Lubrication Science最新文献

Squeeze-film characteristics between a long cylinder and an infinite flat plate system are analysed. Ferrofluid (FF) lubricant controlled by transverse uniformly strong magnetic field is used for reducing wear and prolonging life of the system. The modified combined Reynolds equation is derived using two different FF flow models (Shliomis and Jenkins), and continuity equation. The expression for dimensionless film-pressure, load-carrying capacity and squeeze time are derived and calculated numerically for different control parameters. The results show significant improvement in the performance of the system when smaller value of minimum film thickness is chosen. Moreover, the phenomenon can be simulated by both the models equally with proper choice of the parameters.

This work presents a comprehensive tribological analysis comparing the performance of two types of lubricants—a synthetic and a natural ester—used in industrial reciprocating air compressors. A comprehensive tribological analysis comparing the performance of two types of lubricants—synthetic and natural esters—used in industrial reciprocating air compressors were carried out using surface characterisation methods and lubricant analyses. The formed and detected tribo-films were not efficient to avoid the wear observed on the cylinders, although they may have been to avoid the wear on the rings. Regarding the lubricant analyses, particle analysis showed that none of the lubricants favoured solid particle leaching to a greater extent. A biolubricant such as the one employed in this study would be suitable for replacing a mineral lubricant in situations like the ones observed in this work.

In this paper, a simulation model of reciprocating rod seal systems when there is axial texture on the rod surface due to wear is studied. The model includes macroscopic solid mechanics analysis, microscopic contact mechanics analysis and fluid mechanics analysis, and on this basis, the change of surface pressure when the sealing ring fall into a texture is calculated by the micro-deformation mechanics analysis of the seal surface. Then, the stiffness matrix method is used to find the film thickness when the three pressures in the sealing area are in equilibrium, completing the fluid–solid coupling calculation. Combined with the above simulation process, the performance parameters of the sealing system such as leakage and friction can be obtained. Results show that axial texture will degrade sealing performance, which increases leakage and friction. The simulation results can quantitative characterise the influence of rod wear on sealing performance and provide some theoretical basis for the study of seal failure mechanism and prediction of seal life.

In the actual working condition, due to the manufacturing errors, improper installation, load, thermal deformation or other factors can cause the journal surface to produce the form and position errors. The mathematical models are developed that takes into account the form and position errors, the lubrication performance of four-recess capillary restrictor hybrid journal bearings with different journal tilt angles and cylindricities is studied, and the effect of eccentricity on the oil film lubrication performance is analysed. The results show that the dimensionless oil film pressure and loading capacity increase as the journal tilt angle and eccentricity increase considering journal tilt, and the friction coefficient tends to increase and then decrease. Compared with journal alignment, the oil film thickness distorts, the oil film pressure peak shifts to the edge of bearing, and the horizontal tilt has a greater impact on bearing when the journal is tilted. The oil film pressure distribution has no significant change considering cylindricity errors, while the oil film pressure value increases, the loading capacity increases and the coefficient of friction decreases as the cylindricity and eccentricity increase. The research shows that the presence of a certain cylindricity error contributes to the lubrication performance of four-recess capillary restrictor hybrid journal bearings.

A new type of vibrated drop wettability mechanism on a micro-texture surface is proposed and investigated experimentally and theoretically. In this experiment, the mechanical testing machine is used as the vibration source, and the compound control cabinet is used to adjust the vibration liquid feeding table. By comparing the apparent dynamic contact angle, it is concluded that the surface energy of the second cycle is larger than the first one. A swing model and spring-mass system model are presented to study the vibrated drop motion pattern. The spring-mass system model is built to analyse the adhesion force working process theoretically. The drop surface energy is transmitted by vibration. With the superposition of vibration energy, the displacement of the drop gravity centre becomes larger and larger until the drop migrates. The adhesion force drives the liquid drop to do reciprocating motion, and it changes the liquid drop dynamic wettability.

In the wet rolling process of industrial cold-rolled strips, the tempering lubricant was discarded after one-time use, which resulted in huge waste and high costs for wastewater treatment. In order to explore the reuse value and feasibility of the tempering lubricant, the influences of industrial rolling were to be studied first. In the comparison of before and after-use- tempering lubricant, the surface tension decreased by 34%, and the physicochemical indicators such as electrical conductivity, pH, and total alkali value decreased by 4%–14.3%. In terms of the components and related effects, about 15% of heavy organic matter, such as fatty acids and alcohol amine was responsible for lubrication, rust prevention, and corrosion inhibition. These heavy organic solutes would reduce by 2%–6%, with impurities increasing after rolling. However, the waste tempering lubricant still had a high reuse value. Further from the influence of impurities and microorganisms, it was concluded that if the solid powders were filtered out, the bacteriostatic agent was added after 3 days, and the changes in the effective substance concentration of the tempering lubricant were mastered to replace 1/3 of it in time during recycling, then the reuse of the tempering lubricant was feasible.

In the present work, a comparison between traditional oil-in-water (O/W) based lubricant and nano-TiO₂ additive water-based lubricants was made to explore the lubrication effects during rolling of ferritic stainless steel (FSS) strips. The results show that marked reduction in rolling force and improvement in the surface quality can be achieved by utilisation of water-based nanolubricant, which can be attributed to the synergism of rolling effect, mending effect, polishing effect and protection film. An optimal concentration of 3.0 wt% TiO₂ nanoparticles is found to exhibit excellent lubrication effects with sufficient nanoparticles at real contact regions without aggregation, leading to 10% reduction in the surface roughness during rolling of FSS strips.

A wire corrosion test (WCT) is used to investigate the influence of model organosulfur extreme pressure additives and analogues. The corrosion response from these compounds is discussed with regards to chemical structural type. Corrosion rates were calculated using the guide in ASTM G31 to provide a measurement in mm/year.

Polyol-ester lubricants have been used and developed for aviation gas turbine engines for many decades. The newest MIL-PRF-23699 lubricant class, called enhanced ester (EE), provides the best combination of thermal stability, load carrying capability, boundary lubrication and compatibility with fluoroelastomer O-rings. Two candidate EE Class formulations and one high thermal stability class formulation conforming to MIL-PRF-23699G were evaluated for oil degradation with up to 3000 h of bearing operation. Lubricant degradation was studied using VIM VAR M50 bearings with M50 and silicon nitride balls under two operating conditions using two bearing test rigs. Oil degradation in terms of oxidation time, total acid number and viscosity was studied as a function of time with varying results for the three lubricants.