bluuebunny/crossref_metadata_2025 huggingface dataset:
Models of Friction and Wear of DLC Films
Authors: Borodich Feodor M. , Korach Chad S. , Keer Leon M.
Published: November 2008

Wear and friction of DLC (diamond-like carbon) covered counterparts are under consideration. Experiments showed that abrasion is the leading wear mechanism at the beginning of the wear process. However, the ability of the surface to wear away the counterpart reduces very rapidly, often as a power law function of the cycle numbers. This phenomenon was explained assuming that the initial abrasiveness of a coating is determined by the number of the nano-sharp asperities that were in contact with the counterpart, i.e. by the number of the sharp asperities within the nominal region of contact. On this basis, a model of abrasive wear was developed, using the concept of statistical self-similarity of distribution of the nano-sharp asperities within the current contact region. After the sharp asperities were blunted or removed from the contact region, the wear is related either to phase transformations or to chemical mechanisms. Recent experimental studies of dry sliding between two hydrogenated DLC coated counterparts in low oxygen environment showed that adsorbates have considerable influence on friction and the friction coefficient increases with the increasing of the time interval between contacts. The observed friction phenomena are assumed caused by a reaction between the adsorbate and carbon atoms of the coatings, and when the slider passes a point on the track, it removes mechanically some adsorbate from the surface. The mechanical action leads to re-exposure of the surface to gases in the environment. We assume that there is a transient short-life high temperature field at the vicinities of contacting protuberances that may cause various transformations of the surface. We suppose that first an adsorbate molecule becomes physically adsorbed to the surface and then chemisorbtion may occur between the carbon atoms of the coating and the ‘sticky’ oxygen atoms. The atoms or molecules of adsorbate interact with the conterpart. Our modeling established a direct connection between this kind of molecular friction and gradual wear. Using the new adsorption-desorption model, the numerical analyses of the friction coefficient were compared with experimental DLC friction results.
Behavior of a Horizontal Fluid Filled Crack Under Moving Hertzian Load
Authors: Jin X. , Keer L. M. , Chez E. L.
Published: November 2008

Numerical analysis is presented for a fluid filled subsurface crack in an elastic half plane loaded by Hertzian contact stresses. The opening volume of the horizontal Griffith crack is fully occupied by an incompressible fluid. In the presence of friction, a moving Hertzian line contact load is applied at the surface of the half plane. The stress intensity factors at the tips of the fluid filled crack are analyzed on condition that the change of the opening crack volume vanishes due to the fluid incompressibility. The method used is that of replacing the crack by a continuous distribution of edge dislocations. As a cycle of rolling can be viewed as shifting the Hertzian contact stresses across the surface of the half plane, the results of this analysis may prove useful in the prediction of rolling fatigue of an elastic rolling body containing a soft inclusion.
Methods for Assessing the Bearing Surface Durability Performance of Lubricant Formulations
Authors: Nixon Harvey P.
Published: November 2008

Lubricant formulations and lubricant additives have been demonstrated to have a major impact on the surface durability of rolling element bearings. However, there are very few standard tests used to assess the performance aspects of lubricants as it relates to bearing surface performance. Lubricant formulations have been slanted heavily toward protecting gear concentrated contacts from galling and wear. In addition, much of the performance differentiation of lubricants has been dependent on highly accelerated standardized laboratory tests related to gears. Methods have been developed for properly evaluating a lubricant’s performance characteristics as it relates to bearings. These methods are explained and the corresponding test results are reviewed to show their effectiveness as a lubricant performance evaluation tool. The implications of these findings provide direction and suggestions for ways to minimize or avoid potential detrimental performance effects of lubricant formulations on rolling element bearings.
When Does Continuum Theory Describe Mechanical Contacts?
Authors: Luan Binquan , Robbins Mark
Published: November 2008

The area of molecular contact between surfaces plays a central role in friction and adhesion. Traditionally it is calculated using continuum contact mechanics, which is known to break down as the contact width approaches atomic dimensions. Yet contact mechanics is being applied at ever smaller lengths, even to atomic force microscope (AFM) tips containing a few atoms. Molecular simulations are used to test the limits of contact mechanics under ideal non-adhesive and adhesive conditions. A simple geometry of sphere-on-flat is considered. One surface is an atomically flat crystal and is deformable. The approximately spherical curved surface is rigid and is produced by bending a crystal, or cutting a crystal or amorphous material. While these methods of producing the curved surface differ only in the amount of atomic-scale roughness, they produce very different behavior in some quantities. The normal stiffness is affected very little, the contact area can be modified by a factor of two, and the friction and lateral stiffness can be modified by an order of magnitude. The implications for AFM experiments are discussed.
QCM Studies of Phononic and Electronic Contributions to Sliding Friction in Adsorbed Monolayers
Authors: Krim Jacqueline
Published: November 2008

Studies of the fundamental origins of friction have undergone rapid progress in recent years with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales. The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale mechanisms, which dominate the dissipative process by which mechanical energy is transformed into heat. Measurements of the sliding friction of physisorbed monolayers and bilayers provides information on the relative contributions of electronic to phononic.
Dry Machinability of Aluminum Alloys
Authors: Shareef Iqbal , Natarajan Manikandan , Ajayi Oyelayo O.
Published: November 2008

Adverse effects of the use of cutting fluids and environmental concerns with regard to cutting fluid disposability is compelling industry to adopt Dry or near Dry Machining, with the aim of eliminating or significantly reducing the use of metal working fluids. Pending EPA regulations on metal cutting, dry machining is becoming a hot topic of research and investigation both in industry and federal research labs. Although the need for dry machining may be apparent, most of the manufacturers still consider dry machining to be impractical and even if possible, very expensive. This perception is mainly due to lack of appropriate cutting tools that can withstand intense heat and Built-up-Edge (BUE) formation during dry machining. The challenge of heat dissipation without coolant requires a completely different approach to tooling. Special tooling utilizing high-performance multi-layer, multi-component, heat resisting, low friction coatings could be a plausible answer to the challenge of dry machining. In pursuit of this goal Argonne National Labs has introduced Nano-crystalline near frictionless carbon (NFC) diamond like coatings (DLC), while industrial efforts have led to the introduction of composite coatings such as titanium aluminum nitride (TiAlN), tungsten carbide/carbon (WC/C) and others. Although, these coatings are considered to be very promising, they have not been tested either from tribological or from dry machining applications point of view. As such a research program in partnership with federal labs and industrial sponsors has started with the goal of exploring the feasibility of dry machining using the newly developed coatings such as Near Frictionless Carbon Coatings (NFC), Titanium Aluminum Nitride (TiAlN), and multi-layer multicomponent nano coatings such as TiAlCrYN and TiAlN/YN. Although various coatings are under investigation as part of the overall dry machinability program, this extended abstract deals with a systematic investigation of dry machinability of Aluminum 6061 and 2024 using uncoated carbide, TiN coated carbide, and TiAlN coated carbide inserts. Central Composite Design (CCD) is used to study the effect of speed, feed, depth of cut, workpiece material, and cutting tool material on the resulting forces, surface finish, temperature, chip morphology and tool wear. Each of the machining responses is measured and compared under 15 different machining conditions. Results from CCD experiments have been used to develop linear and logarithmic models for forces (Fx, Fy, Fz, & Fr) surface finish (Ra), and temperature. Furthermore, chip morphology and tool wear have also been compared. From the comparison of forces, surface finish, temperature, chip morphology, tool wear and the corresponding statistical models, it is clear that in general TiAlN results in lower forces, better surface finish, greater fragmented chips, and lesser tool wear.
Initial Wear Characterization of a Spinal Artificial Disc
Authors: Gabriel Stefan M. , Dooris Andrew P. , Ares Paul J. , Kwak S. Daniel , Serhan Hassan A.
Published: November 2008

Local reactions to wear debris generated by hip and knee replacement devices have been shown to lead to failure of some devices via osteolysis and component loosening. This has not been shown to be a clinical issue with the most widely used spinal artificial disc prostheses, but the because of the proximity of these devices to sensitive neural structures in vivo, the issue deserves examination. The purpose of the present study was to investigate the wear characteristics of a lumbar artificial disc under simulated motion and loading conditions. In vitro testing using a modern joint simulator with loads and motions representative of possible lumbar spine motions show a relatively low polyethylene wear rate out to 10 million cycles with a dependence of resulting wear on input load and motion parameters.
Sliding Wear of Non-Hydrogenated Diamond-Like Carbon Coatings Against Al, Cu and Ti
Authors: Konca E. , Cheng Y. T. , Alpas A. T.
Published: November 2008

Magnetron sputtered non-hydrogenated diamond-like carbon (DLC) coatings were tested against Al, Cu and Ti pins using a vacuum pin-on-disc tribometer. The objective was to compare Al, Ti, and Cu transfer to DLC coatings in air (29% RH) and an inert atmosphere (argon). In argon, a significant amount of adhesion and material transfer occurred from the Al and Ti pins to the DLC coating surfaces inflicting severe damage to the coatings. Wear and material transfer of the DLC coating against Cu were negligible in argon. Compared to tests in argon, the tribological performance of the DLC coatings against Al and Ti improved significantly in ambient air. In contrast, the wear rate of the DLC coatings against Cu was much higher in ambient air compared to that in argon.
Studying Shear Behavior of Ductile Metals Using an Atomic Force Microscope
Authors: Ingole Sudeep , Kadri Shabibahmad , Liang Hong , Hartwig Karl
Published: November 2008

The characteristics of sheared surfaces of ductile metals are fundamentally interesting for tribological performance. This research applies an atomic force microscope (AFM) to characterize the shear patterns and characteristics of pure copper metal. Two approaches were used, micro indentation and equal channel angular extrusion (ECAS). This poster discusses our findings in nano scale behavior of shear and compares the process of materials deformation. New insight of ductility for wear is reported.
Dynamic Analysis of Cage Behavior in a Tapered Roller Bearing
Authors: Sakaguchi Tomoya , Harada Kazuyoshi
Published: November 2008

We have developed a three-dimensional dynamic simulation tool for tapered roller bearings using commercially available analysis software, ADAMS (MSC. Software). Cage motion in six degrees was analyzed with the simulation tool and was measured by experiments. The results showed the validity of the simulation tool. Regarding the cage behavior, as the traction forces between rollers and races grew, the amplitude of the cage whirl motion increased up to the radial guide clearance between the roller and its cage pocket.
Investigation of O-Ring Deterioration Due to Polymerized Oil Oxidation Products
Authors: Sasaki Akira , Uchiyama Shinji , Kawasaki Mario
Published: November 2008

Oil leakage itself is not serious for machine operation but it is one of the most troublesome problems for hydraulic and lubricating systems maintenance. Oil leakage endangers the working environment and causes injury and fire in factories. It is generally understood that oil leakage is caused by deterioration or wear of sealing materials like rubber. Maintenance people have sometimes seen some deposits on the deteriorated oil seals. However no studies have been made in the past on the relation between the deterioration of the rubber materials and the deposits. This paper demonstrates by experimental that deposits of polymerized oil oxidation products (hereinafter called as “sludge”) take an important role of deterioration of sealing materials.
Surface Adhesion and Friction in Microelectromechanical Systems: Measurement and Modification Techniques
Authors: Komvopoulos K.
Published: November 2008

Microscopic devices that can perform sensing, actuation, and control, known as microelectromechanical systems (MEMS), are projected to lead to new technologies with profound impacts in science and engineering. However, there are several limitations that must be overcome before MEMS could be fully utilized in various applications. In particular, because of the low stiffness and large surface-to-volume ratio of MEMS, high adhesion and friction forces between proximity and contacting surfaces limit the device efficiency and often lead to premature failure. Basic study of adhesion and friction under MEMS conditions requires special microdevices fabricated by surface micromachining. The basic features of such MEMS devices are presented herein together with suitable surface modification techniques for reducing surface adhesion and friction, such as surface texturing and deposition of low surface energy solid films and self-assembled monolayers.
Coated Valve Train Components and Low Emission Engine Oils in a Fired Engine Enviroment
Authors: Bardasz Ewa , Scott Christopher G. , Cowling Susan V. , Matasic James C.
Published: November 2008

A series of heavy-duty diesel, fired engine tests were run using coated valve train components in combination with low emission diesel engine crankcase oils. Examination of coated rocker arm and corresponding, uncoated crosshead surfaces, showed that greater crosshead wear was encountered using a physical vapor deposition (PVD) chromium nitride coating, as compared with that observed using a tungsten carbide PVD composition, or an uncoated rocker arm surface. Good coating adhesion was observed with both coatings, with no adverse effects on neighboring, uncoated surfaces. Tungsten carbide in combination with the first of two low-emission engine oils out performed either of the oils used in combination with chromium nitride. Test parameters are summarized along with key engine data obtained. Observations from surface characterization of representative rocker arm and mating crosshead components, using optical and scanning electron microscopy coupled with energy dispersive spectrometry also are highlighted and discussed.
Use of Electrochemical Techniques in CMP Process Evaluation
Authors: Brusic Vlasta
Published: November 2008

With the maturing of Chemical Mechanical Polishing Technology, there are many novel, imaginative and challenging applications awaiting its use. Polishing of metals such as tungsten, aluminum, and copper, has been extended to magnetic materials, noble metals, and others, often in the form of alloys of complicated compositions. As metal CMP can also be defined as corrosion enhanced by wear, electrochemical techniques remain a very practical probe into the behavior of metals in novel solutions, under a variety of conditions relevant to polishing. They can be used as a first step approach to determine if the metals will be reactive in selected slurry, what are the predominant reactions and their rate determining steps. This paper will describe several examples, mostly from new applications based on the noble metals, as well as some very practical alloys.
A Micro-IRRAS Study of Lubricant Degradation Under Thin Film Conditions
Authors: Cann P. M. , Spikes H. A.
Published: November 2008

This paper studies lubricant degradation in a rubbing contact under thin film conditions. Friction tests have been carried out in an MTM test device using a steel ball/steel disc configuration. The tests were run with a small amount of lubricant present. At the end of the test the disc was retained for analysis. Micro-reflection FTIR spectroscopy was used to analyse the lubricant chemistry within and close to the rubbed track. The technique offers a more direct method for studying lubricant degradation products during rubbing. The results are compared to those from more conventional experimental methods.
Evaluation of Microindentation Test Results Using FEM Simulations for the Determination of the Mechanical Properties of Various Ferrous or Non Ferrous Materials
Authors: Bouzakis K.-D. , Lontos A.
Published: November 2008

The determination of the mechanical properties using the nano or macroindentation test results was developed in order to predict the mechanical properties of materials such as thin or thick coatings [1]. In the present paper a new method using a continuous FEM supported simulation of the microindentation results through a special tester, is proposed in order to predict the stress–strain curve of various ferrous or non ferrous materials that are being used as constructive materials in several machines or devices. The elasticity modulus is determined using a large spherical indenter tip and the stress strain curve using smaller steel balls. In the case of three deferent ball diameter indenter tips, the adopted experimental-analytical methodology present similar results regarding the constitutive law of the examined steel or aluminum specimens.
An Easy Way to Find a Suitable Amount of Top-Up Oil
Authors: Sasaki Akira , Tobisu Hideaki , Uchiyama Shinji , Kawasaki Mariko
Published: November 2008

All hydraulic and lubricating oils are formulated with oxidation inhibiting additives. When oxidation-inhibiting additives are depleted, oil oxidation progresses, TAN raises and varnish is produced. In order to know depletion of oil oxidation inhibitors, RBOT [1] and voltammetric analysis [2] have been used. However these analyses did not tell us how much top-up of new oil is needed or sufficient. This paper demonstrates a simple method to know how much top-up is sufficient to use the oil without having varnish problems.
Low Friction in Boundary Lubrication: By Structure or Dynamics?
Authors: Heuberger M. , Drobek T.
Published: November 2008

Low friction is an important and desirable attribute for a number of boundary lubricated systems. We ask the question what are the most promising strategies to attain low friction with nanometer thick lubricant films. Is it the structure or the dynamics of the boundary layers, or, maybe both? Using the extended surface forces apparatus we are investigating structural and dynamic effects on friction — in some cases at sub-Ångstrom resolution. Results obtained with different molecular systems exhibiting low friction are presented. A water-soluble, PEG containing co-polymer architecture was used to construct a water-based lubrication system. A high-resolution measurement of the compression isotherm revealed film-thickness transitions under confinement that are due to a water-induced restriction of the conformational space of PEG. These findings are in accord with known solution properties of this polymer. The friction is found to be vanishingly small in a dilute aqueous solution of this co-polymer. Using an alternative approach, the active control of static and dynamic friction was demonstrated using sub-nanometer mechanical oscillations across a nanometer thick liquid layer. The dynamic frustration of molecular arrangements is responsible for this effect. Oscillations of just a few Angstrom are sufficient to reduce friction to a small fraction of the unperturbed system. Molecular film-thickness changes were monitored throughout the contact zone and the effect of the oscillations on the molecular dynamics was measured.
A New Technique for Contact Mechanics and Friction in Microstructures: Controllable Electrostatic Repulsive Forces From Capacitive Coupling to Electret
Authors: Kim Myongseob , Lee Chungho , Kan Edwin C.
Published: November 2008

The use of the electrostatically repulsive force from the capacitive coupling with electret polymer film is demonstrated experimentally. The repulsive forces can be utilized in controlling contact mechanics and friction in microstructures, and serve as an alternative MEMS actuation mechanism to overcome the limitations by the attractive forces. Simple parallel cantilever beams patterns are used to illustrate the magnitude of the repulsive forces and the associated static charge density from the electret polymer films coupling.
Vibrostability Peculiarities of Disk Brake in Automobile Anti-Lock Braking System
Authors: Pogosian A. K. , Bakhshyan A. O. , Tamrazov A. A.
Published: November 2008

On the basis of the automobile braking mathematical model describing brake pads oscillation process taking into account the influence of anti-lock braking system, disk brake vibrostability calculation method is worked out. As a result the algorithm of differential equations solving that describe the dynamics of automobile braking process is proposed. Considered model of braking dynamics establish interaction between braking and tire-road coupling moments. The calculations of disk brake vibrostability taking into consideration the impact of anti-lock braking system action are carried out.
Advances in Nonlinear Rotordynamics of Passenger Vehicle Turbochargers: A Virtual Laboratory Anchored to Test Data
Authors: San Andre´s Luis , Rivadeneira Juan Carlos , Gjika Kostandin , Chinta Murali , LaRue Gerry
Published: November 2008

Passenger vehicle turbochargers (TCs) offer increased IC engine power and efficiency. TCs operate at high rotational speeds and use engine oil in their bearing support system comprising of inner and outer lubricant films acting in series. The hydrodynamic bearings induce instabilities, i.e. subsynchronous shaft motions over wide operating speed ranges [1]. Yet, the motions are well bounded limit enabling the TC continuous operation [2, 3]. Due to the lack of accurate and efficient predictive nonlinear tools, turbocharger rotordynamic design followed, until recently, costly test stand iteration [3]. Presently, a rotordynamics model coupled to a bearing lubrication model calculates the nonlinear motions of TCs and delivers predictions of TC shaft dynamic response for practical conditions [4–6]. The software emulates a virtual laboratory, effectively aiding to design better TC products with increased reliability in a shorter cycle time. Predictions of the nonlinear model compare well with recorded TC shaft motions, both in amplitude and frequency content. The benchmarking lends credence to the validity of the integrated computational model.
A Theory of Cavitation in an Oscillatory Oil Squeeze Film
Authors: Sun D. C. , Zhang Zhiming , Wang Wen , Sun Meili , Chen Xiaoyang
Published: November 2008

The cavitation of oil films in bearings subjected to dynamic loads is not well understood. In order to compute reliably the performance of dynamically loaded bearings, it is important to know the underlying mechanisms of the cavitation phenomenon and be able to predict its occurrence and subsequent development. From previous studies (Sun and Brewe, 1992; Sun, Brewe and Abel, 1993) the following features of cavitation in submerged bearings (i.e. with no air entrainment) are known: (1) Cavitation is confined to one region, which contains residual oil filaments of the fractured film. (2) The pressure in the cavitation region is the vapor pressure of oil. (3) Tensile stress is present in the oil film outside the cavitation region. (4) The occurrence of cavitation requires not only a low pressure level but also some other condition. In this paper a new cavitation model is proposed, that incorporates the above features, considers the effect of surface tension, and preserves mass conservation in the cavitation region. The model is applied to an oscillatory oil squeeze film bounded between two parallel circular plates, a problem that has been extensively studied in the past (Hayes and Feiten, 1964; Rodrigues, 1970; Parkins and May-Miller, 1984; Boedo and Booker, 1995; Optasanu and Bonneau, 2000). New results derived from the model are presented and compared with those of previous studies.
Scaling and Shock Response of Small Form Factor Disk Drives
Authors: Xu Jianfeng , Talke Frank E.
Published: November 2008

The effect of miniaturization on the static and dynamic characteristics of hard disk drive suspensions and disks is investigated. Mechanical scaling of dimensions is discussed and the shock response of the head disk interface is evaluated as a function of the disk form factor.
Vortex-Tube Cooling for Tool Wear Reduction in A390 Dry Machining
Authors: Liu Jie , Chou Y. Kevin
Published: November 2008

This study investigated vortex-tube cooling for dry machining of hypereutectic silicon-aluminum alloys. Experiments and numerical analysis were employed to study vortex-tube cooling effects on tool wear and cutting temperatures. A390 alloy was machined by tungsten carbides with cutting forces and temperatures measured. Vortex-tube cooling was approximated as an impinging air jet to estimate heat convection coefficients that were then incorporated into the heat transfer analysis of cutting tool temperatures. The major findings include: (1) Vortex-tube cooling may reduce tool wear in A390 machining and the minimum temperature setting is more effective, (2) Cooling effects on tool wear also depend upon machining conditions, and (3) Tool temperature decrease due to vortex-tube cooling may indirectly result in tool wear reductions.
Nonlinear Modeling of Mechanical Gas Face Seal Systems Using Proper Orthogonal Decomposition
Authors: Zhang Haojiong , Miller Brad A. , Landers Robert G.
Published: November 2008

A nonlinear reduced-order modeling approach based on Proper Orthogonal Decomposition (POD) is utilized to develop an efficient low order model, based on ordinary differential equations, for mechanical gas face seal systems. An example of a coned mechanical gas face seal in a flexibly mounted stator configuration is presented. The axial mode is modeled, and simulation studies are conducted using different initial conditions and forcing inputs. The results agree well with a fully meshed finite difference model, while the resulting model order is significantly decreased.
The Future of Plasma-Based Surface Engineering Techniques in Tribology (Keynote)
Authors: Matthews Allan , Leyland Adrian
Published: November 2008

Over the past twenty years or so, there have been major steps forward both in the understanding of tribological mechanisms and in the development of new coating and treatment techniques to better “engineer” surfaces to achieve reductions in wear and friction. Particularly in the coatings tribology field, improved techniques and theories which enable us to study and understand the mechanisms occurring at the “nano”, “micro” and “macro” scale have allowed considerable progress to be made in (for example) understanding contact mechanisms and the influence of “third bodies” [1–5]. Over the same period, we have seen the emergence of the discipline which we now call “Surface Engineering”, by which, ideally, a bulk material (the ‘substrate’) and a coating are combined in a way that provides a cost-effective performance enhancement of which neither would be capable without the presence of the other. It is probably fair to say that the emergence and recognition of Surface Engineering as a field in its own right has been driven largely by the availability of “plasma”-based coating and treatment processes, which can provide surface properties which were previously unachievable. In particular, plasma-assisted (PA) physical vapour deposition (PVD) techniques, allowing wear-resistant ceramic thin films such as titanium nitride (TiN) to be deposited on a wide range of industrial tooling, gave a step-change in industrial productivity and manufactured product quality, and caught the attention of engineers due to the remarkable cost savings and performance improvements obtained. Subsequently, so-called 2nd- and 3rd-generation ceramic coatings (with multilayered or nanocomposite structures) have recently been developed [6–9], to further extend tool performance — the objective typically being to increase coating hardness further, or extend hardness capabilities to higher temperatures.
Nano/Micro-Rheology of Perfluoropolyether Lubricants
Authors: Choi Hyoung J. , Guo Qian , Chung Pil Seung , Jhon Myung S.
Published: November 2008

The bulk rheological properties, such as shear viscosity and storage & loss moduli of perfluoropolyether (PFPE) with different molecular weights and endgroup functionalities were examined via a rotational rheometer. Equilibrium and non-equilibrium molecular dynamics simulations were performed to provide a molecular visualization tool to clearly understand the intrinsic nanostructure as well as to predict the bulk shear viscosity, which reveals a strong dependence on temperature and PFPE molecular architecture.
Investigation of Tribological Properties of Slide Bearing (PA 6-15% PTFE1100)
Authors: Anh Tuan Nguyen , Lien Quach Dinh , Khang Le Ba
Published: November 2008

In this paper, the tribology behavior and deformation of slide bearing made from polymer material (PA 6-15% PTFE) are investigated. Different parameters as sliding speed, load, material capacity ect. have influence on wear, friction coefficient and deformation of the bearing. The wear of bearing are determined and analyzed.
A Methodology to Reduce the Wafer to Wafer Thickness Variation in Chemical Mechanical Planarization (CMP)
Authors: Wang Sim Kit , Butler David Lee
Published: November 2008

The requirement to consistently achieve the specific target mean film thickness within a tight tolerance (± 80nm) in the IC fabrication process flow is a great challenge. In general, except process time, all other process parameters such as applied pressure, both carrier and platen velocity, slurry flow rate and pad conditioning duration are kept constant in a typical process recipe so as to reduce the source of variations. This paper describes a methodology that can be implemented with or without the end point detection system to predict the optimal process time for CMP based on the hypothesis of contact mechanics. It captures the variation of incoming wafer thickness, material removal rate and erratic behavior of the process. It cal also serve as a comprehensive framework for better recipe development. Experimental work shows that this approach demonstrates promising results in reducing the target mean film thickness variation and works well with different layers and devices.
The Influence of Tropical Climate-Changing Humidity, Temperature Conditions on the Wear of Some Materials: Steel, Cast-Iron and Their Brush-Plating Coatings
Authors: Anh Tuan Nguyen , Van Hung Pham , Duc Bao Le , Khanh Du Dao , Tuan Phuong Nguyen , Le Thuong-Hien
Published: November 2008

The influence of tropical climate with changing humidity and temperature on the tribological parameters of steel, cast-iron and their brush-plating coatings are investigated. The polluted compositions of environment are also the important factors. The results of experimental investigation on the influence of tropical climate are presented.
Experimental Investigation of Cavitation in an Oil Squeeze Film Subjected to Displacement-Controlled Oscillations
Authors: Sun Meili , Chen Xiaoyang , Wang Wen , Meng Kai , Sun D. C. , Zhang Zhiming
Published: November 2008

To establish quantitative relationships among various parameters in the squeeze oil film between parallel plates, including the displacement and pressure traces and the time-varying cavitation patterns, and excluding the influence of irrelevant factors as far as possible, a special displacement-controlled test apparatus was designed. Experiments were carried out under various frequencies and amplitudes.
Journal Bearings Stability With Consideration of Fluid Inertia
Authors: Javorova Juliana G. , Alexandrov Vassil , Stanulov Kiril , Tzvetkof Tzveti
Published: November 2008

In the analysis of HD journal bearings the effect of fluid inertia is generally neglected in view of its negligible contribution compared with viscous forces. However, there is a necessity to evaluate its influence at moderate values of the modified Reynolds number. An attempt is made to study the effect of inertia forces of the lubricant on the stability of finite journal bearing for a flow in a laminar regime. Furthermore, the stability analysis is extended to bearing with elastic layer on the shaft. In this way a complex solution of the problem is achieved with consideration of the shaft motion, instigated from the unbalanced HD forces of lubricant. The generalized Reynolds equation is obtained by averaged acceleration method. To solve the elastic part of the problem without linear approximations, a new, more precise method of displacements determination is used. In present study modified stability criteria by Hurwitz and Ljapunov are introduced. An adaptive procedure for determination of critical stability of the considered dynamic system is used.
Finite Element Analysis of Ceramic Coating Systems Under Spherical Indentation With Metallic Interlayer: Part I — Uncracked Coatings
Authors: Le Minh-Quy , Yi Jin-Woo , Kim Seock-Sam
Published: November 2008

Spherical indentation problems of ceramic coatings/metallic inter-layer/ductile substrate were investigated numerically by axisymmetric finite element analysis (FEA) for two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel. Various indenter radius-coating thickness ratios and interlayer thickness-coating thickness ratios were used in the modeling. Radial stress distribution and plastic damage zones evolution were discussed in connection with model parameters. The results showed that the suitable metallic interlayer could improve resistance of ceramic coating systems through reducing the peak tensile radial stress on the surface and interface of ceramic coatings and plastic damage zone size in the substrate under spherical indentation.
Determining the Roughness of Contact Surfaces of the Rolling Bearings by the Method of Shock Pulses
Authors: Pozhidaeva Vyara
Published: November 2008

One of the most effective methods for bearing diagnostics is the method of shock pulses. The fixed pulse levels for specific type of bearings and a specific working position are in corresponds with the parameters, characterizing the resource of the bearing. Roughness is one of those parameters. Adaptation and application of that method to slow-revolutionary large rolling bearings of wheel excavators, spreaders and belt conveyers is commented in the paper. A diagnostic system for control directed towards repair is worked out as a result of the adaptation of standard diagnostic approach for application to non-standard (from a vibrodiagnostics point of view) bearing nodes of mechanization at the bulgarian open-pit mine “Maritza-East Mine” Ltd. In Bulgaria.
Aspects of the Rheology of Chemistry of Fresh and Used Engine Oils
Authors: Selby Theodore W.
Published: November 2008

The successful lubrication of the modern engine is essentially dependent on application of present knowledge of a number of interactive physical and chemical factors associated with the choice of base oils, mixture of additives, and the manner in which these components of the lubricant affect both the engine and the environment in which the engine is used. This paper will consider some of these aspects.
Scale Effects on Contact Deformation of Elastic-Plastic Solids
Authors: Komvopoulos K.
Published: November 2008

Surface roughness effects result in asperity contacts spanning a wide range of length scales. In view of the multi-scale roughness of real surfaces, contact deformation of solid bodies exhibits strong scale dependence. Therefore, it is essential that contact mechanics analyses account for the evolution of deformation over a range of length scales, similar to that of the wavelengths comprising the topographies of the interacting surfaces. Results from finite element method (FEM) and molecular dynamics (MD) analyses based on continuum and discrete models of the interacting solids, respectively, reveal important effects of topography, length parameters (e.g., indenter tip radius, coating thickness, and penetration depth), surface traction, and elastic-plastic material properties on the deformation behavior at different length scales.
Computer Program Development Predicting Engine Oil Consumption
Authors: Chun Sang Myung
Published: November 2008

The oil consumption and blow-by gas through piston-cylinder-ring crevices have to be minimized. Meanwhile, the friction losses in the piston ring pack need to be reduced in order to improve fuel economy and engine performance. In these two aspects, study on the optimized design of the piston ring pack has to be carried out. The amounts of oil consumption and blow-by gas are important factors to decide whether an engine is operating under good conditions or not during engine development and engine life cycle. The purpose of this study is to develop a computer program predicting engine oil consumption and blow-by gas by calculating the amount of oil flowing into the combustion chamber and gas flow down to the crankcase through the piston ring pack. Using this program, the condition of an engine can be predicted in advance.
Study on Lubrication Properties of Carboxymethyl Cellulose as a Novel Additive in Water-Based Stock
Authors: Guan Wenchao , Ke Gang , Tang Changyu , Liu Yifeng
Published: November 2008

This paper reports cellulose derivative—carboxymethyl cellulose (CMC) as a novel additive in a water-based stock (water content above 95 wt.%). Cellulose is one of the richest renewable resources on earth and has many peculiar qualities. Several cellulose derivatives such as CMC can easily dissolve in water and form stable thin film on the surface of metal. Several apparatus involving four-ball machine were used to investigate lubrication properties of the based stock containing CMC. The worn surfaces were observed with a scanning electron microscope. As the results, the anti-wear ability of the base stock is effectively increased by addition of a small amount (0.7 wt.%) of CMC. The additive with peculiar molecular structure contributes to abate the adhesion and scuffing of frictional pair effectively, hence improves the antiwear ability of the base stock. Thus CMC provides a potential application in the field of water-based stock lubrication.
Experimental and Theoretical Evaluation of Simultaneous Piston Assembly, Valve Train and Engine Bearing Friction in a Fired Engine
Authors: Mufti Riaz A. , Priest Martin
Published: November 2008

Engineers are constantly challenged to develop advanced products to meet more demanding emissions and fuel economy targets. In the past 20 years the automotive industry has greatly improved vehicle fuel efficiency by detailed engine component design improvement and formulating compatible lubricants, heavily relying on the computer based analytical tools. The sophistication and other complexity of these tools are growing rapidly. It is therefore important that the models, on which these techniques are based, are validated and continually improved by experimental techniques. For validating a predictive friction model, very accurate friction force data is required. Truly representative results can only be obtained if experiments are undertaken on a real fired engine and the friction loss in each component is recorded. The main aim of this research work is to validate an engine friction mathematical model called FLAME (Friction and Lubrication Analysis Model for Engines), over a range of load, engine speeds and lubricant temperatures, using 0W20 lubricant. The model was developed in a separate study and comprises of three parts, addressing each of the main tribological components (piston assembly, valve train and engine bearings). The validation was carried out by characterising the frictional losses generated from the major tribological components of a real fired engine. This was achieved by experimentally determining simultaneously the power loss in each component of a single cylinder, four valve, Ricardo Hydra gasoline engine under fired conditions.
Pressure in Ultra Thin Perfluoropolyether Film
Authors: Kubota N. , Kobayashi A. , Mayeed M. S. , Kato T.
Published: November 2008

The density and pressure variations in the ultra thin liquid perfluoropolyether (PFPE) film (2nm) are carried out by Monte Carlo simulations of Lennard-Jones systems. First of all, the variations of density and pressure of ultra thin PFPE film that has a free surface on the flat substrate are carried out. The substrate is assumed to be continuous without atomic structure and exerting Lennard-Jones potential on liquid molecules in the ultra thin film. Next, the variations of density and pressure in the ultra thin PFPE liquid film between the two solids are examined. This is assumed to be due to the contact between the flying head and the PFPE film. From results of the 2500 steps calculation, it is clarified that the density distribution between two solids becomes symmetrical in shape and the pressure distributions concentrate on the substrate surface and the flying head surface do not occur in the liquid between the two surfaces.
Improving of Tribological Properties of Nanocomposites Sol-Gel Thin Films by Fluorocyclophosphazene Derivatives
Authors: Celichowski G. , Chrobak K.
Published: November 2008

Fluorocyclophospazenes’ derivatives were used as modifiers for improving tribological properties of thin films prepared by sol-gel technique. Thin films were made on the base of aminopropyltriethoxysilane (APTS). All films were deposited by dip-coating method and post-treated by heat, UV radiation and low pressure of RF plasma. Chemical changes in sol-gel films during all steps of post-treatments and modifications were monitored by FT-IR spectroscopy and SIMS spectrometry. Topographies of modified surfaces were imaged by Atomic Force Microscopy (AFM). After final modification significant improvements of frictional properties were observed as well as their very good thermal stability.
The Role of Tribofilm Evolution on Tribological Behaviour of Ti3SiC2 Ceramic
Authors: Souchet Alexandra , Fontaine Julien , Loubet Jean-Luc , Zahouani Hassan , Belin Michel , Barsoum Michel W.
Published: November 2008

The Ti3SiC2 compound is a thermodynamically stable nano-layered ternary carbide, that belongs to a family of over 50 ternary carbides and nitrides, so-called MAX phases. These phases are a new class of solids that possess a unique combination of properties: they are readily machinable, relatively soft for ceramics, but elastically stiff, and electrically and thermally conductive. However, only very few studies are dedicated to their tribological behavior. This paper presents some results on the tribological behavior of Ti3SiC2. During dry sliding on a Ti3SiC2 plane, a first regime of low friction and mild wear can be observed, with the build-up of a tribofilm on the counterface. Then, while in an apparently steady state, the tribological behavior suddenly turns to higher friction and severe wear of both counterfaces. Combining friction experiments and topographical observations of contacting surfaces during the first regime, we propose some explanations for such drastic transition in tribological behavior. While tribofilm thickness and roughness stabilize in the mild wear regime, the covering of the ball surface still increases. Thus, matter accumulation on the ball finally leads to seizure of the contact.
A Technique for the Detection of Liquid Slip at a Load-Bearing, High Shear Contact
Authors: Choo J. H. , Spikes H. A. , Ratoi M. , Glovnea R. P. , Forrest A.
Published: November 2008

This research aims to exploit the physical phenomenon of simple liquids slipping against very smooth solid surfaces, to create a new type of bearing where the lubricant slips against one surface but not the other. To demonstrate the feasibility of this idea, a special test rig capable of measuring milli-Newton forces has been employed to measure friction in high-speed, sliding contacts between a steel roller and sapphire window, lubricated by hexadecane. Sapphire was made either lyophobic by coating with a self-assembled silane monolayer, or lyophilic by O2-plasma cleaning. The roller was made lyophilic. A significant reduction in friction was achieved with lyophobic sapphire but not with lyophilic sapphire. This reduced friction is believed to result from lubricant slip against the lyophobic surface. One possible application of such a bearing will be in microsystems and devices.
The Role of Particle Motion in Abrasive and Erosive Wear
Authors: Hutchings I. M.
Published: November 2008

The traditional classification of abrasive wear into two-and three-body, high and low stress, open and closed etc. does not recognise the essential importance of particle motion, which is better described as either sliding or rolling. Abrasive wear tests with free abrasives can produce either type of motion, depending on the test conditions. The widely-used dry sand rubber wheel test often produces both motions over different areas of the sample. The more recent micro-scale abrasion test tends to favour one or the other over most of the wear scar area. Analytical models can be developed which allow the dominant particle motion to be predicted, and mapped using readily accessible parameters. In erosive wear, particle motion can also be important; recent work suggests that particle rotation is imparted in some types of erosive wear test, and that it may be responsible for the differences in wear rate found in tests under nominally identical conditions with different designs of apparatus. It is suggested that in the use of laboratory abrasion and erosion tests, and in the analysis of practical instances of wear by hard particles, close attention should be paid to the nature of particle motion, since this will influence both the dominant wear mechanisms and also the wear rates.
Formation Mechanisms of Tribo-Coating for Low Friction in UHV
Authors: Adachi Koshi , Sato Hisakazu , Kato Koji
Published: November 2008

Solid lubrication film formed by tribo-coating, which deposits a solid lubricant by evaporation to the contact interface during friction in vacuum, gives low friction coefficient below 0.03 that can not be observed by any other solid lubricants of soft metals. The tribo-coating film formed on the pin has nano-order composite structure which the crystalline indium of nano size are distributed in an amorphous matrix of silicon oxide and chromium oxide. Because of the nano composite structure, a very thin indium film is formed without break down like conventional pre-coated thin film. The thinner indium film can give smaller value of friction coefficient than that of conventional solid lubricant.