bluuebunny/crossref_metadata_2025 huggingface dataset:
Superlow Friction of WS2 Coatings in Ultrahigh Vacuum at Low Temperature
Authors: Iwaki Masanori , Le Mogne Thierry , Fontaine Julien , Martin Jean-Michel , Watanabe Shuichiro , Noshiro Junichi
Published: November 2008

Today molybdenum disulfide (MoS2) is the most commonly used solid lubricant for vacuum applications. Its good tribological performance is considered to be due to its lamellar structure. Coefficient of friction in the millirange (so-called “superlow friction” or “superlubricity”) has already been observed in ultrahigh vacuum at ambient temperaturure for pure and stoichiometric MoS2 coatings. On the other hand, tungsten disulfide (WS2) is also a solid lubricant which has a lamellar structure and works as well as MoS2 in vacuum. However, it is not widely used nor well studied due to its high cost, and until today there is no report of the achievement of the superlow friction in vacuum. In the present work, we report the superlow friction of WS2 coatings obtained in ultrahigh vacuum and at low temperature. Pin-on-disk reciprocating friction test for RF sputtered WS2 coatings on silicon substrates mated against counterpart steel (AISI 52100) pins were conducted in ultrahigh vacuum (3×10−7 Pa) at temperatures ranging from −130 to +200°C. The origin of this superlow friction was discussed.
DLC Coating of Rolling Bearings by Triboadhesion and Its Effect on Their Dynamic Response
Authors: Rodri´guez Lelis Jose´ Mari´a , Rami´rez Flores Eduardo , Coli´n Ocampo Jorge
Published: November 2008

In this work vibration signals were obtained for ball bearings with and without DLC coating. The coating was carried out by triboadhesion, and only the inner rolling surface of the bearings was coated. Here it was found that the amplitude of the vibration signal is modified by the thin film DLC coating, and that this can be related to the stiffness of the system and finally to wear resistance of the ball bearings.
Wear Characteristics of Atomic Force Microscope Probe Tips
Authors: Chung Koo-Hyun , Kim Dae-Eun
Published: November 2008

In the field of nanotechnology, Atomic Force Microscope (AFM) which is based on the interactions between an extremely sharp probe tip and specimen, has been widely utilized. In the AFM and AFM-based applications, the probe tip wear problem should be carefully considered. In this work, the wear characteristics of silicon, silicon nitride, and diamond coated probe tip under light loads were investigated. In order to identify the structure of the AFM probe tips as well as the nature of wear, High-Resolution Transmission Electron Microscope (HRTEM) and Field Emission Scanning Electron Microscope (FESEM) analyses were utilized. Using the Archard’s wear equation, the degree of the probe tip wear was quantitatively assessed. Based on the experimental results and analysis, the plausible wear mechanisms of the AFM probe tips were proposed in an effort to understand the nano-scale wear.
Parameter Effects on Thermal Protrusions of Magnetic Head Sliders
Authors: Kurita M. , Xu J.
Published: November 2008

The heat transfer in the magnetic head sliders in hard disk drives, the thermal protrusion (TPR) of the head elements, and the flying height change of such sliders were numerically simulated. A simulated temperature distribution of the air-bearing surface correlated well with our experimental results. A parameter study showed that decreasing the thickness of the alumina base coat or increasing the size of the pole and shields of the head elements can reduce the magnitude of write-current-induced protrusion (W-TPR). However, a longer pole and shields increase ambient-temperature-induced protrusion (T-TPR). For W-TPR, the reduced flying height of the slider is partly compensated for by increased air pressure on the air-bearing surface. However, almost the entire magnitude of T-PTR translates into a reduction in flying height.
Coconut Oil as Bio Lubricant: Study of the Anti-Wear Properties Using Quantum Chemical Calculations and Tribological Tests
Authors: Jayadas N. H. , Prabhakaran Nair K.
Published: November 2008

In this paper Spartan 02, a molecular dynamics software is used to analyze and predict the tribological properties of coconut oil in a qualitative manner on the basis of carbon chain length of the constituent fatty acids, their polarity (Net electrostatic charge, Qr) and the energies of the molecular orbitals EHOMO (Energy of the Highest Occupied Molecular Orbital) and ELUMO (Energy of the Lowest Unoccupied Molecular Orbital) and the enthalpies of formations (Hform) of the iron soaps of respective fatty acids. Tribological properties of the constituent fatty acids of coconut oil were evaluated using a four-ball tester as per ASTM D4172 method. The experimental results showed good correlation to the selected quantum chemical descriptors. The influence of an anti-wear additive on the tribological performance of coconut oil and the optimum additive concentration were also evaluated experimentally.
Ultrasonic Phase and Amplitude and the Measurement of Oil Film Thickness
Authors: Dwyer-Joyce R. S. , Reddyhoff T. , Drinkwater B.
Published: November 2008

The reflection of ultrasound at an oil film can be used to determine the film thickness. A thin oil film reflects less ultrasound than a thick film. When the film is thin there is a simple relationship between oil film thickness and the proportion of the wave amplitude reflected. The reflection coefficient is in fact a complex quantity with both magnitude and phase. A model for how both the phase and amplitude vary with oil film thickness (and the properties of the bearing materials) has been developed. It has been shown that both can be used to determine film thickness. Tests have been performed to determine the oil film thickness and explore the relationship between reflection amplitude and phase. Experiments are performed both on a static oil film between flat plates, and on an operating journal bearing. Both methods provide a simple accurate method for the measurement of oil film thickness.
Shear and Normal Stiffness of Mixed Liquid-Solid Contacts
Authors: Dwyer-Joyce R. S. , Gonzalez Valadez M.
Published: November 2008

When a wave of ultrasound strikes an interface between two bodies some proportion of the wave amplitude is reflected. A rough surface interface with a low real area of contact will reflect more ultrasound. This is the case for both normal and shear modes of ultrasound. If the ‘gaps’ in the contact are filled with liquid, then more of a longitudinal wave is transmitted through the interface. However, the shear wave should remain unaffected, since it is virtually all reflected at a solid liquid boundary. It is the stiffness of the interface that controls the response. Measurements of reflection can readily be used to determine the interface stiffness. In this work a series of experiments has been performed to measure the reflection of both normal and shear ultrasound from both dry and wet rough contacts. This gives information about the normal and shear stiffness of dry contacts. When the layer is flooded with a liquid the stiffness of the liquid part alone can be deduced. This can be used to determine the film thickness in mixed lubrication. The shear stiffness was found to reduce with the application of a liquid; this is caused by the presence of asperity micro-slip at the interface.
Thermo-Mechanical Model for Moving Layered Rough Surface Contacts
Authors: Kadiric A. , Sayles R. S. , Ioannides S.
Published: November 2008

A numerical model designed to simulate a moving line contact of two rough layered bodies is presented. The model predicts contact pressures and deformations, contact temperature rise and resulting thermal stresses. The heat division between the contacting components is fully accounted for as is the interaction between the mechanical and thermal displacements. Some results are presented to illustrate the potential importance of a full thermo-mechanical analysis as compared to a purely mechanical one.
Elastohydrodynamic Lubrication of Multiple Periodic Ridges
Authors: Olver A. V. , Glovnea R. , Choo J.-W. , Spikes H. A.
Published: November 2008

The lubrication of rolling contacts in which one surface has a roughness consisting of periodic transverse or longitudinal ridges has been widely investigated, both theoretically, by, for example, Venner, Lubrecht, Greenwood, Snidle and Evans [1–4] and by means of experiments [5–7]. The problem is relevant to the lubrication of machined surfaces which have a strong periodic element of roughness.
Lubricant Degradation in the Internal Combustion Engine Ring Zone
Authors: Fox Malcolm F.
Published: November 2008

Development of the ring zone sampling technique for operating internal combustion engines is described. Results show a standing ring of lubricant in the piston ring zone which is substantially degraded compared to that of the sump lubricant. Recent work shows that the degradation of a formulated lubricant can be followed by multiple sampling points in the ring pack, e.g., complementary anti-oxidant degradation/protection of base oil is demonstrated. ‘Residence times’ for lubricant in the ring zone are defined and their determination discussed. The influence of bore and ring surface finish is emphasised. Extension of the technique to differentiate between different quality of lubricants and the different conditions of first ring and the base of the crown land for a piston is described. The principal areas of detailed knowledge which are not known for piston ring lubrication and tribology are examined.
Write Protrusion Modulation for Sub-Nanometer Contact Interference
Authors: Knigge Bernhard , Stipe Barry , Payne Robert , Baumgart Peter
Published: November 2008

With the continual reduction in slider to disk clearance in hard disk drives, new methods to measure this clearance with high accuracy are needed. Understanding the contact dynamics when touching the disk at sub-nanometer interference levels is an important aspect of the problem. We have developed a new methodology to gradually bring the slider into contact with the disk, based on controlled and localized thermal expansion of the slider as it occurs during the regular write process (write induced protrusion). By applying short pulses to produce time controlled thermal protrusion, the duration of contact can be limited to a few milliseconds, by which short contacts and their contact hysteresis can be investigated.
Lubricated Sliding Wear of Textured Surfaces
Authors: Costa H. L. , Hutchings I. M.
Published: November 2008

In this paper, the effects of some geometric characteristics of surfaces textured by photochemical etching on their lubricated sliding behaviour were analysed. Reciprocating tests with sinusoidal velocity variation against cylindrical counterbodies were used. An estimate of the lubricant film thickness was obtained from capacitance measurements. Values of film capacitance, film thickness and coefficient of friction were computed as a function of sliding velocity, averaged over a large number of consecutive strokes after the running-in period. Patterns composed of circles with different fractions of coverage of the surface were tested for different ratios between the width of the individual pockets and the contact width. All the results were compared with those from a standard polished surface.
Power Loss of Tilting 5-Pad Journal Bearing Operating With Turbulent Oil Film
Authors: Strzelecki S.
Published: November 2008

Journal bearings of high speed turbocompressors, compressors and heavy duty high speed turbine gearboxes operate at journal peripheral speeds like 150 m/s. The flow of lubricant in such bearings is not laminar but super laminar or turbulent. It results in the increase in power loss and in the decrease of the bearing stability. The ground for the safe operation of high speed journal bearings at proper oil film temperature and with less power loss is the full knowledge of bearing performances at the turbulent oil film.
Calculation of High Speed Multilobe Journal Bearings
Authors: Strzelecki S. , Piechna J.
Published: November 2008

The bearing systems of turbocompressors, compressors and turbine gear trains consist the multilobe journal bearings. In these bearings, high speed of journal causes, that the oil film of bearing is not laminar but turbulent one. Turbulent oil film affects the bearing operating characteristics. Calculations in this case can not be carried-out on the condition of laminar oil film but on the assumption of turbulent one. The paper introduces theoretical calculations of the high speed multilobe journal bearing affected by turbulent oil film. For the 4-lobe journal bearing the different values of lobe clearance ratio and relative length of the bearing were assumed. The Reynolds, energy and viscosity equations were solved numerically on the assumption of incompressible lubricant and the turbulent adiabatic flow of oil in the bearing gap.
Thermal Deformation of Pads in Tilting 5-Pad Journal Bearing
Authors: Strzelecki S. , Kusmierz L. , Poniewaz G.
Published: November 2008

In high speed compressors and turbine drive trains, the tilting 5-pad journal bearings are applied. Tilting-pad journal bearings are good option because they have very good hydrodynamic stability at high speed and are less sensitive to load direction and shaft misalignment. The paper introduces thermo-elastic deformations of tilting 3-pad journal bearing with asymmetric support of pads and operating at the conditions of adiabatic oil film. The deformations of pads were obtained based on the oil film pressure and temperature distributions. Reynolds, energy, geometry and viscosity equations have been solved numerically on the assumption of aligned orientation of bearing and journal axis and at static equilibrium position of journal.
Considerations About Using Vegetable Oils in Lubricants
Authors: Puscas Cosmina L. , Bandur Geza , Modra Dorina , Nutiu Remus
Published: November 2008

New lubricating oils obtained from mixtures of synthetic diesters (di-2-ethylhexyl-adipate (DOA) and di-2-ethylhexyl-sebacate (DOS)) and vegetable oils (sunflower, SFO, soybean, SO and rapeseed oil, RO) are studied. The characteristics of all these mixtures are given together with differential scanning calorimetry (DSC) and thermal gravimetric (TG) analyses.
CFD Modelling of Elastohydrodynamic Lubrication
Authors: Hartinger Markus , Gosman David , Ioannides Stathis , Spikes Hugh A.
Published: November 2008

Traditionally the problem of elastohydrodynamic lubrication (EHL) has been solved using the Reynolds equations for fluid flow. In this paper we explore the finite volume method (FVM) to model fluid behaviour in rolling-element bearing systems. The effect of cavitation is modelled with a barotropic cavitation model. We investigate two cases with a cylinder on a flat plate, one under rolling and one under sliding conditions. These solutions are compared to the Reynolds-EHL approach. Towards higher loads, stability problems are encountered and strategies for dealing with these are discussed.
Measurement of Force and Displacement for the Tribological Analysis of MEMS
Authors: Wiehn Joshua S. , Dugger Michael T. , Buchheit Thomas E.
Published: November 2008

The tribological interfaces in microelectromechanical systems (MEMS) pose a significant hurdle in the advancement of MEMS. In order to gain a better understanding of these tribological interfaces, meaningful friction and wear measurements of MEMS devices must be made at loads and speeds relevant to MEMS operation. Devices containing isolated tribological contacts from which quantitative friction forces can be extracted have been developed. Since independent in-plane measurement of forces are not available for structures that are on the order of microns thick, the normal and tangential forces between structures are typically estimated based on the calculation of the force output of electrostatic actuators, and the force required to bend compliant suspensions. We will discuss the uncertainties associated with the measurement of applied and friction forces in MEMS tribometers, and metrology needs for improved tribological analysis of dynamic microsystems. We will also present a method of independent force calibration in these devices, and compare measured output characteristics with those predicted from mechanics and electrostatics.
3D Characterization of Surface State in a Knee Prosthesis
Authors: Hilerio I. , Barro´n M. A. , Vite M.
Published: November 2008

From the medical point of view it is important that the surface roughness in a knee prosthesis be small in order to reduce the wear friction due to the physical contact of the prosthesis with bone. Given the complex form of the knee prosthesis, formerly the finishing process was carried out through a manual technique. However, this technique has many drawbacks. In this work a mechanochemical method (MCM) for finishing is proposed in order to obtain a proper surface state of the prosthesis. The selected MCM consisted of a mild wear procedure which employs HLB-11 as tensoactive additive. Composition of the knee prosthesis pieces was as follows: 26.5% Cr, 4.5% Mo, and the balance was cobalt. In order to optimize the prosthesis manufacturing, the evolution of the surface state along the finishing process was studied and a 3D analysis of the surface topography was carried out. To do this, two types of topometers were utilized, one of them with a tactile sensor and another one with an optical sensor. Fourier transform was applied to data roughness in order to determine the skweness (Rsk) and kurtosis (Rku) roughness values.
THD Analysis of Journal Bearings: A Finite Element Algorithm for Groove Mixing Conditions
Authors: Stefani Fabrizio A.
Published: November 2008

A finite element method of solving the mass and energy-conserving lubrication problem, including the energy balance in the feed grooves, is proposed. As mass continuity in the whole film is considered, cavitation is taken into account properly. Both a two-dimensional (2D) and a quasi-three-dimensional (3D) solution of the energy equation in the lubricant film have been adopted. Some results are presented for a two-axial groove journal bearing. The quasi-3D solution method (cross-film conduction included in the model) showed good agreement with experimental results and incurred low computational cost.
Static Characteristics of Low Speed Cylindrical Journal Bearings of the Rope Wheel of Hoist Tower
Authors: Strzelecki S. , Wojcicki W. , Famulski W.
Published: November 2008

The design solutions of bearings carrying the shafts of rope wheels on the hoist tower of coal mines consists the rolling bearings or plain journal ones. Plain journal bearings allow for easy assembling and for smooth operation without vibrations. Static characteristics of journal bearings consist of oil film pressure and temperature distributions, static equilibrium position angles, load capacity, oil flow and power loss and their knowledge is the basis of bearing design. The paper comprises the static characteristics of low speed cylindrical journal bearings that are applied in the bearing system of the rope wheels of hoist tower. The calculations of these characteristics were carried-out on the assumption of adiabatic oil film.
Thrust Bearing-Relieving Disk of Multistage Centrifugal Pump
Authors: Korczak A. , Mikula S. , Strzelecki S.
Published: November 2008

The dewatering pumps operating in the deep level mines show the problems of volumetric losses and wear that are caused by the wear of thrust axial disk. The pumped fluid, contaminated with the hard mineral particles, flows through the gap between the rotating disk and stationary relieving disk and it causes the wear of both elements. The paper describes the grounds and the design of the modernized thrust node of multistage centrifugal pump. This node fulfils the function of axial hydrostatic bearing supplied with the working fluid and transmitting high axial load. The suggested node design consists of relieving disk with flat carrying surface and stationary thrust ring supported elastically on the polymer layer. The disk and ring are separated by the thin water film.
A Model for Analyzing Multi-Asperity Contact of Thin Sheets With Real Surfaces on Both Sides
Authors: Jagodnik John J. , Mu¨ftu¨ Sinan
Published: November 2008

A model for two-sided contact of a thin sheet of material, with real surfaces on both sides is presented. The model combines cylindrical-contact equations, with Euler-Bernoulli beam theory to examine the importance of substrate rigidity in two-sided contact problems. A finite difference program for solving this model is developed. Results for two-sided contact of numerically generated surfaces on thin tapes are presented. The effects of tape thickness and tension are explored. It is shown that substrate’s bending rigidity contributes significantly to the overall equilibrium, for typical tape thicknesses and tension values used by the industry. However, large thickness values exists for which substrate bending is negligible and elastic half-space solutions applied to both sides of the tape are adequate.
Scratch Testing of Nanostructured Films
Authors: Gee M. G. , Evanno N. , Mendels D. A.
Published: November 2008

Nanostructured films offer potential for considerable improvements in mechanical properties by comparison with traditional single composition coatings. This nanostructuring can be carried out in many ways, but one of the easiest methods to implement it is through nanolayering with two or more phases. Alteration of the thickness of the different phases then permits the tailoring of the properties of the coating.
A Retrospective View of Wear Research and Some Emerging Challenges
Authors: Blau P. J.
Published: November 2008

Compared to the study of friction, wear research is a much younger endeavor. While there is historical evidence of attempts to create wear-resistant surfaces, like pounding stones into the soles of wooden sandals or attaching metal strips to wooden plowshares, there was little scientific study of wear before the mid-twentieth century when Ragnar Holm conducted his signal work on electrical contact materials [1]. Modern instruments to magnify and study surfaces, and the use of bench-scale apparatus enabled wear research to be brought into the laboratory. Developments in heat treating, coating processes, and cleaner metallurgical practices for steels drove the desire to better quantify and understand the bases for improvements in wear resistance. Trends in wear research are indicated by the subjects of papers from the International Conferences on Wear of Materials. Near-term challenges in wear research include reaching a better understanding of non-steady-state processes of surface damage, reconsidering the traditional definitions for wear modes, and designing, modeling, and testing components under combined wear modes. Challenges for longer-term wear research include improving first-principles materials design and material selection for wear minimization, wear life-prediction for multi-mode systems, integrated surface engineering, and virtual wear testing as a means to avoid high development costs and to cope with the daunting number of choices of materials, lubricants, and surface treatments for wear mitigation.
A Theoretical and Computational Study of Superlubricity and the Role of the Roughness Exponent
Authors: Mu¨ser Martin H. , Campana Carlos
Published: November 2008

Superlubricity can only be achieved if the intra-bulk elastic interactions dominate interfacial shear forces at every single length-scale in a contact. Otherwise, there will be some type of plucking motion which will lead to friction-velocity relationships akin of Coulomb’s friction law. For nominally flat surfaces, it has been predicted theoretically and demonstrated experimentally that plucking motion and hence kinetic friction can be avoided under certain circumstances. We present theoretical arguments, why these findings may extend to fractal surfaces. The theories are checked by molecular dynamics simulations. It turns out that the roughness exponent and the absolute magnitude of the roughness both play a crucial role in determining whether there can be superlubricity.
Solid Particle Erosion Behaviour of Plasma Sprayed Coatings on a Fe-Based Superalloy
Authors: Mishra S. B. , Prakash S. , Chandra K.
Published: November 2008

In the present investigation plasma sprayed metallic coatings of NiCrAlY and Ni-20Cr were deposited on a Fe-based Superalloy (32Ni-21Cr-1.5Mn-1Si-0.3Ti-0.3Al-0.1C and Balance Fe) by shrouded plasma spray process. NiCrAlY was used as bond coat in both the cases. Erosion studies were conducted on uncoated as well as plasma spray coated superalloy specimens using an air-jet erosion test rig at a velocity of 40m/s and impingement angles of 30° and 90°. Silica sand particles of size ranging between 150 and 212 μm were used as erodent. The coatings have been characterised for porosity, microhardness and microstructure. Erosion behaviours of the superalloy and plasma spray coatings are discussed. Of the two plasma sprayed coatings, the NiCrAlY coating gave the lowest erosion rate regardless of the impact angle.
A Review of DLC Coatings for Biological Applications
Authors: Hauert R.
Published: November 2008

Diamond-like carbon (DLC) is a class of materials with outstanding mechanical, tribological and biological properties. From in-vitro experiments, it is known that by incorporating other elements into the DLC film, the ratios of the different proteins adsorbed on the surface can be changed. These proteins will then subsequently control cell attachment, cell proliferation and cell differentiation. In a total hip joint replacement, the metallic femoral head, which slides against a polyethylene pan, causes polymeric wear debris. These wear particles may then trigger inflammatory reactions, resulting in osteolysis (bone resorption) and subsequent implant loosening. DLC has proven its outstanding tribological properties in many technical applications, mainly due to the build up of a transfer layer on the counterpart. DLC coated load bearing implants sliding against ultra high molecular weight polyethylene (UHMWPE) have been investigated. The different in-vitro experiments apparently showed contradicting results, mainly due to the different experimental setups and especially the different liquids used as lubricants. The synovial fluid present in a biological joint, contains large organic molecules which function as a boundary lubricants. Phospholipids, proteoglycans or proteins can be chemisorbed on the joint surfaces and trap water molecules, resulting in water acting as a viscose lubricant. When a DLC coated femoral head is tested against a polyethylene pan in a hip joint simulator, using synovial fluid as a lubricant, the build up of a transfer layer, protecting the softer counterpart (i.e. the polymer) does not seem to take place and the UHMWPE counterpart still shows wear. However, when DLC slides against DLC in medical applications, the build up of a transfer layer may not be a critical issue or is not drastically altered by the presence of proteins, and very low wear rates could be obtained in different in-vitro tests. Additionally, DLC coatings have an excellent haemocompatibility, which is expressed in a decreased thrombus formation. When exposed to blood, an increased ratio of albumin to fibrinogen adsorption, as well as decreased blood platelet activation is observed on coated surfaces. A few DLC coated cardiovascular implants such as artificial heart valves, blood pumps and stents are already commercially available. When coating a metal with DLC, good adhesion is obtained due to the about one nanometer thick metal-carbide reaction layer at the DLC/substrate interface. Upon implantation, it has to be guaranteed that this reaction layer is also chemically long-term stable under in-vivo conditions.
Study of Surface Films of Overbased Sulfonates and Sulfurized Olefins by X-Ray Absorption Near Edge Structure (XANES) Spectroscopy
Authors: Costello M. T.
Published: November 2008

Four-ball EP tests were completed for lubricating oils containing the synergistic combination of overbased calcium sulfonate and sulfurized olefin. Using XANES spectroscopy we were able to differentiate between FeS, RSO3− and SO42− in the sulfur K-edge and L-edge spectra. It was found while the sulfurized olefin reacts very strongly with the substrate to form FeS, the overbased calcium sulfonate does not react strongly with the substrate unless sulfurized olefin present.
Nano-Tribology of a Polytetrafluoroethylene Transfer Films Using Molecular Dynamics Simulation and Microtribometry
Authors: Jang Inkook , Dickrell Pamela L. , Burris David L. , Sawyer W. Gregory , Phillpot Simon R. , Sinnott Susan B.
Published: November 2008

Polytetrafluoroethylene (PTFE) is a well known solid lubricant and polymer nanocomposites based on PTFE are considered to be promising materials for tribological applications in space. Like other polymer materials, many properties of PTFE depend on morphology. In this study, molecular dynamics (MD) simulations are performed to examine the effect of chain configuration on the frictional behavior of PTFE at the molecular level and compared to microtribological studies on aligned transfer films of PTFE.
Investigation and Validation of a Finite Element Model for the Study of a Small Format Magnetic Tape Vacuum Column
Authors: Milich Edward P.
Published: November 2008

A finite element model of the path of 1/2 inch magnetic tape media as found in a Small Format Tape Evaluation System (SFTES) was created and validated. The model was used to predict tape geometry within the system, specifically in the neighborhood of an inclined-wall vacuum column and an inclined capstan. Parametric study via simulation and testing was used to improve the quality of tape handling within the SFTES.
Self-Organizing at Friction and Development of Wearproof Materials
Authors: Gershman J. S. , Bushe N. A. , Mironov A. E.
Published: November 2008

Now the choice of wearproof materials is carried out, basically, experimentally, i.e. empirically and on the basis of their volumetric and superficial properties. However, metallic or organic materials which properties considerably differ are maintained in many tribosystems. Therefore only properties are the insufficient information for selection of wearproof materials. In the present work it is offered to choose wearproof materials on the basis of their ability to initiate nonequilibrium processes at friction.
A Review of the Evolution of Microcontroller-Based Machine and Process Monitoring
Authors: Rizwan Ahmad , Alvi M. S. I. , Sajid Ali
Published: November 2008

This paper reviews the evolution of intelligent, distributed, microcontroller based machine and process monitoring systems. It considers basic building blocks that support such systems through the development of fault diagnostic methods, intelligent system based approaches and sensor-based machine monitoring. It then identifies three approaches that may be utilized when designing monitoring system architecture: integrated, distributed and embedded. Current applications of these approaches, when deployed individually and in combination with each other, are then discussed. In particular the paper considers the efficacy of micro-controller based embodiments, in both current and future monitoring activities.
Vegetable Oils as Base Oil for Industrial Lubricants: Evaluation Oxidative and Low Temperature Properties Using TGA, DTA and DSC
Authors: Jayadas N. H. , Prabhakaran Nair K. , Ajithkumar G.
Published: November 2008

In this paper oxidative degradation of saturated and unsaturated vegetable oils is studied by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) and their low temperature properties are studied by differential scanning calorimetry (DSC). Both non-isothermal and isothermal thermo gravimetric analysis procedures are used for the study. The onset temperatures of oxidative degradation and weight gain in isothermal TGA are taken as measures of oxidative and thermal stabilities. Three vegetable oils namely coconut oil, sesame oil and sunflower oil with varying degree of un-saturation are selected for the study. The results are found to agree with reported results obtained by conventional methods. Several standard methods are currently available for determining the oxidative and low temperature properties of base oils. These methods are extremely time-consuming and data reproducibility between laboratories is poor. TGA, DTA and DSC are excellent tools to evaluate base oils in respect of their oxidative and low temperature behavior in that they produce results quickly, reproducibly and the sample requirement is very low.
Third Body Effects in the Wear of Polyamide Materials
Authors: Tortech L. , Marcellan A. , van Melick H. , Chateauminois A.
Published: November 2008

This study deals with the micro-wear mechanisms of polyamide materials under reciprocating sliding conditions. Using the resources of in situ contact visualisation through transparent sapphire counterfaces, third body formation and flow processes have been monitored as a function of the sliding amplitude. Under confined contact conditions, the stabilization of coherent third body compacts with distinct microstructural properties was found to have a profound effect on the displacement of wear debris from the contact and on the ultimate wear resistance of the polyamide materials.
Reliability Based Maintenance in the Industrial/Manufacturing Sector(s)
Authors: Paxton Charles H.
Published: November 2008

Reliability Based Maintenance (RBM) programs are commonplace in the Aviation, Power Generation and Chemical / Petrochemical industries. In these sectors, Equipment Failure is not an option. The Industrial / Manufacturing sector(s) have not fully embraced the RBM concept and for the most part routinely suffer loss of production output and the subsequent loss of revenue associated with equipment failures. Two of the Key Elements to the successful implementation of the RBM process in the Industrial / manufacturing sector(s) is the establishment of Reliability and Maintainability Specification and a viable Machinery / Equipment Lubrication and General Preventive Maintenance Program. This Paper will outline procedures for establishing an RBM Program. Methods to evaluate the results will be outlined as well.
Determination of Steady-State Adhesive Wear Rate
Authors: Yang L. J.
Published: November 2008

Wear rates obtained from different investigators could vary significantly due to lack of a standard test method. A test methodology is therefore proposed in this paper to enable the steady-state wear rate to be determined more accurately, consistently, and efficiently. The wear test will be divided into four stages: (i) to conduct the transient wear test; (ii) to predict the steady-state wear coefficient with the required sliding distance based on the transient wear data by using Yang’s second wear coefficient equation; (iii) to conduct confirmation runs to obtain the measured steady-state wear coefficient value; and (iv) to convert the steady-state wear coefficient value into a steady-state wear rate. The proposed methodology is supported by wear data obtained previously on aluminium based matrix composite materials. It is capable of giving more accurate steady-state wear coefficient and wear rate values, as well as saving a lot of testing time and labour, by reducing the number of trial runs required to achieve the steady-state wear condition.
X-Ray Diagnostics for Scuffing: Application to Phase Transformation in Nickel
Authors: Hershberger Jeff , Ajayi Oyelayo O. , Lorenzo-Martin Cinta , Routbort Jules L. , Fenske George R.
Published: November 2008

Through the use of X-ray diffraction (XRD) and other diagnostics, the fundamental physical mechanisms of scuffing are becoming better understood. Peak broadening in the XRD pattern has been analyzed to determine the dislocation structure and crystallite size. Evidence from this technique has led us to conclude that scuffing is an example of adiabatic shear instability, wherein work hardening is exceeded by the thermal softening caused by the work. We are extending this research through scuff testing and XRD of nonferrous materials. For example, members of our team have recently found frictional behavior and surface morphologies consistent with scuffing in single crystals of MgO. Previous work has suggested the use of scuffing as a general method for the formation of metastable phases. Phase identification information available from the XRD data indicated the formation of austenite in scuffed SAE4340 steel, and the present work reports the discovery of a tribologically formed metastable phase in nickel. The formation of this phase was associated with surface roughening and a rapid friction increase of approximately 50%. However, the morphology of the roughened surface indicated abrasion rather than the gross plasticity typical of scuffed surfaces. X-ray diffraction identified the phase as either nickel carbide (Ni3C) or hexagonal nickel, which are similar in structure, and ruled out the presence of crystalline nickel oxides. Analysis of peak widths revealed that the dislocation density in the areas that experienced a higher friction coefficient was lower than that in low-friction areas. This finding is not consistent with dislocation density changes in scuffed steel.
Biotribological Behavior of Ultra High Molecular Weight Polyethylene Composites Containing Nature Coral
Authors: Wang Qingling , Ge Shirong , Huang Xiaolong , Qian Sahnhua
Published: November 2008

It’s important to research on the biotribology of UHMWPE composites for developing the new joint implanted materials and the life of the joint replacements. In this research, UHMWPE-NC composites were prepared using the pressing formation method. The nano-hardness and elastic modulus evaluations of all of UHMWPE-NC composites were obtained by nanoindentation tests (Hysitron, Co.,) with the corresponding load-displacement curves confirming the characteristic properties of these materials. A ball-on disc wear test was run on the Universal Micro-Tribometer (UMT) to investigate the friction and wear behaviors of Si3N4 ceramic cross-sliding against UHMWPE-NC composites in artificial body fluids lubrication.
A Relationship Between Autocorrelation Length and Adhesive Friction Behavior of Rough Surfaces
Authors: Zhang Yilei , Sundararajan Sriram
Published: November 2008

Autocorrelation Length (ACL) is a surface roughness parameter that provides spatial information of surface topography that is not included in amplitude parameters such as Root Mean Square roughness. This paper presents a statistical relation between ACL and the real area of contact, which is used to study the adhesive friction behavior of a rough surface. The influence of ACL on profile peak distribution is studied based on Whitehouse and Archard’s classical analysis, and their results are extended to compare profiles from different surfaces. With the knowledge of peak distribution, the real area of contact of a rough surface with a flat surface can be calculated using Hertzian contact mechanics. Numerical calculation shows that real area of contact increases with decreasing of ACL under the same normal load. Since adhesive friction force is proportional to real area of contact, this suggests that the adhesive friction behavior of a surface will be inversely proportional to its ACL. Results from microscale friction experiments on polished and etched silicon surfaces are presented to verify the analysis.
Super Low Friction Property of DLC Lubricated With Ester-Containing Oil: Part 2 — Nanometer-Scale Morphological, Structural and Frictional Properties
Authors: Ye Jiping , Ueoka Kenichi , Kano Makoto , Yasuda Yoshiteru , Okamoto Yusuke , Martin Jean Michel
Published: November 2008

We have succeeded for the first time anywhere in lowering the friction coefficient of a diamond-like-carbon (DLC) coating to less than 0.01 under boundary lubrication in engine oil [1–3]. This anomalous super-lubrication behavior has been observed for a hydrogen-free DLC-coated (ta-C) disc in an ester-containing oil but not for a hydrogenated DLC (a-C:H) coating. It is thought that some chemical adsorbent may form only on the ta-C sliding surface due to some tribochemical reactions. Our recent studies have suggested that the macro-scale reduction of friction is dependent on nanometer-scale tribological properties [4–6]. The superlow friction behavior seen in a pin-on-disc friction test was taken as the object of this investigation with an eye toward elucidating the mechanism of the anomalous friction reduction. Pin-on-disc tests were conducted by sliding a ta-C/ta-C pair in the presence of poly alpha-olefin based oil containing a modifier additive of glycerol monooleate ester (PAOES1 oil). Nanometer-scale tribological properties were investigated by using atomic force microscopy (AFM), the AFM phase-image technique, and nanoscratch measurements. Attention was focused on the differences in surface roughness, nanostructure and nanofriction coefficient between the sliding and non-sliding areas in an effort to find the origin of the super-lubrication behavior.
Wear of Dental Cutting Tools Coated With Nanocrystalline Diamond Coatings
Authors: Jackson Mark J. , Ahmed Waqar , Woodwards Robert , Sein Htet
Published: November 2008

Dental cutting tools have traditionally been made using resin-bonded diamonds that have a tendency to breakdown during drilling operations with the consequent loss of diamonds and resin binder into the patient’s mouth. Recent developments in chemical vapor deposition have made it possible to create binderless diamond cutting tools that are useful for machining and drilling enamel, dentine, amalgam, and cast alloys used for crowns and bridges. The paper compares newly developed tools with conventional tools that are used for orthodontic and maxillofacial operations. The reduction in wear using coated diamond tools is significant.
Reducing Wear of Abrasive Wheels Grinding Aerospace Alloys by Laser Assisted Cleaning
Authors: Jackson Mark J. , Chen Xun
Published: November 2008

A new method for cleaning loaded grinding wheels is introduced by applying a CO2 laser pulse to the wheel surface. It is shown that effective cleaning can be achieved by the selection of adequate laser power flux and irradiation duration. Fusion and evaporation of clogged chips play an important role in the laser cleaning process and subsequent wear of the grinding wheel. It is suggested that high laser power irradiance of short duration is essential for effective wheel cleaning and reduced wear of the grinding wheel with specially developed bonds.
A Transient Thermoelastohydrodynamic Analysis of a Tilting-Pad Thrust Bearing During Start-up
Authors: Wang X. , Zhang Z. , Pan J.
Published: November 2008

The aim of this work is to study the transient thermoelastohydrodynamic behavior of the tilting-pad thrust bearing during its start-up. The theoretical analysis of bearing performance is based on a three dimensional transient TEHD model. The effects of the running time and load on the bearing’s performance are studied. The results show that the above factors influence the performance of the bearing significantly.
The Analysis of Squeezed Air-Damping on the Planar MEMS Structures
Authors: Wang X. , Wang M. , Liu Y.
Published: November 2008

Squeeze film damping of a planar micromechanical structure that oscillates in the normal direction to the substrate is investigated. Theoretical models influencing the squeeze film damping has been developed for the transversely oscillating plates. The air-film model has been derived from the modified nonlinear Reynolds equation, where the influence of the gas rarefaction is included. The performance of squeeze film such as the variation of the pressure distribution and the air damping load are analysed.
Phase Structure and Lubricity of In-Situ Generated Protective Layer on Worn Metal Surfaces in Presence of Mg6Si4O10(OH)8
Authors: Jin Yuansheng , Yang He , Wang Feng , Minfray C. , Li Shenghua
Published: November 2008

A mechanochemical reconditioner package has been investigated in our laboratory which could be used to generate an in situ protective layer on worn metal surfaces as a result of mechanochemical reactions between worn tribosurfaces, wear debris and a special reconditioner formulation. The main constituent in the reconditioner formulation chemistry is magnesium silicate hydroxide, Mg6(Si4O10)(OH)8. HRTEM analyses have displayed that the protective layer consists mainly of cementite nanocrystals with crystalline anisotropy. Nanoparticles of magnet iron oxide (Fe3O4) and iron peroxide (FeOOH) are dispersed on the habit planes of nanocrystalline cementite matrix. The protective layer obtained exhibits very smooth top surface and excellent tribological characteristics.
Journal Bearing Misalignment as an Extension of Knowledge-Base of Large Power Turboset Diagnostic System
Authors: Luczak Marcin
Published: November 2008

In the paper presented are course and results of investigations of the influence of slide bearing bush and shaft mutual misalignment on the dynamic properties of the large power turboset. Former numerical models used for simulations assumed coaxial position of a bush and journal. Engineering experience and practical cases led to development of a slide bearing model taking into account a misalignment. The defect was simulated by means of numerical model of the turboset. Simulation was performed for each bearing individually in both, horizontal and vertical planes. Maximum values of the skewness angle were calculated for each bearing at both planes with a criterion of minimal oil film thickness. The influence of the misalignment on dynamic properties of turboset was presented with a particular focus on amplitudes of relative and absolute vibration. Those quantities are measured by a condition monitoring system. Basing on the results of the simulation multiple defect-symptom diagnostic relations were built. These diagnostic relations were used as learning and testing data sets for a knowledge base of an diagnostic system based on the inverse diagnostic model. This diagnostic system is implemented at one of Power Stations.
Superlubricity of C60 Intercalated Graphite Films (Keynote)
Authors: Miura K. , Tsuda D. , Sasaki N.
Published: November 2008

The frictional behavior of the C60 intercalated graphite films with a large size of 2.3×2.3mm2 is reported. The C60 intercalated graphite films consist of alternating close-packed C60 monolayers and graphite layers (graphenes), and thus many sliding planes are formed between each C60 monolayer and graphene. The intercalation of C60 molecules into graphite films results in superlubricity where frictional forces are observed to be stationarily zero.
AFM Tip Manipulation of Single Atomic Layer Growth and Dissolution of Inorganic Single Crystals
Authors: Langford Stephen C. , McEvoy Ann , Dickinson J. Thomas
Published: November 2008

We show that single atomic layer growth can be induced, controlled, and characterized using atomic force microscopy (AFM). The controlling parameters include contact force, solution chemistry, and scanning direction relative to the crystal axes. We present new evidence for the role of AFM tip motion across terraces in inducing localized deposition in pre-existing pits on otherwise atomically smooth surfaces. Low contact force scanning also hinders major roughening mechanisms, including 3D nucleation and growth, by tribochemically dissolving these deposits. Consequently, atomically flat surfaces can be generated. Finally, we show a new method of “scribing” <40 nm wide lines a single atomic layer deep on inorganic substrates. The materials under study are model biominerals: calcite (CaCO3) and brushite (CaHPO42H2O). Thus this work relates to the production of smooth surfaces on bone-like materials..