bluuebunny/crossref_metadata_2025 huggingface dataset:
A Second Generation Highly Crosslinked UHMWPE: Vitamin E Stabilization Does Not Adversely Affect the Wear Rate of Irradiated Acetabular Liners
Authors: Oral E. , Wannomae K. K. , Malhi A. S. , Christensen S. D. , Muratoglu O. K.
Published: November 2008

We developed a second generation highly cross-linked UHMWPE by doping and stabilizing irradiated UHMWPE with the antioxidant vitamin E. With this stabilization method, the crystallinity of the irradiated polyethylene is not decreased as with melting, and hence mechanical properties and fatigue strength can be preserved. Vitamin E-doped, irradiated second generation highly cross-linked UHMWPE showed wear comparable to and higher strength and fatigue resistance than that of 100-kGy irradiated and melted first generation highly cross-linked UHMWPE.
Numerical Simulation for Rough Contact Incorporating Plastic Deformation
Authors: Wang Fan , Keer Leon M.
Published: November 2008

An 3D elastic-plastic rough contact solution and code is developed using a modified semi-analytical method. It is supposed that the total surface deflection is induced by the contact pressure and plastic strain. The purely elastic contact and the influence of the plastic deformation are calculated iteratively until convergence is satisfied. The distributions of contact pressure, residual stress and plastic strain are obtained through simulation. The effects of roughness and plastic hardening upon the pressure distribution are discussed.
An Assessment of Statistical Theory of Contact Between Macroscopically Conforming Rough Surfaces
Authors: Farhang K. , Hua D. Y. , Wang P. , Li Y.
Published: November 2008

Most engineering surfaces possess topographies that are anisotropic. Some of the anisotropic surfaces are unintended result of machining process and others are by design for the purpose of lubricant retention or other considerations. Such is the case in problems involving piston liner and mechanical seal performance wherein the conformal contact of two rough surfaces is considered. It becomes critical to component performance to predict average contact pressure and gap between rough surfaces. Two of the well-known asperity-based statistical theories along with a deterministic method, based on Multi Level Multi Summation (MLMS) technique, are used to study the contact of nominally flat rough surfaces. The asperity-based statistical theories are GW model (Greenwood and Williamson, [1]), and its extension proposed by Chang, Bogy and Etsion [2], CEB model, for treating elastic-plastic contact. The contact examined is a set of nominally flat rough surfaces with a smooth flat. This study attempts to address two questions. The first concerns the effectiveness of asperity-based statistical theories in predicting average contact stress of rough surfaces with various degrees of topographic anisotropy. The second question involves the use of directional curvatures to ascertain the appropriateness of plane curvatures when degree of anisotropy is significant. To this end random surfaces are generated for five degrees of anisotropy including correlation length ratios 1, corresponding to an isotropic surface, and 3, 9, 36 and 81, corresponding to an increasing degree of geometric anisotropy. A module of Surface Distress Analytical Toolset (SDAT), for treating dry contact using deterministic approach with MLMS technique, is utilized to compute the contact pressure for these surfaces. This analysis constitutes ten surfaces for each correlation ratio resulting in fifty simulations of SDAT. For each correlation ratio statistical averages and variations of the maximum and mean contact pressures are found. Using the generated random surfaces, GW and CEB models are furnished with the parameters that include the standard deviation of summit height distribution, area summit density and six curvatures associated with asperity summit. These involve four directional curvatures that include curvatures along the x, y, positive diagonal, negative diagonal, and two equivalent curvatures, one based on spherical tip using average of the four diagonal curvatures and the other based on ellipsoidal asperity summit (Fig 1). The study suggests that GW and CEB typically overestimate average contact pressure. The mean pressures predicted using the largest directional summit curvature agrees most favorably with those predicted by SDAT. Surprisingly, agreement is most favorable for highest geometrical anisotropy. Both statistical methods seem effective in predicting mean gap between surfaces for moderate to low nominal pressures.
Improved Fatigue Life Cycle Using Surface Finish and Surface Coating in a Cam-Roller System: Multi-Scale System Analysis and Verification
Authors: Hua D. Y. , Farhang K. , Seitzman L. E.
Published: November 2008

Surface failure in the form of pitting wear is encountered in cam-roller systems. The failure appears to be initiated at micron-scale subsurface region. High stress is a result of the macro-scale requirement on the cam-roller motion event that produces high contact loads due to inertia of the roller and its follower link. Sliding of the roller and its impact onto the cam surface further compounds the detrimental effect of contact load. While conventionally a Hertz contact stress analysis can be used in ascertaining contact stress and maximum subsurface von Mises stress, it generally underestimates the stress when compared to the micron-scale subsurface stresses due to the presence of surface roughness. Contact analyses of cam and roller with rough surfaces are performed to examine the effects of two surface treatments. These involve surface finishing process in which a surface is rendered smooth, and the addition of a coating to the roller surface. Measurements of such cam and roller surfaces are used in micro-contact analysis module of Surface Distress Analytical Toolkit (SDAT) to examine the effect of surface finish and coating on maximum subsurface stress. It is found that smooth surface provides a 53% reduction in maximum subsurface stress. The analysis also shows that the addition of coating reduces subsurface stress nearly 7%. The impact of the combined treatment of the surface is an increase in fatigue life of the cam-roller system by nearly two orders of magnitude. The above findings are based on laboratory tests using six rollers without and with various degrees of finishing processes, and with and without addition of coating to the surfaces. Examination of the rollers indicates a general improvement in roller performance due to addition of coating. Most notably, the combination of finishing process and coating was found to provide the best fatigue life since the corresponding rollers showed no observable wear even after testing for 2161 hours, or the same number of cycles accumulated over about 500,000 truck miles.
Thickness and Processing Effects on the Composition and Actuating Force of Pb(Zr,Ti)O3 Thin-Film Micro-Actuator for Hard Disk Drives
Authors: Jing Yang , Luo Jianbin , Shao Tianmin
Published: November 2008

Sol-gel process associated with integrated circuit (IC) technique was used to fabricate Lead-zirconate-titanate (PZT) films with different thickness and process parameter on Pt/Ti/SiO2/Si substrates. Meanwhile, a new dual-stage actuator system including a piezoelectric micro-actuator and a voice coil motor for positioning a magnetic head for high-density hard disc devices (HDDs) have been designed, fabricated. Fig. 1 shows the structure illustration of the micro-actuator that consists of slider, “U”-type substrate and piezoelectric multilayer elements. The crystalline structure and growth behavior of the films with different thickness have been studied by X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The structure of piezoelectric element is as Pt/Ti/PZT/Pt/Ti multi-layer film.
A Micro-Tribotester for Evaluating Friction and Wear on Side Contacting Surfaces in Bulk-Microfabricated Devices
Authors: Guo Zhanshe , Meng Yonggang , Wu Hao , Su Caijun , Wen Shizhu
Published: November 2008

A micro-tribotester has been designed and fabricated to evaluate friction and wear on lateral contact surfaces of silicon materials. In the design of the tribotester, FEM analysis was used to find the resonant frequency and elastic displacement of the device under electrostatic excitations. The micro-tribotester was fabricated with a standard bulk silicon process. Static and dynamic friction tests were done on the fabricated device under various DC and AC stimulation conditions. From the measured maximum deflections of the detecting beams in the loading and sliding directions, static and dynamic friction coefficients of contacting sidewalls have been obtained. Characteristics of tribological behaviors in MEMS were discussed.
Study on the Wear of Wheel Flange/Rail Gauge Face
Authors: Jin Ying , Ishida Makoto
Published: November 2008

This paper describes the measured results of an actual worn rail, stress analysis of wheel/rail corresponding to a real contact, and laboratory test results of wear simulation. In the research the worn rail in sharp curved track was investigated through residual stress measurements and micrographic observation. The contact stresses of wheel/rail were estimated with a three-dimensional FEM elastic-plastic model to study the effect of applied loads and contact geometry on wear progress of wheel and rail. The experimental wear simulation by using a large rolling contact machine has been carried out to estimate the actual wear of wheel/rail, and clarify the influence of material hardness and contact geometry on wear of wheel flange/rail gauge face.
Performance Evaluation of DIRECT Algorithm in Parallel Optimization for a Thermohydrodynamic Lubrication Analysis
Authors: Tsai Chih-Ming , Wang Nenzi , Chang Yau-Zen
Published: November 2008

In this study the optimization is illustrated by maximizing the load-carrying capacity of a slider bearing represented by a thermohydrodynamic lubrication model. An efficient optimization scheme, DIviding RECTangles (DIRECT), is coded for parallel computing in a single-system image cluster. The main focus of this study was to examine the performance of the standard DIRECT algorithm in coarse-grained parallelism. The parallel efficiency is compared with the results obtained in recent studies of air bearing optimization by using a genetic algorithm and a divide-and-conquer scheme. It was found that the limited possibility for parallelism of the standard DIRECT algorithm contributes somewhat small parallel efficiency.
Effects of Pitch Static Attitude and Roll Static Attitude on the Steady Performance of Air Bearing Sliders
Authors: Zhu Hong , Bogy David B.
Published: November 2008

This paper addresses the effects of pitch static attitude (PSA) and roll static attitude (RSA) on air bearing slider steady performance, especially for ultra-low flying height sliders. We performed simulations for three different low flying sliders with flying heights (FH) of 7nm, 5nm and 3.5nm using the static simulator code of the Computer Mechanics Laboratory (CML). We found that PSA and RSA have quite significant effects on the steady performance of these air bearing slider designs, and the effect is more important the smaller the size and the lower the FH of the slider. We also investigated the effects of suspension stiffness on the air bearing sliders’ flying attitude (pitch and roll) and found that these effects are similar to those of PSA and RSA.
Some Tribological Properties of an Ionic Liquid
Authors: Nogi Takashi
Published: November 2008

Some tribological properties of an ionic liquid were investigated by using a pin-on-disc friction and wear tester. Due to running-in, the coefficient of friction of the ionic liquid decreased with time to a very low value of 0.02 which suggests that the lubrication regime was hydrodynamic at the end of the tests. Anti-wear performance of the ionic liquid was substantially comparable to a paraffin-based oil.
Surfactant Influence on the Tribological Properties of Bentonite-Based Greases
Authors: Pogosian A. K. , Martirosyan T. R.
Published: November 2008

Development of new type plastic lubricants capable of sustaining high pressures is thus important by using natural minerals. The effect of surfactant ration and structure of thickener nano-particles surfaces on the tribological properties of bentonite-based greases was studied. The best anti-friction and anti-wear properties of plastic lubricants were revealed at the particles modified by quaternary amine and urotropine type ammonium salts, and the necessary ratio for the bentonite particles surface modification by quarterly ammonium salts was revealed, which provide the best tribological properties of composites.
A Constant Temperature FZG Test for Open Gear Lubricants
Authors: de Vaal P. L. , Meister B.
Published: November 2008

The 12-stage FZG test (A/8,33/90) was originally developed to determine scuffing load capacity of engine oils [1]. During each load stage, the test is started at the same initial sump temperature. Heat of friction generated during a load stage results in a temperature increase of the lubricant. Final sump temperatures as high as 140 °C are often reached after the final load stage (Load Stage 12). A modified version of the test, (A/2,76/50) is used for laboratory determination of open gear grease performance [2]. In open gear lubrication, typical gear operating temperatures are in the range 50°C–80°C. Test temperatures higher than this may give rise to different wear characteristics than would be found under typical operating conditions. It would therefore be of practical interest to have a laboratory-based means to determine the temperature-dependent characteristics of an open gear lubricant. A compact heat exchanger was designed, built and inserted in the FZG test bed. By manipulating the flowrate of an external cooling medium, the temperature of the test fluid in the sump can be maintained at a desired temperature. Results for four representative open gear lubricants were obtained using the constant temperature test and compared with results obtained with the conventional test. These results indicated that the new test can discern between samples that perform similarly during the conventional test.
The Effect of Inertia on Radial Flows: Application to Hydrostatic Seals
Authors: Brunetie`re Noe¨l , Tournerie Bernard
Published: November 2008

A theoretical study of thin fluid film flows between rotating and stationary disks is presented. Inertia terms are included using an averaged method. It is assumed that inertia effects do not influence the shape of velocity profiles. The model is validated by comparison with experimental data and previous theoretical studies. A ThermoElastoHydroDynamic analysis of a hydrostatic seal is performed. The great influence of inertia terms on leakage rate prediction is shown.
Contact Mechanics Analysis and Initial Stability of Press-Fit Metal-on-Metal Hip Resurfacing Prostheses
Authors: Udofia I. , Liu F. , Jin Z. , Roberts P. , Grigoris P.
Published: November 2008

To ensure potential long-term stability and survivorship for metal-on-metal hip resurfacing prostheses, implant migration would need to be minimised to encourage bone in-growth. This study uses the finite element method to investigate the effects of the surgical press-fit procedure on the bearing and interfacial contact mechanics, and on the initial stability of a metal-on-metal (MOM) hip resurfacing prosthesis. The finite element models simulated the press-fit procedure using different amounts of interference between the cup-bone (1–2mm). The resurfacing prosthesis was implanted anatomically into a 3-D bone model. Resultant hip joint loads were applied to the model through muscle and subtrochanteric forces. Results showed that increasing the friction and the interference between the cup and bone resulted in significant reductions in the relative micromotion between the cup and bone. This would ensure the immediate post-operative stability of the acetabular cup and provide adequate conditions for potential long-term bone in-growth and implant stability. The contact mechanics at the bearing surfaces, which has a large effect on tribological performance, was found to be little affected by changes at the cup-bone interface. These findings are consistent with the general satisfactory short and medium-term clinical results of metal-on-metal hip resurfacing prostheses. This study suggests that interference, friction and a mechanically sound bone structure are important parameters to promote implant stability and support.
Tribological Properties of Carbide Layers Produced in the Vacuum Titanizing Process
Authors: Kasprzycka Ewa , Senatorski Jan , Nakonieczny Aleksander , Szczerek Marian , Babul Tomasz , Bogdan´ski Bogdan
Published: November 2008

Diffusion carbide layers produced on steel surface in vacuum titanizing process have been investigated. Studies of layers thickness, their morphology, titanium, carbon, chromium and iron concentration depth profiles in the diffusion zone of titanized layers have been carried out. The effect of process parameters such as time and temperature on the kinetics of layer growth on steel surface has been investigated. Wear resistance of titanized layers has been determined.
Reynolds Equations for Common Generalized Newtonian Models and an Approximate Reynolds-Carreau Equation
Authors: Bair Scott , Khonsari M. M.
Published: November 2008

Exact, closed form one-dimensional Reynolds equations are presented for the Ostwald-DeWaele model, Ellis model, Spriggs model and the double-Newtonian Rabinowitsch and Ferry models. From numerical solutions for flow rate, an approximate Reynolds-Carreau equation is obtained.
Reuse of Wear Debris in Automotive Disc Brakes
Authors: Polak Adam , Grzybek Janusz , Pytko Stanisław , Voynov Kirill
Published: November 2008

Paper presents an idea of wear debris reuse in the automotive disc brakes. According to this idea, worn material is used as a material building up third body. Application of this idea leads to diminishing of brake discs and brake pads wear.
Opportunities for Replacement of Phosphorus and Dithiophosphates in Lubricating Oil With Borate Ester Additive Containing Nitrogen
Authors: Hu Jianqiang , Yao Junbing , Du Zhanhe
Published: November 2008

The poisoning of exhaust catalysts by phosphorus has lead to research to provide new additives packages to reduce or displace the use of ZDDP. In this research a four-ball tester was used to evaluate the tribological performances of organic borate ester containing nitrogen (BNO) combined with zinc dialkyldithiophosphate (ZDDP) or tin dialkyldithiocarbamates (SnDDC) in base oil respectively. The results indicate that the combination of these additives with organic borates ester can exhibit better antiwear synergism than either component separately without impairing load carrying abilities. Especially, the antiwear properties of oils can be improved significantly under optimal concentration ranges. Accordingly considerable amount of or ZDDP can be partially replaced by BNO in synergetic mixtures, or replaced completely by the combination of BNO with SnDDC. This might provide opportunities for the use of lower concentrations of S, P additives.
Gear Pitting Life Prediction and Comparison With Experiments
Authors: Zhu Dong , Bujold Michael , Keer Leon M.
Published: November 2008

Predicting gear surface fatigue life is vital to gear and transmission design. Although simplified approaches based on the smooth-surface Hertzian contact stress calculations are available, the trend of compact design of high-power gear systems requires the gear design calculation to consider severe operation and lubrication conditions and detailed surface topography. It is needed, therefore, to upgrade the life prediction methods. The research presented in this paper aims to develop a gear pitting life prediction approach based on the rough-surface mixed lubrication model developed by Hu and Zhu [1] and the fatigue life model developed by Zaretsky and modified by Epstein et al [2] with accurate surface-subsurface stress analyses. With this approach, gear design parameters, operating conditions, materials, lubricant, and real tooth surface topography are used as input data. When conducting surface fatigue life prediction, three modules are employed: the mixed lubrication module, the stress analysis module, and the fatigue life module. In the mixed lubrication module, machined gear surfaces are digitized and used for calculating the pressure distribution and lubricant film thickness in the mixed lubrication. The mixed-lubrication pressure distribution is inputted into the stress module to obtain surface and subsurface von Mises stresses. These stresses are then integrated in the fatigue life module for estimating the fatigue life corresponding to a certain failure probability (50% in the present study). In other words, the life prediction is now based on subsurface von Mises stresses in the lubricated rough surface contacts, instead of smooth contact Hertzian pressure. There are a few materials constants involved in the fatigue life module. They are calibrated by comparing the prediction results with available Eaton experimental data. Table 1 lists the experimental data for 15 gear sets (most of them are hobbed and shaved) under combined rolling and sliding. The Hertzian stress ranges from 0.8554 GPa to 2.9494 GPa. It has been found that most conventional pitting life prediction methods tend to give conservative life estimates. With optimized materials parameters in the present life model, predicted pitting life results well agree with available Eaton gear test data, and the correlation appears to be 96.3%. Figure 1 shows the comparison between experimental and prediction data. Obviously, the model prediction well represents the performance of this group of gear surfaces in contact and mixed lubrication.
Boundary Lubricated Friction Experiments With Coarse Surface Texture
Authors: Larsen-Basse Jorn , Ives Lewis , Hsu Stephen M.
Published: November 2008

Low-speed friction experiments were conducted under boundary lubrication in a pin-on-disk tester. The 304 stainless steel disk had smooth areas alternating with areas of coarse surface texture consisting of indents or macroscopic grooves, 0.3–0.4 mm in size and in area fractions varying between 25 and 70%. The 3.2 mm flat pin was also SS304. The coarse texture has detrimental effects. For each pattern the friction coefficient is greater than for the smooth areas. It becomes independent of load as boundary conditions set in. In comparing various patterns it is noted that this friction coefficient increases with pressure or with the amount of area removed to form the texture. It is suggested that partial removal of surface area to form the texture reduces the number of trapped liquid patches, which otherwise can provide low-friction load support. The coarse texture may also conduct lubricant away from the contact area.
In-Vitro Study of Backside Wear Mechanism on Mobile Knee Bearing Components
Authors: Atwood Sara A. , Kennedy Francis E. , Currier John H. , Van Citters Douglas W. , Collier John P.
Published: November 2008

Backside wear in the form of scratching and pitting observed on a series of mobile bearing rotating platform knee retrievals (n = 100) appears to be indicative of third body wear. The appearance of scratching and pitting on the backside does not correlate with duration in vivo or with linear backside wear measurements, but there is a weak correlation with fixation method indicating that some of the third body debris may be bone cement. Tribological tests representing rotation and fretting in the knee were run with bone cement, bone chips, and metal porous coating beads placed as third bodies in the contact. Results with bone cement show scratches similar to those found on retrievals.
Pivoted Inlet Texture Devices
Authors: To̸nder Kristian
Published: November 2008

The paper describes a study of the operation of a wide inlet textured bearing pad, pivoted at the load centre. Scatter in experimental results recently obtained might be interpreted to indicate the existence two modes of operation. This possibility of this phenomenon occurring is established theoretically. Further, the findings are discussed in relation to the results of the experimental scatter. The latter appears to support the theory.
Wear Behavior of W-DLC Coating Under Reciprocating Sliding Motion
Authors: Liu Shuangbiao , Hua Diann Y. , Whittaker Lucy , Taylor Steven C.
Published: November 2008

Tungsten containing diamond like coatings have been used to improve reliability and durability of rubbing surfaces, thus their degradation becomes critical to predict component life. The gradual wear of such coatings is studied in this work using a high frequency reciprocating rig with the ball (coated)-flat configuration. In order to study the relationship between wear behavior and coating properties, two deposition recipes are used to deposit coatings on steel balls and these specimens have been tested in an interrupted manner under the same loading, frequency, and lubrication conditions. The coating wear quantified by measuring the wear scar on the balls with a surface profilometer shows nonlinear relationship with sliding distance. Recipe B with more Tungsten content in the top layer has better wear resistance.
Analysis of Heat Partitioning in Wheel/Rail and Wheel/Brake Shoe Contact: An Analytical Approach
Authors: Tudor A. , Khonsari M. M.
Published: November 2008

An analytical model is developed for assessment of the steady-state temperature distribution in a wheel undergoing heating in contact with the rail and the brake shoes as well as nonuniform cooling in its periphery. The heat partitioning coefficients in the rail and the brake-shoe contacts with the wheel are incorporated in the model. These heat-partitioning coefficients can be used to evaluate the temperature field in the wheel and the brake shoes. It is shown that the wheel contact temperature is confined to a very thin depth within the surface layer (approximately 6% in the radial direction), but the rest of wheel is at the bulk temperature.
White Etching Layer and Rolling Contact Fatigue of Rail
Authors: Carroll Robert I. , Beynon John H.
Published: November 2008

A common surface metallurgical feature of rail is white etching layer (WEL), a martensitic structure formed due to severe deformation of rail while it is in service. The simulation of white etching layer has involved sliding one disc against another to produce the WEL by deformation. Rolling contact fatigue (RCF) of this layer has been investigated in the laboratory using twin-disc testing. The effect of the white etching layer is to reduce the resistance of rail steel to crack initiation because of its brittle nature, with propagation promoted by the continued deformation of the sub-surface pearlite. Rails removed from service have been examined and compared with the twin disc testing samples. RCF cracks initiate at the interface of the WEL and pearlite due to the ductility difference between them.
Development of a Novel Wear Testing Device for the Investigation of Articular Cartilage and Compliant Polymers for Use in Biomedical Implants
Authors: Schwartz Christian J. , Bahadur Shyam
Published: November 2008

Development of new biomaterials for use on the articulating surfaces of total-joint implants is essential to the improvement of implant design and implant lifetimes. Currently, rigid ultra-high molecular weight polyethylene (UHMWPE) is the most commonly used material for implant wear surfaces because of its high wear resistance. However, UHMWPE does not mimic the properties of native articular cartilage, nor does it exploit the full potential of ambient synovial fluid for joint lubrication. Furthermore, implant loosening due to the body’s reaction to UHMWPE particulate is a leading reason for the limited lifetimes of such implants [1]. A new approach is needed in order to increase the pain-free lifetime for those persons requiring total-joint arthroplasty. Such an approach will likely involve synthetic or natural materials with properties that more closely resemble natural articular cartilage.
Determination of Contact Area During Small-Scale Friction Experiments by Means of Continuous Stiffness Measurements
Authors: Rar Andrei , Braiman Yehuda Y. , Oliver Warren C. , Goldsby David L. , Tullis Terry E. , Pharr George M.
Published: November 2008

Despite the hallmark observation of the almost linear relationship between friction force and contact area in the case of “dry” friction, the direct measurement of this dependency is an area of active research [1, 2]. In this study, a new approach to the measurement of contact area during friction experiments is proposed. The method is based on the well known proportionality between the contact area and the contact stiffness raised to the second power [3]. The main benefit of the proposed method is its broad applicability. Preliminary measurements of the dependence between friction and contact area are discussed.
Process Development and Tribochemical Evaluation of Seed Oil Based Antiwear/Antifriction Additive
Authors: Adhvaryu Atanu , Sharma Brajendra K. , Erhan Sevim Z.
Published: November 2008

Antiwear / antifriction additives enhance the ability of lubricant to withstand mechanical stresses of interacting surfaces under boundary lubrication conditions. Majority of the lubricants and additives currently used are petroleum based that are toxic to environment, making it increasingly difficult for safe and easy disposal. There has been an increasing demand for “green” lubricants and lubricant additives in recent years due to concerns about lubricants lost to the environment and increasingly strict government regulations controlling their use.
Scuffing Failure Analysis Due to an Abrasive Contaminant in High Pressure Injection Fuel System
Authors: Sultana Tayyaba , ur Rehman Obaid , Rashid Badar , Malik M. Afzaal
Published: November 2008

The presence of rigid abrasive contaminant between the plunger and sleeve of high-pressure injection fuel system causes scuffing failure. The abrasive contaminant is modeled as a spherically shaped rigid particle. The contaminant is envisioned to penetrate into the sleeve while positioning itself in rubbing contact with the plunger. Excessive temperature rise known as flash temperature between the particle-plunger interface is used as an indication of whether scuffing would take place. The model uses flash temperature in conjunction with the material properties to determine the critical particle size that may result in scuffing failure. The range of critical particle size initiating significant abrasive wear is determined and validated with the experimental results available in literature. Our predicted model can be used as a guide for selecting an appropriate filter size for high-pressure injection fuel system.
Stability and Dynamics of Non-Linear Slider Behaviour Due to Disk Waviness in the Presence of Intermolecular and Electrostatic Forces
Authors: Gupta Vineet , Bogy David B.
Published: November 2008

In this paper we present a theoretical investigation of the stability and the dynamics of the non-linear behavior of a slider at very low head media spacing. A single DOF head disk interface (HDI) model, with constant air bearing stiffness and damping has been used to study the effect of disk waviness on the nonlinear slider dynamics in the presence of intermolecular and electrostatic forces. A variational approach based on the principle of least action was used to derive the equations of motion of the slider. Further, a stability criteria was derived that helped to better understand the instabilities that appear in slider when the slider is flying in close proximity to the disk surface. Due to extremely nonlinear nature of the interaction between the slider and the disk, we observed some strange features of the motion of the slider. In particular the effects of the nonlinear interaction force, air bearing stiffness and damping on the instabilities of the periodic motions of the slider are discussed in detail. We found that the branch associated to the disk waviness frequencies larger than the resonance frequency is always stable and the branch associated to the disk waviness frequencies smaller than the resonance frequency exhibits two stable domains and one unstable domain. This analysis was further extended to include the nonlinear nature of air bearing stiffness and damping as well as contact at the HDI.
A Data Correction Method for the Dynamic Measurements by the Atomic Force Microscope
Authors: Matsuoka Hiroshige , Hoshina Yuki , Fukui Shigehisa
Published: November 2008

This paper clarified the discrepancies between theoretical vibration amplitude of a cantilever used in the atomic force microscope (AFM) and the measured vibration data through the optical lever method. It was theoretically found that the amplitude data of the cantilever in the dynamic mode needs to be corrected and correction factors were newly derived. The correction factors depend on the vibration frequency and the amplitude should be corrected by about 9% at the 1st natural frequency and by about 69% at the 2nd natural frequency. This result can be applied to many AFM in which the optical lever method is used.
Accumulation Process of Liquid-Like Chemicals on the Air Bearing Surface of a Slider in Hard Disk Drives
Authors: Zhang Bo , Nakajima Akira
Published: November 2008

The pumping effect which is proposed by the authors to explain the accumulation of liquid-like chemicals on the air bearing surface has been analyzed by taking into the account the incline of the air bearing surface. Numerical results show that the accumulation rate of the contaminant decreases as the incline of the air bearing surface increases and at the same time the maximum adsorbed film thickness shifts from the outlet to the inner surface.
Using Transient Solutions to Reynolds Equation to Determine Bearing Forces
Authors: Feng N. S. , Hahn E. J. , Lou Y. Q.
Published: November 2008

To evaluate numerically the vibration behaviour (stability and unbalance response) of rotor bearing foundation (RBF) systems such as turbomachinery which incorporate rotors running in several flexibly mounted hydrodynamic bearings, one needs input data parameters which adequately describe the bearings, the rotor, the foundation, the unbalance state and the system configuration state (the relative transverse alignment of the bearings). Adequate parameters for the last three are particularly hard to obtain for existing installations; and worldwide effort has been devoted to trying to identify these parameters, using field obtainable measurements of the instantaneous relative displacements between the rotor journals and their respective bearing housings. These measurements are then processed using Reynolds equation to determine the instantaneous bearing reaction forces acting on the rotor and foundation, which forces are then an essential ingredient of the desired parameter identification procedures [1]. The problem is in the accuracy to which one can reliably calculate these forces, even if it be assumed that Reynolds equation is otherwise a perfect model. This is felt to be particularly problematical because of the nonlinearity introduced into the RBF system by the hydrodynamic bearings.
Numerical and Experimental Investigation of Friction in Cold Strip Rolling
Authors: Lu Cheng , Tieu A. Kiet
Published: November 2008

To obtain a better understanding of friction and contact mechanism in cold strip rolling, a refined asperity ploughing model and an asperity elastic deformation model have been developed. It is found that the asperity angles α1 and α2 significantly affect the tangential force and the coefficient of friction respectively. The theoretical prediction is in good agreement with the experimental results in Ref. [7]. The developed models can predict a reasonable frictional coefficient if it is applied to the cold rolling process.
A2BLT+F2AST: A Rapid Bearing Life and Reliability Evaluation Tool
Authors: Li Xinglin
Published: November 2008

The fatigue failure of almost all mechanical parts is caused by the friction and wear of materials. Bearings are the most widely used machine elements and are critical to almost all forms of rotary machinery. This paper focuses on rolling bearing fatigue failure and its test methodologies. If we use normal life test method, under low load and high speed, the test period will be too long and the cost will be too much. But how do accelerate the test to shorten the test period? In this paper, the A2BLT+F2AST—a rapid bearing life and reliability evaluation tool is introduced, it is the integration of hardware, software and standards for solving problems of Accelerated Automatic rolling Bearing fatigue Life and reliability Tester and Fast Failure Analysis System Technology. A2BLT+F2AST—a rapid bearing life and reliability evaluation tool is successfully applied in more than one hundred rolling bearing manufactures and users all over the world. The ABLT series automatic control bearing fatigue life and reliability is successfully developed by our center based on the life tester and life test method of research. The certificate (ZS type, B type, ABLT type) by contrast test: Under the condition of keeping getting in touch with the consistent premise of failure mechanism, accelerating life test can shorten more than 80% test time compared with the normal regulations life test. It can also shorten the new product development period, especially for the automobile hub bearings. The ABLT are composed by test bed, test head, driving system, loading system, lubricating system, electrical control system and monitored control system.
Tribological Characteristics of Coated Vane Surfaces Under Mixed Environments of Various Oils and CO2 as a Refrigerant
Authors: Oh Se-Doo , Kim Kyung-Soo , Cho Sung-Oug , Lee Young-Ze
Published: November 2008

The CO2 is investigated as an alternative refrigerant to replace HFC refrigerant in air conditioning systems due to the environmental concerns. Because new compressors with CO2 are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressor, especially rotary type, the friction and wear characteristics of sliding surfaces between a vane and a roller in the rotary compressor were evaluated in this paper. Several hard coatings, such as TiN, CrN, WC/C and two types of nitridings, were applied on vane surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. Two types of lubricants were used, namely POE (polyol ester) oil and PAG (polyalkylene glycol) oil. The vane-on-disk type sliding tests were performed with an exclusive high pressure wear tester. From the tests, coefficient of friction and wear volume of vane surfaces applied various coatings were compared. Test results showed that WC/C coatings showed good tribological properties. TiN and CrN coated vanes showed good wear resistance properties but produced high friction. Also, the results of the sliding tests showed that using PAG oil has an advantage over POE oil in CO2 environment.
Wear and Lubrication Characteristics of a Multi-Cylinder Diesel Engine Using Vegetable Oil Blended Fuel
Authors: Kalam Md. Abul , Hassan Masjuki Hj. , Mohamad Edzrol Niza
Published: November 2008

This paper presents experimental results carried out to evaluate wear and lubrication characteristics of a multi cylinder diesel engine when operated on vegetable oil blended fuels. The blended fuels consist of 10%, 20%, 30%, 40% and 50% coconut oil (COIL) (in volume basis) with diesel fuel (DF2). Pure DF2 was used for comparison purposes. The engine was operated at constant speed of 2000 rpm with 50% throttle load for a period of 100 hours for each test fuel. The engine was operated for a total period of 600 hours for six fuels. The same lubricating oil equivalent to SAE 40 was used for all the fuels system. The sample of lube oil was collected through a one way valve connected to the crankcase sump at 50 hour intervals. The first sample was collected immediately after the engine had warmed up. The effect of blended fuel on engine component wear and lubrication characteristics in terms of viscosity, total base number (TBN), moisture content, oxidation, wear metals, contaminant elements and lubricant additive depletions were analyzed. The results showed that wear metals, contaminant elements increase with increasing COIL with DF2. An increasing COIL in blends reduces additive elements; and the reduction rate during blends of up to 30% COIL is quite similar to DF2. Soot and sulfation reduce with increasing COIL in blended fuels due to reducing aromatics and sulfur in comparison to DF2. The water concentration increases from above 30% COIL blended fuels. The TBN and viscosity changes are found almost normal. The engine did not have any starting and combustion noise problems when operating on COIL blended fuels. These lubricating oil analysis data will help to select tribological components and compatible lubricating oil for coconut oil or biofuel operated diesel engines.
Friction Characteristics of Self-Assembled Monolayers Coated on Si-Wafer by Chemical Vapor Deposition at Nano/Micro-Scale
Authors: Singh Arvind R. , Yoon Eui-Sung , Han Hung-Gu , Kong Hosung
Published: November 2008

Friction characteristics of self-assembled monolayers (SAMs) coated on Si-wafer by chemical vapor deposition technique was studied at nano-scale using AFM, and at micro-scale using micro-tribo tester. Three self-assembled monolayers, such as diphenyldichlorosilane, dimethyldichlorosilane and perfluorodecanoicacid, were tested in this work. Results showed that SAMs exhibited superior frictional property than Si-wafer. Friction in the case of Si-wafer was significantly affected by its inherent adhesion, and in the case of SAMs by their physical/chemical properties. At micro-scale, the effect of ball size on coefficient of friction of the test materials was also investigated.
Effect of the Shear Strength of Coating of CNx on Friction Sliding Against Si3N4 Pin in Nitrogen
Authors: Tokoroyama Takayuki , Umehara Noritsugu , Fuwa Yoshio , Nakamura Takashi
Published: November 2008

It was reported that CNx coating showed low friction coefficient less than 0.01 when it slid against Si3N4 ball in dry N2. It is suggested that the super-low friction was caused by the structural change of CNx surface to graphite-like structure during sliding in N2. In this study, to investigate the effect of N2 gas on shearing and adhesive strength of CNx, micro scratching tests were examined in N2 and air with a diamond tip (radius = 2.0 μm). Main results are the followings: (1) CNx surface after sliding in N2 against Si3N4 ball showed lower scratching friction coefficient in N2 than that in air. (2) Adhesive strength Si was estimated as 1/10 times lower than that in air.
New Challenges in Application of Thin Hard Coatings on Heavy-Loaded Machine Components
Authors: Szczerek Marian , Michalczewski Remigiusz
Published: November 2008

The paper describes the state of the art and a brand new achievements in the field of application of thin hard coatings on heavy-loaded machine components, like gear, or rolling bearings.
Decomposition of Perfluoropolyether Fluids Through Reactions With Ambient Air Due to Triboplasma
Authors: Nakayama Keiji
Published: November 2008

In order to clarify the degradation mechanisms of the PFPE fluid under a head/disk sliding contact, decomposition reactions of z-dol fluids were investigated under triboplasma generation and in the atmospheres of oxygen, nitrogen and air in gas-discharge-plasma. The results showed that the PFPF degradation proceeds through intermolecular reactions with ambient air molecules by the tribomicroplasma.
Influences of Additives on the Wear Protection of PVD-Coated and Ester Lubricated Roller Thrust Bearings
Authors: Gold P. W. , Loos J. , Kuhn M.
Published: November 2008

Mixed friction cannot always be avoided in rolling bearings. It is therefore necessary to protect the bearings against wear. Nowadays, extreme-pressure- and anti-wear-additives fulfill this function. As these additives are harmful to the environment it was systematically examined to what extent PVD-coatings are able to take over their function. The effectiveness of the coatings was tested in the FE8 lubricant roller bearing test rig on the basis of cylindrical roller thrust bearings. With the help of this world wide established test rig the roller bearings are tested on boundary friction conditions (κ ≪ 1).
The Influence of Impingement on the Wear of a Metal-on-Metal Articulation: A Hip Simulator Study
Authors: Dirix Y. , Becker A. , Siebels W. , Schmotzer H.
Published: November 2008

Wear magnitude and location for a metal-on-metal bearing couple were studied on a hip simulator with and without the occurrence of impingement. The steady-state wear increased by a factor thirty due to the impingement and the shape and location of the impingment zone closely resembled clinical observations. Metal-on-metal bearings have the advantage of combining low wear with a high toughness. The low wear is only guaranteed if impingement phenomena are excluded, thus showing the importance of proper implant designs and surgical techniques.
Performance Evaluation of a Multiprocessor Cluster for a Thermohydrodynamic Lubrication Analysis
Authors: Wang Nenzi , Tsai Chih-Ming
Published: November 2008

This study presents a performance evaluation of two parallel programming paradigms, OpenMP and message-passing interface (MPI), for thermohydrodynamic lubrication analysis. In this study the performance of parallel computing in MPI cluster is equivalent to a similarly configured single-system image cluster. For a reasonable parallel efficiency (75%) the experimentally determined minimum execution times for the tasks to be conducted in parallel are approximate 0.5 and 5.0 seconds for OpenMP and MPI parallelism, respectively. It is noted that OpenMP programming allows parallel applications to be developed incrementally and supports fine-grain communication in a very cost effective manner. A computer program written in part to perform two or more tasks simultaneously may well be a computation norm in future tribological study.
Movements and Collisions of Nanoparticles in Two Phase Flow
Authors: Luo Jianbin , Xu Xuefeng , Yan Jing , Duan Fangli , Lu Xinchun
Published: November 2008

Nanoparticles have been widely used in oils and polish slurry such as chemical mechanical polish (CMP) process. The movement of nanoparticles in liquid and the interaction between nano-particles and solid surface are very important to obtain an atomic smooth surface in CMP process. This paper presents both experimental and theoretical studies on the movement of nanoparticles in fluid and the collision between nanoparticles as well as that between the particles and solid surfaces in two phases flowing process.
Orientation and Degradation of Polymer Sliding Surfaces Evaluated by Raman Spectroscopy
Authors: Samyn Pieter , Quintelier Jan , De Baets Patrick , Van Craenenbroeck Jeroen , Verpoort Francis , Schoukens Gustaaf
Published: November 2008

Present study investigates changes in the conformation of functional groups at the polymer sliding surface by postmortem Raman spectroscopy, thermomechanical analysis and SEM/EDX. Two case studies on sintered polyimide (SP) and thermoplastic polyethylene-terephtalate (PET) are presented, indicating the influences of sliding temperature, counterface type and internal lubricants (PET/PTFE) on some characteristic absorption bands in the Raman spectrum of the sliding surfaces.
Ultrasonic Measurement of Wheel Hub/Axle Interference Fit Pressures
Authors: Marshall M. B. , Lewis R. , Dwyer-Joyce R. S. , Demilly F. , Flament Y.
Published: November 2008

Interference fits are a commonly used mechanical attachment mechanism. They represent a flexible and cost effective method for joining components having cylindrical geometry. An interference fit is constructed when a bush is shrunk and/or pressed onto a shaft with an interfering radial dimension. The strength of the interference fit assembly depends on the shaft and bush dimensions, and must be sufficient to withstand the force or torque reached during normal service.