bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of oil environments on the initiation of fatigue cracks and propagation of small cracks in plain carbon steel specimens
Authors: Goto M. , Miyagawa H. , Nisitani H. 
Published: July 2006

AbstractIn fatigue tests of plain carbon steel specimens in air, fatigue life is taken up mainly by the life in which a crack propagates from its initial size up to about 1 mm. This means that the behaviour of a small crack in the oil environment must be known in order to evaluate the effect of oils on fatigue life.In this paper, using a series of base oils of different viscosity grades, the effects of oils on fatigue damage are investigated in rotating bending fatigue tests of annealed 0.34% carbon steel plain specimens. Successive detailed observations of the specimen surface are made in order to study the fatigue processes of micro‐crack initiation and small crack propagation. The physical background of the effect of oil environments on fatigue behaviour is shown, and a method for predicting fatigue life in oil environments is discussed.
Velocity fields in grease lubricated contacts
Authors: Mutuli S. , Bonneau D. , Frène J. 
Published: July 2006

AbstractThis paper examines the behaviour of a grease lubricant in open contacts. Analytical expressions of velocity profiles for a Bingham fluid are presented for three cases: flow where all the film thickness is sheared; where a non‐sheared core zone is attached to one contact surface; and where a core zone floats in the middle of the film. An experimental study is described which used visualization through illumination across contact surfaces. Results are presented for two modes of operation: contact of cylinder and fixed plane surface, and pure rolling of two cylinders. In the former case, nine zones of operation are identified.
Modelling the effect of lubrication on friction behaviour
Authors: Avitzur Betzalel 
Published: July 2006

AbstractModels of typical characteristics of the surfaces of two solids interfacing one another under pressure and sliding with respect to each other are described in Models 1 (Figure 1) and 2 (Figure 2). In Model 1 (Figure 1) the asperities, wedges of the harder surface indent into the softer surface due to the applied pressure, thus producing opposing ridges on the surface of the softer component. The gap between the opposing asperities is filled with liquid, establishing boundary lubrication. As sliding is maintained, the ridges are mobilized and an eddy flow is established in the trapped lubricant. The power required to mobilize the ridges and to establish eddy flow in the lubricant is calculated and thus the friction resistance to sliding is determined. Simultaneously, the pressure generated in the liquid due to shear is also evaluated. It becomes clear that the height of the ridge due to indentation is inversely proportional to the speed of sliding. The higher the sliding speed, the higher is the liquid pressure that is countering the loading pressure and the smaller is the indentation. At a high enough speed (to be replaced in due course by the Sommerfeld Number) the entire load is supported by the pressure generated in the liquid, indentation is eliminated and hydrodynamic lubrication commences. The classic model for hydrodynamic lubrication where two inclined surfaces glide atop each other is described in figure 2. Here the gap between the two surfaces (q.J a t their closest point is a monotonically increasing function of Sommerfeld Number (S). The resistance to sliding as established through the shear in the liquid determines thefriction value. This model leads directly to the characteristic of Coulomb or Emontons where for diminishing values of Sommerfeld Number the resistance to sliding is proportional to the pressure (τ = μp) and the proportionality factor is equal to the tangent of the angle of inclination (μ = tana). In the present work, the increase infnction with increasing values of the Sommerfeld Number is also determined. Combining the two models one notices that, a t low speed and Somrfeld Number values, the liquid pressure is not sufftcient tofloat the two surfaces and indentation prevails together with boundary lubrication. With increasing speed (Sommerfeld Number) the height of the ridge (by Model 1) decreases, and when it diminishes to values lower than those predicted for the gap between the surfaces in the second model for the same speed, the boundary lubrication ceases and hydrodynamic lubrication commences.
Studies on the interrelationships between the character of metals and antiwear additives
Authors: Huang Y. W. , Cheng G. X. , Dong J. X. 
Published: July 2006

AbstractIn machines which operate under conditions of potential boundary lubrication, all the lubricants used normally contain antiwear agents. When the antiwear properties of the lubricants are evaluated on a frictional wear tester, because the test peice is made of a single material, it is not certain that the antiwear properties of the lubricants tested are the same as those on real machines. Zhao et al. observed a correlation between the chromium content of steels and antiwear load of an antiwear agent containing sulphur or phosphorus.1 Zang studied the friction decreasing effect of an oiliness agent with different metals.2 In this report, the authors changed the test piece of a four‐ball machine for a plane ring in order to look at the test piece with different metal materials, with the aim of examining the mutual relation between the different materials and antiwear agents. This paper presents the results.
The role of sulphur in ZDDP‐induced reaction films formed in the presence of ZDDP: Contribution of electron spectroscopic imaging technique
Authors: Hallouis M. , Belin M. , Martin J. M. 
Published: July 2006

AbstractThe anti‐wear action of zinc dithiophosphate (ZDDP), extensively used in engine oils, is here studied by analysis of wear particles generated during a friction test between two ferrous substrates. It is known in this case that the interfacial film is complex, and contains elements from surfaces, environment and degradation products of the additive. This paper deals with the presence and the form of sulphur species in the constitution of this film. Analytical Transmission Electron Microscopy (TEM, STEM, EDS and EELS filtered images) of particles shows that sulphur is in the form of small crystallites of iron sulphide Fe7S8, embedded in an amorphous phosphate matrix. Wear tests performed at different normal loads show the variation of the P/S ratio in the particles. The results are discussed.
Industrial oil performance in terms of base oil chemical structure
Authors: Abou Naga H. H. El , Bendary S. A. , Salem A. E. M. 
Published: July 2006

AbstractSome performance properties for turbine, hydraulic and gear oils were correlated with changes in chemical structure for incorporated base oils. Blends with different viscosity grades were formulated from different neutral oils, brightstocks and additives.Different statistical approaches were used to evaluate the degree of fit for these correlations. The derived models were considered at a minimum of 99% confidence. Results clarified the role of non‐hydrocarbons and aromatic compounds, either by type or by content, in changing the performance behaviour for tested industrial oils.
Prediction of lubrication regimes of concentrated contacts
Authors: Schipper D. J. , Vroegop P. M. , De Gee A. W. J. 
Published: July 2006

AbstractFriction experiments are performed on lubricated concentrated contacts (LCCs) to obtain the transitions EHL‐ML and ML‐BL as a function of the operational conditions under which these contacts operate. A transition diagram is developed to determine the lubrication mode of an LCC as a function of the operational conditions. In this investigation the LCCs operated macroscopically in the lubricants' liquid state regime.
The influence of rheological properties of mineral oil in the stick‐slip phenomenon
Authors: Tudor Andrei 
Published: July 2006

AbstractWithin the range of small and very small sliding velocities that are typical of applications such as clutch mechanisms, guideways of machine‐tools, hydraulic or electric drives for robots, and continuous‐indexing mechanisms, the phenomenon of ‘stick‐slip’ occurs. By taking into consideration the dependence of kinetic friction force on sliding velocity during the slip period, three critical velocities of movement stability are revealed. One of the important ways for reducing the amplitude of the phenomenon is by designing lubricating grooves of optimum geometry brought about by oil viscosity and surface tension.
Lubrication of forging under thick film conditions with thermal effects
Authors: Montmitonnet P. 
Published: July 2006

AbstractIn cold upsetting with a liquid lubricant, a film is trapped at the beginning of the process. Then, as plastic deformation proceeds, a non‐lubricated external zone appears, while the film thins out in the central part.1,2 This behaviour is influenced by thermal effects, namely, self‐heating of the viscous fluid4 and heating of the workpiece surface by plastic deformation.3 To improve local computation of friction, these thermal effects are here accounted for; a semi‐analytical Reynolds equation is proposed; and its solution by a finite difference scheme gives the film thickness everywhere in the film, and the extent of the non‐lubricated zone. Inclusion of the rheology of the fluid can then permit computation of the local friction stress, which can be coupled as a boundary condition in a model of workpiece plastic deformation.
Measurement of oil film thickness in big‐end bearings and its relevance to engine oil viscosity classifications
Authors: Bates T. W. , Vickars M. A. 
Published: July 2006

AbstractMinimum oil film thickness MOFT measurements have been carried out in big‐end bearings of V6 and in‐line four‐cylinder gasoline engines during engine operation. MOFT decreases with increasing crankshaft speed above 2000 r/min. The most severe practical steady‐state operation is high‐speed cruising. Maximum shear rates are in the region of 107s−1 at 4000 r/min. the dynamic viscosities at a shear rate of 106s−1 correlate significantly better with monograde MOFT data than with multigrade data; the correlation parameters for mono‐ and multigrade data are also significantly different. Although the dynamic viscosity measurement correlates with multigrade data better than the low‐shear rate kinematic viscosity, the differences are not always significant at the 95% confidence level. Some other rheological parameter or combination of parameters may be better than either kinematic or dynamic viscosities.
Does the automotive industry need a standard engine test to measure journal bearing oil film thickness?
Authors: Spearot James A. 
Published: July 2006

AbstractAutomotive manufacturers are dissatisfied with the high‐temperature portion of the SAE Viscosity Classification, J300. This dissatisfaction occurs because the low‐shear, 100°C conditions at which viscosities are specified are not representative of the conditions to which oils are subjected at operating temperatures in an engine. Recent efforts to modify the high‐temperature viscosity specifications have dealt primarily with developing correlations between oil film thickness measured in the journal bearings of operating engines and viscosity values measured at different high‐temperature, high‐shear rate conditions in laboratory viscometers. However, it has also been suggested that the industry develop a standard engine test for measuring journal bearing oil film thickness, and that oils be ‘classified’ on the basis of film thickness rather than viscosity. This paper reviews the methods which have been developed to measure bearing film thickness, the correlations which have been calculated between film thickness and viscosity, and the conclusions drawn from such efforts. Reasons for relying on high‐temperature, high‐shear viscosity specifications rather than a standard industry bearing film thickness test are offered. In addition, the merits and drawbacks of developing an industry bearing distress test are also discussed.
Effects of directional properties of roughness and tangential force on pressure flow between contacting surfaces
Authors: Nakamura T. , Funabashi K. 
Published: July 2006

AbstractThe fluid flow phenomena between contacting surfaces which exhibit roughness are interesting for the lubrication mechanisms and the sealing problems. The effects of the directional properties of roughness and tangential forces on the pressure flow are examined in this paper. Annular sealing surfaces ground in a radial direction and in a peripheral direction were prepared, and the leakage rates were measured. The experimental results showed that directional properties and tangential forces affected the leakage rates. In the last part of this paper, the directional properties of roughness are discussed, based on two‐dimensional Fourier analysis.
Evaluation of the antiwear performance of aged oils through tribological and physicochemical tests
Authors: Monteil G. , Mérillon A. M. , Lonchampt J. , Roques‐Carmes C. 
Published: July 2006

AbstractExtending automotive engine drain intervals requires a good knowledge of the antiwear aspect of lubricant performance, which is often closely linked to the oxidative degradation of the oils. In this paper, we report the physicochemical analyses and tribological tests carried out on several oils oxidised by laboratory oxidation tests at different stages. An interesting correlation was found between the antiwear efficiency and some characteristics of the eletrochemical impedance spectra of such oxidised lubricants. A promising way of understanding the mechanisms of wear mitigation by aged engine oils is proposed.
A liquid crystal lubricant with partial polymerisation
Authors: Gunsel Selda , Yu Bing , Friberg Stig E. 
Published: July 2006

AbstractLamellar lyotropic liquid crystals were evaluated as lubricants in a slow sliding ball‐on‐disk friction rig. The liquid crystalline structure was modified by addition of a monomer and the influence of polymerisation on lubrication properties was studied. The results showed that partial polymerisation of a monomer located close to the polar group layer in the liquid crystal, followed by addition of a small amount of long‐chain aliphatic hydrocarbon, gives low friction coefficient and enhances load‐carrying capacity.
EP‐efficient 1,2,4‐dithiazolines and their tribological effect on steel bearing balls of different composition
Authors: Bhattacharya A. , Verma V. K. 
Published: July 2006

AbstractThis paper deals primarily with the potential extreme‐pressure (EP) activity of certain cyclic disulphide additives in paraffin oil. The antiwear and antifriction properties of 1,2,4‐dithiazo‐line additives have been evaluated on a four‐ball machine by using 12.7 mm diameter steel ball bearing specimen‐I. The paper also includes a discussion on the effectiveness of 3‐p‐Cl‐phe‐nylimino‐5‐(N‐methylphenyl)amino‐1,2,4‐dithiazoline on steel bearing balls of different compositions. The topography and the surface chemistry of the bearing ball wear scar were studied by Scanning Electron Microscopy (SEM) and Auger Electron Spec‐troscopy (AES).
Laser microprecision treatment to raise EHD lubrication effects
Authors: Guang Lin Zi , Bin Gao Zuo 
Published: July 2006

AbstractLaser microprecision treatment of the surfaces of mechanical parts takes place after machining, where the surfaces of mechanical parts, especially highly‐loaded (counterformal) parts (e.g. gears, rolling bearing and cams with point or line contact) are re‐treated microprecisely by laser to produce an asperity texture with transverse orientation. This man‐made surface topography is favourable to EHD lubrication of parts in relative motion and greatly increases the load capacity of such parts. Timken tests of rings whose surfaces were treated microprecisely by laser demonstrate its ability to raise the Timken OK loads (or anti‐scuffing capacity).
A mixed model to predict friction forces in lubricated contact with non‐newtonian fluids
Authors: Najji B. , Bou‐Said B. 
Published: July 2006

AbstractA mixed model to predict friction forces in thermohydrodynamic lubricated contacts with non‐Newtonian fluids is proposed, with an integral formulation and a finite element method resolution. The mixed model is used here for the first time in lubrication. It takes into account the implicit rheological laws. The shear stress field appears in this formulation as a nodal unknown and eases the use of rheological laws with yield criteria.
Tribochemical behaviour and lubrication characteristics of aromatic compounds
Authors: Nakayama Keiji 
Published: July 2006

AbstractRadical scavenger, radical anion scavenger, and peroxide decomposer were added to aromatic hydrocarbons and phosphates in aromatic rings with and without side chain, and the effect of these inhibitors on tribopolymerisation and the lubrication characteristics of the aromatic compounds were investigated, in various atmospheres, in order to clarify the reaction mechanism. The aromatics of both hydrocarbons and phosphates with a methyl group in aromatic rings react readily at the rubbing surfaces to form polymer or polymer‐like products, improving the lubricating characteristics. The tribochemical reactions of alkylaromatic compounds is shown to differ from those of trialkyl or triarylphosphates. It was concluded that the reaction proceeds through the radical or radicalanion and via peroxide to cause polymerisation.
Adsorption of ZDDP on iron surfaces and its relation with surface tension
Authors: Huang Xin , Ying Yi‐Nan , Zhang Yna‐Hao 
Published: July 2006

AbstractThis paper reports work on the relationship of surface tension of ZDDP solutions to adsorption isotherms. The surface tension of the solutions varies with their composition, and information about adsorption, decomposition or other chemical changes of ZDDP in solution can be obtained from the correlation of solution concentration and surface tension. From this work, the authors conclude that adsorption of ZDDP on iron can occur at even low concentrations, increasing with temperature, and that decomposition, association and interaction between components may occur in solution at high temperatures.
Physical and chemical mechanisms of influence of Cu‐containing additives on grease properties
Authors: Ischuk Y. , Karaulov A. , Lukiniuk M. , Melnik Z. , Nosovsky O. 
Published: July 2006

AbstractThe mechanisms governing the influence of copper additives (powders, oxides, organic and inorganic salts, complex compounds) on tribological, rheological and basic physical properties of greases with various thickeners (lithium, complex lithium, complex aluminium and polyurea) are discussed. The copper plating effect was found to occur only under EP conditions. The physical and chemical patterns of copper‐containing grease additives under antiwear and extreme pressure conditions are discussed together with rational application alternatives in friction couples of equipment and machinery.
Drilling models for a synthetic cutting fluid
Authors: Leep Herman R. , Peak Marie A. 
Published: July 2006

AbstractThe primary objective of this research was to develop relationships which predict tool wear from measured cutting forces. Different cutting speeds and feed rates were examined. The workpiece materials used were a medium‐carbon steel and a titanium alloy. A synthetic cutting fluid was used with a 9.525 mm drill and a 6.350 mm drill, for drilling the medium‐carbon steel and the titanium alloy, respectively.Preliminary testing was conducted to find the optimal values for cutting speeds and feed rates. The main drilling tests were performed using the cutting conditions resulting from the preliminary tests. Statistical analysis of the results of the main drilling tests showed that the axial force was significant at the 5 per cent level in models for both materials. It also showed that the moment about the vertical axis was significant at the 5 percent and the 15 per cent levels in the models for the titanium alloy and the medium‐carbon steel, respectively. The model for the smaller holes drilled into the more homogeneous material, the titanium alloy, was more accurate in predicting tool wear.
An approach to the study of plasto‐elastohydrodynamic lubrication in the wire drawing process part 1: Experimental
Authors: Ei‐Butsh A. M. A. , Ei‐Badrawy R. S. , Mokhtar M. O. A. 
Published: July 2006

AbstractThis paper describes an experimental study of hydrodynamic lubrication in wire drawing in which different types of lubricants (straight oils, emulsions and grease) are used. The experiments were conducted on a specially designed laboratory wiredrawing test rig, to assess the frictional force and film thickness, while drawing an aluminium wire at different speeds. Hydro‐dynamic performance, including frictional force and film thickness, were measured and plotted graphically, showing lubricant and drawing speed as the main influences.Results indicate that the frictional force decreased and the oil film thickness increased using straight oils with high viscosity at high drawing speed.
Spectroscopic studies and electronic properties of heat treated calcium sulphonate
Authors: Bertheville B. , Deroide B. , Zanchetta J. V. , Palermo T. 
Published: July 2006

AbstractOverbased calcium sulphonate and its derivatives have been characterised by means of thermogravimetric analysis, X‐ray and IR spectroscopy. The study was carried out after thermal treatment up to 900°C. Different phases appeared, showing a transition from an amorphous system to a crystallised medium. Electrical measurements showed electron behaviour for compounds obtained at low temperatures. ESR experiments produced classical results connected with the decomposition of organic chains.
Overbased lubricant detergents – a comparative study
Authors: O'Connor S. P. , Crawford J. , Cane C. 
Published: July 2006

AbstractOverbased detergents are commonly used in automotive and marine lubricants. Their main functions are to neutralise potentially corrosive acids and to contribute to engine cleanliness. The major types of overbased detergents that are produced commercially are phenates, sulphonates and salicylates. This paper describes the chemistry of these additive classes and reviews their properties and performance in bench and engine tests. The paper also describes a new class of overbased detergents, where novel chemistry has been used to produce new types of highly overbased phenate, sulphonate, and salicylate. These new products exhibit significant improvements in properties and performance over conventional detergents. Evidence from bench and engine tests is presented to demonstrate the benefits of the new detergent types. An appendix gives more detail on the results of tribological tests on these new detergents.
Experiment and computer simulation of particulate suspensions under shear flow
Authors: Heyes D. M. 
Published: July 2006

AbstractIn this paper is described the role of molecular simulation as a useful quasi‐‘experimental’ tool to help in understanding the interplay between molecular structure under shear flow and the manifested tribology/rheology. The development of non‐equilibrium molecular simulation techniques are discussed, from the molecular dynamics approach through to the modelling of dispersions by brownian dynamics. Recent advances and extensions of the technique to weakly flocculated systems, such as electro‐rheological fluids, are described.