bluuebunny/crossref_metadata_2025 huggingface dataset:
The FITNET Fracture Module: Developments and Content
Authors: Webster Stephen
Published: November 2008

FITNET is a four-year European thematic network with the objective of developing and extending the use of fitness-for-service (FFS) procedures for welded and non-welded metallic structures throughout Europe. It is partly funded by the European Commission within the fifth framework programme and commenced in February 2002. The network currently consists of about 50 organisations from 17 European countries but also includes contributions from organisations in the USA, Japan and Korea. Further information can be found in the FITNET TN website: http://www.eurofitnet.org. The FITNET FFS Procedure is built up in four major analysis modules namely; Fracture, Fatigue, Creep and Corrosion and the procedure is being developed for completion in early 2006 in the form of CEN Document. The aim of this paper is to present the features, main analysis routes and major areas of technical development pertinent to the Fracture Module of the FITNET FFS Procedure. The procedure is based on previous developments carried out within the SINTAP project as well as advances in other standards such as the British Energy R6 rev 4 and the current amendments to the British Standard BS7910. In addition the work from other EU projects has been used to extend the treatment of several problem areas, such as the effect of constraint and the treatment of thin walled structures.
European Fitness-for-Service Network (FITNET): Fatigue Module Development
Authors: Janosch Jean-Jacques , Huther Michel , Taylor Nigel , Maddox Steve , Kocak Mustafa
Published: November 2008

FITNET is a four-year European thematic network with the objective of developing and extending the use of fitness-for-service (FFS) procedures for welded and non-welded metallic structures throughout Europe. It is partly funded by the European Commission within the fifth framework program and it was launched in February 2002. The network currently consists of about 50 organisations from 17 European countries and supported by institutions from USA, Japan and Korea. Further information can be found in the FITNET TN website: http://www.eurofitnet.org. The FITNET FFS Procedure is built up in four major analysis modules namely fracture, fatigue, creep and corrosion. The first official draft is available in early 2006 in the form of an official CEN document. Industrial components are as a rule exposed to fluctuating loads and hence consideration of fatigue damages accumulation or of fatigue crack growth is a critical issue. The aim of this paper is to present the features and the main analysis routes of the FITNET FFE Fatigue Module of the FITNET FFS Procedure to assess the fatigue life of the load carrying metallic components manufactured with and without welds. The paper includes an industrial case from ship structure for the application of two fatigue assessment routes.
Environment Induced Cracking: A Fitness for Service Perspective
Authors: Turnbull A. , Koers R. W. J. , Gutie´rrez-Solana F. , A´lvarez J. A.
Published: November 2008

A summary is given of the key steps in undertaking an assessment of structural integrity where stress corrosion cracking or corrosion fatigue (collectively environment induced cracking) is the dominant failure mode.
The Treatment of Constraint Effects in Integrity Evaluations
Authors: Cicero S. , Ainsworth R. A.
Published: November 2008

Shallow cracks in components subjected to tension have lower hydrostatic and maximum principal stresses near the crack tip than deep cracks in bending stress fields. These lower stresses near the crack tip lead to increased load carrying capacity compared to that estimated using the fracture toughness obtained from deeply cracked bend specimens. This is referred to as ‘loss of constraint’ and fracture assessment procedures such as R6 contain methods for estimating the increased load carrying capacity under these conditions. More generally, low constraint occurs near blunt notches and at small cracks emanating from such notches. Within the European project FITNET, methods are being developed to address constraint effects both for shallow cracks and for notches and cracks at notches. After an initial review, this paper describes the constraint procedures being developed within FITNET. These are separate procedures for cracks, notches and cracks at notches. The paper then discusses how these separate procedures might, in the future, be combined to produce an overall constraint procedure.
Note on the Distribution of Extreme Wave Crests
Authors: Baxevani Anastassia , Hagberg Oskar , Rychlik Igor
Published: November 2008

The sea elevation at a fixed point is modelled by means of a second order model, which is a smooth algebraic function of a vector valued Gaussian process. Asymptotic methods, presented first in [1], are used to estimate the mean upcrossing intensity μ+ (h). The intensity is then used to determine the density of crest height in a second order sea. Numerical examples illustrate the method. The proposed approximation is used to estimate the design crest height for a specified return period.
Integrity Management of Deep Water Floating Production Facilities: Towards Better and Safer Workforce Personnel
Authors: Morandi Alberto C. , Galiotos John K.
Published: November 2008

The oil and gas industry has, over the recent years, invested heavily in multi-billion dollar projects aimed at developing an exploration and production infrastructure in the deepwater Gulf of Mexico. The integrity management of such facilities will be critical for the industry in the coming years. Competency of Personnel stands out as the most important of these areas. Although office-based personnel plays an important part, the personnel working offshore such as OIMs, supervisors, ballast operators and topsides operators will make critical decisions that may affect the safety of an entire production unit. Alliances between offshore industries, contractors and community colleges generate curricula exclusively tailored to provide specific training and retraining to new hires on the duties and tasks performed by the oil and gas production technician and encumbered workers of the offshore industry. Offshore oil and gas extraction organizations are faced with unique challenges, when needing competent, skillful, safe, and well trained workers. Liabilities from non-trained personnel, and the understanding that safety is priority #1 on the platform, are paramount in concepts of the offshore workforce. Unlike other areas of the world, production in the Gulf of Mexico has been predominantly on the shallow water continental shelf and many organizations are faced with the challenges of developing new sets of skills for different types of production facilities used in deep water. Training of technicians, who will be operating an offshore deepwater platform, should cover topics that include ballast control and stability management, vessel station-keeping, riser management, response to hurricanes and loop currents, hydrocarbon and operations safety, process equipment and systems, troubleshooting, sub-surface geology, petroleum engineering and drilling technology. This paper discusses collaborative initiatives and discusses specific solutions. Based on a multi-year experience generating of such curricula, recommendations are provided to industries that want to establish such training programs for their technical personnel.
Girth Weld Qualification for High Strain Pipeline Applications
Authors: Hukle Martin W. , Horn Agnes M. , Hoyt Douglas S. , LeBleu James B.
Published: November 2008

Pipeline applications that are subject to global plastic strains require specific testing and qualification programs intended to verify the strain capacity of the girth welds. Such strain demands are generally beyond the limits of standard ECA applicability which normally cover demands up to 0.5% strain. Therefore, qualification of welding procedures for high strain environments require significantly more testing than weld procedures intended for stress-based designs. The plastic strain capacity of girth welds is a function of the pipe and weld metal properties, as well as the maximum flaw size allowable in the girth weld. Specific weld metal/heat affected zone properties, based on small scale testing, should be combined with full scale curved wide plate testing of girth welds that include artificial flaws.
Octabuoy SDM: A Compact Semi-Submersible Design for Deepwater Applications
Authors: Korbijn Florus , Husem Ida , Pettersen Erik
Published: November 2008

A new floater concept based on proven technology but combining this technology in a novel way has been designed for Deepwater operation in the Gulf of Mexico and other deepwater locations. The Octabuoy SDM (Shallow Draught, Mooring assisted) is a semi-submersible with a design and a tuned mooring system that ensure improved motion characteristics compared to other semi-submersibles. This makes the floater very well suited for accommodating Steel Catenary Risers (SCRs) in the Gulf of Mexico and dry tree solutions for West Africa. Motion results calculated for a typical Gulf of Mexico wave environment, using a coupled time domain approach are confirmed by extensive model testing of the concept, which proves the ability of the proposed concept to accommodate SCRs specifically for the Gulf of Mexico. Because of its relative shallow draught (23m) the platform is less susceptible to vortex induced motions (VIM) in loop currents compared to SPAR and other deep draught floaters. Theoretical considerations and model tests have proved the favorable platform behavior with respect to VIM. The Octabuoy SDM has a favorable topside load-to-hull weight ratio, which makes it a highly competitive solution compared to other semi-submersibles. Another advantage is that the platform may be outfitted and commissioned quayside.
A Review of Fatigue Curves for Mooring Lines
Authors: Rossi Ronaldo Rosa
Published: November 2008

For mooring chains of offshore floating production units, API (American Petroleum Institute) recommends the use of its TxN fatigue curve considering the MBL (Minimum Breaking Load) of an ORQ (Oil Rig Quality) chain even if the chain has a higher grade. This curve has been used in mooring system design of offshore floating production units since the draft edition of API Recommended Practice for Design, Analysis and Maintenance of Catenary Mooring for Floating Production Systems in May 89 and several fatigue tests have been done by petroleum industries, chain manufacturers and research centers. Those fatigue tests show that the use of the MBL of an ORQ chain for higher grades is a conservative assumption. This paper will present an overview of the fatigue curves of materials for mooring lines: stud and studless chains, steel wire ropes and polyester fiber ropes. This overview is based on recent tests, rules and published papers.
Ocean Wave Spectral Estimation Using Vessel Wave Frequency Motions
Authors: Pascoal R. , Guedes Soares C. , So̸rensen A. J.
Published: November 2008

Parametric and non-parametric spectral descriptions are used to estimate the wave spectra from wave frequency motions of a vessel at low advance speed, using minimization procedures based on a constrained gradient search and a genetic algorithm. The parametric description provides smooth power spectral energies as a result of the analytic spectral description. The non-parametric requires a smoothing post processing if very good readability is needed. It has been concluded that the non-parametric description is faster, more robust to model errors and likely to be a better formulation for adaptive algorithms.
Touchdown Analysis of Jack-Up Units for the Definition of the Installation and Retrieval Operational Limits
Authors: Matter Ge´rson B. , da Silva Ricardo Rios M. , Tan Pao-Lin
Published: November 2008

The paper presents the development of a methodology for the definition of the operational limits for Self-Elevating Units, during the “jack-up” and “jack-down” operations. The methodology is based on the structural analysis of the unit during the impact between the spud can and the soil. The mechanics of the impact is based on the first principle of Momentum Theory and the Virtual Work Theory. The study includes the development of a motion analysis in order to obtain the allowable maximum wave heights that guarantee the integrity of the unit.
Tribological Aspects of Wind Power Plants
Authors: Bartz Wilfried J.
Published: November 2008

Using sustainable and renewable energy resources becomes more and more important. One possibility is the use of the energy content of the wind. During the past 20 years the wind energy technology experienced a remarkable development. More than 50 countries world wide are producing wind energy. The forecasts for 2005 are about 8,525 MW installations in Europe and 12,175 MW world wide. The accumulated capacity at the end of 2005 will be in the order of magnitude of 65,000 MW (2). The main growth market is still Europe, followed by the USA and by Asia. In Europe the countries with the highest figures are Germany, Spain and Denmark. Until the end of 2005 in Germany an accumulated power output of about 18,000 MW will be installed (2).
A Test Rig for Air Bearings Dynamic Characterization
Authors: Bellabarba E. , Ruiz R. , Di´az S. , Rastelli V.
Published: November 2008

This paper describes the design and operation of an experimental facility for measurement of equivalent stiffness and damping of air bearings. The rig uses two magnetic bearings to impose any given orbit to the journal, including displacement in two perpendicular directions on the rotation plane and tilting on the conical mode. Dynamic forces are measured directly on the test bearing housing. Data is gathered and processed using PC based data acquisition boards and software. Only the stiffness and damping coefficients of the fluid film are calculated as a function of the excitation frequency, being it synchronous or not. The present design allows testing air bearings up to 44 mm in external diameter and at frequencies up to 1 KHz. Preliminary testing was performed on this research that demonstrates the capability of the apparatus to measure the dynamic properties with ease and accuracy.
Synthetic Lubricants Based on Sebacic Complex Esters
Authors: Mirci Liviu E. , Boran Sorina , Luca Paula , Boiangiu Victor
Published: November 2008

The paper present the results carried out in order to produce synthetic ester oils with a complex structure on the basis of sebacic acid with beneficial tribological properties. Three series of unsymmetrical diesters have been synthesized by taking into account superior aliphatic alcohols such as 2-ethyl-hexanol, isodecanol and isotridecanol along with special alcohols of a complex alkyl-aryl structure, namely 2-phenoxy-ethanol, 2-[(o sec butyl)-phenoxy] ethanol and 2-[(p-nonyl)-phenoxy] ethanol, respectively. There were also synthesized the symmetrical (homogeneous) esters based on these special aliphatic-aromatic alcohols.
Wear Resistance and Self-Organizing of Near-Surface Structure of Stainless Steels Under Boundary Friction
Authors: Novytskyy Viktor G.
Published: November 2008

Influence of initial structure of stainless steels on self-organizing process of second structures under boundary friction is investigated. At the minimal wear rate in near-surface friction layers the syncretic ratio between quantity of γ- and α-phases, and also dislocation density in them is established. This ratio corresponds to fractions which are quotient of Fibonacci numbers taken through one: 1/1, 1/2, 2/3, 3/5, 5/8, 8/13, ....
Statistical Distribution of Tapered Roller Bearing Fatigue Lives at High Levels of Reliability
Authors: Kotzalas Michael N.
Published: November 2008

The original two-parameter Weibull distribution used for rolling element bearing fatigue tends to greatly underestimate life at high levels of reliability. This fact has been proven for through hardened ball, cylindrical and spherical roller bearings, as well as linear ball bearings, by other researchers. However, to date this has not been done with tapered roller bearings (TRB) or case carburized materials, and as such this study was conducted. First, the three-parameter Weibull distribution was utilized to create a mathematical model, and statistical data analysis methods were put into place. This algorithm was then investigated as to its ability to discern the shape of the reliability distribution using known, numerically generated, data sets for two and three-parameter Weibull distributions. After validation, an experimental data set of 9702 TRB’s, 98% of which were case carburized, was collected. Using the developed algorithm on this data set, the overall RMS error was reduced from 26.0% for the standard, two-parameter to 12.2% for the three-parameter Wiebull distribution. Also, the error at 99.9% reliability was reduced from 95.8% to 37%. However, as the results within varied from previously published values at high reliabilities, there is likely a difference in the underlying population and/or dependency on the statistical and mathematical methods utilized. Therefore, more investigation should be conducted in this area to identify the underlying variables and their effects on the results.
Effect of Initial Structure of Cast Composites Fe-Cr-Cu-C-(Me) on the Formation of Near-Surface Structure Under Dry and Boundary Friction
Authors: Novytskyy Viktor G. , Havryliuk Vladimir P. , Kaltchuk Nikolay A. , Panasenko Dina D.
Published: November 2008

In this paper wear resistant characteristics of cast composites (CC) of Fe-Cr-Cu-C- (Me) system containing in initial structure soft copper contained ε- phase (solid lubricant), hard phase (eutectic carbide) are investigated.
Theory of the Limiting States of Active Systems
Authors: Sosnovskiy Leonid A. , Bogdanovich Alexander V.
Published: November 2008

In this work the generalized criterion of the limiting states of active systems taking into account direct and back effects is obtained.
Stiffness and Damping of Molecularly Thin PFPE Lubricant Bridging Between Magnetic Disk and Diamond Probe Tip
Authors: Mitsuya Yasunaga , Ohshima Yasuji , Zhang Hedong , Aoyama Kei , Kawai Toshiyuki , Fukuzawa Kenji
Published: November 2008

Spring constants and damping coefficients of a molecularly thin liquid bridge of PFPE lubricant intervening between a diamond probe tip and diamond like carbon (DLC) surface of a magnetic disk are identified through regression analysis of tip damping vibration. Perfluoropolyether (PFPE) lubricants having functional end groups were used to form the liquid bridge between the DLC surface and a probe tip with the notably small curvature radius of 0.1 μm. The tip was both retracted from and extended toward the disk surface at four different, progressive distances to attain varied elongation of the bridge, and was made to vibrate at each step to provide damping waveforms. By applying regression analysis to observed waveforms, the spring constant and the damping coefficient of the liquid bridge were identified. It is interesting to note that both the absolute value of the spring constant and the frequency-multiplied damping decrease with bridge elongation, and after reaching the minimum, those values begin to increase.
Identification of Tribological Characteristics of the Ablative Stability and Micromechanical Strength of the Lightweight Materials Surface
Authors: Nikitin Yu. A. , Zaporozhets V. V. , Chernysh I. G.
Published: November 2008

The ablative, tribological and micromechanical properties of the composite lightweight materials have been investigated. Technological conditions of formation of the optimum composite structures of the foamed materials and carbon materials based on thermoexpanded graphite (TEG), which provide the increase of the strength and the ablative stability of the surface layer, are determined here.
Wear Rate of Aluminum Alloys Reinforced by Means of Dispersed Intermetallic Compound Fe-Cr Under Dry Friction
Authors: Nebozhak Ivan A. , Novytskyy Viktor G. , Shynsky Oleg I. , Havryliuk Vladimir P.
Published: November 2008

Method of obtaining of cast composite materials (CCM) on the basis of aluminum reinforced by σ- phase (FeCr) is proposed. The wear rate of specimens from CCM is depended on the height of casting, which these specimens were cut out from. The average size of particles FeCr 27.5-35.5 μm and their quantity 184–263 pieces/mm2 make the greatest positive influence on wear rate of CCM under dry friction.
Effective Tribology Testing of Lubricating Oils
Authors: Gitis Norm
Published: November 2008

There are several solutions suggested to develop the unified approach to tribological testing of oils. For evaluation of the coefficient of friction and wear, it is suggested to monitor friction force, normal load, and in-situ wear dynamics, as well as to clearly distinguish the running-in and stable-wear components. Tests on lab-bench testers are recommended to start from obtaining a Stribeck curve in a wide range of loads and speeds. During the tests, monitoring additional parameters of contact acoustic emission and contact electrical resistance is beneficial for sensitive and comprehensive characterization of oils and greases.
Mechanics of the Irreversible Damages Caused by Contact and Non-Contact Load
Authors: Sosnovskiy Leonid A.
Published: November 2008

The theory of material damages and their interaction in friction pairs and active system is developed.
Tribological Properties of Crystalline Hardcoat on Aluminum
Authors: Budinski Kenneth G. , Chapados Phillip
Published: November 2008

This study evaluates the abrasion, solid-particle erosion resistance and system wear characteristics of a crystalline ceramic coating (CIC) for aluminum. Specifically the ASTM G 174 loop abrasion resistance test, the ASTM G 133 reciprocating wear and the ASTM G 99 particle impingement tests were conducted on the crystalline hard coat, eight competitive coatings and reference materials. The study results indicated that CIC has significantly better abrasion and erosion resistance than conventional hardcoat. It also indicates that 52100 is not a suitable counterface for the reciprocating system wear.
Numerical Analysis of a Journal Bearing With a Heterogeneous Slip/No-Slip Surface
Authors: Fortier Alicia E. , Salant Richard F.
Published: November 2008

The no-slip boundary condition is part of the foundation of traditional lubrication theory. It states that fluid adjacent to a solid boundary has zero velocity relative to the solid surface. For most practical applications, the no-slip boundary condition is a good model for predicting fluid behavior. However, recent experimental research has found that for certain engineered surfaces the no-slip boundary condition is not valid. Measured velocity profiles show that slip occurs at the interface. In the present study, the effect of an engineered slip/no-slip surface on journal bearing performance is examined. A heterogeneous pattern, in which slip occurs in certain regions and is absent in others, is applied to the bearing surface. Fluid slip is assumed to occur according to the Navier relation. Analysis is performed numerically using a mass conserving algorithm for the solution of the Reynolds equation. Load carrying capacity and friction force are evaluated. It is found that judicious application of slip to a journal bearing’s surface can lead to improved bearing performance.
Relating Surface Roughness to Subsurface Stress
Authors: Martini A. , Liu S. B. , Escoffier B. , Wang Q.
Published: November 2008

Understanding and anticipating the effects of surface roughness on subsurface stress in the design phase can help ensure that performance and life requirements are satisfied. The specific approach taken in this work to address the goal of improved surface design is to relate surface characteristics of real, machined surfaces to subsurface stress fields for dry contact. This was done by digitizing machined surfaces, simulating point contact numerically, calculating the corresponding subsurface stress field, and then relating stress results back to the surface. The relationship between surface characteristics and subsurface stress is evaluated using several different approaches including analyses of trends identified through stress field visualization and extraction of statistical data. One such approach revealed a sharp transition between cases in which surface characteristics dominated the stress field and those in which bulk, or global contact effects dominated the stress. This transition point was found to be a function of the contact operating conditions, material properties, and most interestingly, the roughness of the surface.
Integration of a Molecular Viscosity Model and a Continuum EHL Solution for Simulation of Thin Film Lubrication
Authors: Martini A. , Liu Y. , Snurr R. Q. , Wang Q.
Published: November 2008

We present a simulation approach for thin film lubrication that integrates a molecular model of the film thickness-viscosity relationship in thin films with a continuum elastohydrodynamic (EHL) lubricated contact solution. Molecular simulation is used to characterize the effect of film thickness on viscosity in terms of solidification, shear thinning, and oscillation. This relationship is then incorporated into a traditional, continuum EHL solution. Film thickness distributions predicted by this integrated model are evaluated. It is found that the effect of the molecular film thickness-viscosity model is small compared to the increase in viscosity with pressure predicted by the Barus equation.
The Instantaneous Friction Force Between Two Sliding Bodies When Observed From a Third Moving Body
Authors: Perumean Don
Published: November 2008

This paper pertains to classical relativity, or using basic science to derive theoretical equations from a frame of reference located on different moving bodies.
Deep Rolling Efficiently Increases Fatigue Life
Authors: Ro¨ttger Karsten , Jacobs Terry L. , Wilcke Gerhard
Published: November 2008

Deep rolling is a manufacturing process that efficiently increases the fatigue life of dynamically loaded components. It combines three effects to enhance fatigue strength, tribological properties and corrosion of a surface. Deep rolling: • Smoothes the surface; • Induces deep compressive stress in the surface zone; • Work-hardens the surface zone. The technology has developed into a modern, widely applicable process that improves part performance and achieves lightweight design. It has successfully been applied on stainless steels, alloy steels, brass, tool steels, nickel alloys, cast and ductile irons, aluminum, magnesium and titanium alloys [1,2,3].
Plastic Deformations of Micro-Spheres by Solidified Lubricants and Lubricants’ Shear Stress Under Very High Pressure
Authors: Nakamura Yuichi , Shimaoka Masanori , Ishibashi Yutaka , Matsui Masahito
Published: November 2008

In order to grasp the possibility of evaluating shear properties for solidified lubricants under high pressure, plastic deformations of metal micro-spheres (about 0.07mm) in solidified lubricants were evaluated by employing a diamond-anvil pressure cell (DAC). Large deformations (2–5 times larger than the original sphere dimensions) were observed for CVT oil and ester oil up to 6 GPa at 23–25°C. Deformation starting pressure agreed with the solidified pressure. These deformations were caused by the non-hydrostatic pressure in the solidified lubricants. Shear stresses of the solidified lubricants were tentatively and roughly estimated from the plastic deformations of the spheres based on some assumptions. They almost agreed with the mean shear stress (traction force / hertzian contact area) from traction test.
Contact and Bending Fatigue of Toothed Gearings
Authors: Sosnovskiy Leonid A. , Zhmailik Valeriy A. , Shcharbakou Siarhei S. , Komissarov Victor V.
Published: November 2008

In this work method of controlling wear-fatigue damages is obtained.
Corrosion-Erosion Fatigue of Pipeline Tubes
Authors: Sosnovskiy Leonid A. , Vorobyev Vladimir V. , Kostyuchenko Alexei A. , Bordovsky Alexander M.
Published: November 2008

Reliability and durability of pipeline tubes are mainly affected by repeated alternative pressure, the processes of corrosion and erosion. These phenomena cause degradation of material on the internal surface of the tube. However the traditional methods (experimental and theoretical) of investigation of such damage processes are developed as if these processes acted separately, independently from each other. There are some works in which the joint effect of two phenomena is observed: corrosion-mechanical fatigue and erosive corrosion (or corrosive erosion). Meanwhile in reality the processes of mechanical fatigue, corrosion and hydro erosion act simultaneously and develop in the same part of the tube.
A Geometrical Optimization Approach to Minimize Contact Stress in Mating Gear Teeth
Authors: Tongele T. N.
Published: November 2008

This paper presents a technique to minimize contact stress in mating gear teeth. The American Gear Manufacturers Association (AGMA) approach uses contact stress equation that is highly detailed and requires many factors, charts, graphs and tables to produce limiting value of the contact stress. Departing from the complex AGMA approach, this paper utilizes the Hertzian contact stress equation to develop an optimization technique based on the geometry of the surface in contact for the minimization of the contact stress.
Modeling of Transient Wear Behaviors During Sliding Wear of Polymers
Authors: Peng Zhu , Pei Huang
Published: November 2008

Thermoplastic polyimide (TPI) composite modified by 20% MoS2 was chosen as research object and the MPX2000 type tribo-tester was improved, which can measure materials wear on-line. A new method, which can determine the transient wear stage, was proposed. Accordingly, the model of wear process was set up, while it was divided into two parts, including the third body production and its remove. The effects of the couple roughness and loading on wear process during the run-in stage were also considered and the wear mechanism was determined by the SEM. It can be concluded that the run-in stage was extended while increasing the couple roughness or loading. Due to its different action on material wear behaviors, the third body formation and remove process were conducted by the couple roughness and loading respectively. The abrasion wear was the main factor during the low loadings and adhesion wear was become more important while the loading reach to 0.75 MPa.
Correlation Between Structural Changes of Materials During Friction and Finite Element Analysis
Authors: Barlam D. , Garbar I. , Levi L.
Published: November 2008

The Finite Element Method (FEM) is widely used for modeling strain distribution during friction contact. One of the necessary conditions for such modeling is the correspondence between structural changes in a material surface layers and Finite Element Analysis results. The present study is dedicated to the possibility of using FEM as a tool to predict structural changes of material surface layers during friction depending on material properties and friction conditions. Contact during friction with reciprocating and unidirectional sliding between two surfaces under condition of plane strain had been modeled using commercial Finite Element (FE) code. The correlation between FE results and structural results, obtaining by electron microscopy and X-ray, were studied for the primary and secondary running-in processes. An elastic-plastic model had been used to learn the influence of different contact parameters such as: pressure, hardening, friction coefficient and geometry of asperities on the FE modeling results. Correlation between the FEM predictions and structural results such as dislocation’s density and distribution, were studied in a qualitative manner revealing that plastic strain results can be used to predict structural changes of material under sliding friction.
Variable Timestepping in EHD Problems
Authors: Bakolas Vasilios , Borchers Wolfgang
Published: November 2008

Transient EHD calculations have moved to the center of the attention in the past years as more machine elements that operate under variable operating conditions, such as automotive engine components, are examined. Almost all of the transient calculations today are carried out with a constant time step using first or second order discretisation for the determination of the time derivatives. Recently, a method was proposed that could control the time stepping of a transient calculation using first order time derivatives. In this paper, a method is presented for the control of the time step in transient calculations. The method employs a second order backward differentiation scheme with variable time stepping for the determination of the time derivatives. The time interval between successive calculations is determined depending on an estimate of the local truncation error without solving additional large linear systems, thus allowing for larger time steps when the time derivative is almost constant. This time stepping control method was implemented in an EHD simulation code that employed multi-grid and multi-level multi-summation techniques. Results presented in this paper prove that the proposed method can significantly reduce the number of necessary time steps of a transient calculation without any loss of accuracy of the results.
Influence of Lubricant and Operating Parameters on EHD Lubrication in Hypoid Gears
Authors: Simon Vilmos V.
Published: November 2008

The influence of lubricant characteristics and operating parameters on the elastohydrodynamic lubrication in hypoid gears is investigated. The full thermal elastohydrodynamic analysis of lubrication is applied, based on the simultaneous solution of the Reynolds, elasticity, energy, and Laplace’s equations. The oil viscosity variation with respect to pressure and temperature and the density variation with respect to pressure are included. Using a computer algorithm, the influence of oil viscosity, pressure-viscosity and temperature-viscosity exponents, supplied oil temperature, speed and minimum oil film thickness on maximum oil film pressure and temperature, EHD load carrying capacity, and power losses in the oil film is investigated. The obtained results are presented and discussed.
Neat Ionic Liquids and Additives in Lubrication of Steel-Aluminum
Authors: Jimenez A. E. , Bermudez M. D. , Iglesias P. , Carrion F. J. , Martinez-Nicolas G.
Published: November 2008

A series of seven room-temperature ionic liquids (IL) have been studied as neat and 1 wt% base oil additives in the lubrication of steel and aluminum contacts under increasing sliding speed, normal load and temperature. IL used as neat lubricants can produce, depending on the composition, tribochemical processes at the aluminum-steel interface associated with an increase in friction coefficients and wear rates. When IL are used as 1 wt% additives, surfaces interactions can give friction and wear values lower than those obtained for the neat IL. The lubricating performance of the additives is more dependent on contact conditions than on composition.
Emulsion for Single Phase Alpha-Brass in Hot Rolling Process: Case Study
Authors: Hu Xianguo
Published: November 2008

According to the hydrophile-lipophile balance (HLB) theory and the evaluation results of friction, wear and lubrication using a four-ball tribometer, a novel oil-in-water emulsion was developed for the hot rolling process of hard brass (single phase alpha-brass, CuZn32 (ASTM C26200) and CuZn30 (ASTM C26000)) by controlling the composition of the emulsion, such as emulsifying, antiwear, extreme pressure, antirust and so on. In the actual hot rolling process, the roller material was the welded-stainless steel ASTM 420 (HRC34-44), in which the lubrication mechanism of brushing grease discontinuously was replaced by emulsion jet directly to the hot roller surface. The actual hot rolling results proved that it was easy to control the accuracy and size of the brass sheet with the emulsion jet. This new process increased the antiwear and anti-galling abilities of the rollers, and improved the surface quality of the brass sheet. For example, the formation of deep, dark streaks in the hot rolled copper sheet is prevented, galling and roughening of the roller surfaces during hot rolling is reduced and it also saved labor, and increased production efficiency and the service life of the hot roller greatly.
Analysis of Surface Roughness and Surface Texture Generated by Pulsating Flexible Magnetic Abrasive Brush (P-FMAB)
Authors: Singh D. K. , Jain V. K. , Raghuram V. , Komanduri R.
Published: November 2008

The direct current magnetic abrasive finishing (DC-MAF) process provides practically no stirring effect on the static flexible magnetic abrasive brush (FMAB) formed by the magnetic field in the working gap. Absence of stirring leads to dullness of abrasive cutting edges in contact with the workpiece which results in a low finishing rate. To overcome this problem, the FMAB has been made pulsating using a DC-pulsed power supply, and the process is hence termed pulsed current-magnetic abrasive finishing (PC-MAF). The surface roughness was found to improve remarkably by the formation and destruction of the FMAB during the on and off time respectively, under selected pulsed parameters. The surface texture indicates that the process consists of microscratches generated on the finished surface. Further, the surface appears to have been generated by the removal of material from peaks of the workpiece surface by rotation as well as lateral movement of the FMAB.
Tribological Properties of Nano-Sized Molybdenum Disulfide Particles
Authors: Hu Xianguo , Wu Yucheng , Yuan Guangcheng , Huang Peng , Jing Hefeng
Published: November 2008

This paper summarizes the tribological properties of MoS2 nano-particles with about 30 nm under different frictional conditions. By four-ball tribometer, the results showed that as the nano-MoS2 content is over 0.5 wt% the extreme pressure of lubricating oil is higher than to 30% than that of lubricating oil with same content of common MoS2. The nano-MoS2 particles can decrease the friction coefficient of lubricating oil obviously. However the results showed that their friction reductions have not obvious difference by the ring-on-block tribometer. The analyses of surface composition conducted by XPS and SEM images showed that the nanoparticles form a protective film (WO3) allowing an increase in the load capacity of rubbed pairs. The main advantage of the nanoparticles is ascribed to the release and furnishing of the nanoparticles from the valley onto the rubbing metal surface and their confinement at the interface.
Effects of Solid Lubricants During Compression Tests
Authors: Banerjee Jayanta
Published: November 2008

During compression of a work-piece between dies or platens, such as in forging, coining and up-setting processes, any impact splashes out the liquid lubricant. Hence a solid lubricant is more effective. In the current study a PTFE, commonly known by the brand name Teflon, and a silicon spray were compared with a motor oil and dry friction (no lubricant). The experimental results were then compared with a finite element simulation model. Both the analyses show that the area under the true stress-strain curve is a minimum in the case of PTFE as a solid lubricant, and increases with silicon spray as the next, and then the motor oil, and finally the dry friction. This area gives the “Specific Forming Energy” for bulk plastic deformation, implying that the frictional losses are the least for PTFE as a lubricant, and increase with spray lubrication of silicon, followed by motor oil and dry friction. The experiments also show that barreling of the cylindrical surface of the work-piece is least for PTFE, and increases exactly in the same order: silicon spray, motor oil and dry friction.
Tribological Behaviour of the Diamond/Steel Couple: Influence of the Temperature
Authors: Schmitt M. , Bistac S.
Published: November 2008

With its excellent mechanical and chemical properties, diamond is expected to find many applications in industrial and engineering fields, and more particularly for the machining process, where the use of diamond coated tools leads to an improvement of their efficiency as well as an increase of the tools lifetime. A better understanding of the tribological behaviour of diamond coatings represents then a considerable stake. Intrinsic characteristics like the crystals orientation or the coatings thickness, have a great influence on the tribological properties of this kind of films. But the way the diamond coatings are used also plays an important part on their friction and wear behaviour: the nature of the counterface, the environment, or the variations of the applied normal load induce modifications of the physico-chemical properties of these coatings. The aim of this work is to study the influence of one of these experimental parameters, on the diamond tribological behaviour: the surrounding temperature. Friction tests were then realised at various temperatures with the diamond (obtained by flame process)/HSS couple, under different normal loads. It was shown that the diamond coatings and the discs tracks were significantly modified when increasing the temperature; both the friction mechanisms and the transfer were greatly dependent on the temperature of the environment. The sliding surfaces of the diamond coating and of the HSS disc were observed by Scanning Electron Microscopy and analysed by Energy Dispersive Spectroscopy and Raman spectroscopy to study the sight and the composition of the transferred layer as well as of the friction areas.
Multiple Loading-Unloading of an Elastic-Plastic Spherical Contact
Authors: Kadin Yuri , Kligerman Yuri , Etsion Izhak
Published: November 2008

A model for multiple loading-unloading of an elastic-plastic sphere and a rigid flat is presented to cover a wide range of loading conditions far beyond the elastic limit. It is shown that although most of the plastic deformation occurs during the first loading, additional plastic deformation may evolve during the first unloading and a few subsequent loading-unloading cycles.
Failure Inception of a Spherical Contact Under Slip and Stick Conditions for Various Material Properties
Authors: Brizmer Victor , Kligerman Yuri , Etsion Izhak
Published: November 2008

Failure inception of a deformable sphere loaded by a contacting rigid flat is analyzed separately for perfect slip and for full stick conditions and various material properties of the sphere. Ductile yielding and brittle failure inception of the sphere is identified by the critical interference and associated normal loading as well as the location of the first yield or failure occurrence. The analysis is based on the analytical Hertz solution for frictionless slip condition and on a numerical solution for stick condition. Failure inception is determined by using either the von Mises criterion of plastic yield or the maximum tensile stress criterion of brittle failure.
Optimum Design of Porous Gas Bearings With Maximum Load Carrying Capacity and Static Stiffness
Authors: Grabovskii V. I.
Published: November 2008

The problem of optimum porous infinite sliding bearings design with isothermal compressed lubricant is solved. The sliders and journal bearings with maximum load carrying capacity or maximum a lubricant film static stiffness in conditions of restriction on the lubricant flow rate through a pored insert are examined. The found optimum shapes of bearings depend on problem parameters, determining property of lubricant and insert, conditions of feed and lubricant flow rate through an insert. Besides the bearings shape a size and position of insert are determined. The optimum shape features are the discontinuity of their gap height function and insert arrangement in the vicinity of this function breaking. In the case of journal bearing at fixed gap height only the best sizes of bushing and their positions from a point of view of maximum load capacity are founded. The method of calculus of variations is used.
Contact Analyses for Bodies With Frictional Heating and Plastic Behavior
Authors: Boucly V. , Ne´lias D. , Liu S. , Wang Q. J. , Keer L. M.
Published: November 2008

The stress field within machine components is an important indicator for contact failures. Since both thermal stresses due to frictional heating and plasticity are significant in engineering application, it is critical to predict the total stress field. In this work, the steady- state thermal effect is considered and a thermo-elastic-plastic contact model is developed. The model is applicable for rolling and/or sliding contact problem, as far as small equivalent plastic strain hypothesis is respected. Influence coefficients for surface normal displacement, temperature, and strain and stress tensors are used with the discrete convolution and fast Fourier transform algorithm. The single-loop conjugate gradient iteration scheme is also applied to achieve fast convergence speed. Simulations are presented for several academic examples ranging from elastic to thermoelastic-plastic.
Artificial Neural Network and Genetic Algorithms for Discontinuously Reinforced Aluminum Composites Frictional Behaviour Prediction
Authors: Qiu Ming , Zhang Yong-Zhen , Zhu Jun
Published: November 2008

By using genetic algorithms and radius basis function (GARBF) neural network, the predicting model of friction coefficient has been established based on a measured database with five sliding velocities of 40, 55, 70, 85, 100 m/s and four different normal pressures of 0.1333, 0.4667, 0.60 and 0.7333 MPa. The modeling results confirm the feasibility of the GARBF network and its good correlation with the experimental results. The predictive quality of the GARBF network can be further improved by enlarging the training datasets and by optimizing the network construction. A well-trained GARBF modeling is expected to be very helpful for selecting composite component under different working conditions, and for predicting tribological properties. Finally, by using GARBF modeling data to predict analysis, the results show that the friction coefficients of these composites were increased with the increase in material thermal capability at some region.
Electrical Performance of Degraded MEMS Ohmic Switches
Authors: Kogut Lior
Published: November 2008

Electrical performance of degraded MEMS metallic switches (ohmic contacts) is studied analytically in this paper. The degradation mechanism is based on gradual growth of an insulating film at the contact interface and the characteristics of the insulating film are assumed to be known without considering details regarding the physical and chemical origins of the growth mechanisms. The present study relies on recently developed theories for electrical contact resistance (ECR) of clean and fully-contaminated (i.e., the entire contact area is coated with an insulating film) rough surfaces thus, bridging the gap between these two extreme cases. A relationship is obtained between the degraded ECR and the metallic conductance area. The effect of tunneling currents on the performance of partially-contaminated surfaces is found to be negligible due to the considerable current flow across the metallic asperity contacts.
Frictional Force Microscopic Detection of Anisotropy and Asymmetry at Various Atom-Flat Surfaces
Authors: Shindo Hitoshi , Kondo Sei-ichi , Shitagami Kozo , Sugai Takashi , Namai Yoshimichi , Kwak Musun
Published: November 2008

Frictional force microscopy (FFM) was applied to the detection of frictional asymmetry due to molecular tilt, and anisotropy at various atom-flat surfaces of ionic crystals. Less tilted S=O bonds at CaSO4(100) face and more tilted C=O bonds at (10–14) face of calcite gave contrasting results of asymmetry, which are explained by describing the bonds as mass-spring systems. Frictional anisotropy arises from different periodicity of atoms depending upon the scan directions of the probe. Alkali halide surfaces showed anisotropy due to arrangement of electric charges. Surface geometry also causes anisotropy at corrugated CaSO4(001), etc. Adsorbed water can reduce or enhance friction depending upon the relative humidity and the nature of the surfaces.