bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Friction Compensation of Servo Mechanisms With Nonlinear Viscous Friction
Authors: Wu Ziying , Liu Hongzhao , Liu Lilan , Yuan Daning , Li Pengfei
Published: November 2008

In this paper, a SDOF system with nonlinear viscous friction under harmonic excitation is studied. A nonlinear viscous friction model is built as an exponential expansion of the relative slip velocity. According to the adaptive control theory, an adaptive controller for the friction compensation of the SDOF system with nonlinear viscous friction is put forward by using the model-based parameterization techniques. The good performance of the proposed control scheme is illustrated through the computer simulation.
Molecular Mechanisms of Anti-Wear Pad Formation and Functionality
Authors: Mosey Nicholas J. , Mu¨ser Martin H. , Woo Tom K.
Published: November 2008

Wear limits the lifespan of many mechanical devices with moving parts. To reduce wear, lubricants are frequently enriched with additives that form protective pads on rubbing surfaces. With first-principles molecular dynamics simulations of pads derived from commercial additives, namely zinc-phosphates, we unravel the molecular origin of how anti-wear pads can form and function. These effects originate from pressure-induced changes in the coordination number of atoms acting as cross-linking agents, in this case zinc, to form chemically connected networks. The proposed mechanism explains a diverse body of experiments and promises to prove useful in the rational design of anti-wear additives that operate on a wider range of surface materials with reduced environmental side-effects.
Considerations Regarding the Analytical Solution of Journal Bearing Lubrication
Authors: Ionescu Mihail G. , Ionescu Vladimir-Codrin M.
Published: November 2008

The paper makes a succinct analysis of the advantages and limitations of the differential equation for pressures proposed by Ionescu [1]. The main theoretical and experimental aspects concerning the quantitative estimation of journal bearings are briefly presented. A variant of the equation ensuring calculation accuracy for lightly loaded bearings is proposed.
The PTT Model in Hip Joint Replacement: Shock Loading
Authors: Tichy John , Bou-Sai¨d Benyebka
Published: November 2008

The Phan-Thien Tanner (PTT) model is one of the most widely used rheological models. It can properly describe all the common characteristics of viscoelastic non-Newtonian fluids. Synovial fluid of human joints, which also lubricates artificial joints, is well known to be highly viscoelastic. Thus it is reasonable to attempt to describe such joint behavior using non-Newtonian flow models. Modeling the geometry of the total hip replacement, the PTT model is applied in spherical coordinates to a thin confined fluid film. As an illustrative problem, the case of a sudden impulsive start of simple squeezing motion is solved, similar to landing on one’s feet after a vertical jump. The phenomena of shear thinning, stress relaxation, and stress overshoot are all exhibited.
Anisotropic Friction in Cold Rolling of Flat Steel Strips
Authors: Legrand N. , Becker B.
Published: November 2008

This work analysed the role of friction and other process parameters on strip edge drop and width variations during cold rolling of flat steel strips. Comparisons of 3D numerical simulations with experimental datas from rolling trials have shown that roll bite friction is anisotropic: friction in the transverse direction is twice to four times higher than that in the rolling direction. Work roll circumferential grinding striations and the associated roll roughness anisotropy are considered to be responsible for this anisotropy. Moreover by modifying friction anisotropy (decrease of transverse friction for the same longitudinal friction), it is possible to compensate for width narrowing usually observed on commercial cold mills (narrowing is due to strip thermal contractions in the mill interstands). Therefore, friction appears as a suitable process actuator for control of cold rolled product dimensions.
Study on Influence of Air Pressure on Braking Condition
Authors: Chen D. , Huang P.
Published: November 2008

In the present paper, air pressure and temperature on the interface of the polymer matrix composite (PMC) brake pads are measured by disc brake under braking condition, and their influences are studied as well. The experimental results show that the air temperature peak is not as high as that on the surface. The air pressure of the interface varies with the applied load. The air pressure is negative under the small applied load, but positive under the large applied load. The analysis of the experimental results shows that the phenomena are caused by the friction heat and the rotate disc. Since the air pressure is very small comparing with applied load, it influences on the friction coefficient slightly. But, the negative air pressure of the interface increases the chance of the drag friction in the non-braking mode for disc brakes.
Effect of Physical Properties of Solid Particle on Erosion Wear of Ductile Materials
Authors: Desale Girish R. , Gandhi Bhupendra K. , Jain S. C.
Published: November 2008

The present work has been carried out to investigate the effect of particle shape, density and hardness on erosion wear of aluminum alloy 6063 (AA6063) and stainless steel 304L (SS 304L) in aqueous mixture of three erodents namely quartz, alumina and silicon carbide (SiC). The wear of the two materials has seen maximum with alumina particles and minimum with quartz particles. Surface topography of the worn surfaces by scanning electron microscope (SEM) has shown that the craters formed due to impact of blocky shaped quartz particles at acute impact angles are flat and short in length compared to that due to the angular shaped alumina or SiC particles. This resulted in higher cutting wear by alumina or SiC particles as compared to the quartz particles.
Atomic-Scale Observation of Superlubricity
Authors: Dienwiebel M. , Verhoeven G. S. , Pradeep N. , Zandbergen H. W. , Frenken J. W. M.
Published: November 2008

Graphite is known to be a good solid lubricant. The low-friction behavior is commonly ascribed to the low resistance to shear. Using a home-built frictional force microscope that is able to detect forces in three dimensions, we have studied the energy dissipation between a tungsten tip sliding over a graphite surface in dry contact. By measuring atomic-scale friction as a function of the rotational angle between two contacting bodies we show that the origin of the ultra-low friction of graphite lies in the incommensurability between rotated graphite layers, an effect proposed under the name of ‘superlubricity’.
A Particle Filtering Framework for Failure Prognosis
Authors: Orchard Marcos , Wu Biqing , Vachtsevanos George
Published: November 2008

Bayesian estimation techniques are finding application domains in machinery fault diagnosis and prognosis of the remaining useful life of a failing component/subsystem. This paper introduces a methodology for accurate and precise prediction of a failing component based on particle filtering and learning strategies. This novel approach employs a state dynamic model and a measurement model to predict the posterior probability density function of the state, i.e., to predict the time evolution of a fault or fatigue damage. It avoids the linearity and Gaussian noise assumption of Kalman filtering and provides a robust framework for long-term prognosis while accounting effectively for uncertainties. Correction terms are estimated in a learning paradigm to improve the accuracy and precision of the algorithm for long-term prediction. The proposed approach is applied to a crack fault and the results support its robustness and superiority.
Modeling of Velocity-Dependent Rolling Friction in Linear Microball Bearings
Authors: Tan Xiaobo , Modafe Alireza , Ghodssi Reza
Published: November 2008

Earlier experimental results showed the dependence of rolling friction on the relative velocity in microfabricated linear microball bearings. In this paper a viscoelastic model is proposed to elucidate the observed phenomenon. Inspired by the work of Poschel et al., we model the bearing groove, on which a microball rolls, as a continuum of mass-spring-damper elements. Given a rolling velocity, the penetration depth of the ball into the groove plane is determined through an implicit equation of force balance and can be solved for by the fixed-point iteration algorithm. The mechanical power required to actuate the continuum of mass-spring-dampers is then calculated, from which the rolling resistance (friction) is derived. The agreement of numerical results with experimental ones shows that the proposed model is able to capture essential characteristics of ball-groove interactions in the bearings.
Changes in Tribological Properties of MoS2 Film Exposed to LEO on SM/SEED
Authors: Matsumoto Koji , Akiyama Masao , Tagawa Masahito , Imagawa Kichiro
Published: November 2008

Service Module / Space Environment Exposure Device (SM/SEED) is experimental system aboard International Space Station (ISS) to evaluate the degradation of various materials for space application under the Low Earth orbit (LEO) space environment. Three sets of exposure pallets of SM/SEED with the same samples have been exposed to LEO since October 2001. One of the pallets returned to Earth after about one-year exposure. A bonded molybdenum disulfide (MoS2) film was also exposed as a tested material of SM/SEED. The changes in tribological characteristics of the film were examined. And effects of ground-based irradiation with LEO environmental factors (e.g., Atomic Oxygen (AO) and Ultraviolet rays (UV)) were also evaluated. At the beginning of the test, low friction coefficient was observed both in the flight and the AO-irradiated samples. MoO3 was detected from the surface of these samples. A large amount of SiO2 was recognized from the flight sample.
An Abbott Curve Based Rough Surface Contact Mechanics Approach
Authors: Almqvist Andreas , Sahlin Fredrik , Larsson Roland
Published: November 2008

The topography of a machined surface significantly influences the performance of both lubricated and unlubricated contacts. In this work the unlubricated frictionless contact of rough surfaces is the subject of study. The numerical deterministic contact mechanics model incorporates linear elastic surface material and the dry contact is simulated using classes of surface profiles randomly generated from a given Abbott curve (Abbott-Firestone bearing ratio curve). In this way all the height information of the surface profile is preserved and not only a few parameters, like Ra, Rq, Rz, Rsk, etc. The aim of this work is to investigate how classes of surfaces based on a single Abbott curve perform in terms of contact mechanical parameters like the real area of contact. The result shows that surfaces taken from a class of random surfaces generated from a specific Abbott curve behaves similar in a contact mechanics simulation. That is, the distribution of for example the real area of contact within such a class is compact, having a small deviation from its mean. This implies that it is possible to simulate classes of surfaces based on Abbott curves and to use the results to predict contact mechanical properties of real surface topographies.
Response of CVD Boron Carbide to Repetitive Indentation Cycles to Simulate Solid Particle Impact Erosion Mechanisms
Authors: Bose K. , Wood R. J. K.
Published: November 2008

Repetitive nanoindentation tests offer a method to examine the time-dependent degradation mechanisms in coatings. In the case of coated systems for tribological and more specifically for erosion resistant applications, repeated indentation cycles can characterise their durability to repeated erodent impact. This paper reports preliminary observations on the response of 13–18 μm thick CVD boron carbide on tungsten carbide substrates to repetitive indentation cycles, at contact loads similar to those generated in previously reported solid-particle erosion tests on these coatings conducted by this laboratory [1].
Adsorption Modeling of Fatty and Oleic Estolide Esters via Boundary Lubrication Coefficient of Friction Measurements
Authors: Kurth T. L. , Cermak S. C. , Byars J. A. , Biresaw G.
Published: November 2008

The frictional behaviors of a variety of fatty esters (methyl palmitate (MP), methyl laurate (ML), and 2-ethylhexyl oleate (EHO)) and oleic estolide esters (methyl oleic estolide ester (ME) and 2-ethylhexyl oleic estolide ester (EHE)) as additives in hexadecane have been examined in a boundary lubrication test regime using steel contacts. Critical additive concentrations were defined and used to perform novel and simple Langmuir analyses that provide an order of adsorption energies: EHE ≥ ME > EHO > MP > ML. Application of a general adsorption model indicates slight cooperative adsorption of EHE, ME, and EHO. MP and ML data require larger attractive interaction terms (α ≤ −2.3) to be adequately fit. Irrespective of ester functionality increasingly negative adsorption energies appear to correlate with molecular weight. This suggests that multiple site coverage and multiple adsorptive interactions are likely for each of the esters studied.
Design, Analysis and Fabrication of a Six-Legged Walking Machine
Authors: Sehgal Rakesh , Tiwari Ashutosh , Sood Vivek
Published: November 2008

This paper presents the steps involved in the design, analysis and fabrication of a six-legged walking machine. The suggested machine uses the basic four bar chain mechanism and slotted lever type quick return mechanism with some modifications. The synthesis of the link lengths is based on Freudenstein’s (algebraic) three accuracy points. The velocity and acceleration analysis of oscillating links explains the effect of change in the crank’s angular velocity and acceleration on all other links. The suggested machine is capable of moving forward and backward, turning right and left and rotating around a point on the commands given.
Clinical and Laboratory Wear Mechanisms of Artificial Hip Joints (Keynote)
Authors: Fischer Alfons
Published: November 2008

Some open questions raised by the reaction of tissue on particles require the knowledge of the acting wear mechanisms. These have to be clarified within the macro-, micro-, and nanoscale. Thus, this contribution focuses on the wear mechanisms of hard-hard artificial hip joints which have been verified to act both in clinical application and both during laboratory simulation. Some aspects of novel developments will be discussed on the basis of these findings.
Study on the Effect of Hydrogenated Lubricant Base Oil Composition to Its Oxidation Stability
Authors: Hu Xiao Li , Wang Hui Dong
Published: November 2008

In this paper, we studied the high temperature oxidation stability of hydrogenated lubricant base oils used in automobile engine oil formations. Different oil from Daqing, Lanzhou and Kelamayi were investigated, and a hydro-isomerised poly alpha olefin oil PAO-6 produced by Mobile company was used as model oil. The influence of aromatic hydrocarbon, sulfur and nitrogen content of the base oils to their oxidation stability was investigated. The result indicated that, the high temperature oxidation stability of all these base oil was not good, but their thermo-stability was very good.
Research and Experiment on Sleeve Damage Mechanism of Oil Film Bearing in Large-Scale Mill
Authors: Huang Qing-Xue , Wang Jian-Mei
Published: November 2008

During the process of set up and disassembly and usage period, the sleeve of oil film bearing in the backup roll of some 1580PC hot strip mill has been dramatically damaged, which results in production accidents and decreases the service life of bearing. Aimed at such puzzles, theoretical research has been quantitatively analyzed by BEM with 3D elastic-plastic contact, variable laws of stress and strain under different hydroform pressures and axial thrust forces during the setup and disassembly process of sleeve have been drawn, the reasons that result in sleeve failure have been analyzed as well. Finally, Detailed experiments have been made on the two sample mills, which have been manufactured for research and analysis.
On Direct Measurement of Forces Between CMP Polishing Pads and Abrasive Nanoparticles
Authors: Sokolov I. , Ong Q. K. , Chechik N. , James D.
Published: November 2008

The forces of interaction between ceria slurry particles, and polyurethane CMP polishing pads were measured by atomic force microscopy. To measure the forces between the ceria particles and the pads with the AFM, we attached the ceria particles to the AFM tip with epoxy. Attachment of large balls to the AFM tip has been reported before, as well as functionalizing the tip surface with various molecules. Here we report the first successful attachment of nanosize (∼50–100nm) particles to the AFM tip and the direct measurements of forces using such tips. Specifically, we report study of adhesion and long-range force between nanosize ceria particles and three different polyurethane polishing pads. The forces were measured in aqueous solutions of different pH’s ranging from 4 to 9.
Optimization of Air Bearing Slider Design
Authors: Fang Wending , Wang Yujuan , Chen Yunfei
Published: November 2008

Hard disk drives continue to increase the data storage density. The parameters of the head slider flying attitude must satisfy very strict performance goals. This paper focuses on the topic of the simulated annealing algorithm when it is applied to the problem of slider air bearing design in hard disk drives. The objective is to minimize the static flying height, to keep the pitch angle within a reasonable range, and to minimize the roll angle. The design variables include recess depth and geometry configuration of the slider air bearing surface. A typical tri-pad slider was taken as the physical model to demonstrate the validity of the optimal algorithm. Results show that simulated annealing is efficient for the optimization of the slider air bearing design. The static air bearing characteristics were enhanced significantly.
Tribomicroplasma Generation in Diamond Like Carbon and Related Films
Authors: Nakayama Keiji
Published: November 2008

Characteristics and mechanism of microplasma generated at a sliding contact is presented and discussed for diamond like carbon and related films.
Modeling Tribological Impact on Overall System Dynamics
Authors: Gupta Pradeep K.
Published: November 2008

While the support bearings are key elements of rotating machinery systems, the overall system performance and design depend on a close integration of several disciplines. For prescribed life and operating environment the applied static loads and speeds on each of the system component may be generally determined by an equilibrium analysis. Conventional rotor dynamics models may be used to model overall system dynamics, rotor response and dynamic loads imposed on the support bearings. As a function of these applied conditions bearing response and dynamic performance is determined by integration of the equations of motion of each bearing element; in the case of rolling bearings, the available bearing dynamics models, such as ADORE (Advanced Dynamics Of Rolling Elements) provide integration of the classical differential equations of motion to model real-time performance of the bearing. With prescribed bearing geometry and applied operating conditions, it is well established that lubricant properties and mechanics play a major role in determining the stability of bearing elements and overall system performance. The rolling-sliding interactions in the concentrated contacts between the bearing elements produce heat, which travels through the bearing and the overall system. This affects temperature of the bearing elements, which in turn changes the bearing geometry and material behavior including the lubricant. Thus overall system design and performance simulation requires a close iteration between the various models at varying levels of sophistication.
Synthesis of the Multifunctional Additive N-acyl Glutamic Acid and Application in Water-Based Lubricating Fluids
Authors: Jiang Haizhen , Tao Dehua , Wang Bin
Published: November 2008

A series of N-acyl glutamic acid were prepared by reaction of glutamic acid with chlorides (1–3) or anhydrides (4–8) in good yield, within the solution of pH 8–10, keeping the reaction at 10∼15°C for 2–3 hours. The tribological behaviors of the resulting N-acyl glutamic acid salts with triethanolamine as additives in water were examined on a four-ball machine. The rust-inhibiting properties were evaluated. The elemental composition of the boundary lubricating film was analyzed by means of auger electron spectroscopy (AES). It was found that the N-acyl glutamic acid with long acyl chain functioned to considerably increase anti-wear and friction-reducing abilities of water. The rust-inhibiting properties got better with increase of the length of acyl-chain of N-acyl glutamic acid triethanolamine slats. And the additives had relative good antimicrobial properties in water.
Finite Element Analysis of Ceramic Coating Systems Under Spherical Indentation With Metallic Interlayer: Part II — Ring Crack Analysis
Authors: Le Minh-Quy , Yi Jin-Woo , Kim Seock-Sam
Published: November 2008

Spherical indentation problems of ceramic coatings/metallic inter-layer/ductile substrate were investigated numerically by axisymmetric FEA for two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel. The fracture mechanics of the ceramic coatings due to occurrence of surface ring cracks extending traverse coating thickness under spherical indenter were considered under the framework of linear fracture mechanics. The J-integral associated to such cracks was computed. The evolution of J-integral versus crack length and indentation depth was studied. The results show that metallic inter-layers can improve the fracture resistance of the ceramic layer under the same indentation conditions.
The Erosion-Corrosion of Intake Valve Sealing Surfaces Due to the Formation of Lubricating Oil Deposits
Authors: Truhan John J. , More Karren L. , Rangarajan Roger S.
Published: November 2008

Intake valves from natural gas-fired reciprocating engines displaying “torching” were examined to determine their failure mechanism. The principal features of the “torched” valves include a relatively thick black deposit on the tulip area of the valve extending to the sealing surface, partial loss of those deposits in various locations, and localized metal loss, oxidation and/or surface cracking in the spalled regions. Electron microprobe, scanning electron microscopy, and optical microscopy were employed to characterize the deposit formation and metal loss mechanisms. The initial cause of the torching appears to be due to the localized spallation of a loosely adherent (Ca,Zn) phosphate oil deposit adjacent to the valve/seat seal which creates a channel of hot, high velocity combustion gases. Within the torched area, significant metal oxidation and metal recession due to erosion/corrosion was observed on the valve sealing face, creating a relatively wide gap where a valve/seat seal should be. In areas where torching is not evident on the valve sealing surface, no appreciable metal recession (but limited metal oxidation) was observed.
Fretting Behaviour of PACVD Deposited DLC Coatings Against Different Counter Bodies
Authors: Palmers J. , Vanhollebeke K. , Celis J. P. , Van der Donck T.
Published: November 2008

The aim of this study was the investigation of the fretting wear of industrial and newly developed multi-layered coatings. The tribological behaviour of flat DLC coated specimens was investigated in fretting mode I and fretting mode II against different ball counterbodies namely, corundum, 100Cr6, and DLC coated 100Cr6 using a broad range of strokes, frequencies, and loads. From Fretting I a dependency of the wear behaviour with the type of DLC coating, and an influence of the normal load with the coefficient of friction was observed. Using Fretting mode II, an attempt was made to study the fatigue and toughness properties of the coatings.
The Measurement of Component Friction Losses in a Fired Engine: Part 1 — Experimental Method
Authors: Mufti Riaz A. , Priest Martin
Published: November 2008

The direct relationship of frictional loss and fuel economy in an internal combustion engine has resulted in increasing interest in understanding the performance of the engine at the component level. Also for the development of new engine lubricants it would be better to have an in-depth analysis of the interaction of lubricants with each individual engine component under fired conditions. With the advances in data acquisition system and sensor technology, extensive study of the main engine components i.e. valve train, piston assembly and engine bearings has been possible resulting in the development of a versatile engine friction measurement system. Total engine and component friction measurement was carried out on a single cylinder Ricardo Hydra gasoline engine under fired conditions at various lubricant temperatures, engine speeds and loads. The engine was fitted with more than fifty different sensors and to sample/log data from such a large number of transducers, an advanced high-speed synchronised data acquisition system was designed/developed. Experiments are reported for total and component friction at a range of engine operating conditions with SAE 0W20 and friction-modified SAE 5W30 lubricants. Due to the nature of the research work, the findings are presented in two parts. The first part, which is this paper, explains the complex measurement methods used to measure component friction whereas the results are discussed in the second part. This system can be used as a powerful tool for screening engine oils and studying the effect of different additives on the performance of each component under realistic conditions.
Development of a Combined Analytical and Empirical Model for Beveling of Quartz Crystal Wafers
Authors: Dong Chensong (Jonathan)
Published: November 2008

Beveling or contouring is an important step in the processing of quartz crystal wafers used in resonators. This paper presents a combined analytical and empirical approach for contouring process modeling. Based on the bevel profile measurement the material removal mechanism is analyzed and new characteristics describing the beveling process are introduced. A process model is developed to determine the process parameters of beveling. Compared to the traditional trial-and-error approach, this approach provides a powerful tool for developing beveling methods for new crystal wafer design and beveling process optimization.
The Influence of Friction Stability on the Success of Lubricated Stamping Operations: Predictive Tools From Plane Friction Tests
Authors: Ca´rcel A. C. , Pe´rez Puig M. A.
Published: November 2008

This work was aimed at analysing the influence of the tribological behaviour on the onset of systematic fractures of car body parts during stamping, and at developing an alternative friction evaluation system, able to detect in advance the risk of failure by galling or seizing when stamping zinc coated (electrogalvanized or hot dip galvanized) steel sheets. The friction test reproduces the severe boundary lubrication conditions found in real practice, and also the progressive deterioration of the initial surface topography that the sheet suffers as a result of the pass through the draw-beads before reaching the die entry. Under these conditions, it was found that the initial values of the coefficient of friction have only a limited effect on the real behaviour, and that successful stamping relies mainly on the stability of the friction values as the length of sheet under pressure between the tools increases. Some index parameters obtained from this test can be used to predict in advance with high reliability the risk of lubricant breakdown and galling during real stamping.
The Impact of Chemical Mechanical Planarization Polishing on a Surface Textured With Deterministic Microasperities
Authors: Kazi Hassan I. , Stephens Lyndon S.
Published: November 2008

In this paper a method for fabricating deterministic microasperities on stainless steel by a photolithographic lift-off technique followed by electrodeposition of nickel is presented. Triangular asperities with an asperity area fraction of 0.20 are deposited onto a stainless steel disk. Chemical mechanical planarization (CMP) polishing is employed for adjusting the heights of the asperities. The surface profiles of the asperities are then characterized. Results show that the surfaces of the as-deposited asperities have a curved profile with one side shorter than the other. The surface profile becomes more uniform after polishing in the CMP machine but polishing tends to round the edges and corners of the asperities. Additionally, polishing results in the grooving of channel in the substrate in between the asperities and chips the asperity walls.
Tribological Behavior of Oil-Lubricated Laser Textured Surfaces in Conformal Flat and Point Contacts
Authors: Kovalchenko Andriy , Ajayi Oyelayo , Erdemir Ali , Fenske George , Etsion Izhak
Published: November 2008

The effects of laser surface texturing (LST), which involves the creation of an array of microdimples on the surface with laser, on friction and wear behavior of oil-lubricated steel surfaces were evaluated. Tests were conducted in unidirectional sliding in both the conformal and non-conformal contact configurations with a pin-on-disc test rig using fully formulated synthetic oil lubricant. In conformal contact, LST expanded the operating conditions for mixed and hydrodynamic lubrication regimes to higher loads and slower speeds i.e. the Stribeck curve was shifted to the left. LST was also observed to reduce the magnitude of friction coefficients in the boundary regime. For the non-conformal contact configuration, LST produced more wear on the rubbing counterface compared to untreated surfaces. This also accelerated the run-in process in the tests with LST treated surfaces.
Near Surface Measurement of Mechanical Properties Using Instrumented Indentation Measurements
Authors: Farhang K. , Seitzman L. E. , Feng B.
Published: November 2008

A two-parameter function for estimation of projected area in instrumented indentation measurement is obtained to account for indenter tip imperfection. Imperfection near indenter tip-end is modeled using a spherical function and combined with a linear function describing the edge boundary of the indenter. Through an analytical fusion technique the spherical and linear functions are combined into a single function with two unknown geometric parameters of tip radius of curvature and edge slope. Data from indentation measurement of force and displacement, using a Berkovich tip and single crystal alumina and silica samples, are implemented in the proposed area function yielding estimated values of Young’s modulus. Results were compared with that obtained from Oliver and Pharr technique for deep as well as shallow indentation regimes. The estimates for Young’s modulus were found to agree quite favorably. More importantly, in contrast to the Oliver-Pharr technique, the use of the two-parameter function resulted in a significantly more accurate estimation of Young’s modulus for shallow indentation depth of 0 to 100 nm. The error in estimation of Young’s modulus was found to be within 10 percent for indentation depths 25 nm to 50 nm and within 20 percent for indentation depths 0 to 25 nm.
Study on the Selection of Critical Electro Discharge Machining Surface Parameters Based on Robust Design of Experiments
Authors: Capela C. , Gaspar M. C. , Fernandes N. O. , Grego´rio F.
Published: November 2008

Design of experiments helps to achieve robust design by establishing product and process parameters that optimize product performance. In this work, the authors have used the Taguchi approach in order to optimize the process parameters of electro discharge machining (EDM) finishing on the surface of a specially developed mould steel workpiece.
Rail Corrugations Caused by Low Coefficient of Friction in a Submarine Railway Tunnel
Authors: Ishida Makoto , Aoki Fusayoshi , Sone Yasutomo , Ban Takumi , Shirouzu Kensuke
Published: November 2008

One of some types of rail corrugations is caused on railway rail surface in a submarine tunnel. It poses a large problem from the aspects of railway vehicle and railway track deterioration. In this paper, the mechanism of the rail corrugations was studied with the focus placed on roll-slip of wheel and rail interface. Traction and vertical force interacting between wheel and rail were investigated by a vehicle/track interaction model, and the coefficient of friction (COF) on rail surface was measured. Also, the rail surface was analysed with infrared to understand the chemical composition of surface layer influenced by salty and very humid atmosphere in the submarine tunnel. β-FeOOH was found out as a cause of reducing COF on rail surface.
Activation of SiC Surfaces for Vapor Phase Lubrication by Chemical Vapor Deposition of Fe
Authors: Kim Donggun , Gellman Andrew J.
Published: November 2008

Vapor phase lubrication (VPL) has been proposed as a method for lubricating high temperature engines. During VPL, lubricants are delivered through the vapor phase to high temperature engine parts and react on their surfaces to deposit a thin, solid, lubricating film. Although ceramics such as SiC are desirable materials for high temperature applications, their surfaces are unreactive for the decomposition of TCP and thus not amenable to vapor phase lubrication. As a means of activating the SiC surface for TCP decomposition we have used chemical vapor deposition of Fe from Fe(CO)5. Modification of the SiC surface with adsorbed Fe accelerates subsequent decomposition of TCP and deposition of P and C onto the surface. In the temperature range 500–800 K, m-TCP decomposes more readily on Fe-coated SiC surfaces than on SiC surfaces. The C and P deposition rates depend on the thickness of the Fe film and are further enhanced by oxidation of the Fe. This work provides a proof-of-concept demonstration of the feasibility of using vapor phase lubrication for ceramics.
Resolving the Contradiction of Asperities Plastic to Elastic Mode Transition in Current Contact Models of Fractal Rough Surfaces
Authors: Morag Yahav , Etsion Izhak
Published: November 2008

The elastic-plastic contact model of fractal rough surfaces offered by Majumdar and Bushan in 1991 (the MB model) is revisited. According to the MB model, the contact mode of a single fractal asperity transfers from plastic to elastic when the load is increased, and the asperity’s contact area grows and becomes larger than a critical area, which is scale independent. This surprising result of the MB model is in contrast with classical contact mechanics where an increase of contact area due to increased load, is associated with a transition from elastic to plastic contact. The present study describes a revised elastic-plastic contact model of a single fractal asperity showing that the critical area is scale dependent, contrary to the MB model prediction. The new model also shows that a fractal asperity behaves as would be expected from classical contact mechanics namely, as the load and contact area increase a transition from elastic to plastic contact takes place in this order.
Adsorption of a Fatty Acid Onto a Deformed Electrogalvanized Steel Sheet
Authors: Vache´ V. , Repoux M. , Mataigne J.-M.
Published: November 2008

During forming operation of electrogalvanized steel sheets, the crystallographic orientation of the zinc coating may evolve from a pyramidal texture to a basal one. As a consequence, the adsorption of lubricant additives onto the zinc surface may be altered. Plane-strain compression tests and XRD analysis are carried out to study the texture evolution. After deformation, the samples are cleaned and their reactivity versus fatty acids are measured by ToF-SIMS analysis. It is shown that fatty acids adsorb much more strongly on a pyramidal oriented zinc surface than on a basal one.
The Selection and Testing of Compression Seal and Chamber Coating Materials for the Pivotal™ Engine
Authors: Miller David J. , Kral Milo V.
Published: November 2008

The Pivotal™ Engine was conceived by Pivotal Engineering LTD to overcome some of the inherent problems associated with a conventional two-cycle engine, such as high wear rates and friction losses due to piston tilt and large port openings, reliability problems due to lack of control over piston temperatures and high oil consumption. The Pivotal engine is an Otto cycle two-stroke engine. The engine is assembled from 500cc modules utilizing a rectangular piston that pivots on a plain bearing at one end. The pivoting motion of the piston allows coolant to enter the piston through the centre of the pivot giving temperature control of the combustion chamber while restraining the piston so it has little or no contact with the chamber walls. Although friction loss, temperature control and oil consumption problems have thus been mitigated, prototype engines still experienced problems with high compression seal wear rates. Compression seals run in a reciprocating motion along a flat chamber wall, somewhat analogous to piston rings in a conventional engine, although velocity varies along the seal length. The goal of this research is therefore to select and test compression seals materials to obtain an adequate working life in the Pivotal engine. Based on the rotational tribometer results, the most promising chamber coating so far is plasma sprayed iron with molybdenum and the most promising seal material is reaction bonded silicon nitride.
Numerical Simulation and Experimental Study on the Effect of Ramp Profile, Friction and Flex-Cable Force on the L/UL Process for Small Form Factor HDD
Authors: Park Kyoung-Su , Chun Jung-Il , Jung Moon-Gyo , Lee Yonghyun , Park No-Cheol , Yang Hyun-Seok , Park Young-Pil
Published: November 2008

So in developing a system with high areal density and that resist external shock and disturbances, the essential mechanism is L/UL system. L/UL system has many benefits when applied to a small form factor (SFF) HDD. It allows for higher areal density increase since it is possible to reduce the flying height of slider and eliminate the texture zone that is used for parking for contact-start-stop systems. In addition, it allows for lower power consumption and prevents the head-slap between slider and disk during non-operating conditions.
Influence of the Pitch Static Torque of the Suspension on the Multiple Flying States of the Air Bearing Sliders
Authors: Hua Wei , Liu Bo
Published: November 2008

This paper studies of the pitch static torque of the suspension on the multiple flying states of two types of the negative pressure slider by simulation. It is revealed that the sliders may have one to three balanced flying states under certain conditions. Only one of the states is lower enough for normal read/write operations. The relationship between the multiple flying states and the pitch static torque is presented, and the methods to avoid of the higher flying states are discussed. A special method to search for the multiple flying states is introduced.
A Simulation Method for Spreading Dynamics of Molecularly Thin Lubricant Films on Magnetic Disks Using Bead-Spring Model
Authors: Tagaya Yoichi , Mitsuya Yasunaga , Ogata Susumu , Zhang Hedong , Fukuzawa Kenji
Published: November 2008

An effective simulation technique for describing the spreading properties of molecularly thin lubricant films on magnetic disks has been developed. We propose a molecular precipitation method that can simulate initial molecule arrangement of the films dip-coated onto the disks. Reptation and Rouse models as the model of the molecular motion, and molecular insertion and molecular precipitation methods as the method for putting molecules in initial positions were compared. From the results of the spreading profiles and diffusion coefficients, it has been revealed that the molecular precipitation method combined with the Rouse model is effective in simulating the spreading of the lubricant films.
Fatigue Life Investigation of Solid and Hollow Rollers in Pure Rolling Contact
Authors: Abu Jadayil W. , Flugrad D. , Qamhiyah A.
Published: November 2008

Two solid and hollow cylindrical rollers in pure rolling contact have been modeled. The two rollers are subjected to a combined normal and tangential loading. The Stress distribution in the contact zone has been determined using a finite element package called ABAQUS. Then fatigue life model for rolling bearings developed by Ioannides and Harris has been used to study the relative fatigue life of the hollow rollers compared to solid rollers. Different hollowness percentages have been investigated; 20%, 40%, 60% and 80%. Two cases were studied- when both rollers are hollow and when only one of them is hollow while the other one is solid. It has been found that making the rollers hollow will result in redistribution of stresses in the contact zone. That decreased the peak stress under the surface when compared to the solid cylinder. Hollow cylinders have more flexibility when subjected to normal and tangential loading. And so, the stresses are redistributed so that the fatigue life is improved. The best fatigue life improvements have been found when both cylinders have almost 60% hollowness.
Radar Sounding Evidence for Buried Glaciers in the Southern Mid-Latitudes of Mars
Authors: Holt John W. , Safaeinili Ali , Plaut Jeffrey J. , Head James W. , Phillips Roger J. , Seu Roberto , Kempf Scott D. , Choudhary Prateek , Young Duncan A. , Putzig Nathaniel E. , Biccari Daniela , Gim Yonggyu
Published: November 2008

Lobate features abutting massifs and escarpments in the middle latitudes of Mars have been recognized in images for decades, but their true nature has been controversial, with hypotheses of origin such as ice-lubricated debris flows or glaciers covered by a layer of surface debris. These models imply an ice content ranging from minor and interstitial to massive and relatively pure. Soundings of these deposits in the eastern Hellas region by the Shallow Radar on the Mars Reconnaissance Orbiter reveal radar properties entirely consistent with massive water ice, supporting the debris-covered glacier hypothesis. The results imply that these glaciers formed in a previous climate conducive to glaciation at middle latitudes. Such features may collectively represent the most extensive nonpolar ice yet recognized on Mars.
Control of Toxic Marine Dinoflagellate Blooms by Serial Parasitic Killers
Authors: Chambouvet Aurelie , Morin Pascal , Marie Dominique , Guillou Laure
Published: November 2008

The marine dinoflagellates commonly responsible for toxic red tides are parasitized by other dinoflagellate species. Using culture-independent environmental ribosomal RNA sequences and fluorescence markers, we identified host-specific infections among several species. Each parasitoid produces 60 to 400 offspring, leading to extraordinarily rapid control of the host's population. During 3 consecutive years of observation in a natural estuary, all dinoflagellates observed were chronically infected, and a given host species was infected by a single genetically distinct parasite year after year. Our observations in natural ecosystems suggest that although bloom-forming dinoflagellates may escape control by grazing organisms, they eventually succumb to parasite attack.
Antimicrobial Defense and Persistent Infection in Insects
Authors: Haine Eleanor R. , Moret Yannick , Siva-Jothy Michael T. , Rolff Jens
Published: November 2008

During 400 million years of existence, insects have rarely succumbed to the evolution of microbial resistance against their potent antimicrobial immune defenses. We found that microbial clearance after infection is extremely fast and that induced antimicrobial activity starts to increase only when most of the bacteria (99.5%) have been removed. Our experiments showed that those bacteria that survived exposure to the insect's constitutive immune response were subsequently more resistant to it. These results imply that induced antimicrobial compounds function primarily to protect the insect against the bacteria that persist within their body, rather than to clear microbial infections. These findings suggest that understanding of the management of antimicrobial peptides in natural systems might inform medical treatment strategies that avoid the risk of drug resistance.
Cross-Reactive Immunity to Clade 2 Strains of Influenza Virus A Subtype H5N1 Induced in Adults and Elderly Patients by Fluval, a Prototype Pandemic Influenza Virus Vaccine Derived by Reverse Genetics, Formulated with a Phosphate Adjuvant, and Directed to Clade 1 Strains
Authors: Fazekas György , Martosne-Mendi Rita , Jankovics Istvan , Szilvasy Istvan , Vajo Zoltan
Published: November 2008

High fatality rates and multiple cases of transmission of avian H5N1 influenza viruses to humans illustrate the urgent need for an efficacious, cross-protective vaccine against H5N1 strains. Extensive genetic characterization of H5N1 strains has elucidated the natural evolutionary relationship of these strains, linking groups known as clades to a common ancestor. Although the clades and subclades probably differ sufficiently in their antigenic structure to warrant the preparation of different vaccines, there is some evidence that cross-reactive immunity can be afforded. We aimed to assess the immunogenicity of a clade 1 H5N1 (NIBRG-14) whole-virus vaccine with an aluminum phosphate adjuvant and to determine whether it can induce cross-reactive immunity against antigenically drifted clade 2 H5N1 strains, both those derived by reverse genetics and wild-type isolates. A total of 88 (44 adult and 44 elderly) subjects, who received one dose (6 μg) of the vaccine, were studied. As judged by U.S. and European licensing criteria based on hemagglutination inhibition, the subjects developed cross-reactive immunity against all studied H5N1 strains belonging to a clade different from that of the strain utilized to produce the vaccine. Our findings highlight the importance of stockpiling, since cross-immune reactions induced by prepandemic vaccines will likely reduce morbidity and mortality in case of a pandemic.
Occurrence and Characteristics of Class 1 and 2 Integrons in
Pseudomonas aeruginosa
Isolates from Patients in Southern China
Authors: Xu Zhenbo , Li Lin , Shirtliff Mark E. , Alam M. J. , Yamasaki Shinji , Shi Lei
Published: November 2008

Class 1 and 2 integrons were detected in 45.8% (54/118) and 19.5% (23/118) of our tested
Pseudomonas aeruginosa
isolates, respectively. Three strains were positive for both the integrons. This is the first report of class 2 integrons in
P. aeruginosa
and also of isolates carrying class 1 and 2 integrons simultaneously.