bluuebunny/crossref_metadata_2025 huggingface dataset:
A Micromechanical Dislocation Model of Rough Surface Contact Plasticity
Authors: Gao Y. F.
Published: November 2008

Rough surface contact plasticity, especially at mesoscale and nanoscale, has been playing a central role in a broad spectrum of novel applications, e.g. nanostructure fabrication and reliability. The multiscale nature of surface roughness, the structure- and size-sensitive material deformation behavior, and the importance of surface forces and other physical interactions give rise to very complex surface phenomena at mesoscale and nanoscale. We present a micromechanical model to study rough surface contact plasticity, based on dislocation nucleation and multiplication. Surface roughness can be sources of dislocation nucleation; though roughness is confined to a thin layer, the resulted dislocation plasticity can extend to a far depth. Depending on interface adhesion, roughness features and slip planes, we get a variety of surface micro-plasticity behaviors that are radically different from classic plasticity behaviors.
Process Map Development for Chemical Mechanical Polishing With Low-k Material
Authors: Sutcliffe M. P. F. , Liu F. , Cheng L. , Le H. R.
Published: November 2008

Three elements of work are described: (i) a contact mechanics model of the polishing pad, used to predict asperity pressures, (ii) micro-tribometer tests on wafers coated with low-k material and (iii) CMP tests on wafer samples. Delamination of low-k samples is observed at higher pressures in both the micro-tribometer and CMP tests. The correlation between the two tests confirms the usefulness of this combined approach to developing process maps of CMP.
Effect of the Substrate on the Fretting Wear of Sputtered W-Si-N Coatings Against Steel
Authors: Gaspar M. C. , Ramalho A. , Cavaleiro A.
Published: November 2008

Fretting tests of sputtered W-Si-N amorphous coatings were performed on both cemented tungsten carbide with 6wt.% of Co and AISI 310 steel substrates against spherical AISI 52100 steel counterbodies. The normal load and the amplitude of relative displacement were varied. The evolution of the tangential force during the test was recorded. At the end of each test, the volume and the surface morphology of the wear scars were measured and analyzed. The relationship between the dissipated frictional energy and the wear volume was calculated. The results allowed plotting fretting maps identifying the occurrence of different fretting regimes.
Theoretical Analysis of Piston Ring Frictional Loss in an Innovative Rotating Liner Internal Combustion Engine
Authors: Xu H. , Kim M. , Bryant M. D. , Matthews R. D. , Kiehne T. M.
Published: November 2008

This paper presents a new lubrication model to predict piston ring friction. The average Reynolds equation is adopted to obtain the hydrodynamic component of restoring force against the cylinder liner surface. The dry or boundary lubricated component is derived from Greenwood-Tripp model. The influence of surface irregularities or roughness on the lubricant flow will be described by statistical parameters. Unlike classical piston ring mixed lubrication models, a sideslip rolling friction model is incorporated with contact simulation. Numerical results show that piston ring friction is reduced dramatically by the liner rotation.
The Static Performance Analysis of Air Foil Journal Bearings Considering Three-Dimensional Structure of Bump Foil
Authors: Lee Dong-Hyun , Kim Young-Cheol , Kim Kyung-Woong
Published: November 2008

The calculation of bump foil deflection is very important to predict the performance of foil bearings more accurately, because the foil bearings consist of top foil and its elastic foundation usually called bump foil. For the purpose of this, a finite element model considering 3-dimensional structure of the bump foil is developed to calculate the deflection of inter-connected bump. The results obtained from the suggested model are compared and analyzed with those from the previous proposed deflection models. In addition, load capacity of the foil bearings is analyzed by using this model.
Adhesive Contact Modeling of Ultra-Low Flying Head-Disk Interfaces With and Without Roughness Effects
Authors: Suh A. Y. , Polycarpou A. A.
Published: November 2008

The head-disk interface (HDI) designed for sub-5nm pseudo-flying to obtain extremely high areal recording (EHDR) density of 1 Tbit/in is susceptible to strong adhesive interfacial forces, and the accurate predictions of these interfacial forces are critical in ensuring successful implementation of ultra-low flying HDI’s. In this paper, the effect of surface roughness on the adhesive forces at sub-5 nm flying-height regimes is investigated through a comparison to a simple two flat parallel surface counterpart. It was found that the effect of roughness promotes adhesion at higher separations than if a two flat parallel surface configuration is adopted. Prior to the onset of contact (during flying), however, the total adhesive force for an interface with low roughness is comparable to the two flat parallel surface approximation, thus significantly simplifying the analysis.
Analysis of Cycle Lifetimes and Failure Modes for RF MEMS Switches
Authors: Brown Chris , Krim Jacqueline , Morris Art
Published: November 2008

RF MEMS switch lifetimes are limited by stiction of the moving components and degradation of the metal to metal contact points during cycling. Currently, maximum switch lifetimes are around 10 to 25 billion cycles. Past experimentation has shown that some stiction problems can be overcome by carefully controlling the operating parameters, but problems at the contact points remain [1]. It is believed that by developing a set of tribological design rules which limit the factors leading to catastrophic failure, switches can operate in excess of 100 billion cycles. Recent research has quantified the reliability and durability of gold contact points on RF MEMS switches as a function of current [2]. Most experimentation on RF MEMS switches has focused on controlling the operating parameters such as current, voltage, electrode materials, contact area, switching mode and force; however, limited work has been performed on a single device type in multiple environmentally controlled testing conditions such as vacuum, cryogenic temperatures, etc. This presentation will discuss performance of the wiSpry RF MEMS switch focusing on quantification of device reliability and failure mechanisms under various atmospheric and temperature conditions. Environmental testing conditions include switching in open air, vacuum and inert gasses, in temperatures ranging from 294 K to 4 K.
Nanodynamics of Vapor-Phase Organophosphates on Silicon and OTS for MEMS Lubrication Purposes
Authors: Neeyakorn W. , Lee S. M. , Parker O. , Burnette J. E. , Bilbro L. S. , Nemanich R. J. , Krim J.
Published: November 2008

We have performed a quartz crystal microbalance (QCM) study of the nanotribological properties of organophosphate (tricresylphosphate and t-butyl phenylphosphate) layers adsorbed from the vapor phase onto silicon (amorphous silicon and MEMS-like polysilicon), and octadecyltrichlorosilane (OTS) treated silicon and gold surfaces. The latter systems have been studied in order to explore whether organophosphates and OTS in combination might prove synergistic from a tribological point of view [1]. There is a strong possibility that this combination will also exhibit synergistic tribological behaviors when tested on actual MEMS devices. Therefore, it is important to perform QCM measurement on silicon that is as close to that of MEMS devices. In order to perform this study, we have developed a deposition method involving a Si-Ge layer that enables the growth of polycrystalline silicon on top of Cu QCM electrodes. The structural and morphological properties of these samples have been characterized with Raman spectroscopy and atomic force microscopy (AFM), confirming that they are similar in nature to the silicon in actual MEMS devices.
Tribological Study of Ti3SiC2 and Its Derivatives
Authors: Gupta Surojit , Sun Z. M. , Barsoum M. W. , Palanisamy T. , Passman E.
Published: November 2008

In this paper, we report on the tribological and wear properties of Ti3SiC2 and its derivatives. Coarse-grained Ti3SiC2 was not wear resistant at room temperature. Preoxidation of the material at 700 °C for 5 h also failed to ameliorate the situation at room temperature. Addition of 20 vol.% Cu in the matrix improved the wear rate for up to 1500 m; beyond that distance the friction and wear increased. Ti3SiC2 tested at 500 °C showed improved wear resistance most probably due to the formation of oxide tribofilms. More work is being done to understand the basic mechanism behind this behavior.
Major Advances in Tribology for Low Heat Rejection Engines: A Ten-Year Overview
Authors: Sutor Paul , Schwarz Ernest E. , Pangilinan Harold
Published: November 2008

In the last decade, Surfaces Research and the U.S. Army have made very significant advances in tribology for high-power-density, low-heat-rejection (LHR) diesel engines. High-temperature tribology issues, which had been major technological hurdles for LHR engine technology, have now been solved. We have developed totally new and economical Group V-based lubricants and self-lubricating coatings in our laboratories. These new lubricants enable reliable, long-term operation of diesel engines with oil sump and engine coolant more than 38°C (100°F) higher than conventional operating temperatures. Over 1300 hours of engine testing have provided detailed data on lubricant and engine component performance at high-temperature, high-BMEP LHR engine conditions.
Novel Ionic Liquid Lubricants for Aerospace and MEMS
Authors: Kinzig Barbara J. , Sutor Paul , Sawyer Gregory W. , Rennie Alison , Dickrell Pamela , Gresham Jennifer
Published: November 2008

Room temperature ionic liquids (RTILs) are molten salts with melting points at or below room temperature. RTILs have recently been recognized as novel lubricants. Only a few have previously been evaluated.
Behavior of Sucking Disks Under Vertical and Tangential Load
Authors: Washio T. , Mizuhara K.
Published: November 2008

The behavior of sucking disks, used to stabilize human tissue during surgeries, was investigated using conventional plastic sucking disks. The contact load to control a sustainable tangential load was calculated from the pressure and area of the internal cavity and the normal load. We observed an interesting phenomenon wherein the more the disk was pulled, the more it was pressed against the counter-surface. We also investigated the maximum tangential frictional force for several pre-loads applied perpendicularly to clarify the potential for sticking. We found that higher the pre-load, the lower was the maximum tangential friction force obtained.
Friction and Wear Studies of Hydrogenated Amorphous Carbon Films Containing Silicon
Authors: Schall J. D. , Gao G. T. , Workum K. V. , Mikulski P. T. , Harrison J. A.
Published: November 2008

The ratios of sp2 to sp3 content for a series of hydrogenated amorphous carbon-silicon systems were determined using molecular dynamics simulation. The values of elastic modulii were then determined for each system using constant tension and constant temperature molecular dynamics simulation method. The relationship between sp2 to sp3 content and modulii was investigated by varying Si and H content in the films. The thermal conductivity and heat capacity were also calculated for each system. A series of sliding simulations was used to determine which properties had the greatest effects on the resulting friction and wear behavior of the films.
The Influence of the Design Parameters on Performance of Thin Film Temperature Sensor
Authors: Jia Yi , Araya Guillermo
Published: November 2008

Embedded thin film temperature sensor onto the surface of lubricated mechanical component shows promising for real-time machine condition monitoring because the sensor could provide a minimally intrusive way of measuring temperature distribution in a lubricated contact in order 1) to early detect sudden changes in the lubrication condition that could have led to catastrophic failure for machinery; 2) to identify the early onset of incipient failures so that predictions can be made about their most likely progress and suitable actions can be planned, 3) to provide experimental verification of computational models that simulate extreme variations of temperature and pressure in a elastohydrodynamic lubrication film, and 4) to evaluate advanced materials for use in highly loaded tribological system [1]. Therefore, embedded thin film temperature sensors are becoming the system of choice for the industry to achieve higher machine reliability and, in turn, to be cost competitive in the market.
Adhesion, Friction and Mechanical Properties of CF3- and CH3-Terminated Alkanethiol Monolayers: A Comparative Study
Authors: Houston J. E. , Doelling C. M. , Vanderlick T. Kyle , Hu Y. , Scoles G. , Wenzl I. , Lee T. Randall
Published: November 2008

Self-assembled monolayers (SAMs) have received considerable recent attention as molecular-level lubricants in, for example, micro-electro-mechanical systems (MEMS).[1] Of particular interest as tribological films have been SAMs terminated by fluorocarbon groups, because of their inert nature and enhanced thermal stability. Surprisingly however, fluorocarbon films were shown to actually produce higher coefficients of friction (relative to CH3-terminated films) in atomic force microscopy (AFM) studies. Subsequent work has concluded that the increased van der Waals radius of the fluorine groups (∼45%) causes a steric disruption of the order of the molecular surface giving rise to an increased friction.[2] We present results from a direct comparison of the adhesive, mechanical and frictional properties of SAMs terminated by CF3 and CH3 groups using both Interfacial Force Microscopy[3] (IFM) and the AFM. IFM results are shown for a two micron tungsten tip interacting with C16 alkylthiol molecules assembled on Au(111) single-crystal surfaces. AFM results involve a ∼20 nm tip interacting with the same two molecules assembled on Au films deposited on mica surfaces. A direct AFM comparison is accomplished by using a “nanografting technique”.[4]
Dynamic Analysis of the Test Stand: The Key to a Successful Sliding Friction Testing
Authors: Lubinski Jacek I.
Published: November 2008

In a typical tribological research vibration is only considered, when it is judged as excessive, otherwise it is not regarded as the key issue. Still even a small amplitude vibration can disturb the desired input load and sliding velocity in a test. Tribological tests carried out without the analysis of the accompanying vibration are always threatened by vibration related erroneous interpretation of results. It must be emphasised, that a test stand is a dynamic mechanical system in which friction is evoked for experimental reasons and that friction interacts with the entire system just as in real life machine.
Vapor Phase Lubrication of Gold/Gold Interfaces
Authors: Perry Scott S. , Laboriante Ian , Yan Xiaoping
Published: November 2008

The extension of current micro-satellite development efforts calls for a reduction in size by up to two orders of magnitude. Such a reduction in size necessitates the development of novel actuators, switches, and sensors operating on the micron length scale. The leading technology for creating such devices involves microfabrication processes currently used in the production of integrated circuits. Devices generated by these means are referred to as Micro-Electro-Mechanical Systems (MEMS). While many challenges remain in the design and production of MEMS, a critical aspect of their successful deployment involves lubrication of the devices to prevent wear and permanent, undesired adhesion (seizure) of the miniature moving parts. Results from research addressing the vapor phase lubrication of gold-gold contacts, modeling interfaces expected to be encountered in future RF MEMS devices, will be presented. Such interfaces will require high frequency intermittent contact, the absence of irreversible interfacial adhesion, the general absence of sliding within the contact, and the requirement of electrical conductivity upon contact. Work in this area has focused on the use of alklythiols as a means of controlling interfacial adhesion. Experiments have been carried out using atomic force microscopy to characterize adhesion as a function of alkylthiol chain length. In addition, these experiments have incorporated the simultaneous measurement of interfacial currents to explore load versus conductivity relationships. These measurements have been supported through measurements of surface composition through correlated quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS) measurements.
Two-Phase Hydrodynamic Modeling of Particulate Fluids in Sliding Contacts
Authors: Terrell Elon , Garcia Jonathan , Higgs C. Fred
Published: November 2008

Chemical mechanical polishing (CMP) is a manufacturing process that uses controlled wear to planarize dielectric and metallic layers on silicon wafers. The wafer is polished by pressing it against a rotating pad that is flooded with slurry. The slurry itself is a fluid containing abrasive particles. Material removal rate (MRR) results have shown that the distribution of suspended particles in the slurry is significantly related to the wafer surface wear distribution during CMP. In this study, a simple model has been developed and solved as a preliminary step in analyzing the migration of the particles.
Experimental Verification of an Improved Elastic-Plastic Static Friction Model Including Roughness Effects
Authors: Lee Chul-Hee , Polycarpou Andreas A.
Published: November 2008

An experimental study was performed to measure the static friction coefficient under different experimental conditions. These include different surface roughness conditions, the effect of dwell time, the effect of acceleration (sliding velocity) as well as the presence of traces of lubricant and wear debris at the interface. The static friction tester provides accurate measurement of friction, normal and lateral forces at the interface (using a high dynamic bandwidth piezoelectric force transducer) as well as precise motion control and measurement of the interface motion. The experimental measurements were subsequently compared with an improved elastic-plastic rough surface static friction model, and it was found that the model captures the experimental measurements well, especially in terms of surface roughness. However, the data also shows the limitations of the model as it fails to accurately capture the effects of experimental conditions such as the presence of wear debris and start up velocity.
New Estimations of Surface Properties for Tribological Studies by Neutron Reflectometry
Authors: Hirayama Tomoko , Takemoto Hiroki , Inoue Kazuko , Ebisawa Toru , Tasaki Seiji , Hino Masahiro , Torikai Naoya , Shimizu Hirohiko , Ikeda Kazuaki
Published: November 2008

Tribological phenomena usually occur at a solid surface or an interface of solids. To carefully examine a tribological phenomenon, information on the state at the surface or the interface must be tried to be gotten from different angles. Estimations of the state, however, are generally considered to be difficult because there are few methods suit for adequately picking up the information on profiles and/or properties of the only nearest region to the surface. Especially for the case that the target is at the interface of metals, the estimation is more difficult because a standard electron beam cannot penetrate into either of the metal. The authors have, accordingly, developed a new estimation method applying a ‘neutron reflectometry’ to such a metal surface or a metal-metal interface. The reflectometry is suitable for analysis of vertical structures of the nearest regions to a surface as less than 1 μm. In addition, since a neutron beam can penetrate into many kinds of common metals, the estimation by the neutron reflectometry can be useful even for the metal-metal interface. In this paper, we report some results obtained by some of several basic experiments on neutron reflectometry. Surface profiles and ultra-thin film thickness of PFPE lubricant at a metal surface and/or a metal-metal interface were estimated in the study.
Non-Linear Description of Floating Ring Bearings Rotordynamics
Authors: Di´az S. E. , Castro R.
Published: November 2008

Floating ring bearings are commonly used in automotive turbochargers for their low manufacturing costs. However, the strong non-linearity of this configuration prevents the use of traditional rotordynamic techniques to describe their behaivior, thus relegating its design process to a costly trial and error process. A numerical characterization of this non-linearity is hereby presented for a flexible rotor supported on two FRBs. Non-linear techniques such as Poincare´ and Bifurcation maps, along with traditional rotordynamic techniques, show ranges of periodic, quasiperiodic, and chaotic motion, being the most stable ones related to high unbalance and/or low speeds, though in some cases the periodicity of the motion is reestablished at higher speeds. In all cases chaos is reached through a period doubling route. Shaft flexibility is shown to retard the occurrence of chaos, while excitation of conical motion seems to favor it.
Quantitative In-Situ Measurement of Asperity Compression During Chemical Mechanical Planarization
Authors: Gray Caprice , Apone Daniel , Rogers Chris , Manno Vincent P. , Barns Chris , Moinpour Mansour , Anjur Sriram , Philipossian Ara
Published: November 2008

Modifications to the Dual Emission Laser Induced Fluorescence (DELIF) procedure used to collect images of the slurry layer between the polishing pad and wafer during Chemical Mechanical Planarization (CMP) have provided a means to attain instantaneous, high spatial resolution images of slurry film thickness. Presented here is a technique to determine the calibration factor that correlates image intensity to slurry film thickness. This presentation will discuss how to determine slurry layer shape near wafer features, pad roughness, and pad compressibility.
Electrostatic Generation in Dielectric Fluids: The Viscoelectric Effect
Authors: Balmer Robert T.
Published: November 2008

Simultaneous energy transfer modes have been known to interact to produce unusual “coupled” effects. This coupling now has its theoretical basis in the concept of entropy production (or dissipation or irreversibility) central to nonequilibrium irreversible thermodynamics. Over the years, many examples of coupled phenomena have been identified and studied (thermoelectricity, electrokinetics, piezoelectricity, and so forth). Electrohydrodynamics (the effect of fluid motion on electric fields and the reverse effect of electric fields on fluid motion) can be explained as a thermodynamically coupled phenomenon characterized by the viscous and electrical properties of a fluid that contain mobile charges at the molecular (e.g., ions) or macroscopic (e.g., dust) levels. This is called the “viscoelectric” effect. In the first part of this paper we apply the concepts of irreversible thermodynamics to electrohydrodynamic systems to develop the relevant relationships. The second describes experiments carried out with a new type of Couette electrostatic generator. The resulting experimental data is then discussed in light of the coupled phenomenon relations previously developed.
Thermal Elasto-Plastic Contact Model of Rough Surfaces
Authors: Liu Geng , Liu Tianxiang , Xie Qin , Shi Fanghui
Published: November 2008

A thermal elasto-plastic contact model is developed in this paper to investigate the influences of steady-state frictional heating on the contact performance of surface asperities and subsurface stress fields. This model takes into account the asperity distortion caused by temperature variation in a tribological process, micro plastic flow of surface asperities, and the coupled thermo-elasto-plastic behavior of materials, with and without considering the strain-hardening property of the materials. The model is verified through the contact analysis between a rigid, isolated cylinder and a plane. Furthermore, the thermal effects on the contact pressure, real contact area, and average gap of rough surfaces in contact with different frictional coefficients and heat inputs under the thermal elasto-plastic contact conditions are studied.
Elasto-Plastic Asperity Contacts of Layered Media
Authors: Xie Qin , Liu Geng , Liu Tianxiang , Tong Ruiting , Zeng Quanren
Published: November 2008

An elasto-plastic asperity contact model for layered media is developed in the work reported in this paper to analyze the influences of coating-substrate materials on contact when yielding and the strain-hardening properties of materials are taken into account. The finite element method, the initial stiffness method and the mathematical programming technique are employed to solve the model. The von Mises yield criterion is used to determine the inception of plastic deformation. The effects of different layer thickness and different coating-substrate materials on the contact pressure, real area of contact, average gap of rough surface, and stresses in layer and substrate under the elastic-perfectly-plastic and the elasto-plastic contact conditions are numerically investigated and discussed.
The Relative Friction Force Contributions of Polishing Pads and Slurries During Chemical Mechanical Polishing
Authors: Levert Joseph A. , Korach Chad S.
Published: November 2008

Next generation integrated circuits (IC’s) will require the use of porous dielectric materials with shear strengths much lower than the currently used dense silicon dioxide. The high friction of CMP (chemical mechanical polishing) may damage these porous dielectric materials. This research is being performed to define the nanoscale source of this poorly understood CMP friction to enable development of less damaging CMP processes. It is proposed that the nanoscale friction on the IC from CMP is a variable combination of two-body pad nanoasperity to IC contact and three-body nanocontact of the slurry particle between the pad nanoasperity and the IC surface. This research uses a combination of individual nanoscale friction measurements for CMP of SiO2, an analytical model to sum these effects, and bench scale CMP experiments to guide the research and validate the model.
A Mechanism of Sliding on the Nanometer-Thick Ag Layers
Authors: Honda F. , Goto M.
Published: November 2008

Tribological performance of sub-nano to nanometer-thick Ag layers deposited on Si(111) have been examined to understand the role of surface thin layers to the wear and friction characteristics. The slider was made of diamond sphere of 3 mm in radius. Sliding tests were carried out in an ultra-high vacuum environment (lower than 4 × 10−8 Pa) and analyzed in-situ by Auger electron spectroscopy (AES) for the quantitative thickness-measurements, by reflection high-energy electron diffraction (RHEED) to clarify the substrate cleanliness and crystallography of the Ag films, and by scanning probe microscopy (SPM) for the morphology of the deposited/slid film surfaces. As the results, a minimum of the friction coefficient 0.007 was observed from the film thickness range of 1.5–10 nm, and exactly no worn particles were found after 100 cycles of reciprocal sliding. Results have directly indicated that solid Ag(111) sliding planes allowed to reduce the friction coefficient very low without any detectable wear particles, and Ag nanocrystallites in Ag polycrystalline layers increase the size to 20–40 nm order, during sliding. The friction coefficient was slightly dependent to the normal load. Results were discussed on the role of the surface atoms to the friction, and a mechanism of sliding on Ag thin layers.
Wear of Sliding Triboconjugations With Irregular Profile Peak From a Position of a Damages Accumulation on the Plastic Contact Condition
Authors: Kharlamov V. V.
Published: November 2008

In this paper we conside wear of roughness surfaces on the mixed friction conditions.
Effect of Molecular Weight (MW) and End-Groups on the Thermal and Lewis-Acid Catalyzed Decomposition of Fomblin Z-Type Lubricants
Authors: Li Lei , Jones Paul M. , Merzlikine Alexei G. , Hsia Yiao-Tee
Published: November 2008

The high-temperature stability of disk lubricants has attracted a lot of interest in recent years because smaller head-media spacing may cause head-media contact and thus a local temperature rise. At elevated temperatures, the lubricant may either evaporate or decompose, leading to the eventual failure of the head-media interface. The decomposition might result from heating and/or may be catalyzed by the presence of a Lewis acid site at the head-disk interface (HDI). In this paper, we study how the chemical structure, namely, molecular weight (MW) and end-groups (see Fig. 1), of disk lubricants will affect the thermal and Lewis-acid catalyzed decomposition of the lubricant.
Simulation of In-Plane Transverse Displacement of Tape
Authors: Taylor R. J. , Chung M. , Talke F. E.
Published: November 2008

The equations of motion for a thin strip of flexible material are used to describe the in-plane transverse motion of an axially moving magnetic tape in a tape transport. The relative contribution of the tension term compared to the bending stiffness term is analyzed for typical tension values and the frequency range of interest. The bending stiffness term is found to be 10–20 times larger than the tension term in the frequency range of interest in typical tape drives. The full equation of motion for the displacement of a single span of tape between two reels is solved numerically subject to boundary and initial conditions and the result is compared to experimental measurements. The agreement between measurement and numerical simulation is very good.
Viscoelastic Contact of Nominally Flat Rough Surfaces
Authors: Farhang K. , Lim A.
Published: November 2008

Approximate closed-form equations are derived for normal and tangential contact forces of rough surfaces in dry friction. Using an extension of the Greenwood and Tripp model, in which the derivations permit asperity shoulder-to-shoulder contact and viscoelastic asperity behavior. Mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the proximity of the two surfaces but also the rate of approach and relative sliding. A statistical approach is forwarded in which dependence of the asperity tangential contact force on relative tangential velocity of two asperities can be cast as a corrective factor in the mathematical description of tangential force. In this regard two corrective coefficients are derived: force directionality corrective coefficient and force-velocity directionality corrective coefficient. The results show that for a moderate to high load ranges the contact force can be analytically described to within 20 percent accuracy, well below the uncertainties due to surface profile measurement.
Effect of Oil Supply Pressure on the Maximum Oil Film Temperature of 2-Lobe Journal Bearing
Authors: Strzelecki S. , Kapusta H. , Swiatek J.
Published: November 2008

Two-lobe journal bearings are applied in the responsible bearing systems of steam turbines, turbogenerators and compressors. As compare to the bearing with the cylindrical bush they have better stability in the range of higher rotational velocities and loads simultaneously assuring very good cooling conditions for the oil film. For the two-lobe journal bearing the oil film pressure, temperature and viscosity distributions have been obtained by iterative solution of the Reynolds’, energy and viscosity equations. An effect of supplied oil pressure on the maximum oil film temperature was investigated.
Effect of Journal Misalignment on the Oil Film Pressure and Temperature Distribution of 3-Lobe Offset Journal Bearing
Authors: Strzelecki S. , Towarek Z.
Published: November 2008

The design of turbines and compressors operating at the high rotational speeds applies the 3-lobe journal bearings. In many cases the classic 3-lobe journal bearings supporting the rotors, are showing the problem of rotor stability. This problem can be avoided by the application of 3-lobe Offset bearings. This type of bearing fulfils the conditions of reliable bearing design and good stability in the case of high speed rotating machines.
Temporomandibular Joint Arthroplasty: Using Metal-on-Metal and Acrylic-on-Metal Configurations
Authors: Christensen Robert W.
Published: November 2008

In the long-term performance of the temporomandibular joint (TMJ) implant, wear and durability must be considered. Thus retrieved and laboratory test implants were examined both optically and in a scanning electron microscope (SEM). In laboratory testing, the volumetric wear of metal-on-metal was about an 10x order of magnitude less than that of metal-on-acrylic TMJ implants. This metal-on-metal wear was also about 1/60 of that reported in the literature for a laboratory test of (UHMWPE) polyethylene-on-metal TMJ implants. The retrieved TMJ implants showed some abrasive wear occurred during multi-directional articulation with smaller wear zones for the metal-on-metal compared to the metal-on-acrylic configuration. Further efforts to characterize and minimize wear were recommended as prudent in the continuing development of TMJ arthroplasty. In TMJ laboratory wear testing, the protocol for mass loss measurements must be improved to yield realistic and repeatable mass loss values. In laboratory wear testing, multi-directional motion must be imposed in the surface articulations. Further examination of retrieved TMJ implants is required, particularly in-situ for more than 10 years. The retrieval process should include study of tissue samples collected from surrounding tissues so that both the wear particles and the response to wear particles can be studied. New approaches in design and materials should be explored to further reduce wear.
Fretting Corrosion in the Pin Joints of the Rope Mounting of Skip Buckets Operating in the Coal Mines Deep Pit Shafts
Authors: Kowal A. , Strzelecki S.
Published: November 2008

The paper describes the mechanism and introduces the analysis of fretting corrosion as well some examples of surfaces’ destruction, presents the amplitude of oscillation movements as well as the results of investigations of fretting in the cylindrical joints, e.g. pin joints applied in heavy duty conditions in coal mines such as in the case of suspension of hoisting devices.
Tribological Process Characterization With In-Situ Quantitative Nano-Scale Metrology
Authors: Daugela Antanas , Meyman Alex , Knyazik Vladimir , Yeremin Nikolai
Published: November 2008

A novel quantitative nano+micro-tribometer with integrated nanoindenter, SPM and optical microscope imaging has been used to characterize mechanical properties of Cu coated Si wafers at various test stages. A 2D Finite Element Model was developed to study changes on workhardened contacts assessed via nanoindentation experiments.
Lubrication With Water-Based Clay Suspensions
Authors: Briscoe B. B. , Cann P. M. , Delfino A. , Maitland G.
Published: November 2008

The lubricating behaviour of a water-based rock drilling fluid (bentonite clay suspension) has been studied in a simple tribometer. Friction measurements were carried out with a model contact formed between a rotating shaft and a loaded planar counterface. The experiments were designed to investigate the tribology of the contact between the drillstring and the metal wall of an oilwell. Friction measurements were made for a range of loads and contact velocities and clay concentrations. The results are presented in the form of classical Stribeck-Hersey curves in order to identify the lubrication regime and to illustrate the combined effects of load and speed on the friction coefficient. Optical interferometry experiments were also carried out, using a ball-on-disc apparatus, in order to visualise the flow of the suspension through the contact. In a separate series of tests the interfacial shear stress of the mud formulations was measured for different contact metallurgies and operating conditions. Two basic lubrication regimes are identified: at high loads a regime characterised by the deposition of layers of solid clay onto the contacting surfaces and at low loads, a regime in which the main lubricating action is provided by the base fluid. In the transition between the two regimes, an intermediate region is characterised by changes in the fluid composition and rheology within the contact. The general trend of the Stribeck curve is obtained and a peculiar scattering of the data is evident in the region between the boundary lubrication regime and the mixed lubrication regime. The intrinsic nature and the complex rheology of the fluid appear to be the parameters that may control this effect and in part define the lubrication regime.
Influence of Contact Geometry and Third Body on Squeal Initiation: Experimental and Numerical Studies
Authors: Vayssie`re C. , Baillet L. , Linck V. , Berthier Y.
Published: November 2008

Brake squeal is an everyday problem, so it has been widely studied, mostly in vibration parlance studying modes, noise energy and frequencies. We propose to study the phenomenon from its origin — i.e. the contact — in a tribological approach that combines contact geometry, third body aspect and squealing initiation: thus, a temporal analysis was necessary. Experimental and numerical approaches have been used to identify influential parameters and they give similar results: a really strong correlation exists between the disk geometry and the squeal initiation.
Analysis of Oil Film Temperature Distribution of the High Speed Shaft Journal Bearings of Gear Box Applied in the Coal Mine Hoisting Machine
Authors: Strzelecki S. , Spalek J.
Published: November 2008

The paper describes the analysis of oil film temperature distributions that are generated in the gear train journal bearings of high speed shaft. The oil film temperature distributions were obtained on the assumption of adiabatic, laminar oil film for the finite bearing length, parallel axis of journal and bush and radial load of bearings. Maximum oil film temperature was determined based on the obtained oil film temperature distributions. The calculation were carried-out on the condition of static equilibrium position of journal.
Frictional Behavior and Tribo-Carbonization of a Synthetic Engine Oil (SJ/CF/5W-30) With Different Tribo-Materials Under Stepwise Heating Conditions
Authors: Zhang Ruijun , Li Shenghua , Jin Yuansheng
Published: November 2008

Frictional behavior of a synthetic engine oil, SJ/CF/5W-30, was investigated on a SRV reciprocating tribotester with tribo-materials consisting of Mo-sprayed coating, nitrided coating and Cr-plated coating sliding against cast iron operating under stepwise heating conditions. It was observed that, for the three tribo-materials, as operating temperature rose, there invariably existed a local minimum for frictional coefficient (μ), and the specific minimal μ value depended on the type of tribo-materials. Chemical characterization of worn cast iron surfaces using Raman spectroscopy indicated the existence of carbonaceous substances derived from the applied engine oil. There existed some correlation between microcrystal graphitic planar size (La value) and the local minimal frictional coefficient. Of the three tribo-materials, the maximal La value of the carbonaceous species was founded on the Mo-sprayed coating, and correspondingly, the lowest frictional coefficient occurred, indicating a more obvious anti-friction effect.
Sliding Wear Behavior of Plasma Sprayed Zirconia Ceramic Coating Under Different Conditions
Authors: Le Thuong Hien , Chae Young-Hun , Kim Seock Sam
Published: November 2008

The sliding wear behavior of ZrO2-22wt%MgO (MZ) and ZrO2-8wt%Y2O3 (YZ) deposited on a cast aluminum alloy with bond layer (NiCrCoAlY) by plasma spray against a SiC ball was investigated under dry and lubrication conditions at room temperature. At all load conditions, the wear mechanisms of the MZ and YZ coatings were almost the same. The wear mechanism involved material transfer and pullout under dry condition, but micro-fractures and spallation under lubrication condition. When oil was used for lubrication, the friction coefficient of the sliding pairs and the wear loss of the ceramics were reduced. The wear loss of the MZ coating was less than that of the YZ coating under dry test, but more than that of the YZ coating under lubrication test. The test conditions and the mechanical properties of the ceramic coatings were correlated to the wear performance.
Simulation and Optimum Design of Journal Porous Metal Bearing Under Elastohydrodynamic Lubrication
Authors: Marinkovic´ Aleksandar , Franek Friedrich , Pauschitz Andreas
Published: November 2008

With some new simulation methods and software tools it is possible to make qualitative analysis of sliding bearing behavior taking elastic deformations in account. This paper presents simulation and structural optimization of journal porous metal bearing under complex load distribution. Surface of porous metal bearing is loaded inside with pressure distribution that is calculated by hydrodynamic lubrication theory. Besides there is also frictional force loading inner surface and nonuniform temperature distribution on bearing volume. The structure analysis is made for each kind of load separately and for complex load distribution of bearing. This simulation is realized by finite elements method (FEM) in structure analysis module of CATIA V5 software. Based on this simulation in second part of paper is given parameter optimization of porous metal bearing with taking elastic deformations of bearing shell into account.
Stability of an Axially Accelerating String Subjected to Frictional Guiding-Forces
Authors: Zen Giampaolo , Mu¨ftu¨ Sinan
Published: November 2008

The dynamic response of an axially translating continuum subjected to the combined effects of a pair of spring supported frictional guides and axial acceleration is investigated; such systems are both non-conservative and gyroscopic. The continuum is modeled as a tensioned string translating between two rigid supports with a time dependent velocity profile. The equations of motion are derived with the extended Hamilton’s principle and discretized in the space domain with the finite element method. The stability of the system is analyzed with the Floquet theory for cases where the transport velocity is a periodic function of time. Direct time integration using an adaptive step Runge-Kutta algorithm is used to verify the results of the Floquet theory. Results are given in the form of time history diagrams and instability point grids for different sets of parameters such as the location of the stationary load, the stiffness of the elastic support, and the values of initial tension. This work showed that presence of friction adversely affects stability, but using non-zero spring stiffness on the guiding force has a stabilizing effect.
Evaluation of Near Frictionless Carbon Coatings Using Four-Ball Wear Tester
Authors: Rai A. K. , Bhattacharya R. S. , Massey M. , Eryilmaz O. L. , Erdemir A.
Published: November 2008

Near frictionless carbon (NFC) coatings were deposited in a large-area filtered cathodic arc system by plasma-enhanced chemical vapor deposition. An NFC coating with carbon-enriched TiC bond layers was deposited on half inch diameter steel (M50) balls. The four-ball wear test was used to evaluate the performance of the NFC coating. The endurance limit of the NFC coating was determined by starting the wear test at a relatively low load and increasing the load by a fixed amount after a given time interval to a final load at which the friction force reached a certain level. The four-ball wear test was conducted in fully flooded, starved, and dry lubrication conditions. MIL-PRF-23699 oil was the lubricant. Test results indicated a much higher endurance limit for the NFC-coated balls compared to that of uncoated balls.
A Study Into the Parameters Affecting Nickel Oxide Glaze Formation
Authors: Reynolds Alison
Published: November 2008

At elevated temperatures Nickel Alloys have the ability of forming a ‘glaze’ layer. If the test conditions are favourable, this layer can protect components from subsequent wear and fretting damage. This phenomenon has been previously shown by several researching bodies. Unfavourable conditions, on the other hand, can either delay or prevent its formation, rendering a component susceptible to further damage. This study investigates the effect that various test parameters have on the formation of these glaze layers, and how this may impact the fretting fatigue life. Parameters investigated include normal load and cycle frequency. Tests were carried out at two temperatures: 20°C was used as the control group, and 680°C as the experimental ‘glaze’ group. Experimental results are provided, and explained in terms of wear rate and frictional effect.
Simulation of Wear in a Worm Gear Under Elastohydrodynamic Conditions
Authors: Sharif K. J. , Evans H. P. , Snidle R. W. , Egorov I. M.
Published: November 2008

The paper is concerned with the prediction of wear of worm gear wheel teeth. The wear model that has been developed is based upon a full elastohydrodynamic lubrication (EHL) analysis of the contact between the teeth at various stages of meshing. Wear over the contacting region on the wheel tooth is calculated from a modified Archard-type law, taking pressure, film thickness and sliding values from the EHL results. The development of wear is obtained by an iterative process in which the shape of the contacting surfaces, as modified by wear, is updated in the EHL solution. This process leads to the prediction of wear contours on the gear teeth from which the increase in backlash (a practical measure of worm gear wear) can be obtained.
Experimental Study on Superlubricity of Ag Nanometer-Thick Layers by Sliding on a Macroscopic System
Authors: Goto Minoru , Honda F. , Nakahara T.
Published: November 2008

The experimental study on the Ag film was carried out using a diamond pin-on-plate type tribometer under ultrahigh vacuum (UHV) conditions. The coefficient of friction varied with the film morphology in nanometric scale up to 170 nm, and superlubricity as minimum coefficient of friction 0.007 was obtained on 5-nm Ag film with network structure. RHEED and STM observation of the film showed that the film morphologies changed drastically during rubbing, and that the superlubricity of this system is attributed to the lamella gliding of Ag (111) sheets.
Water Lubricated Sliding Wear of Si3N4/BN Fibrous Monoliths
Authors: Gutierrez-Mora F. , Erdemir A. , Goretta K. C. , Domi´nguez-Rodri´guez A. , Routbort J. L.
Published: November 2008

Water-lubricated friction and wear of silicon nitride (Si3N4) and Si3N4/hexagonal boron nitride (H-BN) fibrous monoliths (FM) were investigated using a ball-on-flat tribometer. The effect of the BN matrix on the overall sample tribological behavior is discussed and correlated to microstructural observations. Experimental data are compared to dry and oil-lubricated wear and friction in the same materials.