outlines such an approach to obtain a set of global optimum design parameters for partially textured surfaces. The optimised results are expressed in dimensionless form, which enables their use for a variety of applications. The performance of optimised partially textured sliding surfaces is compared with the other conventional bearing geometries in their optimum state.

The main purpose of this research was to establish the effectiveness of the V844* corrosion inhibitor for seawater on various metallic materials: carbon steel, aluminum and copper alloy at different concentrations via colloid formation. The changes in both physical and chemical properties of seawater, including pH, total hardness, alkalinity, total dissolved solids (TDS) and conductivity at different concentrations of V844 were assessed, too. The test procedure involves dissolving the V844 corrosion inhibitor (CI) powder provided by Magna International Private Limited in seawater to obtain a stock solution of 4% V844 in seawater, which was further diluted to obtain the remaining concentrations. The analysis of parameters begun when various metal species, polished beforehand, were placed into the solutions. The analysis was observed over a period of 26 days and a total of 9 sets of readings were obtained. From our observation and ear power stations burning fossil-fuels generating acidic rains, the pH can diminish to 6.

Kita didalam hampir semua aktivitas dan kegiatan memerlukan energi, demikian juga semakin tinggi peradabandan kualitas kehidupannya maka semakin tinggi pemakaian dan ketergantungannya terhadap energi.Energi didalam penggunaannya sering dirubah dari satu bentuk kebentuk yang laindan alatnya disebut mesin. Perubahan misalnya dari energi kalor menjadi energi mekanis, alatnya adalah mesin kalor, energi mekanis menjadi energi listrik, alatnya adalah generator, energi listrik menjadi energi mekanis, alatnya adalah motor listrikdan sebagainya. Pada saat ini kita hampir setiap saat beraktivitas dengan pergi dan pulang dengan menggunakan alat transportasi kendaraan yang digerakan oleh mesin kalor, baik mesin penyalaan api atau disebut mesin bensin maupun mesin penyalaan kompresi atau disebut mesin Diesel. Kedua mesin ini meskipun banyak persamaannya tetapi juga banyak perbedaan, baik proses maupun karakternya. Mesin bensin menggunakan bahan bakar bensin atau gasoline, sedangkan mesin Diesel menggunakan bahan bakar Solar, yang keduanya dihasilkan dari penyulingan minyak bumi (crude oil) dengan cara pemisahan dengan berbagai tingkat titik didihnya. Minyak bumi terbentuk oleh timbunan fosil pada jaman purba dan tidak ada proses pembentukan lagi, sehingga keberadaannya terbatas dan tidak terbarukan (unrenewable). Ketersediaan minyak bumi sudah diperhitungkan jumlah serta pemetaan lokasinya, dan akan segera habis, sehingga terus meningkat harganya. Seperti yang kita rasakan, dulu Negara kita adalah pengekspor sekarang jadi negara pengimpor bahan bakar minyak. Minyak bumi, atau lebih dikenal dengan Petroleum adalah senyawa antara atom Hydrogen dan Carbon yang membentuk molekul yang disebut Hydrocarbon. Gambar dibawah menunjukan skema proses refining crude oil secara garis besar. Dibagian dalamtower fractioning berisi rak-rak dengan tingkatan-tingkatan berbeda. Crude oil dituang dari bagian atas tower fractioning dan dipanaskan dari bawah. Bila proses ini berlangsung , temperature dibagian atas dari tower fractioning, komponen-komponen yang mempunyai titik didih rendah (komponen-komponen yang mudah menguap) akan menguap lebih dulu, dan komponen –komponen sisanya mengalir turun ke-rak bagian bawah berikutnya. Komponen-komponen crude oil yang mengalir turun kerak berikutnya menguap pada temperature baru, dan komponen-komponen sisanya terus mengalir turun ke-rak berikutnya. Dengan cara demikian, selagi crude oil mengalir dari atas tower fractioning kedasar, komponen-komponen dengan titik didih rendah berurutan menguap. Oil yang diuapkan dikelompokan pada setiap tingkatan, dan kemudian didinginkan untuk mendapatkan jenis-jenis fuel oil. Dari skema gambar dibawah dapat diperoleh urut-urutan pertama-tama dengan gas oil oleh separator dipisahkan gas dari bahan cair diperoleh natural gas dan natural gasoline dan bahan cair.Kemudian masing-masing diproses untuk memperoleh produk yang bersih dari kandungan-kandungan yang merugikan (uap air misalnya) serta berbahaya atau beracun. Sedangkan bahan cair akan diproses secara fractioning dan akan diperoleh : 1. Petroleum gas dengan titik didih yang rendah. 2. Light gasoline (bensin) dengan titik didih antara 30 hingga 180 o C. 3. Heavy gasoline dengan titik didih sama dengan no 2). 4. Kerosene (minyak tanah) dengan titik didih 170 hingga 250 o C. 5. Light Diesel oil dengan titik didih 240 hingga 350 o C. 6. Heavy Diesel oil dengan titik didih sama no 5). 7. Residual oil dengan titik didih minimum 350 o C.

One of the major costs incurred by railway companies is the maintenance of turnouts. This situation occurs because the large dynamic forces between the wheels of a train and the rails of a turnout cause excessive wear, rolling contact fatigue and rapid degradation of other components. A thorough understanding of the dynamic interaction between a train and a turnout could lead to a better design of the vehicle and track structures, deeper insight into the damage mechanisms and subsequently to smarter maintenance planning.

The study of textured surface performance is one of the highly researched topics in recent times. This is mainly due to the advantages that such surfaces can potentially provide in practice, in mitigating adverse tribological conditions, such as friction and wear. However, considering the complexities found in practice, a methodological analysis and evaluation procedure is essential in order to gain an understanding of the benefits from utilising such features in a given contact. The current study provides a combined analytical and experimental approach towards an enhanced understanding of the behaviour of textured surfaces relative to their untextured counterparts. The developed analytical models are invaluable in providing an insight into the relationship between the many parameters involved in defining even simple surface texture feature geometry and the expected outcomes in practice, when corroborated with experimental results. The current study reports on such an endeavour. With the studied texture configuration, the results have shown the possibility of reducing friction by as much as 25%.

In this study, a review of the available literature on lubrication techniques during machining processes was conducted. Factors such as workpiece material, tool material and machining conditions were observed to be vital to the performance of any of the techniques. The performance and drawback of each technique were highlighted based on the machining conditions. It concludes by making a case for minimum quantity lubrication (MQL) method using vegetable oil-based lubricant in different machining processes, as a way of addressing the environmental health issues and cost associated with the application of lubricant in machining processes.

A systematic approach is required in order to determine the frictional characteristics of a contacting pair in the presence of a tribofilm. Despite the clear benefits in functionality and in reducing wear, the generation of ZDDP-based tribofilms often lead to increased frictional losses. Such an increase is also observed in the tribometric tests reported here, as well as in open literature. This paper investigates the underlying mechanics for the rise in friction using an integrated methodology, based upon Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). The use of an analytical contact mechanics model demonstrates that the pressure coefficient of boundary shear strength, measured using lateral force microscopy, provides an explanation for the observed increase in measured friction at micro-scale.

The purpose of the project is to fabricate a Personal Transporter (PT).This vehicle is designed to overcome the cost of the actual Segway Vehicle and to provide zero pollution within the campus or industries and this transporter doesn’t use the gyroscope unit and sensors to keep the vehicle in the flat position, Instead this is achieved by the supporting wheels.

The project aims at fabricating a vehicle which can reach a maximum speed of 20kmph (can be programmed up to 50kmph) and travel a distance of approximately 8- 10 kms. The time for which the vehicle runs is roughly 2 hours and vary depending on the speed at which the vehicle travels.

The torque and power of the motor and are selected from the various
configurations available in the market and which satisfies our requirements also. The wheels used are hub motor type wheels in which the motor is situated inside the hub of the wheel at the center. These wheels are not generally available in India and need to be imported. These wheels require less torque and power when compared to motor driving the wheel.

The input to the wheel is given through an accelerator and is controlled using an electronic controller. Brakes can be applied to any wheel and turning the vehicle can be done by applying brakes on any of the side required depending on the direction of turn to be taken. For the vehicle to stop completely both the brakes need to be applied.

Tribofilms are activated using precision sliding strip microscale tribometry with a base and a fully formulated lubricant with a ZDDP anti-wear additive. The employed tribometry uses combined pressure, shear and temperature activation. The chemical compositions of the formed tribofilms are ascertained through use of Photo-electron X-ray Spectroscopy (XPS). Nanoscale frictional measurements of the tribofilms are reported using fluid cell lateral force microscopy (LFM). The measured coefficient of interfacial boundary shear strength is used with analytical contact mechanics to relate the in-situ conditions to the activation energy components of the Eyring potential cage model. The paper shows that combined LFM and the Eyring model can explain the variations in the frictional characteristics of formed tribofilms.

This paper deals with the tribological performance of carbon nanoparticles dispersed in polyalphaolefin PAO6 oil. Stribeck curves are obtained under various operating conditions, using a fully instrumented pin-on-disc tribometer under controlled conditions. A detailed multi-physics thermal fluid flow model with Lagrangian low concentration discrete solid phase and Eulerian multi-phase fluid with cavitation represented by modified Rayleigh-Plesset and vapour transport equation is presented. The numerical predictions under identical conditions to the experiments show good conformance with the measurements, and provide a fundamental understanding of the role of nanoparticles. Results show improved heat transfer from the contact with the presence of nanoparticles even at low levels of concentration. The analysis shows that this leads to higher lubricant viscosity, load carrying capacity and reduced friction. Furthermore, a resulting small region of cavitation at low volume fraction does not unduly affect the enhanced heat transfer of nanoparticles. This combined experimentation and detailed numerical analysis has not hitherto been reported in literature.

Frictional losses are one of the main causes of reduced energy efficiency in all machines and mechanisms. In particular, there is mounting pressure upon manufacturers of all forms of vehicle to comply with increasingly stringent legislation and directives with regard to harmful emissions. Therefore, reduction of friction has become an imperative issue. The traditional approach of dealing with surface material and lubricant formulation in isolation has been replaced by a lubricant–surface system approach. This paper presents multi-scale experimentation from nano/meso-scale lateral force microscopy of ultra-thin surface adsorbed films through to micro-scale precision sliding tribometry to investigate lubricant–surface friction optimisation within the mixed regime of lubrication, using lubricants with different organic and inorganic friction modifying species. These affect the parameters of the system, commonly used as input to models for mixed and boundary regimes of lubrication. Therefore, the precise measurement of these parameters at different physical scales is important. The study also makes use of detailed numerical predictions at micro-scale through combined solution of the average Reynolds equation as well as interaction of wetted asperities in mixed and boundary regimes of lubrication. Good agreement is found between the predictions and measurements at micro-scale tribometric interactions. Furthermore, the same trends are observed in testing across the physical scales.

A tribo-dynamics model of a differential hypoid gear pair is presented, integrated with lubricated contact of meshing teeth pair with lubricants of varying rheological properties. Particular attention is paid to the effect of lubricant formulation and gear geometry on the system efficiency. The  influence of gear torsional dynamic response is taken into account in a 4-Degree of Freedom (DoF) model. The contact geometry and kinematics of the hypoid gear pair are estimated, using Tooth Contact Analysis (TCA). Two fully formulated gear lubricants of the same viscosity grade (SAE 75W-90) blended with the same additive pack, but with different types and concentration of viscosity modifier (VM) are considered. Conjunctional friction is predicted for viscous shear of fully characterised lubricants as well as boundary interaction of rough surfaces. The results show loss of friction resulting in resonant response of the gear pair with impact of meshing teeth exhibiting non-linear jump phenomenon. The predictions also show that lubricants with higher pressure – viscosity (PV) coefficients tend to exhibit increased power loss.

A tribo-dynamics model, predicting the conjunctional inefficiency and dynamic response of automotive hypoid gear pairs is presented. A dynamics model is coupled with an analytical friction model (viscous and boundary). The temperature rise at the centre of the conjunction is accounted for through use of thermal network model and Time Temperature Superposition (TTS) method, as well as the time varying geometry of the meshing gear teeth. Newtonian and non-Newtonian lubricant shear behaviour are both considered Surface topography measurements of a run-in pinions are obtained. Inefficiency calculations are performed for typical automotive drive cycle snapshots. Precisely measured lubricant shear characterstics for lubricants different blended viscosity modifiers and evolving surface topography are used in the study of transmission inefficiency. The integrated thermal-tribodynamic analysis is shown to distinguish between different viscosity modifier types, an approach not hitherto reported in literature.

Starvation occurs when the lubricated contact uses up the lubricant supply, and there is not enough lubricant in the contact to support the separation between solid surfaces. On the other hand, the use of textures on surfaces in lubricated contacts can result in a higher film thickness. In addition, a modification of the surface's geometrical parameters can benefit the tribological behaviour of the contacts. In this article, for parallel sliding surfaces in starved lubricated conditions, the effect of surface texturing upon the coefficient of friction is investigated. It is shown that surface texturing may improve film formation under the conditions of starvation, and as a result, the frictional behaviour of the parallel sliding contact. Furthermore, the effect of starved lubrication on textured surfaces with different patterns in the presence of a cavitation effect, and its influence on frictional behaviour, is investigated. It is shown that surface texturing can reduce the coefficient of friction, and that under certain conditions, the texturing parameter could have an influence on the frictional behaviour of parallel sliding contacts in the starved lubrication regime.

Improved fuel efficiency and reduced emissions are key drivers for modern drivetrain systems. Therefore, in recent years, dry sumps with air-oil mist lubrication have been used for efficient transmission design in order to reduce the churning losses. With dry sumps appropriate cooling measures should be implemented to dissipate the generated contact heat in an efficient manner. This paper integrates a tribological model with three dimensional thermofluid analysis in order to predict the heat generated in the lubricated meshing gear contacts and its dissipation rate by an impinging oil jet in air-oil mist environment. Such an approach has not hitherto been reported in literature. The results show that the generated heat under realistic conditions cannot be entirely dissipated by the impinging oil jet in the air-oil mist transmission casing. Numerical results are used to derive extrapolated regressed equations for heat transfer purposes for time-efficient analysis. These conform well with the detailed numerical results.

In industrial applications, a starved lubrication condition may occur, leading to a reduction in film thickness; by modifying the surface geometry, the tribological performance of the contact is enhanced. In this paper, the influence of surface texturing as a method for reducing the friction on the film thickness in parallel sliding surfaces for starved lubricated contacts is investigated. The results in this study have shown that surface texturing can improve film formation for starved lubricated contacts and, respectively, the load carrying capacity. The effect of starvation on several texturing patterns with several texturing properties was investigated and the film thickness for these conditions was studied. With the numerical algorithm developed and taking cavitation into consideration, the effect of shape, depth, size, and texture pitch on the film thickness was studied.