bluuebunny/crossref_metadata_2025 huggingface dataset:
Adhesion and Friction on the Nanometer Scale: Energy Dissipation During Sliding of Antimony Islands on Graphite and MoS2
Authors: Schwarz Udo D. , Ritter Claudia , Heyde Markus , Rademann Klaus
Published: November 2008

Antimony nanoparticles grown on highly oriented pyrolytic graphite and molybdenum disulfide were used as a model system to investigate the contact area dependence of frictional forces. Controlled translation of the antimony nanoparticles was induced by the action of the oscillating tip in a dynamic force microscope. During manipulation, the power dissipated due to tip-sample interactions was recorded. We found that the threshold value of the power dissipation needed for translation depends linearly on the contact area between the antimony particles and the substrate. Assuming a linear relationship between dissipated power and frictional forces implies a direct proportionality between friction and contact area. Particles smaller than 10000 nm2, however, were found to show dissipation close to zero. To explain the observed behavior, we suggest that structural lubricity might be the reason for the low dissipation in the small particles, while elastic multistabilities might dominate energy dissipation in the larger particles.
Boundary Lubrication of DLC Coatings With Conventional Oils
Authors: Kalin M. , Vizˇintin J. , Roman E.
Published: November 2008

In this work we present results that show the effect of the type of mating surfaces, the doping elements in the DLC coatings, the type of the base oils and the additives used on the tribological performance of the boundary lubricated DLC coatings. We discuss the results in terms of various physical and chemical effects and we present some recent results of surface analyses under different temperature regimes.
The Stress-Dependence of Phase Changes in Silicon Under Indentation
Authors: Zhang L. C.
Published: November 2008

This paper investigates the stress effect on the phase transformation events in silicon under varying indentation loads, cycles and environment. It was found that the combination of hydrostatic and deviatoric stresses in indentation plays an important role. With a single indentation cycle, the deformed zone can be amorphous, a mixture of crystalline and amorphous, or purely crystalline, depending on the level of the maximum indentation load. Under cyclic indentations, some phases can be initiated from the second indentation cycle and stabilized in the subsequent cycles. Water has an obvious effect on the indentation deformation, with which silicon becomes less ductile. Different shapes of indenter tips leads to dissimilar phase transformation processes.
Magnetic Bearing for Reaction Wheels in Space Applications
Authors: Haridas T. R. , Ravichandran M. H. , Unnikrishnan P. V. , Joseph C. C. , Devasahayam Robert
Published: November 2008

Reaction wheels are used as actuators for attitude control of satellites. Ball bearing is being used in reaction wheel application since many decades. Even small variations in friction torque in ball bearings affects the pointing stability of the satellites used for high resolution imaging application. Also the bi-directional operation of reaction wheel requires frequent zero speed crossing. The stiction present in ball bearing wheels affects the stability during zero speed cross over. Magnetic Bearings have distinct advantages over conventional bearings, like zero friction (due to non-contact operation), no lubrication, long life, less power, etc. Absence of lubrication in magnetic bearing makes it compatible to harsh environments like vacuum. It provides smooth zero speed cross over due to negligible stiction, which is advantageous to achieve better pointing stability. The context of this paper benchmarks the design, simulation and test results of a two axes actively controlled magnetic bearing. The wheel is designed to have adequate slew rate capability to ensure non-contact operation during satellite maneuvers.
Contact Problems and Nanoindentation Tests for Indenters of Non-Ideal Shapes and Effects of Molecular Adhesion
Authors: Borodich Feodor M. , Galanov Boris A. , Keer Leon M.
Published: November 2008

Depth-sensing nanoindentation, when the displacement the indenter is continuously monitored is widely used for analysis and estimations of mechanical properties of materials. Starting from pioneering papers by Bulychev, Alekhin, Shorshorov and their co-workers, nanoindentation tests are connected with Hertzian contact problems and the frictionless BASh relation is commonly used for evaluation of elastic modulus of materials. We discuss further the connections between Hertz type contact problems and nanoindentation tests and derive fundamental relations for depth-sensing nanoindentation for indenters of various shapes and for various boundary conditions within the contact region. For the loading branch, relations are derived among depth of indentation, size of the contact region, load, hardness, and contact area, using authors’ scaling formulae. The relations are valid for indenters of non-ideal shapes, whose shape function is a monomial function an arbitrary degree d, in particular for blunted pyramidal indenters when 1 < d < 2. We show that some uncertainties in nanoindentation measurements, which are sometimes attributed to properties of the material, can be explained and quantitatively described by properly accounting for geometric deviation of the indenter tip from its nominal geometry. Then relation is derived for the slope of the unloading branch of adhesive (no-slip) indentation. The relation is analogous the frictionless BASh relation and it is independent of the geometry of the indenter. Further, the JKR theory of contact the presence of forces of molecular adhesion is extended to describe contact between a monomial indenter of an arbitrary degree d and an elastic sample. Finally, some exact formulae are obtained for adhesive contact (both the no-slip contact and the contact in the presence of molecular adhesive forces) between indenters and isotropic, linear elastic materials. In particular, it is shown that the BASh formula is still valid for contact between a flat punch and a soft elastic sample in the presence of molecular adhesive forces (the Boussinesq-Kendall problem).
Taylor Vortices Induced Instability and Turbulence in Concentric Cylinder Separated by Microscale Clearance
Authors: Deng D. , Braun M. J.
Published: November 2008

This paper attempts to elaborate on the relationship between the onset of Taylor instability and appearance of what is commonly known as “turbulent flow” in the narrow gaps of concentric cylinders, with the inner cylinder rotating. A question that we dare open to debate is whether the flow formations observed during Taylor instability regimes are, or have to do with the actual “turbulence” that we model in microscale clearance flows through the turbulent formulation of the Reynolds equation.
Super Low Friction Property of DLC Lubricated With Ester-Containing Oil: Part 1 — Friction Properties Evaluated in Rig Tests
Authors: Kano Makoto , Yasuda Yoshiteru , Ye Jiping , Konishi Shozaburo , Martin Jean Michel , De Barros Isabel , Le Mogne Thierry
Published: November 2008

This paper presents a material combination that reduces the friction coefficient markedly to a super low friction regime (below 0.01) under boundary lubrication. Friction tests were conducted with a test rig consisting of three pins pressed against a rotating disc, as shown in Fig. 1. The pins were made of bearing steel AISI52100 and the disc was made of carburized steel SCM415, which was coated with a diamond-like-carbon (DLC) film. The test conditions were as follows. Pins: Fixed, not rotating; DLC: CVD a-C:H, PVD ta-C; Lubricant: 5W-30 API SG Engine oil; Ester-containing oil (PAOES1): Poly alpha-Olefin containing 1 mass% of glycerol mono-oleate; Pressure: 0.7 Gpa; Sliding speed: 0.03–1m/s; Oil temperature: 353K (80 deg. Celsius).
Application of Energy Principle to Dry Sliding Friction
Authors: Xu Zhongming , Huang Ping
Published: November 2008

A new method named as energy principle method is used to calculate and research the friction force and friction coefficient of two flat elastic surfaces. The studies reveal the relationships between friction coefficient and parameters of a tribo-system such as microstructure of interface, performance of material, operational parameters and geometry parameters. When the height of an asperity increases in the model, the friction coefficient increases rapidly to a critical value, and then hardly increases after that.
A Cavitation Algorithm for Arbitrary Lubricant Compressibility
Authors: Sahlin Fredrik , Almqvist Andreas , Glavatskih Sergei , Larsson Roland
Published: November 2008

A general cavitation algorithm is presented that accommodates for an arbitrary density-pressure relation. Here it is possible to model the compressibility of the lubricant in such way the density-pressure relation is realistic from sub-cavity to high pressure regions respectively. The algorithm preserves mass continuity which is of importance when inter-asperity cavitation of rough surfaces is considered. Results with this algorithm for different density-pressure relations are presented and discussed.
Contact Analysis of Multilayered Elastic/Plastic Solids With Rough Surfaces for Decreasing Friction and Wear
Authors: Cai Shaobiao , Bhushan Bharat
Published: November 2008

A numerical three-dimensional contact model is presented to investigate the contact behavior of multilayered elastic-perfectly plastic solids with rough surfaces. The surface displacement and contact pressure distributions are obtained based on the variational principle with fast Fourier transform (FFT)-based scheme. Von Mises yield criterion is used to determine the onset of yield. The effective hardness is modeled and plays role when the local displacement meet the maximum displacement criterion. Simulations are performed to obtain the contact pressures, fractional total contact area, fractional plastic contact area, and surface/subsurface stresses. These contact statistics are analyzed to study the effects of the layer-to-substrate ratios of stiffness and hardness, surface roughness, and layers thickness of rough, two-layered elastic/plastic solids. The results yield insight into the effects of stiffness and hardness of layers and substrates, surface roughness, and applied load on the contact performance. The layer parameters leading to low friction, stiction, and wear are investigated and identified.
Effect of Aging on Wear Life of Sputtered MoS2 Films
Authors: Sagara Kazuhito , Suzuki Mineo , Nishimura Makoto
Published: November 2008

Sputtered MoS2 films deposited on SUS440C stainless steel disks were stored in a desiccator or in a vacuum of 10−5Pa to examine the effect of aging on their tribological performance. Five years’ storage in a desiccator (25%±5%RH, room temperature) elongated the wear life in a vacuum of sputtered MoS2 films in average by a factor of four. A sputtered MoS2 film stored in a vacuum for seven years showed tenfold increase in wear life when tested in a vacuum.
Wear of Coated Carbide Tools in the Ultra-Precision Machining of Stainless Steel
Authors: Liew W. Y. H. , Ding X.
Published: November 2008

Ultra-precision machines are widely used to turn aspherical profiles on mould inserts for the injection moulding of optical lenses. During turning of a profile on a stainless steel mould insert, the cutting speed reduces significantly to 0 as the cutting tool is fed towards the center of the machined profile. This paper reports on experiments carried out to study the wear of uncoated, PVD-coated and CVD-coated carbide tools in the ultra-precision machining of STAVAX (modified AISI 420 stainless steel) at low speeds.
A Parametric Analysis of the Thermal Shear Localization in EHL Films
Authors: Chang L.
Published: November 2008

Experiments and computer simulations [1] have revealed some unusual results of elastohydrodynamic lubrication (EHL) associated with a high degree of thermally induced inhomogeneous shear across the lubricant film, or thermal shear localization. The results include the development of a sizable film dimple in the central EHL region [2] and a dramatic reduction in EHL traction [3, 4]. In this study, a theoretical analysis is carried out to determine the conditions under which the thermal shear localization may develop in EHL films. For a Newtonian lubricant obeying the Barus law of viscosity, a dimensionless group-parameter is identified that fully governs the degree of the thermal inhomogeneous shear. Results are presented that show the critical range of values of this parameter corresponding to the onset of the shear localization. The analysis is also extended to lubricants with non-Newtonian behavior. Results suggest that the same dimensionless group-parameter may be used to measure the degree of the shear localization when the lubricant viscosity in the parameter is replaced by an effective viscosity that accounts for the non-Newtonian effect. Reference [5] presents details of the theoretical formulation and results analysis.
An Approximate Analytical Model of Thermohydrodynamic Estimation of Finite Length Journal Bearings
Authors: Ionescu Mihail G. , Ionescu Vladimir-Codrin M.
Published: November 2008

The present paper proposes an original analytical solution of the thermohydrodynamic lubrication, and the validation of the model in the case of journal bearings. The simplicity and accuracy of the method and the computing times of the order of seconds necessary for bearing estimation constitute important advantages of this model over the numerical method.
On the Friction and Wear Performance of Boric Acid Lubricant Combinations in Extended Duration Operations
Authors: Deshmukh P. V. , Lovell M. , Sawyer W. G.
Published: November 2008

Lubrication is critical for minimizing wear in mechanical systems that operate for extended time periods. Developing lubricants that can be used in engineering systems without replenishment — particularly those that are environmentally friendly — is very important for increasing the functional lifetime of mechanical components. In the present investigation, extended duration pin-on-disk experiments were carried out to determine the relative performance of a wide range of lubricant combinations in a commercial brake valve assembly. In the experiments, the lubricants were initially applied to the disk surface but were not replenished over a sliding distance of more than 6000 m. The experimental results revealed that the environmentally friendly lubricant boric acid was inefficient for reducing the wear in the surfaces tested. When combined with a commercial transmission fluid, however, the boric acid mixture proved highly effective in terms of both friction and wear performance. Based on the success of the combined lubricant experiments, the boric acid was then mixed with canola oil to form a completely natural lubricant combination. Based on further pin on disk experiments, this lubricant combination yielded the best wear performance of all the lubricants tested. The importance of these results, as related to the use of the natural lubricant combination in other engineering systems was subsequently ascertained and discussed.
Investigation of Sliding Friction Pairs With Electro-Pulse Sprayed Micro-Coats
Authors: Andriusis Albinas , Jankauskas Vytenis , Padgurskas Juozas , Rukuiza Raimundas , Zunda Audrius
Published: November 2008

Electro-pulse spraying (EPS) is the coating technology of “electric explosion of conductive materials” when high-voltage and powerful impulse flows through a wire conductor. Object of our investigation — tribological properties of sliding pairs with copper micro-coats made by EPS after one time explosion. Small-grained dense structure coat with evaluated thickness about 4–6 ?m was obtained. Tribological tests, performed at marginal lubrication with multi-stage load, shows that using EPS-specimens the value of friction coefficient is lower as control version. At instantaneous setting of load for long-term running the copper films adopts well to the change of load. The wear of friction pairs according to worn mass show that EPS-specimens worn 79% less than CV-specimens. The investigations point out that copper micro-coats have better tribological properties comparing to control version of friction pairs.
A Novel Particulate-Fluid Lubrication for Environmentally Benign Forming Processes
Authors: Lovell M. , Higgs C. F. , Mobley A. J.
Published: November 2008

Forming sheet metal parts in the absence of lubricants is not practical in production operations. In practice, large amounts of liquid and grease lubricants are utilized in sheet forming to ensure that there is sufficient lubrication to reduce asperity interaction and increase formability. In the present investigation, an alternative environmentally friendly lubricant is introduced for sheet metal forming processes. This lubricant is based on a combination of boric acid and canola oil, both of which are natural, environmentally friendly, and have independently demonstrated good lubrication potential. Utilizing a specialized sheet metal stretching apparatus, an optimized boric acid and canola oil formulation was evaluated for use in metal forming operations. Based on the experimental results, the optimized lubricant shows substantial potential for providing the manufacturing community with a commercially viable and environmentally friendly lubricant that will eliminate expensive disposal costs.
Superlubricity and Near-Wearless Sliding in Carbon Films
Authors: Erdemir A.
Published: November 2008

Systematic studies on carbon-based materials and coatings in our laboratory over the past 15 years have led to the discovery of an amorphous carbon film that can provide friction coefficients as low as 0.001 and wear rates of less than 10−10 mm3/N.m when tested in inert or vacuum test environments. This paper provides an overview of the recent progress made in the synthesis and characterization of such films and of the importance of near-surface chemistry and chemical interactions on friction and wear. Based on extensive surface analytical and tribological studies, a mechanistic model is proposed to explain the superlubricity and near-wearless sliding behavior of these carbon films.
A Comparison of Lateral Calibration Techniques for Quantitative Friction Force Microscopy
Authors: Kanaga Karuppiah K. S. , Sundararajan Sriram
Published: November 2008

A comparison of two lateral force calibration techniques for friction force microscopy is presented. We used methods developed by Ogletree et.al. [1] and Ruan and Bhushan [2] to measure the friction response between the atomic force microscope (AFM) probe and a silicon sample and to obtain lateral force calibration factors. The factors were used to characterize the friction behavior and interfacial shear strength of a silicon nitride (Si3N4) probe-ultra high molecular weight polyethylene (UHMWPE) interface.
Modeling and Measuring Friction-Generated Temperature of Polymers and Their Composites
Authors: Price Howard L. , Ghorieshi Jamal A.
Published: November 2008

An instrument is being developed to simultaneously measure friction and friction-generated temperature of polymers and composites in a dry sliding configuration. This thermo tribometer is being carefully evaluated and characterized with nylon specimens to ensure that material response and instrument response are separable and identifiable. The thermo tribometer will be used to evaluate and qualify more advanced polymers for tribological applications.
Influence of Cam Surface Finish and Roughness on Frictional Power Loss in Valve Trains With Roller Tappets
Authors: Soejima Mitsuhiro , Nagafuji Masashi , Ogawa Eiji , Kuwahara Takeshi
Published: November 2008

In order to reduce the frictional power loss and the wear in the valve train of internal combustion engines, the cam follower mechanism tends to be shifted from the sliding contact to the rolling contact such as a roller follower [1–5]. Design criteria for the valve train with roller tappets have been investigated by making obvious the effect of the cam lobe surface finish and its surface roughness on reduction of the friction loss. In particular the friction loss in the case of a cam lobe finished by shot-peening was compared with that of one finished by grinding. Also the influence of surface roughness on the friction loss was examined.
Role of Surface Topography on Friction and Transfer Layer Formation: A Study Using Inclined Scratch Test
Authors: Menezes Pradeep L. , Kishore  , Sasidhar Y. , Kailas Satish V.
Published: November 2008

Tribological interaction between two contacting surfaces is influenced by many factors such as relative motion, normal load, environment, and lubrication apart from surface characteristics of the mating surfaces. Though surface characteristics such as roughness was dealt by many researchers for decades, the other important characteristic of surfaces, surface topography, has not got its share of attention. In the present investigation, basic studies were conducted using Inclined Scratch Tester to understand the role of surface topography on friction and transfer layer formation. A tribological couple made of copper pin against EN8 flat was used in the tests. Two surface parameters of steel flats — roughness and texture — were varied in tests. Care was taken to ensure that the surface roughness, measured along the scratch direction, had similar values for different textures, namely Unidirectional, 8-ground, and Random. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely adhesion and plowing, are controlled by the nature of surfaces and are independent of surface roughness. The plowing component of friction was highest for the surface that promotes plane strain conditions near the surface and was lowest for the surface that promotes plane stress conditions near the surface.
Effect of Directionality of Grinding Marks on Friction at Different Surface Roughness Using Inclined Scratch Test
Authors: Menezes Pradeep L. , Kishore  , Kailas Satish V.
Published: November 2008

Surface topography of a tool plays an important role as it predominantly controls the frictional behavior at the interface. In the present study, Inclined Scratch Tester was used to understand the effect of directionality of surface grinding marks on coefficient of friction and transfer layer formation. EN8 steel flats were ground to attain different surface roughness with unidirectional grinding marks. Then Al-Mg alloy pins were scratched against the prepared EN8 steel flats. Grinding angle (angle between direction of scratch and grinding marks) was varied between 0° and 90° during the scratch tests. It was observed that the coefficient of friction and transfer layer formation depend primarily on the directionality of grinding marks of the harder mating surface, and independent of surface roughness of harder mating surface. The grinding angle effect on coefficient of friction was attributed to the variation of plowing component of friction with grinding angle.
Fundamental Wear Mechanisms on the Nanoscale
Authors: Dienwiebel M. , Shakhvorostov D. , Po¨hlmann K. , Scherge M.
Published: November 2008

Friction and wear are coupled dynamic processes. In the nominal contact area a considerable number of asperities simultaneously experience an energy input that is often high enough to initiate plastic flow. Parallel to the flow the material intermixes with foreign elements, changes morphology and develops a new topography. The wear mechanism resembles a squeezing process that removes the flowed material. As a result, the surfaces wear with retention of its topography features in which the number of asperities and their height almost remain constant but the location of asperities continually changes.
Strategies for Constructing Reaction Networks of Lubricant Degradation
Authors: Pfaendtner Jim , Broadbelt Linda J. , Wang Q. Jane
Published: November 2008

Automated mechanism generation is an essential tool to be able to create mechanistic models of lubricant degradation chemistry. To date, modeling of lubricant degradation has been accomplished only through the use of lumped or pathways-style approaches. These methods have yielded important insights into major degradation pathways but lack predictive power and fail to produce some key trends in the product distribution, even qualitatively. Mechanistic models of lubricant degradation include reactivity of individual species as well as the role of secondary reactions. Such models have much to offer in terms of fundamental understanding of degradation chemistry. Furthermore, they may be exploited to directly study the effect of radical stabilizers and additives. Key results obtained include a quantitative description of the degradation of a model lubricant as well as detailed kinetic correlations for estimating rate constants. This poster presents our efforts to construct detailed reaction mechanisms of lubricant degradation. The underlying theories of automated network generation and preliminary results are presented.
Scuffing Resistance of Laser Textured Surfaces
Authors: Kazmanli M. K. , Eryilmaz O. L. , Erdemir A. , Ajayi O. , Etsion I. , Urgen M.
Published: November 2008

In this study, the scuffing resistance of laser-textured (LT) H13 samples was investigated. Furthermore, thin copper and nanocomposite films were produced on some of the textured samples, which were later subjected to scuffing tests in a reciprocating wear test machine. Test results indicated that Cu and nanocomposite coatings can substantially enhance the scuffing resistance of H13 steel samples. The best scuffing resistance and the lowest friction coefficient were observed for the nanocomposite coating on as-received H13 samples. This coating could not be scuffed even at 1780 N normal load which was the maximum load available in this test machine. Furthermore, the presence of Cu within the dimples considerably improved the scuffing resistance of LT surfaces.
Variational Approach in Elastic-Indentation Problems
Authors: Riznychuk Roman V.
Published: November 2008

The indentation problem of rigid punch with curvilinear base on elastic half-space is solved by variational method. The method is based on Betti theorem and on condition of absence of stress singularity at the edge of contact spot. Variation condition of absence of stress singularity at the edge of contact spot gives the equations connecting the displacement and the size and the shape of the contact spot and gives the expression for contact stress under curvilinear base of punch. The case of elliptical contact spot is considered.
On the Frictional Behavior of an Incipient-Sliding Contact of Sphere-on-Flat With High Normal Loads
Authors: Chang L.
Published: November 2008

Levinson et al [1] present experimental results that show a steep reduction in the static coefficient of friction of a dry sphere-on-flat contact as the normal load increases. The experiments cover a range of loading conditions from elastic contact to contact with significant plastic deformation. A theoretical analysis is carried out in this study using a contact model of an elastic-plastic sphere on a rigid flat. The shear strength of the contact interface is assumed to be proportional to the contact pressure until it reaches a limiting value that is below the bulk shear strength of the sphere. The theory predicts a friction behavior that is consistent with that from the experimental results in [1] in all key aspects. The analysis reveals that a relatively low limiting shear strength in the contact interface is likely the key factor leading to the dramatic reduction in the friction coefficient and the negligible junction growth obtained in the experiments.
Friction and Wear Behavior of Silicon Carbonitride Processed From the Polymer-Derived Ceramic Route
Authors: Cross Tsali , Prasad Somuri , Raj Rishi
Published: November 2008

Polymer derived ceramics (PDC’s) are processed from liquid organometallic precursors by cross-linking the polymers into infusible solids, followed by controlled pyrolysis. No previous work regarding their tribology has been reported. Further, the synthesis of PDC’s as thin films, and the role that the nanostructure plays on the mechanical properties has not been reported. The objective of this research was to evaluate the fundamental tribological behavior of polymer derived SiCN in both bulk and thin film form. Friction and wear evaluations were made on bulk materials and thin films using a Si3N4 ballon-disk linear wear tester at various contact pressures and in different environments that contained various amounts of humidity. The micro/nanostructure was characterized by FTIR, microRaman, and scanning electron microscopy. Bulk SiCN gave a low friction coefficient and good wear resistance in humid environments but showed significant fracture and gouging in dry environments at higher contact pressures. Although there is ambiguity regarding the tribology of the thin films there seems to be a dependence upon the nitrogen content within the materials derived from the polymeric stage. The future work will focus on optimizing processing conditions of thin films and investigating the role that nitrogen plays in both bulk and thin film SiCN materials.
A Molecular Dynamics Study on the Static and Dynamic Properties of Lubricant PFPE in Hard Disk Driver
Authors: Li Xin , Hu Yuanzhong , Wang Hui
Published: November 2008

The static and dynamic properties of lubricant PFPE are important for the service durability and reliability of the computer head-disk device. Thus molecular dynamic simulations based on a coarse-grained, bead-spring model are adopted to study those properties. On the one hand, we investigate the static properties and infer the structure of both nonpolar and polar PFPE films. For a nonpolar PFPE film, there is a layering structure in the surface layer. And for a polar PFPE film, besides layering structure, there is a bi-polymer structure in the bulk layer. On the other hand, we investigate the dynamic properties and find that for nonpolar PFPE film, a precursor film around one atomic diameter thickness develops according to layering structure; while for polar PFPE film, besides a precursor film, a much steeper and slower spreading shape appears according to bi-polymer structure.
Tribocatalytic Enhancement of Methane Oxidation
Authors: Abe Tomotaka , Hiratsuka Ken’ichi , Kajdas Czesław
Published: November 2008

Oxidation reaction of methane is one of the most fundamental reactions in organic chemistry. This reaction is enhanced by silver catalyst [1]. In this study, we confirmed that the catalytic activity of silver is enhanced more by the friction. This effect is called tribocatalysis. In previous studies about tribocatalysis, we have shown that the oxidation reactions of hydrogen [2], carbon monoxide [3] and ethylene were promoted by the friction. According to NIRAM (negative-ion-radical action mechanism) approach, exo-electron emission triggers the promotion of chemical reactions [4]. Insulator such as aluminum oxide, when it is worn, emits larger number of negative particles including electrons compared with metals [5]. Therefore we expected that the friction of aluminum oxide promotes tribochemical reactions more than metals.
A Finite Element Study of Elastic-Plastic Contact Between Multiple Hemispherical Asperities
Authors: Shankar S. , Mayuram M. M.
Published: November 2008

The objective of this paper is to elucidate the deformation behavior of elastic-plastic contact between hemispherical asperities. A finite element model for frictionless contact between two asperities is developed using a commercial FEM package and verified by comparing the numerical results in the elastic deformation regime, with the Hertzian theory. Analysis is then extended to multiple asperities to understand the influence of nearer asperities on deformation and load distribution behavior, covering the elastic-plastic regime. The analysis yields parameters like contact area, interference and maximum contact pressure for various values of normal loads.
Shaft Center Orbit in Dynamically Loaded Radial Bearings
Authors: Klit Peder , Volund Anders
Published: November 2008

The bearing damping coefficients may be utilized to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker [1] in 1965. Several authors have refined this method over the years. In 1966 Jorgen W. Lund [2] published an approach to find the dynamic coefficients of a journal bearing by a first order perturbation of the Reynold’s equation. These coefficients made it possible to perform a rotor-bearing stability analysis for a statically loaded bearing. In the mid seventies Jorgen W. Lund pointed out in lecture notes that the dynamic damping coefficients of the bearing could be used to find the shaft orbit for dynamically loaded bearings. The connection between the “Booker Mobility Method” and the “Lund Damping Coefficient Method” will be explained.
Characteristics of Tribolayers Observed in A356 Al Alloy — SiCP Composite Discs/Brake Pad During Sliding Wear Tests
Authors: Shivamurthy R. C. , Surappa M. K.
Published: November 2008

Tribological characteristics of A356 Al alloy-10 vol. % SiCP composite discs/brake pad has been studied under dry sliding conditions at sliding speeds in the range 2 to 5 m/s and at loads in the range 1–3 MPa. In these tests, disc of Al MMCs and pin of friction pad made of polymer based composite were used. Wear rates of Al MMC disc as calculated by weight loss method, found to be negative at high sliding speed and high load. Worn surface of disc has been analyzed using EDAX. SEM analyses of worn surfaces of composite disc infer transfer of material from pin to the disc resulting in the formation of tribolayers. Two types of tribolayers were observed on the worn surface, one having shiny appearance of copper rich layer and other is dark in colour consisting of Mg, S, Fe, Ba, Ca, Si, Cu, In and Al. In the later layers were rich in copper and appear as bright patchy layers under SEM. Coverage of copper rich layers increase all along and across the worn track at a sliding speed of 4 and 5 m/s in the load range 2 to 3 MPa. Atomic percent of copper increase with load and consequently affect the wear rate of disc. EDAX analysis of dark tribo layers on wear track of composite disc show continuous increase in the amount of Cu and Ba with increase in speed and load. Hence, wear rate of composite discs were relatively low under all test conditions. These results clearly indicate composition of friction material having profound influence on the wear rate of Al MMC discs.
Tribochemical Polishing of Aluminum Oxide in the Atmosphere of CHF3
Authors: Soejima Takao , Okubo Katsuyuki , Hiratsuka Ken’ichi , Sakamoto Yukihiro
Published: November 2008

Fluorinated hydrocarbon has been used as lubricants on the surface of magnetic hard disk drive. This is because this compound is thermally stable. However it has been found that fluorinated hydrocarbon was degraded on the surface during friction to generate radicals1,2). Therefore we considered that hard ceramics will be worn out in the gaseous atmosphere of fluorinated hydrocarbon by radical reactions. If the interaction of gas to ceramics is strong, we can expect that the surface will be polished through tribochemical processes. In the present paper, we investigated the characteristic of tribochemical polishing of aluminum oxide against glass in CHF3 gas atmosphere.
Prediction of the Coating Durability Under Oscillating Sliding Contact: Introduction of a Local Energy Density Parameter
Authors: Fouvry S. , Fridrici V. , Liskiewicz T.
Published: November 2008

The knowledge of wear kinetics of thin soft lubricant or hard coatings under alternated sliding contact is of great interest for many industrial applications. Because the coating endurance is related to the substrate reaching condition, it has been shown that classical wear volume descriptions are not appropriated. A local damage description, based on a local friction dissipated energy density variable is then introduced. It consists to compare the coating endurance (i.e. number of sliding cycles) versus the maximum local energy density dissipated through the interface per sliding cycle. A “life time vs maximum dissipated energy density master curve” is obtained and rationalized through a parabolic evolution. The coating endurance is modelized through a simple ratio between an energy capacity variable, representative of the durability of the studied coating. Applied to hard coatings (TiN) the stability of this approach has been confirmed for solid lubricant coatings.
Dependence of Gas Transportation in Radial Lip Seals on Oil and Gas
Authors: Sugimura J. , Gondo S. , Yamamoto Y.
Published: November 2008

Experimental studies are made on transportation of gas across radial shaft seals. Gas flow rates are determined with gas chromatography. Gas is pumped in, while gas also leaks at about half of the pump rate. The flow rates increase with shaft speed and oil viscosity, though paraffinic mineral oils allow more gas to move than polyalphaolefin of the same viscosity. The rate also depends on gas. These suggest that gas is conveyed by hydrodynamic flow of oil at the seal lip.
Wear of Polyethylene Rubbed Against Metals and Ceramics
Authors: Inoue Harutaka , Hiratsuka Ken’ichi , Sekii Yasuo , Kajdas Czesław
Published: November 2008

With the development of polymer materials in recent years, their tribological properties have been investigated from the viewpoints of material properties (viscoelastic properties, hardness, roughness, etc), test conditions (atmosphere, humidity, specimen geometry, etc) and operating conditions (load, velocity, contact area, lubricating, etc). However their friction and wear characteristics have not been fully clarified because they are influenced by many factors. In the present paper, a tribological property of polyethylene has been investigated from a viewpoint of the effect of antioxidant and mating materials, i.e. eight kinds of metals and aluminum oxide.
Forms of Static Friction, Sliding Friction and Rolling Friction
Authors: Xu Y. , Yung K. L.
Published: November 2008

Although, it seems that the concepts of static friction, sliding friction and rolling friction are common knowledges, their real sources are ironically not so clear. Inappropriate descriptions of them may have hampered the theoretical analyses and calculations of the frictions and deterred their applications in real world. In this paper, we are proposing a new method to model the static friction, sliding friction and rolling friction by three mechanical elements: spring, translatory damper and rotary damper respectively. It is shown that proper descriptions of the frictions, e.g. rolling friction, can help in correcting discrepancies in previous research works.
Design of a Linear Ultrasonic Motor With the Bi-Directional Movement
Authors: Huang Yuan Mao , Huang Shih-Shun
Published: November 2008

This study presents a design of the linear ultrasonic motor. The major components consist of a slider and a vibrator with a piezoceramic piece. The input signal on the piezoceramic piece causes vibration of the vibrator. The development of the vibrator is based on vibratory analysis of a beam with both ends clamped. The resonant frequencies and the vibratory mode shapes of the vibrator are calculated and compared with those obtained by using the finite element method. By only changing two frequencies of the input signal on the piezoceramic piece, the vibrator is excited and the slider can achieve forward and backward bi-directional movement due to friction between the vibrator and the slider. The calculated results are compared with results obtained by Grant and using software ANSYS.
Sliding Wear and Friction Properties of Stitched RTM Base Carbon–Carbon Composites
Authors: Surappa M. K. , Shivakumar Kunigal N.
Published: November 2008

This paper presents wear and friction properties of carbon-carbon composites (CCC) manufactured by resin transfer molding (RTM) process. During composite fabrication thickness stitching was employed to improve inter laminar tension and shear properties. Wear and Friction characteristics of carbon-carbon composites were evaluated using pin-on-disc set up. Results of test indicate that surface of composites having stitches in a perpendicular direction show increase in wear rates with increase in load.
Comparative Tribological Behavior of TiN-, CrN-, ZrN-, and MoN -Cu Based Nanocomposite Coatings
Authors: U¨rgen Mustafa , Kazmanli K. , Ezirmik V. , Oztu¨rk Ahmet , Eryilmaz O. L. , Cakir A. F. , Erdemir A.
Published: November 2008

Nanocomposite structures composed of hard and soft phases are very promising candidates for tribological applications involving both dry and lubricated sliding. This study aims to compare the wear behavior of copper doped hard nanocomposite nitride coatings under dry and lubricated sliding conditions. These nanocomposite coatings are produced in a cathodic arc-based hybrid PVD coating system and their mechanical and structural properties are fully characterized using electron microscopy and other relevant techniques. Tribological tests were performed in pin on disc and reciprocating wear test machines under dry and lubricated sliding conditions. The differences observed in the tribological behavior of nanocomposite coatings are discussed by taking into consideration the structure and mechanical properties of the coatings and the chemical character of the tribo films formed on sliding surfaces during wear testing.
On the Casing Wear Mechanism in Deep and Ultra-Deep Well Drilling
Authors: Zhang Laibin , Fan Jianchun
Published: November 2008

Casing wear in the deep and ultra-deep well drilling is regarded as one of the most important technical problems in the petroleum exploration in the west of China. It is necessary to realize the casing wear mechanism for the solution of this problem. A tribo-system model for the deep section of the drilling-pipe and casing is presented based on log data and mechanics analysis in this paper. In the model the lateral vibration of the drilling-pipe is taken into account which can cause a great dynamic load on the casing. Then the tribological interaction relationships in this situation are built up. Moreover, the wear mechanism of impact-sliding contact surfaces between the casing and the tooljoints is revealed by combining theoretical analysis with the field monitoring tests. It is noticed that the surface contact fatique play a very importan role to speed up the casing wear. The results can provide guidance for actual wear prevention in the drilling engineering.
Tribology of PFPE Overcoated Self-Assembled Monolayers Deposited on Silicon Surface: Effect of Thermal Treatment
Authors: Satyanarayana N. , Sinha S. K.
Published: November 2008

Effect of thermal treatment on the friction and wear of monomolecular layers of SAMs (Self-assembled monolayers) overcoated with PFPE was studied using ball-on-disk tribometer. Two SAMs, Octadecyltrichlorosilane (OTS) and 3-aminopropyltrimethoxysilane (APTMS) were formed on the Si substrate by self-assembly followed by dip-coating with perfluoropolyether (PFPE). Modified Si samples are thermally treated at 150 °C under vacuum for 2h. The physical and chemical properties of modified samples, before and after thermal treatment, are analyzed using contact angle measurements, X-ray photoelectron spectroscopy (XPS). Tribological properties are evaluated using Universal Micro Tribometer (UMT). A Si3N4 ball of 4mm diameter is used as the counterface. Thermal treatment of the PFPE coated SAMs and Si surface reduced the coefficient of friction to slightly lower values in all cases. Thermal treatment has shown slight increase in wear life in the case of PFPE coated APTMS SAM surfaces whereas it decreased the wear life in the case of PFPE coated OTS SAM and Si surfaces. The exact reasons for this behavior are not clear at present, but it is being speculated that thermal treatment effects the extent of bonding between the surface groups of PFPE and SAMs and mobile characteristics of the PFPE, which finally influence the wear durability characteristics. Therefore, the differences in the wear durability characteristics are analyzed using changes in the surface energies and the amount of strongly adsorbed PFPE, as a result of thermal treatment.
Modeling Abrasive Wear for Polymers Using Intersecting Scratching Technique
Authors: Chong Wai Lup Mark , Sinha Sujeet K. , Lim Seh Chun
Published: November 2008

This paper aims to model abrasive wear for polymers using intersecting scratching technique. Scratch test and pin-on-disc test were conducted on five different polymers. Wear debris generated by intersecting scratching test was compared and correlated with the specific wear rates of the same polymers in a pin-on-disk test using ground steel surface as the counterface. It is the purpose of this paper to establish that an intersecting scratching test can be used as a means to qualitatively and quantitatively characterize wear performance of polymers.
Gear Oils Based on Polyglycols: New Solution for the Lubrication of Large Industrial Gear Drives
Authors: Siebert Hermann , Mann Ulrich
Published: November 2008

Increasingly stringent requirements for large enclosed geardrives, nowadays necessitate the use of synthetic oils.
ZDDP-Additive-Catalyst Interactions in Engine Oil
Authors: Parekh K. , Mourhatch R. , Aswath P. B.
Published: November 2008

The phosphorous content in engine oil is found to be the major cause of the poisoning of Catalytic converters in automobiles, hence environmental regulations limiting the phosphorous level in GF4 and GF5 oils have been introduced. Zinc dialkyl dithiophosphate (ZDDP) being the only major source of phosphorous in current engine oils, is also an indispensable component of the additive package in these oils for it has been the primary anti wear — as well as anti oxidant — additive for over fifty years. Efforts are made to replace the ZDDP with other materials with the same properties which would not be harmful to the environment and also an economically feasible substitute. Another solution to this problem is to reduce the amount of ZDDP used while improving its antiwear performance. Anti-wear action of ZDDP, involves its break down reaction with the steel surface by Zn Fe ion exchange and subsequent formation of an amorphous chemisorbed film containing zinc, phosphorus, oxygen and sulfur and also iron in the form of polyphosphates and sulfates of zinc and iron. The efficiency of this mechanism is reduced by parallel reactions between ZDDP and other additives as well as their antagonistic effects. Introduction of a material with catalytic properties which would reduce the negative effects of the presence of the other additives on the anti wear properties of ZDDP is an option that was explored in this paper. Both triboligical wear tests (Ball on cylinder lubricity evaluation tests) as well as mechanism studies (DSC, FT-IR and NMR) were used to evaluate the performance of ZDDP in the presence of the most common additives (i.e. Anti-oxidants, Detergents and Dispersant). Iron Fluoride is also introduced as a potential additive to improve the efficiency of wear protection mechanism of ZDDP. The improvements observed in the presence of the Iron Fluoride will allow further reducing the amount of ZDDP in engine oils containing this material as an additive [1].