bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation on the Characteristics of Honeycomb Seals and Its Application to Steam Turbine
Authors: He Li-Dong , Shen Wei , Zhou Wei-Hua
Published: November 2008

The contrast tests of honeycomb seals have demonstrated the inner surface of the honeycomb seal is characterized by a high roughness, which aggravates the air flow disturbance and induces a multi-peak spectrum, contributing to energy dissipation and achieving the goal of suppressing seal gas flow excitation. The test results have demonstrated that the honeycomb seal, which has a special ratio of cell size to depth, provides the best leakage performance. A new kind of honeycomb seals has been designed and used as shaft end seals and stage seals in steam turbines. By utilizing honeycomb seals, the steam leakage is reduced evidently and vacuum degree is raised. At the same time, not only the problem of the water component mixed in the lubrication oil is solved, but also the efficiency and stability of steam turbines are improved.
Experimental Study on Influences of Electric Double Layer on Thin Film Lubrication
Authors: Wang X. J. , Bai S. X. , Huang P.
Published: November 2008

Theoretical and experimental researches have showed that electro-viscosity induced by electric double layer influences apparently on thin film lubrication. In order to consider the influence of electric double layer, in the present paper, experiments are carried out on a self-made oil lubrication tester with a composite sliding block and with adding an external electric field to reconstruct electric double layer. The results show that electric double layer has an apparent effect on friction coefficient. To ensure the results, further experiments are carried out with additives’ being added to change the ionic concentration of lubricants. The results indicate that electric double layer has more apparent effect on friction coefficient in thin film lubrication.
Turbojet Engine Demonstration With a High Temperature Air Foil Bearing
Authors: Heshmat Hooshang , Walton James F. , Tomaszewski Michael J.
Published: November 2008

Recent tests demonstrated successful operation of a turbojet engine with a compliant foil air bearing using a new high-temperature solid lubricant coating. The hot section rolling element bearing and corresponding lubrication system were replaced with a compliant foil air bearing using a composite solid lubricant coating capable of operating at temperatures well above 650°C (1200°F). Detailed engine integration studies, bearing component rig testing and hot engine simulator tests were completed prior to the successful engine test. The rig and simulator tests verified high temperature capabilities of the bearing and its surface coating, the bearing journal design, bearing dynamic performance, and rotor-bearing system dynamic stability, prior to engine integration and test. Based on these preliminary efforts, the engine and bearing were assembled and tests were conducted that included over 70 start stop cycles (including hot restarts), seven simulated mission cycles and more than 14 hours of run time. The foil bearing and engine operated flawlessly throughout the test. Vibrations were very low and all temperatures and pressures were as expected. The post-test inspection revealed that the bearing, journal and coating were all in excellent condition.
Towards Superlubricity Under Boundary Lubrication
Authors: Martin J. M. , De Barros Bouchet M. I. , Le Mogne T. , Kano M.
Published: November 2008

Fuel economy and reduction of harmless elements in lubricant are becoming crucial in the automotive industry. An approach to respond these requirements in engine components is the potential use of low friction coatings exposed to specific boundary lubrication conditions. Superlubricity is a new research field in tribology, dealing with very low friction values, typically below 0.01, and this even in dry or vacuum conditions. It is to be noticed that any friction coefficient below 0.001 is hardly measurable with the equipment at hand. Superlow friction was already experimentally observed only in ultrahigh vacuum and inert gas environment, with pure molybdenite (MoS2) coatings [1] and in presence of some hydrogenated DLC coatings [2]. Under boundary lubrication, we show here that the coupling of hydrogen-free carbon coatings and selected organic lubricant additives permits to reach friction values approaching superlubricity and also a wearless behavior.
The Analysis of a Mechanism of Mineral Tribotechnical Compounds Influence on Wear Resistance of Tribocontacts
Authors: Shabalinskaya L. , Levkin G.
Published: November 2008

One of important factors, determining of the reliability of tribocontacts, is their good lubrication. That is why the paper discusses a number of questions affecting the wear: a base oil type and wear resistant coatings (a Cr layer) and a layer working as a solid lubricant after chemical and thermal processing, deposited on piston rings. As lubricating compositions with different trbotechnical compounds (TC) are widely used today for lubricating tribocontacts in internal combustion engines of all types, the paper contains the information on how different mineral TC affect the work of tribocontacts that simulate rather conditions of cylindro-piston group (CPG) in today’s high- augmented engines. The results of the investigation on the comparative evaluation of wear resistance and tribotechnical characteristics made for 6 variants of friction contact lubrication (gray cast iron–electroplated chromium, steel–steel, steel–aluminium), carried out on a test bed simulating hard condition of boundary friction typical for CPG parts working in augmented engines, show any positive influence on the CPG operation for TC by type written in Patent RF 2188227 (2002 y.). Researches of a friction surface state were carried out with employment of such methods as Auger electron spectroscopy. The analysis of received results makes it possible to come to next conclusion: – The processing of friction surfaces by mineral TC improves antifriction and anti-wear properties of different tribocontacts differently, forming in each event different modified layers (by a composition and a thickness within 50–20000 A), having different wear resistance.
Antiwear Chemistry in Presence of ZDDP
Authors: Martin J. M. , Minfray C.
Published: November 2008

Antiwear chemistry is related to the role of tribochemical reactions in controlling abrasive wear, adhesive wear as well as physical and mechanical properties of tribofilms. In the case of additives in boundary lubrication, three different chemical reactions have been found to be directly connected to mechanical response. First one is the digestion of hard metal oxides in the glassy tribofilm formed from the antiwear additives, thus combating with abrasive wear. Second reaction is the reaction of sulphur species with nascent metal surfaces, reducing adhesive wear between antagonist metal surfaces. The third reaction is an equilibrium one in the stressed tribofilm, leading to a change of mechanical properties of the tribofilm and explaining its smart behavior.
Friction and Wear of Engineering Polymer Gears
Authors: Kala´cska Ga´bor , Kozma Miha´ly , DeBaets Patrick , Keresztes Ro´bert , Zsidai La´szlo´
Published: November 2008

Technical polymers are widespread in the machinery owing to their beneficial properties against metals as operation without lubrication, low friction and wear, light weight, corrosion resistance, low manufacturing costs etc. There are many sorts of technical polymers available of which sliding elements can be produced. To choose proper polymers for a given tribological application is not a simple task owing to many different parameters influencing the performance of a polymer sliding element. We launched a broad research project to clarify the friction and wear phenomena of plastic gears.
Tribological Properties of Nano/Micro-Patterned PMMA Surfaces on Silicon Wafer
Authors: Yoon Eui-Sung , Singh Arvind R. , Kong Hosung , Kim Byungkyu , Kim Doek-Ho , Suh Kahp Y. , Jeong Hoon Eui
Published: November 2008

Nano/micro-patterns made of polymethyl methacrylate (PMMA) that are biomimetic in nature, were fabricated on silicon wafer using capillary force lithography. Patterns with three different aspect ratios were investigated for their adhesion and friction properties at nano-scale using AFM, and for friction at micro-scale using mirco-tribo tester. The patterned samples exhibited superior tribological properties, both at nano and micro-scales when compared to that of the non-patterned PMMA thin film.
Contact Evolution in a Micromechanical Switch
Authors: Chen Lei , McGruer Nicol E. , Adams George G.
Published: November 2008

An AFM-based test station has been established for rapid mechanical and electrical characterization of contacts in a micromechanical switch. A wide contact force range is accessible, from nN to mN, determined by the mechanical properties of the microfabricated contact test cantilevers. During testing the contact force, deformation, and contact adhesion are measured. Periodic observations of material transfer are made. The cycling rate can reach 200 kHz.
Friction and Wear Performance of Surface Coatings in Brake Applications
Authors: Deshmukh Pushkaraj , Lovell Michael , Mobley A. J.
Published: November 2008

To improve the wear performance of contacting components, novel surface coatings have been developed over the past decade. In the present investigation, extended duration pin-on-disk experiments were carried out to determine the relative performance of tungsten disulphide, electroless nickel (MP6 and LP9) and hard chromium coatings for use in a commercial brake valve assembly. In the experiments, 100 μm thick coatings were applied to the disk surface and tests were conducted in both lubricated (transmission fluid with 5% weight boric acid additive) and unlubricated conditions. To establish the overall performance of the coatings, the friction coefficient and disk wear rate values were recorded over a sliding distance of 6280 m. Based on the experiments, it was observed that both the electroless nickel and the chromium coatings had moderate friction and insignificant wear over the sliding distance examined. Self lubricating tungsten disulphide, in contrast, exhibited very low friction, but completed degraded over time making it unsuitable for the application of interest.
Dishing and Erosion in Cu-CMP
Authors: Yoon Inho , Ng Sum Huan , Osorno Andres , Danyluk Steven
Published: November 2008

Chemical Mechanical Polishing (CMP) of copper in trenches and vias of patterned silicon wafers is routinely used in CMOS processes as well as MEMS applications. Although the main goals of CMP are to achieve a planar surface at the nano-scale without scratches, it is generally the case that copper is preferentially polished, a condition called dishing and erosion, relative to the pattern geometry. We have measured dishing and erosion of electroplated copper on patterned silicon wafers with specially-designed patterns containing combinations of line-width and density. One hundred millimeter diameter wafers were patterned using a standard etching process and electroplated with copper. The polishing was done on a modified laboratory-scale bench top polisher which allows ranges of normal loads and velocities. A commercial pad (Rodel IC1000 plain) and slurry were used along with a slurry-delivery rate fixed by a peristaltic pump. The pad conditioning and other process parameters were chosen to represent those used in standard industrial practice. Dishing and erosion were measured as a function of the pattern geometry and polishing conditions. The measured dishing and erosion were then compared to other models.
Effect of Test Environment on Lifetime of a Vacuum Lubricant
Authors: Pepper Stephen V.
Published: November 2008

The liquid lubricant of a bearing system operating in the starved or boundary lubrication regime is subject to tribochemical degradation that can deplete the lubricant supply and cause bearing failure. This depletion or consumption of the lubricant is a function of both lubricant and substrate chemistry. It can also depend on the test environment. In this paper, the relative consumption rates of Krytox 143AC™, a popular perfluoropolyether (PFPE) vacuum lubricant, in rolling contact with 440C stainless steel are studied for test environments of ultrahigh vacuum (UHV), dry oxygen, dry nitrogen, nitrogen containing water vapor and pure water vapor. The consumption rate is expressed as the lifetime of a finite charge of lubricant in a test.
Modeling Oil Evaporation From the Engine Cylinder Liner With Consideration of the Transport of Oil Species Along the Liner
Authors: Liu Liang , Tian Tian , Yilmaz Ertan
Published: November 2008

To estimate oil evaporation from an engine cylinder liner, an evaporation model has been implemented and incorporated with an existing 3-D piston ring-pack lubrication model. In this evaporation model, oil is modeled as being composed of distinct hydrocarbon species. Due to the depletion of light species and temperature variation, oil composition changes with space and time. Great emphasis was placed on the change of oil composition caused by oil transport through the ring-pack movement along the liner. The model was applied to a gasoline engine, and it was demonstrated that due to the movement of piston ring-pack, oil can be transported from the lower liner region to the upper liner region during the compression stroke, which gives a continuous supply of light species for oil evaporation.
Partial Contact of a Smooth Elastic Wavy Strip Pressed Between Two Flat Surfaces
Authors: Block J. M. , Keer L. M. , Duddu R.
Published: November 2008

The contact of a smooth elastic wavy strip pressed between two surfaces is solved by considering a curved beam in contact with a rigid half-space. In assuming so, the Michell Fourier series expansion for elastic bodies is shown to satisfy the resulting mixed boundary value problem. When the contact region is small compared to the radius of curvature of the beam, semi-analytical solutions are obtained by exploiting dual series equation techniques. The relation between the level of loading and the extent of contact, as well as stress on the surface and in the beam, are found. Various boundary conditions on the ends, which arise as lower order terms in the Michell solution, are considered. This semi-analytical solution may prove useful in analyzing the contact of a corrugated seal.
Conductive Atomic Force Microscopic (C-AFM) Studies of Au/MoS2 Nanocomposite Films
Authors: Kim Hyun I. , Lince Jeffrey R.
Published: November 2008

Au/MoS2 nanocomposite films with high Au concentrations (75 to 90 at%), recently developed at The Aerospace Corp., have shown properties that are promising for use in sliding electrical contacts, such as slip rings and relays. For such applications, it is critical to maintain low contact resistance while maintaining low friction with controlled wear (i.e. removal and transfer of material). In this report, we present results from conductive atomic force microscopic (c-AFM) investigations of Au/MoS2 nanocomposite structures and their dynamic material transfer phenomena under a sliding contact, which are both important in understanding the friction, wear and conducting mechanisms of the films. We have performed c-AFM to obtain topography, friction and current images simultaneously. Remarkable morphological changes were observed in a series of current images which initially showed distinct nanoscale metallic (Au) and semiconducting (MoS2) phases that were relatively well dispersed, but repeated contact sliding in the same area resulted in gradual disappearance of the metallic phase and reduction of the overall friction. These results reveal that MoS2 is transferred across the surface to provide lubrication while Au particles at or near the surface provide electrical conductivity. The c-AFM results provide real-time and real-space visualization of the lubrication mechanism occurring inside a nanoscale sliding contact.
Atomistics of Friction
Authors: Hirano Motohisa
Published: November 2008

The atomistic mechanisms are proposed for the origin of the static and the dynamic friction forces. The mechanism for the origin of the static friction force resembles the mechanical locking mechanism in a surface roughness model. The origin of the dynamic friction force is formulated as a problem of how the given translational kinetic energy dissipates into the internal relative motions of constituent atoms of bodies during sliding. From studying that the available phase space volume of the translational motion becomes negligible small for a large system size, compared with that of the internal motions, it is concluded that the energy dissipation occurs irreversibly from the translational motion to the internal motions. A phenomenon of superlubricity, where two solid bodies move relatively with no resistance, is discussed.
Asymptotic Methods Applied to the Correlation of Fretting Fatigue Lives
Authors: Hills David A. , Churchman Christopher M. , Dini Daniele
Published: November 2008

Local or asymptotic states of stress relevant to the characterization of the state of stress adjacent to the edges of incomplete contacts are discussed. It is shown that the multipliers for the asymptotic solutions effectively characterize the nucleation propensity of the geometries. This idea is tested by applying the approach to reliable fretting fatigue data in the literature, and re-examining it in this light.
Study on Biodegradable Lubricants: Improvement in Oxidation Stability of Vegetable Oils
Authors: Li Jiusheng
Published: November 2008

To improve the oxidation stability of vegetable oil, several chemical reactions such as transesterification, polymerization and epoxidation were used to reduce the content of unsaturated bonds in their molecules. The results of oxidation test indicate that epoxidation is an available method to improve the oxidation stabilities of vegetable oils. The efficiencies of antioxidants used for protection of rapeseed oil from oxidation were studied using PDSC, and the active energies of oil samples were calculated by using Arrhenius equation.
Numerical Investigation of Choked Flow in Padded Finger Seals
Authors: Cioc Sorin , Fleming David P. , Keith Theo G. , Cioc Carmen
Published: November 2008

The aim of the present work is to continue to improve the modeling of the high-pressure seal pads by two means. First, by using a set of governing equations that, unlike previous models, incorporates the inertial effects, including choking. This way, the additional approximations at the interface between two separate models are avoided. Second, since the flow may be choked, the equations are solved using a shock capturing numerical scheme. The method used in this case is the space-time conservation element and solution element (CE/SE) scheme, which can accurately predict flows in thin films with discontinuities. Special attention is given to the choked flow cases, for which the flow becomes discontinuous near the exit boundary. The analysis should prove useful in the design process, and also in the general level of understanding the phenomena that occur in more severe cases.
Quantum Chemical Studies of Free-Radical, Hindered Phenol Stabilizers
Authors: Pfaendtner Jim , Broadbelt Linda J. , Wang Q. Jane
Published: November 2008

Quantum chemical investigations of the action of hindered phenol radical stabilizers in lubricant degradation chemistry have been completed. We are currently developing the first mechanistic models of lubricant degradation with the aim of including the chemistry of additives such as radical stabilizers that are found in commercial lubricant formulations. A key component of development of these models is obtaining reliable estimates of the kinetic parameters for all reactions. Specifically, rate constants and structure-reactivity correlations for the interaction of hindered phenol radical stabilizers with small peroxy radicals have been sought using quantum chemistry and transition state theory. Accurate thermodynamic properties of hindered phenol radical stabilizers and structure-reactivity relationships have been obtained. Such relationships provide researchers the ability to quickly estimate reactivity of hindered phenol stabilizers using their thermodynamic properties and therefore may be useful in additive design.
Mechanical Properties of ZnDTP Tribofilms Measured by Nanoindentation at Controlled Temperature
Authors: Bec Sandrine , Demmou Karim , Loubet Jean-Luc , Pavan Sophie , Minfray Clotilde , Martin Jean-Michel
Published: November 2008

Zinc dialkyldithiophosphates (ZnDTPs) are known to be anti-oxydant and antiwear additives under boundary lubrication conditions and are thus extensively used for car engine lubrication. It was demonstrated that their anti-wear action is associated with the formation of a protective tribofilm on the rubbing surfaces. In this study, mechanical properties of a ZnDTP tribofilm were measured by nanoindentation at various temperature ranging from room temperature to 80°C. From these first tests, it was found that the hardness of the tribofilm measured at 80°C is half the hardness value measured at room temperature, while the Young’s modulus remains constant in the tested temperature range.
Adhesive Force Reduction and Molecular Aggregation on Lubricin-Coated Contacts
Authors: Torres J. R. , Jay G. D. , Warman M. L. , Kim K. S.
Published: November 2008

The atomic force microscope (AFM) was employed in dry conditions in order to test the surface modifying ability of lubricin. The present work shows that lubricin forms independent aggregates, which coalesce once a threshold concentration is reached providing uniform coating of a hydrophobic surface.
Lubricin Interaction With Hyaluronate Promotes Interchain Association Leading to Network Formation
Authors: Torres J. R. , Jay G. D. , Warman M. L. , Laxer R. M. , Laderer M. , Breuer K. S.
Published: November 2008

The present work is the first instance where a novel multiple-particle tracking microrheology technique has been applied to study molecular interactions of clinical significance. Herein we describe the molecular changes due to lubricin-hyaluronate interaction and their effect on mechanical properties of synovial fluid. Along with bulk rheology studies it was found that lubricin, a boundary lubricant, increases the HA network formation conducive to the enhanced molecular layering of HA under stress which results in increased shear thinning. This interaction may also allow HA molecules to bind to the cartilage surface, providing boundary lubrication, by virtue of its interaction with lubricin.
Copper CMP Mimicked With Atomic Force Microscopy
Authors: Sokolov Igor
Published: November 2008

To optimize chemical mechanical polishing CMP process, one needs to get information on the interaction between the abrasive slurry particles and the surface being polished. To study such interactions, we used atomic force microscopy (AFM). An AFM tip was used to mimic a single abrasive silica particle typical of those used in CMP slurry. Studying copper CMP, we found that the AFM scanning removes the surface oxide layer in different rates depending on the depth of removal and the pH of the solution. Oxide removal happens considerably faster than the CMP copper removal. This is in agreement with generally accepted models of copper CMP. Both long-range and the friction forces acting between the AFM tip and surface during the polishing process were measured. The correlation between those forces and the removal rate is discussed.
Fault Detection and Lubricant Health Monitoring for Slow Bearings in Extreme Operating Conditions
Authors: Kallappa Pattada , Byington Carl , Donovan Bryan
Published: November 2008

Slow rotating bearings are an integral part of aerospace and turbomachinery actuation systems. These actuation systems may be driven by electric, hydraulic or fueldraulic power and often operate under high loads and extreme temperatures. This makes these actuation systems and their slow rotating bearings highly susceptible to degradation and failure. Vibration monitoring techniques are not applicable to the PHM of these bearings, because their slow speeds are unable to produce a measureable vibration signature. Furthermore, the slow bearings are sealed and use grease lubrication, thus eliminating traditional oil debris monitoring. To address these problems, Impact Technologies, LLC has developed a PHM system that relies on system identification and uses available control system data and sensor measurements. This PHM system consists of algorithms and models that perform fault detection and identification for the bearings and its actuation train components like valves, pumps, motors, gears and bearings. The PHM process is divided into two stages — diagnostics and prognostics. Diagnostics is the process of detecting and isolating faults, while prognostics is the process of predicting remaining useful life (RUL) or time to failure. The authors demonstrate the PHM system through simulation on a dynamic model that is representative of hydraulic-mechanical actuation systems used in new and existing manned aircrafts, UAVs and Short Take-off and Vertical Landing aircrafts.
Experimental and Numerical Study of Emulsion Lubricated Strip Rolling
Authors: Kosasih P. B. , Tieu A. K.
Published: November 2008

An experimental and numerical study of cold rolling lubricated by O/W emulsion has been carried out. The experimental measurements are compared to the computed results from the numerical scheme developed by the authors. The scheme, which is based on two-phase lubricant model, is able to calculate oil concentration at any point within the inlet zone and work zone, rolling pressure, film thickness, and fractional contact ratio associated with strip rolling under mixed film lubrication at different rolling speed. The study encompassed extensive mixed film regime for speed, S ranges from 10−5 to 10−1, and supply oil concentration level λds ranges from 1% to 10%, and oil droplet size ranges from Ds from 5 to 20. The numerical results show the occurrence of moderate oil concentration increase in the inlet zone followed by a sharp one at the beginning of the work zone. The effect of the concentration process is predominantly seen in the film thickness and the lubricant pressure whilst its effect on the total pressure is less pronounced. The analysis of the results suggests that it is possible to lower the emulsion oil concentration without detrimental effects on the rolling process and indeed use this principle to control the outlet lubricant film thickness.
Friction Behavior of CMP Slurries Based on Novel Organic Particles
Authors: Li Yuzhuo , Wang Ning
Published: November 2008

With the integration of copper as interconnect and low k materials as dielectric, the CMP community is facing an ever increasing demand on reducing defectivity without scarifying production throughput. One such strategy is to significantly lower the polishing pressure to below 1 psi. Such a move has placed tremendous challenges to the tool manufactures, consumable suppliers (especially the slurry vendors), and end-users. It is a challenge to remain the high throughput (MRR and selectivity) at low down force without using harsh abrasives. For the first time, we recently report the use of novel hydrophilic organic particles for metal CMP. Unlike conventional abrasive particles such silica or alumina, these unique particles are designed to specifically interact with the metal surface to be polished and significantly modify the rheological behavior of the slurry. The obvious advantage of using such particles is the reduction of defects during CMP. The consequence of using such particles is also its ability to provide unsurpassed high selectivity in removal rate for copper over barrier and dielectric materials due to their weak interaction with these particles. The added benefit for slurry that uses such particles is to allow CMP process conducted at a lower down force without compromising the throughput. In this talk, some basic physical and chemical characteristics of the particles and slurry will be first presented. The friction beavior of these new slurries in relation to conventional slurries on blanket wafers will be discussed. The impact of particle hydrophobicity on the friction behviors of the slurries will be explored.
Lubricating Oil Performance Assessment Using Signed Digraph and Matrix Approach
Authors: Sharma B. C. , Gandhi O. P.
Published: November 2008

In this paper, a new approach for lubricating oil performance is assessed as an index by considering its pertinent properties and their interaction, modeled in terms of lubricating oil performance signed digraph (LOPSD). Its equivalent matrix is defined to obtain lubricating oil performance function. Numerical value of the function is called lubricating oil performance index (LOPI) and is a measure of lubricating oil performance and its residual life at a given time. This is obtained by substituting results of the identified oil tests.
Bifurcation Approach to the Analysis of Multiple Flying Height States in Load/Unload Hard Disk Drive Systems
Authors: Hwang Pyung , Khan Polina V.
Published: November 2008

The application of numerical continuation methods to calculate suspension force-equilibrium position curve for hard disk drive sliders is proposed. The method efficiently detects multiple equilibrium positions. The relationship between suspension force offset and critical preload is found for the femto slider.
Investigation of Scuffing Resistance and Tribological Performance of Laser Modified Surfaces
Authors: Aldajah Saud , Ajayi Oyelayo O. , Fenske George
Published: November 2008

Latest development in high-power lasers made possible a wide variety of laser surface modifications. Such surface modifications include: glazing, shock peening, alloying, cladding and texturing. The main reason behind applying these treatments is to improve the tribological performance of the modified surfaces. In addition to reducing friction and wear, it is favorable to improve the scuffing resistance. Scuffing can be defined as a sudden catastrophic failure of a lubricated sliding surface characterized by a sudden rise in friction; resulting in severe surface damage through localized plastic flow. This paper investigates friction and scuffing performance of laser glazed 1080 steel and laser textured H13 stainless steel. Results showed that laser glazed surfaces reduced sliding friction under dry conditions by approximately 35% and improved wear resistance. In addition, laser glazed surfaces showed high resistance to scuffing compared to unglazed surfaces. Also, laser surface texturing technique reduced sliding friction under lubricated conditions and improved scuffing resistance.
A New Simulation Method of Interaction Between a Liquid Crystalline Polymer and Two Serrated Walls
Authors: He Lan , Yung K. L. , Xu Yan , Shen Yun Wen
Published: November 2008

This paper presents a new molecular model to define the interactions of a liquid crystalline polymer (LCP) flowing between two serrated walls. The wall is modeled by a rough atomic serrated wall. The roughness characteristics are given by the space and height of the serrated wall. Molecular model of the liquid crystalline polymer is described by an improved model that consists of GB (Gay-Berne) sites as rigid segments and LJ (Lennard-Jones) sites. There are two nonlinear springs each connecting from a GB site to a LJ site that situate between two GB sites as flexible segments. This improved model is newly developed to reduce the computational cost from that of the hybrid GB/LJ model, which has provided an effective way to investigate the boundary problems and flowing behaviors of LCPs at nano-scale. The molecular dynamics (MD) simulation using this reduced computational cost method to study the effect of boundary conditions on alignment and rheological properties of the LCP is shown in the result.
Rolling Contact Fatigue of Bearing Steel in Hydrogen Environment
Authors: Tanaka Hiroyoshi , Hashimoto Masaaki , Sugimura Joichi , Yamamoto Yuji
Published: November 2008

In the future renewable energy systems where hydrogen is used as secondary energy carrier, bearings, seals, and valves may operate in hydrogen. It is important in ensuring reliability and safety to know any deviation of their tribological behaviors from those in normal atmosphere. It is well known that hydrogen causes embrittlement in many of commercially available steels, and the bearing steels are not the exception.
The Influence of Surface Roughness on Elastohydrodynamic Journal Bearing With Non-Newtonian Lubricants
Authors: Mongkolwongrojn Mongkol , Aiumpornsin Chatchai , Yawong Somnuk
Published: November 2008

In this paper, the effect of surface roughness and elastic deformation of bearing liner on the static characteristics of journal bearings are presented. A power law model is developed for the elastohydrodynamic lubrication regime. The modified Reynolds equations with elasticity equation were formulated for the elastohydrodynamic journal bearings under heavy load conditions. Multigrid and multilevel technique with Newton’s method were used to calculated the elastohydrodynamic bearing to obtain the oil film pressure profile, oil film thickness profile, load capacity, attitude angle and friction coefficient at various surface roughness parameters. The static characteristics of the rough elastohydrodynamic journal bearing were compared with that of the rough hydrodynamic journal bearings. The results show that the surface roughness and elastic deformation significantly affect the static characteristics of journal bearings under severe operating conditions.
A Web-Based Intelligent System for Used-Oil Analysis
Authors: Fan Jianchun , Zhao Xuehong , Zhan Laibin
Published: November 2008

The analysis of oil in an operating machine is considered as a very useful means to assess the condition of the machine. However, classical techniques of oil analysis are strongly dependent on the analyst’s expertise to perform wear particle inspection, condition classification, colligation of the test results by ferrography, AES. and physical or chemical detection and interpretation of the possible existing faults in a machine. To solve these problems and realize the intelligence of oil analysis, a Web-based intelligence system for oil analysis has been devised. This system is composed of an automatic ferroscope controlled by a computer to obtain improved wear debris images, a platform to process the images and to connect the field analyst with the experts in machine diagnosis through internet and an intelligent software platform to evaluate the tribological conditions and diagnose the faults. Furthermore, some intelligent diagnosis methods used in the system are introduced.
Cross-Sectional Analysis of Antiwear Films and Near-Surface Material From Tapered Roller Bearings
Authors: Evans Ryan D.
Published: November 2008

Transmission electron microscopy (TEM) was performed on cross-sectional samples from tapered roller bearing cone raceways. The bearings were tested in mineral oil with and without sulfur- and phosphorus-containing gear oil additives. Focused ion beam techniques were used for TEM specimen preparation. Imaging, electron diffraction, and x-ray energy dispersive spectroscopy revealed the structure and composition of near surface material (depth < 500 nm) and surface layers.
Effect of Reciprocal Sliding on Severe-Mild Wear Transition
Authors: Hiratsuka K. , Sayama H. , Prakash B.
Published: November 2008

It is well known that adhesive wear is strongly dependent on load, sliding velocity, temperature and several other operating parameters. Besides these parameters, test configuration and type of motion also significantly affect the wear mode. For example, severe-mild wear transition is strongly dependent on the orientation of a test rig and the possibility of retention of wear particles on rubbing surface. It has earlier been shown that the retention of mild wear particles is crucial for severe-mild wear transition [1].
Wear Characteristics of Metals Using Disk on Disk Type Wear Test Rig
Authors: Hiratsuka K. , Yoshida T.
Published: November 2008

Wear of metals is influenced by many factors such as material, surrounding atmosphere and sliding conditions. Besides these factors, type of the wear test also has a significant effect on wear results. For example, when pin on disk test rig is used, wear of disk is usually more than that of pin [1]. This is because the contact time of each specimen is asymmetric. In this case, the transfer particle at the tip of the pin protects pin against wear. So the wear of dissimilar metals depends on the pin-disk combination. In order to fully characterize the adhesive wear, we have developed a disk on disk type test rig [2]. In this rig, the circumferential surfaces of the two identical disks are in sliding contact thereby resulting in a symmetrical contact. In this paper, the wear characteristics of ten different metals sliding against emery paper as well as against themselves have been presented along with the wear of 43 dissimilar metal combinations.
Quantifying the Effect of Lubricant Elasticity on Micro Textured Surfaces
Authors: Hupp S. J. , Hart D. P.
Published: November 2008

An experimental study is performed on micro textured surfaces using both elastic and Newtonian fluids in order to understand the effect of fluid rheology on the sliding friction of textured surfaces. Nickel micro textured surfaces containing 50 to 125 micron diameter pores and 1 to 20 percent area densities of pores are friction tested using a triborheometer, and the resulting data is examined using a Stribeck diagram. This research reveals that the Stribeck curve will experience a shift according to the lubricant elasticity, and that shift is independent of the texturing parameters. By modifying the Gumbel number to form a new dimensionless parameter, the effect of lubricant elasticity is normalized for all surfaces.
The Tribological and Chemical Analysis of Top Ring Zone Samples of Fully Formulated Oil Taken From a Four Stroke Gasoline Engine
Authors: Lee Peter M. , Priest M. , Stark M. S. , Wilkinson J. J. , Lindsay-Smith J. R. , Taylor R. I. , Chung S.
Published: November 2008

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet the new CEC, ILSAC and OEM specifications, there is an ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines [1]. This work samples oil from the rear of the top piston ring of an engine during the first 15 minutes from cold start and operating at steady state under three different loads. These samples, used 40 hour sump oil and fresh oil have been subjected to tribological tests and chemical analysis.
Development of Low Phosphorous Engine Oils
Authors: Patel K. , Aswath P. B. , Elsenbaumer R. L.
Published: November 2008

ZDDP is the industry standard anti wear additive used by oil formulators for the past 50 years to provide the antiwear and load bearing capacity of engine oil. The breakdown of ZDDP results in the formation of sulfides and phosphates which provide anti-wear protection. In addition to its role as an anti-wear additive ZDDP also performs the role of an antioxidant. The performance of ZDDP is reduced by other parts of the additive package which include dispersants, pH stabilizers, and detergents. These constituents stabilize ZDDP and reduce its activity. The breakdown of ZDDP also creates S and P that can poison catalytic converters resulting in higher hydrocarbon and NOx emissions. GF-4 oils have lower ZDDP content to meet federal emission standards. In addition, to meet CAFE´ fuel economy standards, the industry is moving towards lower weight 5W-20 oil. The lower weight base oil coupled with lower ZDDP content have put additional constraints in developing high performance GF-4 oil. An additive package developed by Platinum Research Organization and the Tribology Group at University of Texas at Arlington is evaluated. This additive package enhances the activity of ZDDP and increases its anti-wear performance. This paper presents results from bench top tribology tests that were conducted to evaluate the performance of GF-4 oils with different amounts of ZDDP, additive package and an Fe based active ingredient. Results are discussed with respect to the extent of wear for a fixed number of wear cycles in a ball on cylinder test conducted under boundary conditions. In the presence of FeF3 active ingredient fully formulated oils with as little as 0.01% P exhibits antiwear performance comparable to oils with as much as 0.05% P and oils with 0.05%P are comparable to oils with 0.1%P. Differential scanning calorimetry indicates that the decomposition temperature of ZDDP is reduced by as much as 20°C in the presence of FeF3. This reduced decomposition temperature results in the efficient formation of anti-wear films even with lower ZDDP amounts.
Development and Evaluation of a High Performance Universal Grease
Authors: Aswath P. B. , Munot S. , Patel K. , Elsenbaumer R. L.
Published: November 2008

Lithium based grease constitutes a large fraction of the grease consumed in the aviation and automobile industry. The durability and performance of the grease depends upon the additives added. The additive package used here includes PTFE (Poly Tetra-flouroethylene) for low coefficient of friction, ZDDP (Zinc Dialkyl Dithiophosphate) for anti wear properties, and Molybdenum sulfide for high load applications. We have developed a catalyst that helps PTFE to adhere to the metal surface at a low temperature. Block-on-cylinder tests and 4-ball weld tests were carried out to evaluate the effect of these variables. After carrying out matrix of tests at a low load and at high load, it is seen that the formulation with the combination of ZDDP, PTFE and the catalyst work in synergy. At low loads PTFE and catalyst provide wear protection and at higher loads thermal decomposition of ZDDP occurs which forms sulfates and phosphates, which adhere to metal surface to provide protection. Under extreme pressure conditions a synergistic interaction between PTFE, ZDDP, MoS2 and catalyst is responsible for enhanced weld loads.
A Surface Analytical Study of the Effects of Water and Oxygen on Tribological Behavior of DLC Films
Authors: Eryilmaz O. L. , Erdemir A. , Johnson J. A. , Mehta N. , Prorok B.
Published: November 2008

In this study, we explored the effects of water and oxygen molecules on friction and wear of diamond-like carbon (DLC) films. Specifically, using Raman and x-ray photoelectron spectroscopies we attempted to analyze the near surface chemistry and microstructure of sliding contact surfaces and correlated these findings with changes in friction and wear of DLC films. Tribological tests were run in a ball-on-disk machine under 2 to 5 N loads and in dry and moist nitrogen and oxygen environments. Based on the tribological and surface analytical findings, a mechanistic explanation is provided for the high friction and wear of DLC in dry and humid oxygen environments.
The Robust Stability of a Wave Bearing
Authors: Ene Nicoleta M. , Dimofte Florin , Keith Theo G. , Handschuh Robert F.
Published: November 2008

The purpose of this paper is to compare the stability of a three wave journal bearing with the stability of a hydrodynamic plain circular journal bearing. The study of the stability of a bearing can be reduced to the study of the stability of a fourth order linear system. In this paper, a perturbation method is used to compute the dynamic coefficients of the bearing. The critical mass is determined at every relative eccentricity, for both the circular hydrodynamic wave bearing and the three wave bearing. The influence of the amplitude of the wave on the stability of the wave bearing is also studied. However, not all the phenomena which affects the bearing’s operation can be taken into account, but it is important that the bearing preserves its stability in face of different types of uncertainty. This property is known as robust stability. In this paper, the robust stability of a bearing is evaluated by determining how great the perturbations of the dynamic coefficients could be so that the bearing remains stable. The robust stability is analyzed using the Kharitonov’s theorem.
Film-Forming Properties of Estolides
Authors: Biresaw Girma , Isbell Terry A. , Cermak Steven C.
Published: November 2008

Estolides are biobased materials obtained from synthesis of ingredients derived from agricultural products. They are oligoesters obtained by the reaction of fatty acids and/or methyl esters with a double bond. By varying the chemistries of the starting materials and the reaction conditions, estolides of varying chemical structures, and physical properties are obtained. Estolides have been found to have suitable properties for some lubrication applications. However, the effect of estolide chemical/physical characterstics on its tribological properties have yet to be understood. In this work, the effect of estolide physical/chemical variability on its film-forming properties is examined.
Effect of Atomic-Scale Surface Roughness on Friction
Authors: Robbins Mark , Luan Binquan , Hyun Sangil , Harrison Judith , Bernstein Noam
Published: November 2008

Simulations of friction between clean, atomically flat surfaces indicate that the friction force per unit area decreases to zero with increasing area. In previous work, we showed that the presence of mobile atoms between surfaces suppresses this superlubric behavior. The current paper examines the effect of atomic scale roughness. Both single asperities and random self-affine surfaces are considered in two and three-dimensional geometries. We have also examined the effect of commensurability, and elastic or plastic deformation within the bounding solids. The friction force on single asperities decreases to zero as the contact area and radius of curvature increase, but can still be significant at the scale of scanning probe tips. Introducing mobile atoms leads to friction forces that rise linearly with area in large contacts. Frictional forces on random self-affine surfaces can be quite complex. If self-affine scaling extends down to atomic dimensions, the average contact between elastic solids only contains a few atoms and the friction can be large. Plasticity increases contact dimensions and may lower the friction.
Friction of Microscale Contacts on Diamond-Like Carbon Nanocomposite Coatings
Authors: Chromik Richard R. , Wahl Kathryn J.
Published: November 2008

Microtribology of diamond-like carbon (DLC) nanocomposite coatings was studied using a commercially available nanoindentation system. Reciprocating sliding tests were conducted at 4 μm/s over track lengths of 8 μm with diamond and sapphire counterfaces with nominal diameters of 20 and 300 microns, respectively. Measured contact stresses were between 0.2 and 2.0 GPa for both tips. The friction behavior as a function of the contact stress was explored in the elastic regime. Measured interfacial shear stress for these sliding contacts were 12 ± 1 MPa for sapphire and 31 ± 3 MPa for diamond against DLC coatings.