bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the Tribological Chemistry of Chlorine- and Sulfur- and Phosphorus-Containing Additives
Authors: Tysoe Wilfred T.
Published: November 2008

Chlorine- and sulfur- and phosphorus-containing compounds are commonly added to the base fluid to synthesize lubricants used under extreme-pressure (EP) conditions. Analyzing the resulting tribological films on iron reveals that chlorinated hydrocarbons thermally decompose forming a layer that consists of iron chloride (FeCl2) or carbide (Fe3C), and that dialkyldisulfides react to form FeS and Fe3C. Alkyl phosphates thermally decompose on iron oxide to form alkyl and alkoxy, as well as POx species, on the surface. The alkyl and alkoxy species thermally decompose on heating to evolve gas-phase products and deposit carbon onto the surface. The POx species rapidly diffuse into the oxide forming a film that consists of a carbonaceous layer covering a phosphate film. The tribological properties of evaporated and reactively grown thin films have been investigated in ultrahigh vacuum. This strategy eliminates contamination and allows films of known composition and structure to be grown on well-characterized substrates. Three tribological regimes are identified depending on film thickness. In the first regime, an initial rapid decrease in friction is found when a film that is a few nanometers thick (corresponding to a monolayer) covers the surface. The friction coefficient increases once again in the second regime as the film becomes thicker, due to the increased contact area between the film and the rough tribotip, and the behavior is well described by a modified Greenwood-Williamson model. A third regime is found when the film becomes thicker than the interfacial roughness, where the surfaces are completely separated by the film. Finally, measuring the friction coefficients of thin halide films deposited onto various substrates, where the local pressure at the asperity tips depends on the substrate hardness, shows that the shear strength of the “monolayer” films depends on pressure.
Experimental Thermal Study of Contact With Third Body
Authors: Majcherczak D. , Dufrenoy P. , Berthier Y.
Published: November 2008

The thermal study of sliding contact is complex due to numerous physical aspects highly coupled. Heat generation mechanisms are still badly known due to the complex interactions between mechanical, thermal and physico-chemical behaviours and surface degradations. In the goal to better appreciate the third body role on the thermal aspect, an experimental set-up has been realized. It consists in two rings sliding to each other, the first one is made of sapphire (rotating ring) and the second one is made of steel (fixed ring). The temperatures are obtained by an infrared camera scanning through the sapphire and by thermocouples on the contact surface specially realized for this experimental setup. The contact surfaces of the two rings have been observed with a scanning electronic microscope. Comparison between the thermal scene and the surface observations has allowed connecting the third body accumulation with local surface heating.
Observations of Tool Life and Wear Mechanisms in High Speed Machining of Ti-6Al-4V With PCD Tools Using High Pressure Coolant Supply
Authors: Ezugwu E. O. , Bonney J. , Sales W. F. , da Silva R. B.
Published: November 2008

Usage of titanium alloys has increased since the past 50 years despite difficulties encountered during machining. In this study PCD tools were evaluated when machining Ti-6Al-4V alloy at high speed conditions under high pressure coolant supplies. Increase in coolant pressure tend to improve tool life and minimise adhesion of the work material on the cutting tool during machining. Adhesion can be accelerated by the susceptibility of titanium alloy to galling during machining.
Modeling Multiscale Contact in MEMS
Authors: Bora Can K. , Plesha Michael E. , Carpick Robert W.
Published: November 2008

A model is presented to investigate contact and friction between sliding microelectromechanical systems (MEMS) surfaces. Roughness of MEMS surfaces exhibits multiscale structure. This was observed with analysis of asperities on atomic force microscope (AFM) images of real MEMS surfaces. The contact model is developed using multiple scales of surface roughness, with a single asperity contact model for the behavior of an asperity at a particular length scale, including effects such as surface forces (adhesion). The roughness information for the model is obtained from the AFM image of the MEMS surface under consideration. Results for true contact area and a prediction of the macroscopic coefficient of friction are discussed.
Effect of Glide Head and Suspension on Glide Detection
Authors: Kim Dongman
Published: November 2008

The glide head displays flying height characteristics in conjunction with suspension. Its sensitivity affects glide test performance. To enhance the sensitivity, it was found that change of gram load in suspension was the main feature that can contribute to higher glide detection resolution. In this paper, improved resolution of glide detection is illustrated in terms of the least square slope of the disk rotational speed to flying height.
Detection of Modulation and Contact at HDI With Electrical Current
Authors: Feng Zhu , Zhang Xiaofeng , Cha Ellis , Fu Yen
Published: November 2008

In the present work, a novel technique for detecting head-disk contact and modulation is presented. The technique involves measuring electrical current at HDI in the ultra-low flying cases. It is found that the electrical current is very sensitive to head-disk contact and head modulation, which are confirmed with Guzik measurements. Acoustic emission (AE) is also used in the same measurements for contact detection and found to be less sensitive than the electrical current. The electrical current at HDI can be generated through either the tribo-charging/discharging at HDI or externally applied bias voltage. Potential applications of this technique for both head modulation/contact testing and disk glide testing are discussed.
Analysis of Molecular Conformation of PFPE on Hard Disk Surfaces by Considering the Dip-Coating Process
Authors: Zhang Bo , Nakajima Akira
Published: November 2008

The paper provides some new insight of the molecular conformation of the PFPE with functional end groups on hard disk surfaces by considering the dip coating process. It is proposed that the change in the molecular conformation during the dip coating process can be divided into three stages: adsorbing stage, developing stage and drying stage. A formula of predicting the monolayer thickness of the PFPE lubricant on hard disk surfaces is also proposed.
Thermal and Non-Newtonian Numerical Analyses for Starved EHL Line Contacts
Authors: Yang P. , Wang J. , Kaneta M.
Published: November 2008

Numerical analyses have been carried out for the elastohydrodynamic lubrication (EHL) in line contacts under both fully flooded and starved conditions. The thermal effect and the Ree-Eyring non-Newtonian flow have been taken into account. The relation between the inlet meniscus and the thickness of the available lubricant layer has been investigated and it has been found that a very thin layer of available lubricant film on the moving surface is enough to fill the gap downstream the meniscus, making the contact work under a fully flooded condition. The pressures, film profiles, temperature distributions and the traction coefficients have been discussed. The thermal non-Newtonian results have been compared with the thermal and isothermal Newtonian results.
Effect of Mechanochemical Activation on Surface Oxidation of Steel Ball in Milling Serpentinite
Authors: Yang He , Li Shenghua , Jin Yuansheng
Published: November 2008

Serpentinite is the main component of the worn metal reconditioner formulation chemistry and is supposed to be functioning by converting, under shearing strain forces, into oxygen-releasing species through mechanochemical / tribochemical activation and relaxation. Research in this effort employed a high energy planetary ball mill to conduct simulation experiments for understanding the mechanically activated oxidation of GCr15 steel ball surfaces in the course of milling the serpentinite powders in sealed steel containers at room temperatures. As a function of milling time, variations of chemical states of the milled ball surfaces were characterized with SEM, EDX and XPS. Examinations evidenced that plastic deformed layers emerged on the working surfaces of the milled steel balls. Analyses of the milled serpentinite powders were correlated to observations of the chemical and structural changes on the working surfaces of the milled steel balls. Role of the milled serpentinite powder in stimulating the mechanochemical oxidation of the working surfaces of steel balls was briefly expounded.
Analysis of Gas Foil Bearings With Piecewise Linear Elastic Supports
Authors: Kim Tae Ho , San Andre´s Luis
Published: November 2008

Gas foil bearings (GFBs) rely on their underlying elastic foundation to support radial loads at high rotor speeds. The bump foil strip compliance determines the maximum load capacity with large rotor excursions, well in excess of the bearing nominal clearance. GFBs must be designed properly to permit their reliable (predictable) usage in aircraft engines and other heavy load applications because an elastic foundation that is too soft results in a limited load capacity. Configurations in practical use include a second bump-strip layer or stop-pins underneath the original bumps which become active above a certain load threshold. In these last configurations, the overall stiffness of the support structure has piecewise load versus deflection characteristics. Presently, a simple physical model for GFBs with piecewise linear elastic supports follows. The analysis couples the Reynolds equation for the thin film flow of an ideal gas to the elastic supports motion. An exact flow advection model is adopted to solve the partial differential equations for the zeroth- and first- order pressure fields, thus rendering the GFB load capacity and frequency dependent rotordynamic force coefficients. Predictions show that heavily loaded GFBs comprising two bump layers in series and including stop pins prevent too large bump deflections which may induce permanent plastic deformations. The structural damping or loss factor in a GFB with a two bump strip layer enhances the bearing direct damping force coefficients.
Fretting Wear Characteristics of Tube-Support Components for a Steam Generator in Elevated Temperature
Authors: Jeong Sung-Hoon , Lee Young-Ze
Published: November 2008

Tubes in nuclear steam generators are held up by supports because the tubes are long and slender. Fluid of high-pressure and high-temperature flows in the tubes and the flows cause oscillating motions between tubes and supports. This is called FIV (flow induced vibration) which cause fretting wear in contact part of tube-support. The fretting wear of tube-support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. This work is focused on investigations of fretting wear characteristics and wear mechanisms of tube-support. Results are that the wear rate of tube is proportional to that of support and as water temperature increases the wear volume of tube-support decreases because the oxidation rate decreases due to lack of the oxygen concentration in contact surfaces. Also, the wear mechanisms of tube-support are abrasive and oxidational wear.
Research of New Factors Affecting Rolling Contact Fatigue Life
Authors: Fujita Shinji , Mitamura Nobuaki , Murakami Yasuo
Published: November 2008

Conventional life theory defines the rolling contact fatigue (RCF) life as being determined by the maximum contact pressure (P) and the total number of stress cycles (N). However, when the life test results of bearings were analyzed, it was found that there were cases where there was little correlation between the RCF life, maximum contact pressure and the number of stress cycles. An extensive investigation has revealed that the slip velocity is an additional factor that influences the RCF life of bearings. Under special test conditions it was discovered that when the PV value, which is a product of contact pressure and slip velocity, was higher than the threshold value, a unique type of flaking occurred. The flaking originated from white microstructure that was generated at the point of the maximum PV value. Although regarded as a conventional means of increasing the maximum contact pressure, increasing the raceway curvature is an effective counter measure against the formation of white microstructure. It was also found that adding chromium to bearing material was an additional counter measure.
Design of the Stator Inner Contour for a Compressor
Authors: Huang Yuan Mao , Chung Chen Sheng
Published: November 2008

A rotary compressor with a single sliding-vane was designed. A specific stator inner contour was designed by using the envelope theorem for the vane to have good motion characteristics. The mathematical model was generated, and the stator contour with three lobes was selected for a specified volumetric flow rate.
Tribological Performances of Some Piston Ring Materials Lubricated With Low Acidity Fuel Alcohol
Authors: Xiao Liu , Li Shenghua , Zhao Wancheng , Jin Yuansheng , Wang Yucong , Tung Simon C.
Published: November 2008

The tribological performances of some current or candidate piston ring material\coatings named as CrN, WS2, nitroded iron and B4C against cast iron cylinder bores which were lubricated by the current Chinese fuel alcohol with low acidity which measured up GB18350-2001 for the Denatured Fuel Ethanol were researched by the SRV tester, SEM and EDX were used to observe the wear trace of the specimen surface, the width and depth of the specimen surface was measured also, the results of the experiments show that, alcohol with low acid can lubricate the materials some well while the adherence wear mainly take place. To the materials under the research, CrN shows the best tribological performance.
Tribological Performance Prediction Using an Artificial Neural Network Optimized by the DIRECT Algorithm
Authors: Chang Yau-Zen , Wang Nenzi
Published: November 2008

Many tribological problems are expensive to solve due to the requirement of heavy and iterative computation. In this study, a direct mapping between design variables and merits is obtained using a neural network. Data from limited numerical simulations of the behaviors of fluid film of a slider in the thermohydrodynamic regime were used to train the network, which replaces further lengthy simulations. A balance between the modeling accuracy and generalization capability of the network is achieved by optimizing the network size using an efficient optimization scheme, DIviding RECTangles (DIRECT). Performance comparison of the optimization method is based on a hybrid learning strategy that combines the steepest descent and Levenberg-Marquardt method.
Serum Absorption and Ageing of Polyethylenes During a Hip Simulator Study: Comparison Between Conventional and Crosslinked UHMWPE
Authors: Dirix Y. , Zurbru¨gg D. , Becker A. , Schmotzer H.
Published: November 2008

Highly crosslinked polyethylenes have been developed as an alternative bearing material for total joint replacements with an improved wear resistance. These polyethylenes are also expected to have an enhanced oxidative stability during shelf ageing compared to γ-sterilized, conventional polyethylene due to the reduced content of free radicals.
A Fundamental Study on Derailment of Wheel Flange Under Rolling-Sliding and Pure Sliding Conditions
Authors: Rahman Md. Ziaur , Ban Takumi , Kakishima Hideshi , Yamamoto Takashi
Published: November 2008

A newly developed full scale wheel-rail contact testing machine is used to obtain detailed data on flange climb behavior with covering various loads and displacements at the wheel flange and rail contact under both rolling-sliding and pure sliding conditions. The effects of different surface roughness of the wheel flange on coefficient of friction at the contact point in wheel flange climb mechanism were investigated. A correlation between different state of the interface (i.e. surface of dry, wet, rust, oily and different lubricated condition by solid lubricant) and wheel flange surface roughness with rail were drawn. The coefficient of friction was significantly influenced in pure sliding conditions than that of rolling-sliding conditions by the degree of the asperities on the wheel flange surface. Moreover, solid lubricant showed better performance to reduce coefficient of friction. However, the rust on the rail surfaces was one of the important factors to destabilize the friction behavior.
The Effect of AW/EP Additives on Rolling Contact Fatigue of the Coated Parts
Authors: Michalczewski Remigiusz , Piekoszewski Witold , Szczerek Marian
Published: November 2008

The paper concerns the influence of lubricants on surface fatigue of coated elements. As lubricants a mineral base oil and its mixtures with AW/EP additives were used. TiN and CrN coatings were deposited using the arc-vacuum technique, and WC/C by reactive sputtering. The tests were performed using a cone-three ball tester. The worn surfaces were observed employing SEM and analyzed using EDS technique. The results show that coatings like TiN and CrN do not exhibit a satisfactory resistance to cyclic stress. Only WC/C coatings, in rolling contacts may prolong the life of heavy-loaded machine components.
Effects of Grooving in a Circular Step Thrust Bearing
Authors: Razzaque M. Mahbubur , Hossain M. Zakir
Published: November 2008

Assuming narrow grooves and considering inertia effect, an equation for the pressure distribution in a grooved circular step thrust bearing has been derived. A parametric study has been performed to investigate the effects of step and groove geometry on pressure distribution, load capacity and lubricant flow rate. Three arrangements of the bearing surface have been studied and it has been found that the maximum load capacity is obtained by putting grooves only on the step. Inertia significantly affects the load capacity. To get increased load capacity with increase of inertia, the step inner radius should be larger than 0.45 times of the outer radius. For the most enhancement of hydrodynamic load, the groove inclination angle should be 135° with the direction of rotation and the depth should be twice the minimum film thickness.
The Scuffing Resistance of the Coated Tribosystems Lubricated With Ecological Oils
Authors: Michalczewski Remigiusz , Szczerek Marian , Tuszynski Waldemar , Wulczynski Jan
Published: November 2008

The objective of the paper is to show that thin, hard coatings deposited on heavy-loaded machine components working in a non-conformal contact (e.g. gears) and lubricated with ecological oils, make it possible to increase the service-life of these components. The scuffing resistance was assessed by employing a high-resolution four-ball test method realized in a tester with continuously increasing load. Also another test method — FZG scuffing test — was realized using a back-to-back gear test rig. The test balls and gears were coated with thin, hard TiN and WC/C coatings deposited using arc-vacuum and reactive sputtering techniques respectively. The performed tests indicate that the presence of thin coatings on machine components gives a possibility of eliminating or reducing the content of toxic AW/EP additives in lubricating oils, as well as using ecological oils made of renewable resources, without any risk of a scuffing failure.
Investigation of Some Liquid Lubricants for Potential Aerospace Application
Authors: Liu Weimin , Weng Lijun , Feng Dapeng , Wang Haizhong
Published: November 2008

Some liquid lubricants for potential aerospace application were prepared. The lubricity of lubricants including silicon oil with and without chlorobenzene group, cyclotriphosphazene derivative X-1P and perfluoropolyether (PFPE) for both steel/steel and steel/bronze sliding pairs were investigated. Gel percolation chromatography (GPC) was used to detect the tribo-polymerization of the tested silicone oil. Materials related to friction pairs is essential, silicon oil and PFPE are not quite effective for lubrication of a steel/steel pair, but be able to reduce both friction and wear of a steel/bronze pair. Chemical reactive elemental such as chlorine, which is substituted into silicon oil, is helpful to improve the antiwear and load-carrying capacity of liquid lubricant. X-1P is also an effective liquid lubricant for both steel/steel and steel/bronze sliding pairs.
Roughness Amplitude Reduction Under Non-Newtonian EHL Conditions
Authors: Chapkov A. D. , Venner C. H. , Lubrecht A. A.
Published: November 2008

The influence of surface roughness on the performance of bearings and gears operating under ElastoHydrodynamic Lubrication (EHL) conditions has become increasingly important over the last decade, as the average film thickness decreased due to various influences. Surface features can reduce the minimum film thickness and thus increase the wear. They can also increase the temperature and the pressure fluctuations, which directly affects the component life. In order to describe the roughness geometry inside an EHL contact, the amplitude reduction of harmonic waviness has been studied over the last ten years. This theory currently allows a quantitative prediction of the waviness amplitude and includes the influence of wavelength and contact operating conditions. However, the model assumes a Newtonian behaviour of the lubricant. The current paper makes a first contribution to the extension of the roughness amplitude reduction for EHL point contacts including non-Newtonian effects.
The Resistance to Scuffing, Seizure and Pitting as a Result of the Chemistry of Lubricating Oils
Authors: Tuszynski Waldemar , Michalczewski Remigiusz , Osuch-Slomka Edyta , Szczerek Marian
Published: November 2008

The research aimed at finding an effect of the type and concentration of lubricating additives on the resistance of a tribosystem to scuffing, seizure and pitting (surface fatigue). Lubricating oils of various chemical composition were tested. A base mineral oil was blended with commercial packages of lubricating additives of AW and EP type, at different concentrations. The AW additives contained ZDDP, and EP ones — organic S-P compounds. The tests were performed in two different four-ball testers. One was used to investigate scuffing and seizure at pure sliding friction. The second instrument was employed to test pitting at rolling movement. It is shown that although the lubricating additives improve the resistance to scuffing and seizure, great care must be taken when increasing their content, since at higher concentrations they accelerate pitting. SEM, EDS, GDOES and FTIRM analyses of the worn surface were performed to find the reason.
Ionic Liquid Thin Films: Potential Solution to Lubricate Miniaturized Devices
Authors: Xue Qunji , Yu Bo , Zhou Feng , Gao Ping , Liang Yongmin , Liu Weimin
Published: November 2008

The tribological properties of ultra-thin ionic liquid films (IL films) were evaluated using a Universal Micro-tribometer-2MT tester. The morphologies of the wear tracks of the films and the counterpart surfaces were examined using a JEM-1200EX scanning electron microscope (SEM) equipped with a Kevex energy dispersive X-ray analyzer (EDXA) attachment. It was found that the tribological performances of IL films were closely related to the chemical characteristics of the substrate surfaces. The films of vinyl group functionalized ionic liquids on hydroxylated substrate and vinyl group modified substrate exhibited very good friction-reduction and wear-resistant properties. IL films can be a potential solution to the lubrication of miniaturized devices.
Effect of Applied DC Voltage to Stainless Steel Pin and CNx Coated Disk in Pin-on-Disk Sliding Test on Tribological Properties
Authors: Umehara Noritsugu , Yamamoto Takahiro , Fuwa Yoshio
Published: November 2008

The effect of applied DC voltage on the friction and wear of CNx sliding against stainless steel pin in air was clarified. Friction coefficient decreased with the increasing negative voltage to apply to the ball and disk in air. On the other hand, positive voltage increased friction coefficient. Friction coefficient of CNx in air decreased from 0.22 to 0.05 by applying electric voltage of DC −200 V. Specific wear rate was decreased with the increasing applied positive and negative voltage. It was considered that the oxidation of CNx was controlled by electric field.
Friction Force Microscopy Investigation of Elastic Instabilities in Nanolubricated Junctions
Authors: Buzio R. , Boragno C. , Buatier de Mongeot F. , Valbusa U.
Published: November 2008

We present experimental results concerning the Friction Force Microscopy (FFM) investigation of smooth mica and Si surfaces lubricated by a model lubricant. We have studied the friction force as a function of normal load and sliding velocity, analyzing results in the framework of interfacial liquid structuring and drainage effects.
Development of Highly Hydrogenated DLC Coatings for Solid Lubricant Applications in Space
Authors: Vanhulsel A. , Jacobs R. , Van Acker K. , Roberts E. , Velasco F. , Sherrington I. , Gaillard L.
Published: November 2008

The development of advanced solid lubricants is of considerable importance to space tribology. The most common solid lubricant coatings today are based on MoS2, lead or PTFE. However, none of these coatings can simultaneously fulfill all specifications, with regard to friction and wear, under ambient atmosphere and in vacuum. Consequently research is currently being aimed at further improvements in advanced solid lubricant coatings. One approach is to optimize Diamond Like Carbon (DLC) coatings to meet the specifications. In this study, the feasibility of highly hydrogenated DLC coatings (∼ 50 at% hydrogen) for solid lubricant applications is assessed. The coatings were deposited on AISI 52100 steel substrates and tested in ball-on-disc tribometers in air, vacuum and dry nitrogen environments. It was found that the test environment has the most decisive effect on both friction and wear rate, while these parameters are only slightly affected by varying the applied load under a given atmosphere. It was concluded that highly hydrogenated DLC coatings are capable of yielding ultra-low friction values in vacuum (μ = 0.008). The average friction coefficient range obtained in humid air, dry nitrogen and vacuum for the range of applied loads were respectively 0.22 to 0.27, 0.02 to 0.03, and 0.007 to 0.013. Coating lifetime was over 100 000 cycles for the entire load range tested in air and nitrogen, but was affected by the applied load as far as tests in vacuum are considered. The specific wear rate was lower than 1×10–5 mm3 N-1 m-1 under all test conditions, which was considered favourable.
A Comprehensive Elastic-Plastic Model to Predict Wear and to Define the Optimum Geometry of Fretting Surfaces
Authors: Gallego L. , Ne´lias D. , Jacq C.
Published: November 2008

In turbine engines the contact between blades and disk may be subjected to fretting fatigue or fretting wear. This is due to the centrifugal force acting on the blade, which causes a relative displacement of the contacting surfaces producing either mixed stick-slip or gross slip.
Wear Properties of Metal-Impregnated Carbon Fiber-Reinforced Carbon Composite Sliding Against a Copper Plate Under an Electric Current
Authors: Kubo Shunichi , Tsuchiya Hiroshi
Published: November 2008

The metal-impregnated carbon fiber-reinforced carbon composite (C/C composite) is expected to be a candidate material for pantograph contact strips of high-speed electric railway vehicles, because its mechanical strength for flexure and impact is much higher than that of the conventional metal-impregnated carbon. The authors have investigated the wear properties of copper-titanium-alloy impregnated C/C composite sliding against a copper disk under an electric current and frequent arc discharges. The tested C/C composite was prepared by press molding and baking of laminated carbon fiber woven sheets. There exists anisotropy in the physical properties originated from the orientation of carbon fiber woven sheets lamination. The C/C composite was slid in two directions, in parallel with or perpendicular to the sheet layer. The test results show that the wear rate in sliding in the parallel direction exceeds that in the perpendicular direction, especially in the cases where the material is subjected to higher current density and more frequent arc discharges.
Increasing the Performance of Motor Vehicle Clutches by the Use of Ceramics as Friction Material and the Resulting Effects on System Design
Authors: Albers A. , Mitariu M. , Arslan A.
Published: November 2008

The experimental and constructive results illustrate that engineering-ceramic materials have a high potential in the field of dry running friction systems. According to first estimations, it is possible to build the vehicle clutch 53% smaller or to transmit up to 180% higher torque with the same size by an appropriate selection of the system friction pairing and an adequate ceramic design [1, 2]. The friction coefficient characteristic (decreasing friction coefficient above sliding speed) is unfavourable with regard to comfort (self-induced grab oscillations [3]) of the vehicle clutch. Furthermore, it is important to select the test procedure of the experimental analyses to be as close to the system as possible in order to obtain exact information concerning the target system.
Optimization of the Cylinder Liner Surface for Reduction of Oil Consumption
Authors: Johansson Staffan , Nilsson Per H. , Ohlsson Robert , Anderberg Cecilia , Rose´n Bengt-Go¨ran
Published: November 2008

A decrease of oil consumption in the modern truck engine would mean decrease of particulate matter and hydrocarbon emissions. This decrease has a positive impact on the environment. One important source of oil consumption is the piston/piston-ring/liner system. One way of decreasing oil consumption is to optimize the surface topography of the liner. In this study different liner surfaces and different piston rings were investigated. The investigation shows that it is possible to decrease both the oil film thickness and the friction without sacrificing wear properties of the piston-liner system. A new surface parameter for quick wear estimation of this system is presented.
Increasing Seizure Resistance of Friction Pairs Using Combined Micro Relief
Authors: Shamshidov Boris , Ignatovsky Alex , Mandel Kostia
Published: November 2008

This paper presents the Combined Micro Relief (CMR) method developed by the authors. CMR is a two-step process: grooving and FriCSo lapping. The grooves, produced through plastic indentation in the metal, serve both as lubricant reservoir and debris removal means. The FriCSo lapping, done with polymer and abrasive paste, produces low roughness area, thin densified layer and increased surface participation in the contact area. In repeated tests and experiments, CMR was found to be highly effective in addressing extreme lubrication conditions such as oil starvation, boundary and mixed lubrication. CMR application results include reduction of friction and superior resistance to scuffing wear and seizure.
Maintenance-Free, Low Stick-Slip ELGOGLIDE® Plain Bearings for Industrial Applications
Authors: Schwarz Sergej , Nollek Heinrich , Breutinger Falk , Schlar Max
Published: November 2008

In the following article, a new development from the Schaeffler Group Industrial will be presented in the ELGES maintenance-free plain bearing sector (brand name: ELGOGLIDE®). The bearings feature very smooth operation (low stick-slip) even in very unfavorable conditions. The friction coefficient is low and is only marginally dependent on the running velocity and the temperature. At the same time, the bearings feature a very high load carrying capacity and a long life. Application examples will be discussed and explained.
Modelling the Effects of Head Diameter and Cup Wall Thickness on Contact Mechanics and Wear of Cross-Linked UHMWPE Cups
Authors: Kang Lu , Galvin Alison L. , Jin Zhongmin , Fisher John
Published: November 2008

A three-dimensional contact-coupled wear model was developed and used to predict the long-term wear in both conventional and cross-linked ultra high molecular weight polyethylene (UHMWPE) cups, particular to examine the effect of the head diameter and the UHMWPE cup wall thickness. The wear factors were determined from the simulator testing of 28 mm diameter cups. The maximum contact pressure was found to decrease with the increase of head diameter up to 48 mm, corresponding to the decrease in the cup wall thickness for a fixed outside diameter of the cup. Volumetric wear rate was predicted to increase as the head size increased for the conventional UHMWPE, as well as the cross-linked UHMWPE, although at a much lower rate for the latter due to the smaller wear factor.
Nano-Wear of Polystyrene in Contact With Hydrophilic and Hydrophobic Substrates: Influence of Interfacial Interactions
Authors: Bistac Sophie , Schmitt Marjorie , Ghorbal Achraf
Published: November 2008

The aim this study is to analyse the influence of interfacial interactions in the nano-wear behaviour of polymers. Studies will be focussed on the analysis of the transfer layer induced by the friction of a polystyrene cylinder in contact with a flat and smooth substrate. In order to change the nature of interfacial interactions, two different substrates are used. The first one is a hydrophilic silicon wafer (hydroxylated by a piranha treatment) and the second one is a hydrophobic silicon wafer, obtained by a chemical grafting with a CH3 terminated silane. Friction experiments are performed with a translation tribometer which measures the tangential force between the polymer and the substrate for controlled normal force and friction rate. The transfer layer is analysed using atomic force microscopy (AFM) and IR spectroscopy (reflection mode) Tentative correlations between transfer layer characteristics and interfacial properties are proposed.
Effect of Crosslink Density and Mechanical Properties on the Wear of Silica-Filled Styrene-Butadiene Rubbers
Authors: Uchiyama Yoshitaka , Iwai Tomoaki , Amino Naoya , Shimosaka Kiichiro
Published: November 2008

In this study the effects of silica size (or specific surface area), mechanical properties and crosslink density on the wear of silica-filled SBRs (styrene butadiene rubbers) were examined. The modulus of each silica-filled SBR examined was proportional to crosslink density. The wear rate of silica-filled SBRs was reduced as the modulus and crosslink density increased. The wear rates increased as the specific surface area of the silica fill particles decreased, when the content of silane coupling agent was constant. As a result, the wear rate was shown to be lower as the modulus and crosslink density increased.
Thermohydrodynamic Behavior of a Slider Pocket Bearing
Authors: Dobrica Mihai B. , Fillon Michel
Published: November 2008

Pocket-pads or steps are often used in journal or thrust bearings, as a source for hydrodynamic pressure and dynamic stability. A literature review shows that, to date, only isoviscous and adiabatic studies of such geometries, involving film thickness discontinuities, were performed. This paper presents a full thermohydrodynamic (THD) numerical model, applied to the case of a slider pocket bearing.
Sunflower Based Grease for Heavy Duty Applications
Authors: Barriga J. , Igartua A. , Aranzabe A.
Published: November 2008

There is a great consumption of grease in an excavator (∼200 Kg/year). This big amount of lubricant is poured directly to the environment. A grease based in sunflower oil and polymer thickener has been developed. An extensive tribological characterization has been carried out in order to ensure a good compromise between EP and AW properties so that the grease could be used in two different applications: in the reduction gear (crown) and in the articulations (bushing/pin). The performance of the biogrease has been compared with two reference mineral lubricants.
Modelling the Wear Process of Inhomogeneous Bodies
Authors: Goryacheva I. G.
Published: November 2008

The approaches of contact mechanics are used to evaluate the evolution of the contact characteristics in wear process of inhomogeneous bodies (coated bodies, two-phase composition, bodies with inclusions, etc.). The mathematical model is formulated and used to study the kinetics of the wear process depending on the parameters of inhomogeneity such as size and density of inclusions, waviness at the coating-substrate interface, local hardening parameters, etc.
Packing Structure of OTS on Silicon Surfaces: A Computational Approach
Authors: Barriga J. , Coto B. , Ferna´ndez B.
Published: November 2008

Optimal packing structure of Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) adsorbed on a SiO2 surface with a Si (100) substrate was studied performing molecular dynamics (MD) computational simulations. Molecular substitution, substitution pattern and molecular orientation of the OTS molecules on the SiO2 (100) are the main factors studied in order to determine the optimal packing structure taking into account energetic balance. We have used the optimal packing structure to study other properties usually used to characterize SAMs as molecular and system tilt angles, film thickness and gauche defects. These properties and monolayer stability were studied performing MD simulations in a temperature range from 100 K to 600 K and we found that results obtained agree with those from experimental measurements. We found that OTS films are stable up to 500 K. The optimal structure obtained could be used in further MD simulations studies in order to determine tribological properties of OTS-SiO2 systems.
Measuring Pressure in Apple Contacts
Authors: Lewis R. , Yoxall A. , Marshall M. B. , Canty L. A.
Published: November 2008

A large number of apples are wasted each year due to bruising. A novel ultrasonic technique has been used to assess apple contacts to provide a greater understanding of the bruising process and to provide validation for an FE apple model which will be used as a design tool to optimise apple packaging to reduce the advent of bruising.
Environmentally Acceptable Lubricants: Current Status and Future Opportunities
Authors: Battersby Nigel S.
Published: November 2008

This paper discusses the environmental and performance requirements for ‘environmentally acceptable’ lubricants (EAL), and the reasons for their small market share in Europe and the USA. Several initiatives, which could stimulate the uptake of EAL in the marketplace, are summarized.
Numerical Modelling of High Pressure Gas Face Seals
Authors: Thomas Se´bastien , Brunetie`re Noe¨l , Tournerie Bernard
Published: November 2008

A numerical model of face seals operating with compressible fluids at high pressure is presented. Inertia terms are included using an averaged method and thermal effects are considered. The real behaviour of gases at high pressure is taken into account. An original exit boundary condition is used to deal with choked flow. The model is validated by comparison with experimental data and analytical solutions. Finally, the influence of the operating conditions on the performance of a high-pressure gas face seal is analysed.
Tribomechanical-Chemical Effects and Visualisation of Additive’s Layer Formation in Engine Crankcase Oil Between Sliding Pairs
Authors: Kaleli Hakan , Berthier Yves
Published: November 2008

Examination of worn surfaces by optical, electron microscope detection and X-Ray diffraction analysis indicated that the replacement of the pin (steel 52100) by another pin (steel Stub 51115) facilitated and increased the influence of surface degradation which allows the sliding surface to be satisfactorily reactive to form high percentage of protective additive’s layers and to cover uniformly the whole wear track in boundary lubricated conditions. A few minutes of dry test well determined the production of the surface degradation to promote an optimal layer formation. The same type of tests were repeated using pin (sapphire) on the plate (steel Stub 51115) in order to be able to visualize the formation of layers. High speed camera has got images of layers and demonstrates the layer formation during experiment. This study suggests that the surface deterioration is a mechanical process and promotes chemical reactions at solid surfaces. Satisfactory degradation of the surface permits activating lubricant additives to form protective layers. The temperature has a significant chemical influence on the mechanical effect of the material type on the formation of additive’s layer.
Effects of Boundary Films on the Frictional Behavior of Rough-Surface Contacts in Incipient Sliding
Authors: Chang L. , Zhang H. , Lococo J.
Published: November 2008

Research has shown that the interfacial shear strength in an asperity contact is generally a linear function of the asperity pressure with a maximum value below the shear strength of the substrate material. Research further suggests that the properties of the surface-film materials in the micro-contact largely govern the shear-strength-pressure relation and the maximum attainable interfacial shear strength. This paper studies the effect of boundary films on the frictional behavior of rough-surface contacts in incipient sliding. Two parameters are used to describe the shearing properties of the boundary film. One is the shear-strength-pressure proportionality constant and the other, the ratio of the maximum interfacial shear strength to the substrate shear strength. The study uses an asperity-based mathematical model for frictional sliding-contact of nominally flat elastic-plastic rough surfaces incorporating the above interfacial shearing properties in the asperity contacts. A sequence of parametric studies is carried out to study the frictional behavior of the contact system. The parameters include surface plasticity index, contact load, and boundary film properties. More details of the results along with literature studies and references are presented in a full paper [1].
The Frictional Stability of Wet Clutch Friction Materials Investigated on a Small Scale Test-Rig
Authors: Ost W. , De Baets P.
Published: November 2008

The work presented in this paper is part of a European project (COST 532, project E2) to study clutch shudder and its influences, together with wear testing of clutch materials. The relation between the friction force and the relative velocity, and the dynamics thereof are investigated for typical wet clutch materials (oil lubricated paper/steel contact) on a small scale test rig, using a ground and polished steel ring onto which a coupon from a friction clutch plate was slid. The results clearly show that although momentarily the relative velocity of the sliders vs. the rotating ring reaches zero, no stick episode ensues. The mechanical parameters (stiffness, damping and normal load) of the test-rig were varied and the influence thereupon on the friction during sliding was investigated.
High Oleic Plant Oils With Hydroxy Fatty Acids for Emission Reduction
Authors: Grushcow J.
Published: November 2008

The lubricating properties of vegetable oil are well known. However, with the advent of petroleum oils, castor oil and other vegetable oils fell out of favor. The quality of petroleum oils has improved significantly in the last few years with the introduction of Group III base oils. However, even Group III oils fall short of the inherent lubricity of vegetable oils. Analogous to advances in petroleum oils, improvement of vegetable oils by genetic modification to obtain high oleic oils has led to better acceptance of these oils as lubricants. Studies have shown significant reduction in tail pipe emissions when using these types of oils in an engine crank case. We have successfully expressed a hydroxylase gene in a high oleic canola variety. The combination of a high oleic background and hydroxy fatty acids produced an oil with properties that improve further on high oleic oils. The presence of the hydroxy group provides improved lubricity. This technology will allow us to create oils with varying hydroxy fatty acid content depending on the application. These applications can range from use in lubricants, as chemical feedstocks, and reactive components in polymers.
On the Definition and Laws of Friction
Authors: Al-Bender Farid
Published: November 2008

The basic definitions, laws, notions and concepts employed in the study of friction are reviewed. It is shown that accepted definitions contain elements of laws, that accepted laws are formally ill-stated, and that basic notions such as contact, adhesion, etc. need critical revision and new syntheses. It is suggested that an international committee should undertake this task.
Next Generation Feedstocks From New Frontiers in Oilseed Engineering
Authors: Grushcow J. , Smith M. A.
Published: November 2008

Recent advances in molecular breeding techniques along with developing tools for Genomics and Proteomics are delivering new oil seed profiles for industrial applications. Ultra high Oleic, Erucic and blends including Hydroxy fatty acids are now, or will be shortly, available in a variety of oilseed crops including Soybean and Canola as well as Flax. As a result, vegetable oils need to be re-examined by industry for specific applications. Feedstocks and base oils derived from oil seeds are renewable as well as biodegradable. A brief summary of recent progress is presented together with a description of new research into the development of an alternative source of Hydroxy fatty acids to replace castor oil and an overview of an enzyme engineering approach to create new enzymes for seed oil modification.
An Investigation Into Fatigue Life Prediction of Engine Bearings
Authors: Xu Hao
Published: November 2008

In this study, work was carried out to investigate the fatigue life of engine bearings. A mathematical model was developed which utilises Miner’s rule to work out the total damage to an engine bearing when it is subject to all sorts of operational conditions. Given the fact that bearing fatigue rating has been traditionally tested against the specific load applied to bearings in test rigs, it was appropriate to develop a model using the specific load applied to a bearing, instead of the stress values in the bearing lining material. The model was then used to compare the life of con-rod bearings of a high performance diesel engine used on the road to that tested in the lab on test beds. The analysis showed the test procedure used in lab tests induced more severe damage than in the engine bearings in normal road use for design life.
Fretting Behavior of Coated and Treated Titanium Alloy Using an Open-Loop System
Authors: Yantio Njankeu G. R. , Paris J.-Y. , Denape J. , Pichon L. , Rivie`re J.-P.
Published: November 2008

Titanium alloys are well known to present poor sliding behaviour and high wear values. Various coatings and treatments have been tested to prevent such an occurrence under fretting conditions at high frequency of displacement (100 Hz). An original test apparatus, using an open-loop system instead of a classical imposed displacement simulator, has been performed to directly display the phenomenon of seizure, defined as the stopping of the relative motion between the contacting elements. A classification of the tested coatings has been proposed on the basis of their capacity to maintain full or partial sliding conditions, to present low wear rates and to prevent seizure.