bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Influence of the Supply Pressure on the Dynamic Stability of Hybrid Gas Journal Wave Bearings
Authors: Dimofte Florin , Cioc Sorin , Handschuh Robert F. , Fleming David P.
Published: November 2008

Gas journal bearings are very sensitive to the hydrodynamic instability known as subsynchronous whirl motion, especially when they are unloaded. The wave bearing concept can improve the bearing stability, meaning that the wave bearing can run stably up to higher speeds than the plain bearing. In addition, when whirling motion occurs due to the fluid film instability, the orbit of this motion can be contained within the bearing clearance. Another step ahead for improving bearing stability is to pressurize the bearing. Tests were conducted to verify the threshold of subsynchronous whirl motion of bearings with a 35 mm diameter and 30 mm length. Pressurized air is admitted to the bearings through inherent compensated holes located in two planes along the bearing length. Various numbers of holes and diameters were used. The tests were conducted at speeds up to 30,000 rpm and the supply pressure was varied from zero to 0.14 MPa. The pressure was measured within a 2% precision. Two values for the wave amplitude to bearing clearance ratio were used. Pressurizing the bearing with 0.14 MPa can make the bearing run stably up to a speed of 20,000 rpm, unlike an unpressurized bearing that can experience subsynchronous motion at speeds less than 1,000 rpm. It was found that the supply pressure has a strong stabilizing effect. As a general rule, a 10% change of the value of the supply pressure can modify the stability threshold speed with more than 1000 rpm.
Effects of Bubble on the Viscosity Properties of Lubricant
Authors: Ng W. S. , Levesley M. C. , Priest M.
Published: November 2008

Air ingestion and entrapment is prevalent in the lubricant circulating around internal combustion engine and can lead to formation of two-phase flow system referred to as bubbly oil which affecting the oil viscosity and overall damping capability. Experimental work is conducted to study the effective viscosity of bubbly oil in a simple shear rheometer with the aim of gaining a general understanding of the two-phase mixture flow and developing lubrication models to be used in subsequent analysis. A laboratory simulator is used to produce bubbly oil by controlling the system pressure, temperature, and gas content entrained from atmosphere and an enclosed rheometer is employed to measure the mixture viscosity. A new detailed design is incorporated into the commercial rheometer with the purpose of maintaining the distribution of bubbles within the lubricant. The transparent test chamber is initially pressurized with air to control the bubbly oil level and the bubbly oil viscosity is tested over a wide range of shear rates. Under shearing motion, the viscosity of bubbly oil varies with time and the results obtained are compared to that of single-phase oil.
Poisson Ratio Effects on the Von Mises and Maximum Shear Stresses in Cylindrical Contacts
Authors: Green Itzhak
Published: November 2008

This work determines the location of the greatest elastic distress in cylindrical contacts based upon the distortion energy and the maximum shear stress theories. The ratios between the maximum pressure, the von Mises stress, and the maximum shear stress are determined and fitted by empirical formulations for a wide range of Poisson ratios, which represent material compressibility. Some similarities exist between cylindrical and spherical contacts, where for many metallic materials the maximum von Mises or shear stresses emerge beneath the surface. However, if any of the bodies in contact is excessively compressible the maximum von Mises stress appears at the surface. That transitional Poisson ratio is found. The critical force per unit length that causes yielding onset, along with its corresponding interference and half-width contact are derived.
On the Kinematics and Kinetics of Mechanical Seals, Rotors, and Wobbling Bodies
Authors: Green Itzhak
Published: November 2008

Mechanical seals, rotors, and wobbling bodies are characterized by a kinematical constraint that prevents them from having integral motion with respect to their own frame. A valid kinematical model is a prerequisite to subsequent dynamic analyses. Three previous works have suggested distinctly different kinematical models to the same problem. The analysis herein presents yet another kinematical model that preserves (actually enforces) the proper kinematical constraint. The outcome reaffirms one of the previous models. The equations of motion are derived using Lagrange’s equations to complement results obtained previously by Newton-Euler mechanics.
Experimental and Numerical Investigations of Vibration Signatures in Damaged Gear Systems
Authors: Choy Fred K. , Zhou Jianyou , Chen Hongliang
Published: November 2008

Current on-board condition monitoring systems for transmission systems often fail to provide sufficient time between warning and failure in order to implement the safety procedures. On the other hand, inaccurate interpretation of operational conditions may result in false alarms leading to unnecessary repairs and downtime. The early detection of incipient failure in a transmission system is of great practical importance as it permits scheduled inspections without costly shutdowns and indicates urgency and location for repair before any catastrophic failure occurred. The major objective of this paper is the numerical and experimental investigations of vibration signatures due to localized multiple teeth damages in a gear transmission system. Experimental results from a gear set with controllable damage are compared with those based on numerical simulations. General and specific conclusions are drawn based on the comparisons of the results.
Vibration Monitoring and Damage Quantification of Ball Bearings for Household Appliances
Authors: Choy F. K. , Konrad D. , Labus E. , Wu R.
Published: November 2008

The main objective of this paper is to determine the relationship between bearing vibration/noise and the amount of flaws existed in a ball bearing assembly. In this study, 30 “good” and 30 “bad” typical ball bearings used for transmissions in household appliances are used for experimental vibration testing and measurements of flaws. While the “good” bearings are obtained form the lot of bearings tested for acceptable noisy level and the “bad” bearings are obtained from the lot with high rejection level. Although some irregularities are found in the ball elements, but most of the flaws are found in the outer races of the “bad” bearings. The levels of the flaws are measured using micrometers and vibration levels of the bearings are obtained from the accelerometers attached to the bearing supports at the bearing test rig. Time domain, frequency domain, and chaotic vibration signatures for the bearing are examined to correlate with the levels of flaws in the outer races of the bearings. The results from the FFT spectra show that the average vibration amplitude of the “bad” bearing is about 5 times higher than those of the “good” bearings.
Studies of Machining Parameters of Al Alloy A-390 During Turning
Authors: Dhiman Suresh , Sehgal Rakesh , Sharma S. K.
Published: November 2008

Selection of any casting alloy is dependent on a wide variety of factors such as casting process, service requirement and economy of processing viz. weldability, castability and machinability. Out of these, machinability plays an important role in the selection of material for its commercial exploitation. In general, more than 80% of the manufactured parts are machined before they are ready for use. Thus machinability of a material controls significantly its economy in various applications. In this paper, machinabilty is evaluated by studying various data/parameters of Al alloy (A-390) such as cutting forces, tool tip interface temperature, surface finish and power consumption during turning at different cutting speed, depth of cut and feed rate. In this study, Al-Si alloys with different composition were subjected to machinability testing by varying the cutting speed, depth of cut and by keeping feed rate constant.
Effects of Asperity Shape on the Tribological Behaviour During Stamping of Zinc Coated Steel Sheets for Car Bodies
Authors: Ca´rcel A. C. , Rodilla M. E.
Published: November 2008

This work was initially focused to analyze the onset of systematic fractures of car body parts (Ford Focus model) during stamping. Fractures were attributed to unexpected high values of friction between the tools and the steel sheets. All the sheets that failed fulfilled the required standard mechanical properties and topographical surface requirements (Ra between 1.0 and 1.7 μm and peak count Pc >50 peaks/cm, according to the German SEP 1940 standard), and were processed with the same lubricant. A detailed study of the surface features showed that, having similar and correct values of the conventionally used parameters for surface texture requirements, such as Ra and peak count Pc, those sheets that failed had some different asperity features, related to the asperity peak shape. Experimental work (measurement of real values of surface contact Sc and friction behavior under boundary lubrication conditions) confirmed that these differences in the asperity shape have an important effect on the friction behavior, controlling the rate of surface roughness flattening and therefore determining the real values of surface contact area and the remaining valley areas able to carry lubricant. The differences in asperity shape were reproduced in single roughness models and the flattening process of the asperities was simulated by finite element analysis. The agreement between simulation and experimental observation was excellent. The influence of asperity shape was found to be very important, justifying the real differences found in the values of real surface in contact and hence in the friction behavior during stamping real car body parts.
Variations of a Ni-P Surface Layer After Nanoparticle Impacts
Authors: Xu J. , Luo J. B. , Pan G. S. , Zhang W. , Lu X. C.
Published: November 2008

In CMP, erosive wear regarded as one of the wear mechanisms underlying the interaction between the abrasive particles and polished surfaces can occur when materials are removed from surface collision of particles which are carried by a fluid medium. In this paper, the microscopic examination of the NiP coatings after nanoparticle impacts is performed. The experimental results indicate that craters and scratches can be observed in the surface after nanoparticle impacts, and crystal grains in nano-scale and element phosphorus concentration can be found in the sub-surface layer of the impacted surface.
Optimizing Coated Contacts by 3D FEM Stress Modelling and Fracture Toughness Determination (Keynote)
Authors: Holmberg K. , Laukkanen A. , Ronkainen H. , Wallin K. , Koskinen J.
Published: November 2008

A general approach to controlling and modelling friction and wear in sliding contacts with coated surfaces is presented. The tribological aspects of the main material parameters, elasticity, plasticity and fracture are discussed. The contact condition with a rigid sphere sliding over a steel plate coated with a very thin hard coating is analyzed. The dominant parameters for friction and wear performance are identified and the appropriate material parameters needed for controlling the tribological contact is proposed. A Three Dimensional Finite Element Method (3D FEM) model has been developed for calculating both the first principal stress distribution and real stress components in the scratch tester contact of a diamond spherical tip moving with increased load on a titanium nitride (TiN) coated steel surface. The three dimensional model is comprehensive in that sense that it considers elastic, plastic and fracture behaviour of the contacting surfaces. Three main regions of stress concentration during the scratching action are identified and shown by simulated stress animations. The loading mechanisms and the stress development in each of these regions are described. The first cracks to occur on the surface of a steel plate coated with a 2 micrometer thick TiN coating sliding against a spherical diamond tip are shown. They are in an angular direction to the formed contact groove at the side edge of the groove due to the two directional high stresses in the side-stress region. This corresponds to empirical observations. By identifying from a scratch experiment the location of the first crack and using this as input data can the fracture toughness of the coating be determined. The influence of the coating thickness and elastic modulus on the stresses and strains generated during the sliding process is demonstrated.
Numerical Modeling of Surface Temperature Rising on Imperfect Sliding Electrical Contact
Authors: Kim Wan-Sik , Liu Shuangbiao , Wang Q. Jane , Asta Mark , Cheng Herbert S.
Published: November 2008

This paper describes a model for numerical prediction of surface temperature rising due to frictional and electrical Joule heating between rough surfaces with discrete and continuous convolution fast Fourier transform (DC-FFT and CC-FFT). Contact resistance in non-conformal rough contact is defined and also surface temperature is simulated with frictional and Joule heating components of heat fluxes in rough surface contact. The computational prediction of temperature rising of sliding rough surface contact with electrical current may facilitate the understanding of imperfect electrical contact (ImPEC) and extreme condition lubrication.
Abasiveness of Boron Carbide (B4C) Coatings
Authors: Siniawski Matthew , Wang Jane , Harris Stephen J.
Published: November 2008

Hard coatings, such as boron carbide (B4C), can quickly polish the surface of the mating material during sliding contact. The abrasiveness of such coatings directly relates to their ability to polish and sharply decreases as sliding progresses. The abrasiveness also strongly depends upon the sharpness of the individual coating asperities. Various parameters influence the rate at which the abrasiveness decreases and therefore control the run-in process. Such coatings can serve as finite-life run-in coatings for specific applications such as gears.
Micro-Abrasion-Corrosion Mapping of Bio-Materials: Some New Perspectives
Authors: Stack M. M. , Rodling J. , Mathew M. T.
Published: November 2008

Recent developments in the studies of micro-abrasion have resulted in the construction of mechanistic maps where the change in micro-abrasion is presented as a function of the main tribological parameters. However, in many practical situations where micro-abrasion occurs, the environment tends to be corrosive. In such cases, the interaction of micro-abrasion and corrosion is of interest because the combined interaction may lead to “synergistic” or “antagonistic” effects, where corrosion may have a deleterious or beneficial effect in modifying the mechanical properties of the surface. In this paper, the micro-abrasion of a Co-Cr specimen against an ultra high molecular weight polyethylene (UHMWPE) ball was studied in Ringers solution. The effects of applied load at a range of electrochemical potentials were investigated. Atomic force and scanning electron microscopy techniques were used to identify the extent of wear and the role of the corrosion film on the micro-abrasion rate enabling the various wear, corrosion and the interactive effects to be evaluated for the system. The results showed that various micro-abrasion-corrosion mechanisms could be identified in active and passive conditions. These were used to generate micro-abrasion-corrosion mechanism maps showing the change in mechanism as functions of load and applied potential and the extent of interaction between the wear and the corrosion processes was demonstrated on such maps. Possible uses of the generic form of these maps to identify micro-abrasion-corrosion mechanisms in other bio-medical applications are addressed in this paper.
HDD Slider Air Bearing Design Optimization Using a Surrogate Model
Authors: Tsuda Naozumi , Bogy David B.
Published: November 2008

This report addresses a new optimization method in which the DIRECT algorithm is used in conjunction with a surrogate model. The DIRECT algorithm itself can find the global optimum with a high convergence rate. However the convergence rate can be much improved by coupling DIRECT with a surrogate model. The surrogate model known as the Kriging model is used in this research. It is determined by using sampling points generated by the DIRECT algorithm. This model expresses the shape of a hyper surface approximation of the cost function over the entire search space. Finding the optimum point on this hyper surface is very fast because it is not necessary to solve the time consuming air bearing equations. By using this optimum candidate as one of the DIRECT sampling points, we can eliminate many cost function evaluations. To illustrate the power of this approach we first present some simple optimization examples using known difficult functions. Then we determine the optimum design of a slider with 5nm flying height (FH) starting with a design that has a 7nm FH.
Shear Cavitation
Authors: Kottke P. A. , Bair S. , Winer W. O.
Published: November 2008

The importance of cavitation in lubrication hydrodynamics is well recognized. Cavitation can also act as a source of experimental error in rheological measurements. Therefore, the ability to understand and predict cavitation is important for tribology. Nearly all models for cavitation prediction are based on the local hydrodynamic pressure. The appropriateness of this approach when viscous stresses are of the order of the hydrodynamic pressure is questionable. One cavitation model that considers the state of stress in a flowing liquid is the principal normal stress cavitation criterion (PNSCC), which proposes that cavitation will occur when the most tensile principal normal stress exceeds some critical value. Although this hypothesis can accommodate many experimental observations, its theoretical foundations are weak. In particular, it fails to account for the tensile strength of liquids and resulting need for nucleation sites; it neglects the role of transport of dissolved gases; and it does not consider the effect of a growing bubble on the local flow, and hence local state of stress. We demonstrate cavitation in low Reynolds number Couette flow, and present a model for cavitation in shear in the limit of creeping (Stokes) flow, which corrects for the theoretical failures of the PNSCC. We use numerical simulation to analyze cavitation onset, and obtain a more general cavitation criteria from which the PNSCC is recovered under certain conditions.
Lobatto Point Quadrature for Thermal Lubrication Problems Involving Compressible Lubricants
Authors: Moraru L. , Keith T. G.
Published: November 2008

Refined solutions of thermal lubrication problems generally require fine mesh and many iteration steps. To resolve these difficulties, Elrod and Brewe (1) proposed an efficient algorithm based on the use of Lobatto point quadrature. Within this approach, the unknown temperature across the film is written in a series of Legendre polynomials. This paper presents a Lobatto point quadrature algorithm which is applicable for thermal lubrication problems with compressible lubricants. In this case both density and viscosity of the lubricant are taken to be temperature and pressure dependent. The transverse velocity is obtained from the continuity equation. Use of the Labatto point calculation method has resulted in greater accuracy without the use of a large number of grid points.
Adhesive Contact of Bodies Having an Elliptical Contact Area
Authors: Johnson K. L. , Greenwood J. A.
Published: November 2008

The so-called JKR theory of adhesion between elastic spheres in contact (Johnson, Kendall & Roberts 1971, Sperling 1964) has been widely used in micro-tribology. In this paper the theory is extended to solids of general shape and curvature. It is assumed that the area of contact is elliptical which turns out to be approximately true, though the eccentricity is different from that for non-adhesive contact. Closed form expressions are found for the variation with load of contact radius and displacement, as a function of the ratio of principal relative curvatures of the two bodies in contact. The pull-off force is found to decrease with increasing eccentricity from its value of 3πΔγR/2 in the case of contact of spheres of radius R.
Overview and Future Trends of Manufacturing Lubrication and Conditioning Monitoring Technologies (Keynote)
Authors: Tung Simon C. , Paxton Charles , Liang Fenggang
Published: November 2008

The longevity of component and fluid life can be greatly extended by controlling, within acceptable limits, root-cause aberrations. In fluid lubricated systems, the stability of a basic lubrication program and a vehicle for prediction of potential root-causes of failure must be considered and incorporated in the equipment design process. Condition monitoring and proactive maintenance are critical tools for achieving significant improvement in tribological performance of mechanical components and extended lubricant life.
Investigation of Tribological Mechanism of Near Dry Machining (NDM)
Authors: Fujimura Satoshi , Inasaki Ichiro , Min Sangkee , Wakabayashi Toshiaki , Suda Satoshi
Published: November 2008

This paper describes tribological mechanism of Near Dry Machining (NDM). Two special setups to understand Tribological mechanism of near dry machining are designed. One is mainly to measure the behavior of some fed gases in controlled atmosphere. The other is to make sure the effectiveness of gasses like oxygen or nitrogen, and that of lubricants. As a result, oxygen has a very important roll in lubrication when steel is cut.
Numerical Simulations for Friction Induced Vibrations Considering Temperature-Dependence Effect
Authors: Nagata Yusaku , Suzuki Kenichi , Kumemura Yoichi , Nagasaka Mitsuhiro , Yamamoto Takashi , Hirayama Osamu
Published: November 2008

A two-dimensional friction induced vibration model taking the effects of change of material properties due to the temperature rise of a brake-pad into consideration is introduced in order to explain the experimental behavior of a brake pad and rotating disk system. Numerical simulations based on this model are conducted and results such that before the onset of the large amplitude vibrations it takes some minutes after the beginning of the contact was obtained, which is consistent with those of experiments.
A Very Effective Stabilizer for Perfluoropolyether Lubricants
Authors: Maccone P. , Boccaletti G. , Petricci S. , Radice S.
Published: November 2008

A new stabilizer for fluorinated lubricants, either oils or greases, was developed stemming from the chemistry of perfluoropolyethers. The additive shows good efficiency in improving the stability of perfluoropolyether oils at very high temperatures in presence of metals and under oxidative environments, extending thus the life of the formulated lubricants. Some specific tests were carried out in order to assess performances in applications. Furthermore, as a first approach, grazing infrared reflection-absorption spectroscopy was used as a probe for studying structural and topological issues relative to additive-surface interactions.
Friction-Induced Change of Boron Hybridization in Lubricant Additives
Authors: Philippon D. , De Barros M. I. , Le Mogne Th. , Martin J. M. , Kasrai M.
Published: November 2008

Tribochemical interactions between antiwear zinc dithiophosphate (Zndtp), friction modifier molybdenum dithiocarbamate (Modtc) and overbased detergent calcium borate (OCB) lubricant additives have been investigated. A Cameron-Plint friction machine was used to generate large tribofilm areas in mild tribological conditions. Two analytical techniques, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure spectroscopy (XANES), have been employed to characterize the chemical species in tribofilms. XANES spectroscopy at the P K and L-edges, S K-edge, Mo L and M-edges and B K-edge was carried out in order to investigate phosphate, sulfide and borate species in tribofilms. The XANES spectra were recorded in both the total electron yield (TEY), surface sensitive and fluorescent yield (FY), bulk sensitive mode. This was completed with XPS analyses in the same location in the tribofilm. The ternary system Zndtp + Modtc + OCB provides a low wear rate comparable to the binary system Modtc + OCB. XANES analyses have shown that adding OCB to the binary system Zndtp + Modtc increases the formation of MoS2 and reduce the formation of ZnS. It has been seen that few quantity of boron is consumed during the tests, meaning that boron does not react with other additives, we only observe a formation of calcium phosphate. A special attention has been paid on the hybridization of boron (trigonal sp2 and tetrahedral sp3). All tribofilms show a higher proportion of trigonal borate than the additives alone. However, this proportion is the highest in the case of tribofilms produce with the ternary mixture OCB + Zndtp + Modtc. Borate has a planar conformation and could be friction-oriented in the sliding interface. The oriented borate planar molecule might be at the origin of the MoS2 sheets orientation in the ternary system.
A Novel Test Method to Measure the Fracture Toughness of Ceramic Balls Used in Bearings
Authors: O’Brien Michael
Published: November 2008

A novel mechanical test has been developed to measure the fracture toughness of the silicon-nitride balls used in modern hybrid bearings important for many defense, space and industrial applications. The ball is compressed diametrally between two hemispherical conforming dies, which causes the ball’s equator to bulge, generating a tensile hoop stress. Under applied load, a precrack placed at the equator grows. To calculate the ball’s fracture toughness at crack instability, finite element calculations of the applied stress field and an analytical solution for the stress intensity factor are used in the “two point plus semiellipse” method. The new technique appears more accurate than the indentation technique used to measure the toughness of ceramics.
Investigation on the Wear of Well-Tubing in the Oil Exploitation
Authors: Xuan Vu Hoang , Anh Tuan Nguyen
Published: November 2008

In this paper, the results of investigation of wear of well-tubing with the sea depth from 3000 to 5000 meters are presented. The theory of erosion for tubing is established basing on the flow of exploited products and the principles of erosion and corrosion, for calculating the wear of thickness of tubing and the influence of environment and exploited oil products flow (pressure, velocity, temperature etc.). The long-life of tubing is determined for the maintenance service. Various proposals for increasing effectiveness of tubing exploitation are presented as materials changing, manufacturing, improving etc.
The Behavior of Tribological Characteristics of Diesel Crank-Shaft Bearing
Authors: Le Thuong Hien , Ho Phan Manh , Anh Tuan Nguyen , Kim Seock Sam , Van Hung Pham , Phuong Nguyen Tuan
Published: November 2008

In this paper, the various methods of wear and lubrication calculation for crankshaft sliding bearing are presented basing on the solution of dynamic problem for hydrodynamic equation of lubrication and wear. The concrete parameters as lubricant film thickness, eccentricity, pressure and velocity distribution, friction coefficient and wear intensity are determined. The proposals of concrete parameters of bearing are discussed.
Temperature-Dependent Tribological Improvements in Low-Energy Nitrogen Ion Implanted Vanadium-Titanium Alloys
Authors: Ballesteros C. , Garci´a J. A. , Orti´z M. I. , Rodri´guez R. , Varela M.
Published: November 2008

A detailed tribological characterization of low-energy, nitrogen implanted V5 at. %Ti alloy is presented. Samples were nitrogen-implanted at an accelerating voltage of 1.2 kV and 1 mA/cm2, up to a dose of 1E19 ions/cm2. The tribological properties of the alloys: microhardness, friction coefficient and wear resistance, have improved after ion implantation and this improvement increases as the implantation temperature increases. The microstructure of the alloys were analysed by transmission electron microscopy. A direct correlation between structural modifications of the nitrogen implanted layer and the improvement in their tribological properties is obtained. For samples implanted at 848 K a nanocomposite layer where the reinforcement particles are TiN precipitates forms. TiN precipitation appears as the responsible of the improvement in the tribological properties.
Bionic Lubrication System of Artificial Joints: System Design and Mechanics Simulation
Authors: Su S. H. , Zhang J. H. , Tao D. H.
Published: November 2008

A new structure of artificial joints with bionic joint capsule was proposed and designed to overcome the feedback of current prostheses that omitted many functions of lubricant and joint capsule. The new structure was composed of three components: therapeutic lubricant, artificial joints and artificial joint capsule. The lubricant sealed by capsule not only can reduce the wear of artificial joints but also can prohibit the wear particles leaking to the body liquid. So the unwilling reactions between the wear particles and liquid may be avoided completely. Meanwhile, a three-dimensional (3-D) finite element analysis (FEA) model was created for the bionic artificial joints with joint capsule. The effects of capsule thickness and the flexion angels on the stress values and distributions were discussed in detail.
Study of Relationship Between Structure of the Organic Aliphatic Acid and Rust-Inhibiting and Tribological Behavior in the Water-Based Cutting Fluid
Authors: Jiang Haizhen , Tao Dehua , Wang Bin
Published: November 2008

Effect of chemical structure of the aliphatic acid on rust-inhibiting properties and tribological behaviors of the water-based cutting fluid was studied in systematically. It was obtained that (1) the rust-inhibiting property became better with increase of the length of alkyl-chain of the aliphatic acid salts of triethanolamine. (2) The rust-inhibiting property of the aliphatic binary acid triethanolamine salts was better than that of the aliphatic monoacid triethanolamine salts. But the tribological behavior of the aliphatic monoacid triethanolamine salts was favor. Compared with base water, anti-wear and friction-reducing abilities of the soluble aliphatic acid triethanolamine salts would be improved greatly. (3) The adsorption and tribo-reaction films on the metal wear scar surface were monitored by auger energy spectrum.
Multi-Scale Study of Abrasion Signature by 2D Wavelet Decomposition
Authors: Zahouani H. , Mezghani S. , Vargiolu R. , Dursapt M.
Published: November 2008

The high performance of industrial applications, requires increasingly technical functional surfaces, particulary from the point of view of topography and microtexture. To study the effect of abrasive finishing in a wide range of wavelengths of surface topography, we developed a multi-scale approach, based on the decomposition of surface topography by 2D continuous wavelet transform. This new approach made it possible to determine the multi-scale transfer function of machining by abrasion for each stage of finishing. The methodology can be extended to characterize abrasive wear in a wide range of scales.
Acoustic Tribology of Human Skin
Authors: Zahouani H. , Flament F. , Vargiolu R. , Le Bot A. , Mavon A.
Published: November 2008

From the point of view of the tribology of the touch quality, when one speaks about softness of an object, one very easily associates it his roughness, the friction and the mechanical properties of materials [1,2,3]. With regard to the human skin, the stratum corneum (SC), or cornea layer, is the part of skin surface, which is permanently requested during a friction test. In this work, we present a new approach developed in our laboratory, in order to understand the friction mechanisms of the human skin, and to identify the acoustic, signatures which can be correlated with the touch quality. The results show that the acoustic emission is correlated the stiffness and roughness of the stratum coreneum. The application to the analysis of ageing, show clearly the increase of acoustic emission during ageing of human skin.
An Analysis of Hydraulic Fluid Wear Performance Discrimination Based on a Statistical Evaluation of a Standard Vane Pump Test
Authors: Dixon Richard T. , Clare Jamie , Wenham Maggie , Bakker Ronald
Published: November 2008

This paper discusses recent work at Shell Global Solutions’ laboratory to investigate the factors affecting vane pump test wear measurements made using mineral oil hydraulic fluids.
Some Tribological Aspects of the Duplex Coatings With Additional Ion Bombardment
Authors: Sˇkoric´ B. , Kakasˇ D. , Rakita M.
Published: November 2008

A duplex surface treatment involves the sequential application of two surface technologies to produce a surface composition with combined properties. A typical duplex process involves plasma nitriding and the coating treatment of steels. In the paper are presented characteristics of hard coatings, type TiN, produced by classic technology PVD (physical vapour deposition) and IBAD (ion beam assisted deposition). The synthesis of the TiN film by IBAD has been performed by irradiation of Ar ions. The evolution of the microstructure from porous and columnar grains to densel packed grains is accompanied by changes in mechanical and physical properties (1). Subsequent ion implantation was provided with N ions. Wear tests were carried out using a pin-on-ring geometry with no lubrication.. Varieties of analytic techniques were used for characterization, such as scratch test, calo test, SEM, XRD and EDAX. X-ray diffraction studies were undertaken in an attempt to determine the phases present, and perhaps an estimate of grain size from line broadening. The results were correlated with properties determined from mechanical and tribological characterisation.
Coupled Evolution of Load Distribution and Wear on Lead Screw Threads
Authors: Blanchet Thierry A.
Published: November 2008

To prescribe simulative contact pressures in benchtop wear tests on materials and lubricants for threads of lead screws, it is necessary to understand how applied load is distributed over those threads. While in threaded fasteners it is known that the first engaged nut thread carries the greatest load and experiences the highest contact pressure, in a lead screw application with considerable sliding this most heavily nut thread will correspondingly wear most rapidly. This suggests instead an eventually uniform steady-state load distribution over the nut threads that should be considered in arriving at a lower contact pressure for simulative wear testing. A model is therefore developed for this coupled evolution of thread load distribution and wear.
Thermo-Mechanical Deformation in Heat Sink Seal Rings
Authors: Stephens Lyndon Scott , Hayden Matthew A.
Published: November 2008

Heat sink mechanical seals use a heat exchanger built directly into the stationary seal ring to control the temperature at the seal interface. This paper presents the latest analytical and experimental results showing the thermal deformation of the heat sink seal at the sealing interface. The results show that the virgin interface contact pattern (before wear) is non-conformally convex with point contact towards the outer diameter. These results are discussed in relation to positive and negative coning that is found in conventional seal rings.
The Challenges of Sliding Wear
Authors: Rigney D. A.
Published: November 2008

The production of nanocrystalline wear debris containing components from the worn specimen, from the counterface and from the environment does not support any of the better known wear models or wear equations based on adhesion, delamination, fatigue or oxidation. In this presentation, plastic deformation, mechanical mixing and patterns of flow determined from experiments will be compared with molecular dynamics (MD) simulations and a continuum analysis of two ‘fluids’ shearing in opposite directions. Together, these suggest generic behavior that needs to be included in any realistic sliding wear model.
The Surface Buckling in Static and Dynamic Rough Contact of Solids
Authors: Riznychuk Roman V.
Published: November 2008

The contact buckling, caused by some rotation at the surface material due to mutual partial gripping of bodies during friction contact, with leads to the loss of stable state, is described. Material before such gripped spots takes the shape of buckle and its shear strain transforms into the compression strain. The rotation generated by the buckle propagates along the surface and causes further buckling. Such pattern is typical for loss of stable state of two elastic rough bodies under shear loading as a whole and it corresponds to the static friction coefficient.
Plasma-Enhanced Surface Modification of Biopolymers
Authors: Komvopoulos K.
Published: November 2008

Recent advances in polymer surface science have been largely due to the well-recognized need to control the surface properties of polymer materials and the development of sophisticated surface-specific characterization techniques. While the majority of the research and development efforts have been mostly focused on bulk properties, demands for low surface energy polymers exhibiting low adhesion (friction) and good biocompatibility have generated significant interest on physical and chemical properties of polymer surfaces. For instance, ultra-high molecular weight polyethylene (UHMWPE) and low-density polyethylene (LDPE) are the principal materials used to replace damaged cartilage in total joint arthroplasty and to fabricate catheters for balloon angioplasty, respectively. Therefore, surface treatments to improve adhesion and biocompatibility of these polymer surfaces are of paramount importance in the medical field. Radio frequency (rf) plasma-enhanced surface modification (PESM) provides an effective means for altering the biochemical properties of polymer surfaces without affecting the bulk behavior. The main process steps of PESM are discussed here and its effectiveness is demonstrated by representative friction coefficient, contact angle, and biocompatibility results for LDPE and UHMWPE surfaces treated with various plasma chemistries.
Chemical Mechanical Polishing Slurry for Tungsten in ULSI With Large Particle Size Colloidal Silica Nano-Abrasive
Authors: Zhang Kailiang , Song Zhitang , Feng Songlin
Published: November 2008

Silica sol nano-abrasives with large particle are prepared and characterized by TEM, PCS and Zeta potential in this paper. Results show that the silica sol nano-abrasives about 100nm are of higher stability (Zeta potential: −65mV) and narrow distribution of particle size. And then alkali CMP slurries for tungsten containing self-made silica sol nano-abrasives are prepared and applied. CMP results show that the removal rate has been improved to 367nm/min and the RMS of surface roughness has been reduced from 4.4nm to 0.80nm. In sum, one kind of alkali slurry containing 100nm silica sol for tungsten CMP is studied.
The Measurement of Component Friction Losses in a Fired Engine: Part 2 — Experimental Results
Authors: Mufti Riaz A. , Priest Martin
Published: November 2008

Bench testing can provide rapid and cost effective information for developing new lubricants. But there is general agreement that the only satisfactory means of evaluating the behaviour of engine oil is by actual use in engine. Also for detailed analysis of the tribological interaction it is important to analyse the engine performance at the component level. With the help of advance data acquisition system and sensor technology, experimental measurement of friction losses at the component level have been measured at realistic engine operating conditions, using the technique explained in Part 1. This paper describes the outcome of the experimental results at a range of engine operating conditions using mainly SAE 0W20 lubricant and some results from a friction-modified SAE 5W30 lubricant. The results clearly show considerable changes in the percentage contribution of power loss between low and high lubricant temperatures. The change in mode of lubricating regime from boundary to fluid film lubrication can be seen at the component level with increase in engine speed and decrease in lubricant temperature. This system can be used as a powerful tool for screening engine oils, analysing component design, validating friction models and studying the effect of different additives on the performance of each component under realistic operating conditions.
The Effect of Thin Lubricant Films on Acoustic Emission Characteristics
Authors: Taura Hiroo , Takaki Toshihiko , Kawaguchi Masahiro , Kaneko Satoru , Kato Takahisa
Published: November 2008

This paper shows the effect of ultrathin lubricant films between sliding bodies on Acoustic Emission (AE) signals induced by the sliding friction. Experiments were conducted with a ball-on-disk friction tester to measure the friction coefficient, the raw AE signals and the root-mean-squarevalues of the AE signals (the AErms signals). The ball was a glass ball of 5mm diameter. The disk was a magnetic disk used for 2.5 inch HDD with a DLC protective layer on its surface, and was coated with PFPE Z-dol 4000 about 1.5nm thick. The AErms signals kept a low level for some time after the start of the test, and then increased. Its time variation was similar to that of friction coefficient. After the friction test, the circumferential distribution of the lubricant film thickness was measured with an ellipsometer. The distribution demonstrated the reduction of the lubricant film thickness at the circumferential position where the magnitude of AE signals became large. These facts showed that the AE signals correlated well with the lubricant film thickness.
Evaluation of Rheological Properties of Magnetorheological Polishing Fluid and Their Effect on Surface Finish in Ultra Precision Finishing Processes
Authors: Jha Sunil , Jain V. K.
Published: November 2008

Magnetorheological finishing (MRF) process for automated lens finishing and Magnetorheological abrasive flow finishing (MRAFF) for internal geometries rely on unique smart behavior of MRP-fluid. The rheological properties of MRP-fluid depend on carbonyl iron particle (CIP) and silicon carbide (SiC) particle size, their volume concentration, magnetic properties and applied magnetic field strength. To study the effect of particle size on rheological properties of MRP-fluid, a hydraulically driven specially designed capillary rheometer is fabricated. The best surface finish improvement was obtained with MRP-fluid containing approximately equal diameter of abrasive particles and CIPs. Least improvement was noticed with smaller CIPs and bigger abrasive combinations used. This is because the smaller size CIPs are incapable of providing the necessary finishing forces for bigger abrasive particles, which results in weak bonding strength.
Study of Contact Bouncing Vibration of Flying Head Slider in Near-Contact Regime
Authors: Yamane Masami , Ono Kyosuke
Published: November 2008

We experimentally and analytically investigated detailed characteristics of the bouncing vibrations of a flying head slider in a near-contact regime. In the experiment, we found that the hysteresis of touch-down and take-off pressure and the rate of instability become small as the pitch angle increases. Moreover, we measured the 3-dimensional slider motion by using two laser Doppler vibrometers simultaneously and found that the bouncing vibration is a coupled vibration between translation and pitch with a small phase shift. These experimental features can be explained analytically if we consider strong shear force due to lubricant and small amount of microwaviness for the previous two-degrees of freedom slider model with nonlinear air bearing stiffness.
In-Cylinder Fuel and Lubricant Effects on Gasoline Engine Friction
Authors: Smith O. , Priest M. , Taylor R. I. , Price R. , Cantley A.
Published: November 2008

Reducing engine friction remains an important goal of the automotive industry. Reduced engine friction has been partly achieved by using low viscosity, friction modified lubricants, reducing the energy required to shear the fluid in the hydrodynamic lubrication regime (which is the primary lubrication mode in the piston assembly). It has long been understood that the piston ring / cylinder liner interface is responsible for a significant proportion of engine friction and can significantly influence the fuel consumption of an engine. This paper describes research conducted to develop understanding of both the interfacial relationship of the compression ring and cylinder liner and the synergistic relationship of fuel and lubricant at the top ring zone of a single cylinder gasoline engine. A portfolio of engine testing, laboratory work and computer simulation has been conducted.
KRL Thrust Bearing Rig: Effects of Test Conditions on Bearing Performance
Authors: Kernizan Carl F. , Cerda de Groote Carlos L. , Bartlett Melinda E.
Published: November 2008

This work explains and tests the relationship between tribological test conditions, grease rheology and the performance of grease lubricated tapered bearings. These conditions were simulated in a KRL thrust bearing rig, through six test sequences, which targeted the lubrication regimes depicted by the Stribeck-Hersey curve. Sequence completion, severity, grease type and loading determined bearing performance. The starved flow model together with grease rheology explained performance and matched a lubrication regime to each sequence. Grease type and loading are application dependent and are critical to meet performance and cost requirements.
The Effects of Static Frictions on the Drilling Process of Hammer-Drill System
Authors: Xu Y. , Yung K. L. , Ko S. M.
Published: November 2008

Static frictions are neglected in many dynamic analyses mainly due to inappropriate modeling of them. A new dynamic model describing the nonlinear and discrete features of static frictions is proposed in this paper. Using the new model, the drilling process of the hammer-drill system utilized in the EAS’ Mars mission is analyzed. It is shown that most important functions of the hammer-drill system are realized by static frictions, which were not observed before the introduction of the new model of static frictions. Static frictions provide the torsional force on the drill and make the normal impact happen before the rotation, which is critical to the efficiency of the cutting process of the hammer-drill system.
Experimental Investigation of the Design Parameters and of the Working Conditions on the Global Characteristics of a Squeeze Film Damper
Authors: Defaye Cyril , Carpentier Philippe , Debailleux Charles , Arghir Mihai¨ , Bonneau Olivier , Imbourg Fre´de´ric
Published: November 2008

Squeeze film dampers (SFD) is a topical subject since almost four decades [1, 2] but the need of experimental result is still stringent. The present work introduces the results of an experimental program aimed to investigate the influence of the design parameters and of the working conditions on the global characteristics of sealed SFD.
Soft EHL Lubrication of Complex Multiphase Fluids
Authors: de Vicente J. , Spikes H. A. , Stokes J. R.
Published: November 2008

The lubrication properties of a series of multiphase water-based fluids of complex rheology and microstructure, including o/w emulsions, have been studied in a rolling-sliding steel ball-on-elastomer flat contact. The results show that friction curves of Newtonian fluids made over a wide range of entrainment speeds and viscosity can be used to identify the prevailing mechanisms of lubrication for more complex fluids and, for emulsions, to show the predominant film-forming phase.