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To develop a fairly different EHL inlet zone analysis for investigating the contact‐lubricant interfacial limiting shear stress effect on line contact EHL film thickness in isothermal conditions. This analysis is purposed to give fast and qualitatively correct results.

A Grubin‐like EHL inlet zone analysis is derived with closed form of the analytical results of the EHL film thickness, the EHL film pressure, the contact‐lubricant interfacial shear stress and the contact‐lubricant interfacial slipping velocity in the EHL inlet zone based on the assumption of the contact‐lubricant interfacial limiting shear stress in the EHL inlet zone. In this analysis, the lubricant is allowed to slip at the contact surface; The inlet contact surface shape is known from results referenced in this paper; The physical condition for the presence of the film slippage is incorporated; The lubricated area is divided into different kinds of film slippage zones where are, respectively, applied different governing equations. Three deterministic equations in this analysis are obtained and solving these coupled equations gives the solutions of the boundaries of the slip zone and the percentage reduction of the central film thickness by the contact‐lubricant interfacial limiting shear stress effect in this EHL.

Compared with the earlier approaches to the present problem, the present analysis has the advantage of giving fast and qualitatively correct solutions. The results obtained from the present analysis show that the contact‐lubricant interfacial limiting shear stress effect on EHL film thickness is usually strong when the contact‐lubricant interfacial limiting shear stress in the EHL inlet zone is low; This effect can greatly reduce the global EHL film thickness especially in severe operating conditions.

A very useful material for the academic researcher and the engineer who are engaged in the study and measurement of the effect of the contact‐lubricant interfacial limiting shear stress on EHL film thickness and EHL film pressure.

A fairly different EHL inlet zone analysis is originally developed based on the assumption of the contact‐lubricant interfacial limiting shear stress in the EHL inlet zone. The physical condition for the contact‐lubricant interfacial slippage is first incorporated in this analysis. Deterministic governing equations in this analysis are derived and solving these coupled equations gives the final solutions of the present problem. This analysis has the advantage of giving fast and qualitatively correct solutions. It convincible shows the contact‐lubricant interfacial limiting shear stress effect on EHL film thickness and EHL film pressure in the present EHL.

To make a derivation of the load‐carrying capacity of elastohydrodynamic lubrication for special operating conditions, i.e. extremely heavy loads or extremely low rolling speeds based on the Newtonian fluid model by taking the Grubin‐type EHL inlet zone analysis, justify the load‐carrying capacity of elastohydrodynamic lubrication film in these operating conditions, and propose future trends of the research in EHL and mixed EHL based on the obtained results in the present paper.

A Grubin‐type EHL inlet zone analysis is carried out for the isothermal EHL of line contacts in special operating conditions, i.e. extremely heavy loads or extremely low rolling speeds based on the Newtonian fluid model. Comparison is made between the central EHL film thickness in line contacts, respectively, predicted by conventional EHL theories and accurately predicted from the present analysis for these operating conditions. An interpretation is made for the EHL film thickness in these operating conditions by taking the approach of the transportation and flow of the fluid through elastohydrodynamic contact when the EHL film is, respectively, thick and molecularly thin in the Hertzian zone. Conclusions are drawn on the load‐carrying capacity of EHL, EHL contact regimes and mixed EHL regimes in these operating conditions.

The present EHL inlet zone analysis shows that the EHL film thickness in the Hertzian zone is on the nanometer scale and the lubricant is non‐continuum across the film thickness in the Hertzian zone at relatively heavy loads in line contact EHL when the dimensionless rolling speed is lower than the dimensionless characteristic rolling speed U_ch=0.0372W^1.50/G. In this case, the central EHL film thickness in line contact EHL predicted by the conventional EHL theory may be several orders of magnitudes higher than that accurately predicted. This difference may be greater for heavier loads.The present results for line contact EHL based on the Newtonian fluid model show that in line contact EHL, for relatively heavy loads and the dimensionless rolling speed lower than the dimensionless characteristic rolling speed U_ch=0.0372W^1.50/G, the EHL analysis needs to further incorporate the lubricant non‐continuum effect across the film thickness in part of the lubricated area to investigate the EHL film thickness and the EHL film pressure in the contact in this very low film thickness condition; only the results based on such an analysis are believable for the EHL stage where the lubricant film thickness in the Hertzian zone approaches to zero and then vanishes; the results for EHL based on the Newtonian fluid model is unable to conclude that the EHL film thickness in the Hertzian zone is zero and dry contact occurs between the contact surfaces in EHL in any operating condition for ignoring the lubricant non‐continuum regime governing the EHL stage preceding the occurrence of the zero lubricant film thickness in EHL.

A very useful source of information for academic scientists, engineers and tribologists who are engaged in the study and application of the theory of elastohydrodynamic lubrication.

A derivation is first carried out for the isothermal EHL of line contacts in extremely heavy loads or extremely low rolling speeds by taking the Grubin‐type EHL inlet zone analysis by the present paper. Results and conclusions on the load‐carrying capacity of EHL in these operating conditions are first strict and thus convincing. These results are also original in clarifying the future trends of the researches in EHL and mixed EHL.

This paper studies elastohydrodynamic lubrication (EHL) of line contacts for the slide‐roll ratios 0‐2 based on the assumptions of interfacial shear strength and interfacial slip. It is shown that the viscoelastic, viscoplastic and non‐continuum fluids distribute from the inlet zone to the Hertzian contact zone in order for a given operating condition when the load and rolling speed exceed critical values. For the rolling speed below the critical, the distributing fluids from the inlet zone to the Hertzian contact zone in order are viscoelastic and non‐continuum when the load exceeds a critical value. These show a multirheological behavior EHL film, formed in a contact, which may represent a mode of mixed lubrication. For this mode of lubrication, the fluid model should handle both inlet and Hertzian contact zones where the fluids are, respectively, continuum and non‐continuum. A new EHL analysis and theory, therefore needs to be established.

This paper aims to assess the adsorption behaviour and the adhesion strength of lubricant films formed by polypropylene oxide-polyethylene oxide-polypropylene oxide (PPO-PEO-PPO) with phosphate ester additive on Ti-coated surface and to identify the influence of molecular architecture and phosphate ester additive.

The thickness of the adsorbed PPO-PEO-PPO with phosphate ester lubricant films on Ti surfaces was measured by ellipsometry. The adhesion strength of the copolymer and the copolymer with phosphate ester lubricants was studied by the micro-scratch tests; the scratch tracks on the surfaces were observed by atomic force microscopy and scanning electronic microscopy.

The copolymer with a higher weight percentage of PPO not only formed a thicker film but also showed stronger adhesion and better lubrication performance. The added phosphate ester increased the film thickness and improved the tribological behaviour. The finding reveals that the adsorbed film thickness which depends on the PPO chain length and the presence of phosphate ester has a considerable effect on the scratch behaviour.

This paper fulfils the studies about adsorption behaviour and lubrication mechanism of this new lubricant which has not been adequately investigated on the metal surface.

The purpose of this paper is to present a novel method to investigate the microscopic mechanism of the oil film under the pure squeeze elastohydrodynamic lubrication (EHL) motion. An optical EHL squeeze tester is used to explore the effects of squeeze velocity, load, temperature, and lubricant viscosity on the dimple film thickness that occurs when a ball approaches a flat plate covered by a thin layer of oil.

The grayscale interferometric technique was used to study the thickness of the lubricating film in an EHL point contact. The light source was a He‐Ne laser. Through the transparent optical glass and by means of optical interference, the interference fringe patterns of the contact region were observed by a charge‐coupled device camera recording. The two elastic bodies were a sapphire disk and a steel ball. The contact was lubricated with paraffin‐based oil.

Results show that increasing the squeeze speed, load, viscosity, and decreasing the temperature, make the dimple deeper, and the contact area increases. Moreover, as the squeeze speed and load decrease and temperature increases, the fluidity of the lubricant increases and less time is needed to extrude. The maximum thickness of the dimple increases with increasing squeeze speed, load, lubricant viscosity, and decreasing temperature. The greatest effect of pure squeeze EHL motion is found with squeeze velocity, followed by load, and then temperature for the same lubricant viscosity.

The paper usefully describes the use of a self‐development optical EHL squeeze tester to explore the effects of temperature, squeeze velocity, load, and lubricant viscosity on the dimple film thickness which occurs between two components approaching each other.

The purpose of this study is to investigate lubricant film-forming capability of oil-impregnated sintered material in highly loaded non-conformal contacts. This self-lubrication mechanism is well described in lightly loaded conformal contacts such as journal bearings; however, only a little has been published about the application to highly loaded contacts under elastohydrodynamic lubrication regime (EHL).

Thin film colorimetric interferometry is used to describe the effect of different operating conditions on lubricant film formation in line contacts.

Under fully flooded conditions, the effect of porous structure can be mainly traced back to the different elastic properties. When the contact is lubricated only by oil bleeding from the oil-impregnated sintered material, starvation is likely to occur. It is indicated that lubricant film thickness is mainly governed by oil bleeding capacity. The relationship between oil starvation parameters corresponds well with classic starved EHL theory.

To show practical, relevant limitations of the considered self-lubrication system, time tests were conducted. The findings indicate that EHL contact with oil-impregnated sintered material may provide about 40 per cent of fully flooded film thickness.

For the first time, the paper presents results on the EHL film-forming capability of oil-impregnated sintered material by measuring the lubricant film thickness directly. The present paper identifies the phenomena involved, which is necessary for the understanding of the behavior of this complex tribological system.

The modified Reynolds equation for non-Newtonian lubricant is derived using the viscous adsorption theory for thin-film elastohydrodynamic lubrication (TFEHL) of circular contacts. The proposed model can reasonably calculate the phenomenon in the thin-film lubrication (TFL) unexplained by the conventional EHL model. The differences between classical EHL and TFEHL with the non-Newtonian lubricants are discussed.

The power-law lubricating film between the elastic surfaces is modeled in the form of three layers: two adsorption layers on each surface and one middle layer. The modified Reynolds equation with power-law fluid is derived for TFEHL of circular contacts using the viscous adsorption theory. The finite difference method and the Gauss–Seidel iteration method are used to solve the modified Reynolds equation, elasticity deformation, lubricant rheology equations and load balance equations simultaneously.

The simulation results reveal that the present model can reasonably calculate the pressure distribution, the film thickness, the velocity distribution and the average viscosity in TFL with non-Newtonian lubricants. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction.

The present model can reasonably predict the average viscosity, the turning point and the derivation (log film thickness vs log speed) phenomena in the TFEHL under constant load conditions.

The purpose of this is to study the mechanism of an oil film thickness formation in the nanoscale. A polar lubricant of propylene carbonate is used as the intervening liquid between contiguous bodies in concentrated contacts. A pressure caused by the hydrodynamic viscous action in addition to the double-layer electrostatic force, van der Waals inter-molecular forces and solvation pressure owing to inter-surface forces is considered when calculating the ultrathin lubricating films.

Using the Newton–Raphson iteration technique applied for the convergence of the hydrodynamic pressure, a numerical solution has been ascertained.

The results show that, at separations beyond about five molecular diameters of the intervening liquid, the formation of a lubricant film thickness is governed by the combined effects of viscous action and surface force of an attractive van der Waals force and a repulsive double-layer force. At smaller separations below five molecular diameters of the intervening liquid, the effect of the solvation force is dominant in determining the oil film thickness.

This paper fulfils an identified need to study the behavior of polar lubricants in concentrated contacts in ultrathin conjunctions. The effect of the hydrodynamic action, electrostatic force and surface action of van der Waals and solvation forces is considered when calculating the lubricant oil film thickness.

Cavitation in piston-ring lubrication is studied as part of the performance of piston-ring assemblies. Cavitation degrades performance in engineering applications and its effect is that it alters the oil film pressure, generated at the converging-diverging wedge of the interface. Studies tried to shed light to the phenomenon of cavitation and compare it with cavities that have been identified in bearings. The paper aims to discuss this issue.

Lubricant formulations were used for parametric study of oil film thickness (OFT) and friction providing the OFT throughout the stroke and LIF for OFT point measurements. Lubricant formulation affects cavitation appearance and behaviour when fully developed.

Cavitation affects the ring load carrying capacity. Different forms of cavitation were identified and their shape and size (length and width) is dictated from reciprocating speed and viscosity of the lubricant. A clear picture is given from both techniques and friction results give quantifiable data in terms of the effect in wear and cavitation, depending on the lubricant properties.

Engine results are limited due to manufacturing difficulties of visualisation windows and oil starvation. Therefore, full stroke length sized windows were not an option and motoring tests were implemented due to materials limitations (adhesive and quartz windows). Lubricant manufacturer has to give data regarding the chemistry of the lubricants.

The contribution of cavitation in piston-ring lubrication OFT, friction measurements and lubricant parameters that try to shed light to the different forms of cavitation. A link between viscosity, cavitation, shear thinning properties, OFT and friction is given.

This study aims to compare cavitation shapes between the simulating test rig and the engines to strengthen the findings that were first observed in the simplified experiments. Different forms of cavitation were identified, and their shape and size (length and width) were dictated from reciprocating speed and viscosity of the lubricant. Cavitation degrades performance in engineering applications and its effect is that it alters the oil film pressure.

Lubricant formulations were used for parametric study as well as different operating testing parameters in a simulating test rig and single cylinder engines with visualisation windows. An algorithm was used for extracting cavitation data from imaging, and comparison was made.

Similar phenomena at the simulating test rig and the engine were investigated and compared. The effect of different operating conditions was assessed along with the variations produced from the parametric lubricant study.

Engine results are limited due to manufacturing difficulties of visualisation windows and oil starvation. Firing tests are another difficult challenge as the modified section pressure is under more pressure and the window view is affected by combustion process. Limited pictures can be captured before cleaning is required. A lubricant manufacturer has to provide data regarding the chemistry of the lubricants.

The effect of cavitation in piston ring lubrication along with variable operating and lubricant parameters is further studied with quantification of cavitation results through image processing. These forms of cavities are affected by lubricant properties and operating conditions. A link between viscosity, cavitation, shear thinning properties, oil film thickness (OFT) and friction is given.