高速滚动轴承油气润滑试验研究

对高速滚动轴承7006C进行了油气润滑试验研究。测试了油气润滑供油量、润滑油粘度、油气压力和转速对被试轴承温升的影响，确定了高速滚动轴承合理的油气润滑参数。试验表明：随着供油量增大，轴承温度呈现由大变小，再由小变大的渐进变化；随着粘度指数的增大，轴承温升同样呈现由大到小，再由小到大的变化过程；在本试验装置额定的油气压力范围内，随着油气压力增加，轴承温升呈单调下降趋势；随着转速的升高，轴承温升相应地增加。     

The Boundary Lubrication Properties of Model Esters

The friction of three chemically distinct esters was measured in order to determine how molecular architecture influences friction. The friction coefficients of mica surfaces separated by a thin film (<2 nm) of -chlorodecyl benzoate, -chlorodecyl pentafluoro benzoate, and -chlorodecyl perfluoro hexanoate were measured to be 0.15±0.015, 0.13±0.012, and 0.12±0.02, respectively. The friction coefficients for the esters are lower than the previously measured friction coefficients of simple hydrocarbon liquids such as n-tetradecane (=0.8), but are comparable to the friction coefficients of surfactant monolayer coated surfaces (=0.001–0.2). The results suggest that the ester molecules adsorb onto the mica surface with the (phenyl or hexyl) carbonyl next to the surface and the hydrocarbon tail pointing away from the surface. Hence, the friction is controlled by the packing density and properties of the hydrocarbon tail. Changes in the chemistry and structure of the carboxylic acid portion of the ester only give rise to small changes in the friction coefficient.     

SCUFFING MODEL CONSIDERING INFLUEN OF HYDRODYNAMIC LUBRICATION

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Effects of lubrication and humidity on the abrasiveness of a thin boron carbide coating

Studies using thin boron carbide (B₄C) coatings have previously been performed in order to investigate their potential use as finite-life run-in coatings. Such coatings have been shown to polish the mating surface in a relatively short time. The inherent ability of these coatings to polish can potentially allow them to function as finite-life run-in coatings. Employing such coatings requires a thorough understanding of the parameters which directly influence the changes that occur in the coating abrasiveness throughout the duration of the polishing process. In past studies, changes in the coating abrasiveness during dry sliding wear under ambient conditions have been investigated. However, both lubrication and humidity can strongly influence the abrasive wear process. In this study, the influences of the operating environment, namely humidity and lubrication, on the coating abrasiveness are directly investigated. The coating abrasiveness decreases at a slower rate when a lubricant is added and when the humidity decreases.     

复合织构化压裂泵柱塞密封副动压润滑性能仿真研究

为改善压裂泵柱塞密封副的摩擦磨损性能,在压裂泵柱塞密封副表面建立不同的复合表面织构(不同复合织构类型、不同分布方式、不同截面形状等),并在结合柱塞密封副几何结构特征、压力边界条件及雷诺方程的基础上,建立织构化柱塞密封副动压润滑理论模型,采用有限差分对雷诺方程进行求解,仿真分析复合织构对柱塞密封副动压润滑性能的影响规律。数值仿真研究结果表明:复合织构对动压润滑性能的影响与外织构深度有密切关系;内织构为凹坑或凸起,以及内织构为不同截面形状的复合织构,主要是通过影响织构平均深度与摩擦副间隙的大小关系,而对复合织构的动压润滑性能造成不同的影响规律;内织构分布于外织构右侧(润滑介质入口一侧)对复合织构动压润滑性能的提升最大。     

Performance of supercritical carbon dioxide sprays as coolants and lubricants in representative metalworking operations

This paper investigates the cooling and lubrication properties of supercritical carbon dioxide (scCO₂) sprays as potential substitutes for aqueous emulsions and straight oils used in the metalworking industry today. Sprays of rapidly expanding scCO₂ act to cool and lubricate machining and forming processes by delivering a mixture of dry ice and lubricant deep into the cutting/forming zone. In this work, experiments with turning, milling, drilling, thread cutting, and thread forming were performed with scCO₂ and other metalworking fluids (MWFs) to evaluate their relative performance with respect to tool wear and machining torque. Observations reveal that scCO₂–MWFs are more effective in removing heat from the tool-workpiece interface than conventionally delivered (flood) aqueous MWFs as well as other gas-based MWF sprays. In addition, scCO₂–MWFs delivered in lubricant-expanded phase, where scCO₂ is used to increase volume of lubricant in the spray field, are shown to provide better lubricity than straight oils and oil-in-air minimum quantity lubrication (MQL) sprays. As a result, scCO₂–MWFs can reduce tool wear and improve machining productivity in a wide range of manufacturing operations leading to appreciable improvements in the economics of manufacturing. Also given that CO₂ is a recovered waste gas that is non-toxic, scCO₂–MWFs can improve the environmental and worker health performance of manufacturing operations.     

A novel approach to measure slip-length of thin lubricant films under high pressures

Abundant evidence of boundary slip at liquid/solid interfaces has been presented by experiments and theoretical analyses. Recent research reveals that the boundary slip effect of lubricants can be obvious in small confined gaps, even with simple Newtonian fluids. Therefore, it is appropriate to ask if there is boundary slip of thin highly pressurized lubricant films in EHL contacts, and, if so, how to quantify it. This paper proposes a method for measuring the slip-length of lubricant films within a small gap under high pressure. Measurement principles have been addressed in details in the paper. The idea makes use of the phenomenon whereby a tiny quantity of lubricant can be entrapped and forms a dimple film by impacting a steel ball against a lubricated glass plate. The slip-length can be extracted from the relative movement of the dimple against the solid surfaces. Case experiments are also presented to validate the feasibility of the method.     

Causes of chatter in a hot strip mill: Observations, qualitative analyses and mathematical modelling

Severe vibrations, known as chatter, occur often in both hot and cold rolling of steel. A recent chatter outbreak at the second stand of hot strip mill in Hastings, Australia, prompted an investigation into the causes of chatter by a literature review, the development and deployment of mathematical models, and a rigorous analysis of plant observations. The investigation suggests that the frictional conditions in the roll gap are the principal cause of chatter in this mill, though residual chatter marks on work rolls can occasionally cause it. The frictional conditions appear to be associated with the thickness and properties of oxide formed on rolls.     

Astringency sub-qualities of red wines and the influence of wine–saliva aggregates

Astringency is a sensory attribute, related to the quality and mouthfeel of red wines. However, the origin of astringency sub-qualities, such as the typical drying astringency found in immature grapes, is still unknown. Astringency of red wines with similar tannin content but different astringency sub-qualities, from different harvest dates, is studied. Astringency was characterised in terms of friction coefficient, polyphenol content, sensory analysis and tannin/salivary–proteins aggregates characterisation. A different evolution during ripening was found for both Cabernet Sauvignon and Carménère, and tannin–protein aggregates showed differences in size, shape and surface. The velvety sub-quality appears to be related to aggregates with low precipitation, and with specific surface characteristics as roundness and Feret diameter. Results from this work propose an effect of aggregates on sensory perception and opens the possibility to explore their effect on oral lubrication.     

Reduced order finite element model for elastohydrodynamic lubrication: Circular contacts

This paper presents an extension of the reduced order finite element model to the case of circular elastohydrodynamic lubricated (EHL) contacts under isothermal Newtonian considerations. The line contact model was developed and validated in a previous work (Advances in Engineering Software, 2013; 56:51−62). The model is based on a finite element discretization of the EHL equations: Reynolds, linear elasticity and load balance with a reduced order model for the linear elasticity part. All equations are solved simultaneously in a fully-coupled framework using a damped-Newton procedure allowing fast convergence rates for the global solution. This model combines fast convergence rates, reduced memory requirements and negligible model reduction errors compared to the full model which makes it an attractive tool for EHL contact performance prediction.