有序薄膜润滑的速度场

基于有序膜分子模型分析薄膜润滑中的速度场分布。薄膜润滑中有序膜分子的取向与向列相液晶分子有类似性,可用“向矢”表示。利用液晶理论可以分析薄膜润滑的速度场和润滑剂分子的取向,为分析薄膜润滑的特性提供依据。薄膜润滑区别于弹流润滑之处在于有序膜分子的弹性。粘弹比可以很好地表征这种差异。给出了不同粘弹比下的“向矢”角度和等效粘度的分布情况以及速度场的分布情况。     

薄膜润滑的等效粘度模拟计算

应用粘度修正公式对超薄膜润滑进行模拟计算，其计算结果与目前国内外的报导及实验结果相一致，公式化描述为实际工程设计和科学分析提供了依据     

微机电系统中微摩擦特性及控制研究

针对微机电系统设计中存在的微摩擦问题，论述了开展微观摩擦研究的意义和必要性。全面总结了微摩擦基本特性研究的进展，包括微观摩擦与宏观摩擦的对比，微观摩擦与表面形貌的相关性，以及粘滑现象等。提出了控制微摩擦特性的一些主要研究方向。     

薄膜润滑的等效粘度模型与实验

对作者提出的在薄膜条件下的等效粘度修正模型的计算结果与实验值进行了比较 ,检验等效粘度模型的正确性 ,其计算结果与实验结果相一致 ,同时给出了公式化描述 ,为实际工程设计和科学分析提供了依据     

MoS_2基复合润滑薄膜的制备及其摩擦性能

采用磁控溅射法在不锈钢基体上制备了MoS2/Ni复合润滑薄膜,研究了添加DLC(类金刚石薄膜)中间层对于MoS2/Ni复合薄膜的影响,探讨了复合润滑薄膜的减摩机理;使用EDS与XRD测定了复合薄膜的主要成分和物相结构,使用多功能摩擦试验机测定了薄膜的摩擦因数.结果表明:复合薄膜的主要成分为MoS2和Ni;薄膜中主要晶面为平行于基面的(002)晶面;复合薄膜的摩擦因数在0.06～0.18之间变化,且在高速重载的环境下具有更低的摩擦因数和更高的摩擦稳定性;中间层的加入进一步降低了复合薄膜的摩擦因数,达到0.04左右.     

类金刚石薄膜水润滑摩擦学特性研究进展

综述类金刚石薄膜水润滑摩擦学特性的研究进展,评述薄膜在水环境中的摩擦磨损特性,分析薄膜种类、元素掺杂、对摩材料以及微结构对DLC薄膜水润滑摩擦学特性的影响,并阐述DLC薄膜在水中的摩擦磨损机制。指出:DLC薄膜水润滑摩擦学特性受薄膜制备参数和摩擦试验环境影响,通过与微结构的耦合可以进一步改善类金刚石薄膜的摩擦学特性。同时还展望了类金刚石薄膜水润滑摩擦学未来研究方向。     

CrSiCN薄膜的力学性能及水润滑特性研究

运用非平衡磁控溅射技术,通过改变硅烷的流量,在Si(100)和316L不锈钢片基材上沉积不同元素含量的CrSiCN四元薄膜;运用X射线衍射仪、扫描电子显微镜和纳米压痕仪分别研究薄膜的结构、表面形貌和纳米硬度;运用球-盘摩擦磨损试验机研究水润滑下CrSiCN薄膜与Al_2O_3小球对摩的摩擦学特性。结果表明:由于固溶强化和纳米复合结构的形成,CrSiCN薄膜在硅烷流量为10 sccm获得最大硬度19.3 GPa和最大弹性模量306.9 GPa,继续增加硅烷流量,由于薄膜结构向非晶态转变,薄膜硬度降低;硅烷流量为10 sccm得到的薄膜CrSiCN具有最低的摩擦因数0.24,随着硅烷流量的增加,由于硬度的降低和过量非晶相的形成,薄膜抗磨性能降低,摩擦因数波动较大。     

薄膜润滑与润滑状态图

讨论了速度、固体表面能、滑动比、润滑剂粘度和化学性能对薄膜润滑状态下油膜厚度的影响,以及弹流润滑向薄膜润滑转化条件和液体膜失效条件。进而提出了新的润滑状态划分准则以及不同润滑机理下膜厚的变化情况。     

新型可逆转动压推力滑动轴承的摩擦与润滑特性

1 主要试验参数及符号轴承材料:铸铁,障性模量E=9768kg/mm~2,泊松比v=0.276。表面变形前研磨粗糙度σ_r=0.12μm。润滑剂:30号机械油,浸油润滑。     

金属切削中的摩擦磨损与润滑

本文就金属切削加工中的摩擦学问题作了系统性的概述。着重分析了刀具一切屑间的摩擦磨损特性。报道了刀具材料、表面涂层及表面改性、超低温处理技术等工艺在提高刀具使用寿命的研究成果。     

The tribological properties of nanofluid used in minimum quantity lubrication grinding

Minimum quantity lubrication (MQL) grinding using nanofluid showed superior grinding performance by reducing the grinding force and surface roughness in comparison with that of pure base fluid MQL grinding. In this study, the conditions of the grinding interaction between the grinding wheel and the workpiece were simulated by a pin-on-flat tribotester. The role of nanofluid in MQL grinding process was investigated through friction and wear experiments. The results show that nanoparticles, especially Al₂O₃, added to base fluid exhibit noticeable friction reduction and anti-wear properties. The addition of Al₂O₃ nanoparticles in deionized water decreased the friction coefficient and the worn weight by 34.2 and 43.4 %, respectively, as compared to the pure deionized water. Furthermore, investigation was performed using scanning electron microscopy and surface profilometer to interpret the possible mechanisms of friction reduction and anti-wear with nanoparticles.     

The tribological characteristics of JS material under lubrication of oil

A material composed of a steel backing, a sintered porous bronze middle layer and a layer of reinforced PTFE, which is named JS material, was prepared. The friction, wear and limiting PV values of this material under dry friction as well as the lubrication of number 20 mechanical oil were studied using a MPV-1500 friction tester. The worn surface of JS material and the transfer film formed on the counterface of carbon steel were investigated using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results show that the friction, wear and limiting PV values of JS material can be greatly improved with the lubrication of oil. The results of SEM and EPMA analyses indicate that, under dry friction conditions, the solid lubricant PTFE and Pb easily transfer to the steel counterface and results in the reduction of friction and wear; while under the lubrication of oil, little transference of PTFE and Pb to the steel surface occurs and very small friction and wear are achieved. Analyses of frictional surfaces also suggest that the Pb filler gets enrichment on the rubbing surfaces, which is beneficial in increasing the adhesion of the transfer film with the steel surface.     

Effect of hydrogenated DLC coating hardness on the tribological properties under water lubrication

Hydrogenated diamond-like carbon (DLC) coatings were deposited using unbalanced magnetron sputtering (UBM) equipment with different hardnesses. Effects of coating hardness on tribological properties were investigated with tribo-tests under water lubrication. Results showed that the wear volume increased rapidly during the initial running-in process, but remained nearly constant after the running-in process. The ball wear rate increased as the hardness of the DLC coating increased when metals (stainless steel and brass) were used as counter parts. In contrast, the UHMWPE ball wear rate was independent of the DLC hardness. TEM analysis and nano-indentation measurements were conducted of the transfer layer on the counter bodies’ contact surfaces. The transfer layer consisted mainly of Fe, O and C. The low friction of DLC coating is attributed to this low hardness transfer layer, which acts as a boundary-lubricating layer with low shear strength.     

The study of tribological properties of laser‐textured surface of 2024 aluminium alloy under boundary lubrication

The tribological property of aluminium alloy is critical for its reliable operation in practical applications. In this paper, the tribological performance of laser‐textured 2024 aluminium alloy is studied in unidirectional sliding tests under boundary lubrication. The dimples were produced on the aluminium alloy surface by using a pulse Nd : YAG laser. The topographical microstructures of these laser‐induced textures were characterised by optical and scanning electron microscopy. In comparison with untextured surfaces, a significant improvement in friction behaviour was observed for the textured surfaces. The influences of dimples density on the tribological properties were investigated. Two types of oil with different viscosities were evaluated as lubricants. It was found that the beneficial effects of laser surface texturing are more pronounced at higher speed and load with higher viscosity oil. The optimum dimples density of 8.5% was found to have a lower friction coefficient. On basis of the experimental results, the mechanism of friction reduction and anti‐wear is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparative study of the tribological properties of various modified mild steels under boundary lubrication condition

AISI1045 steel was modified by laser heat-treatment and conventional heat treatment. The friction and wear behaviors of the steel specimens after various surface modifications sliding against SAE52100 steel under the lubrication of liquid paraffin containing sulphurized olefin were comparatively investigated on an Optimol SRV oscillating friction and wear tester. The worn surface morphologies of the modified steel specimens were analyzed using a scanning electron microscope. The elemental compositions and chemical states of some typical elements on the worn surfaces of the modified steel specimens were analyzed with an energy dispersive X-ray analyzer and X-ray photoelectron spectroscope, respectively. It was found that the laser heat-treated specimen showed the highest hardness and best wear-resistance. The laser heat-treated and conventionally heat treated AISI1045 steel specimens sliding against SAE52100 steel under the lubrication of liquid paraffin containing sulphurized olefin registered smaller friction coefficients than under the lubrication of liquid paraffin alone. This was partly attributed to the increased hardness of the modified specimens. The tribochemical reaction between the steel and the active elements in the additive was involved in the sliding of the modified steel specimens against SAE52100 steel ball under the boundary lubricating condition, with the formation of a surface protective film composed of various tribochemical products. This also contributed to improve the friction and wear behavior of the modified steel specimens. The steel specimens subject to different surface modifications showed differences in the wear mechanisms under the boundary lubricating condition as well. Namely, the tempered steel specimen was mainly characterized by plastic deformation and pitting, the quenched specimen by grooves and delaminating, and the laser heat-treated one by polishing and mild adhesion.     

Review of engineered tribological interfaces for improved boundary lubrication

Recent advances in smart surface engineering and coating technologies offer unique possibilities for better controlling friction and wear under boundary or marginally lubricated rolling, sliding or rotating contact conditions. Specifically, such coatings can be tailored to meet the increasingly multi-functional application needs of future engine systems by enabling them to operate in lower viscosity oils with reduced sulfur and phosphorous. Using these technologies, researchers have already pioneered the development of a variety of nano-composite and super-hard coatings providing longer tool life in demanding machining and manufacturing applications. The same technologies can also be used in the design and development of novel coating architectures providing lower friction and wear under boundary-lubricated sliding conditions. For example, such coatings can be tailored in a very special way that while one of the phases can favorably react with certain additives in engine oils to result in an ideal chemical boundary film; the other phases can provide super-hardness and hence resists wear and scuffing. Because of their very dense microstructure and high chemical inertness, these coatings can also provide superior protection against oxidation and corrosive attacks in aggressive environments. The use of solid lubricant coatings may also improve the tribological properties of sliding contact interfaces under boundary lubricated sliding conditions. When fluid and boundary films fails or is broken down, such coatings can carry the load and act as a back-up lubricant. Other smart surface technologies such as laser texturing and/or dimpling, laser-glazing and -shotpeening have also become very popular in recent years. In particular, laser texturing of control or coated surfaces have opened up new possibilities for further manipulation of the lubrication regimes in classical Stribeck diagrams. Controlling dimple size, shape, orientation, and density, researchers were able to modify both the width and the height of the boundary lubrication regimes and thus achieve lower friction and wear at sliding and rotating contact interfaces. Overall, smart surface engineering and coating technologies have matured over the years and they now become an integral part of advanced machining and manufacturing applications. They can also be used to meet the increasingly stringent and multi-functional application needs of demanding tribological applications. In this paper, selected examples of recently developed novel surface engineering and coating technologies are introduced, and the fundamental tribological mechanisms that control their friction and wear behavior under boundary lubrication regimes are presented.     

Synthetic lubricants for air cooled two cycle engine oils: Effect of esters on lubrication and tribological properties

This paper reports the development of an air-cooled two-stroke engine lubricant using esters as synthetic base stocks, and performance additives. The viscosimetric and terminological properties as well as the performance in two-cycle gasoline engines are described in comparison with standard lubricants. It is shown that the use of suitable esters can make possible the formulation of high performance lubricants for the severity of use.     

Improvement of tribological characteristics under water lubrication of DLC-coatings by surface polishing

To achieve a hydraulic power system, it is important to control tribology because water has a lack of lubricity. Therefore, coated surface is necessary under water lubrication. Diamond-like-carbon (DLC)-coating is known as a useful material because of its high hardness and low friction, therefore it can be used as a coating durable for the water lubrication. Deposition methods of DLC-coating are developed in various ways. Particles called “droplets” are observed on the surface of DLC-coating depends on deposition methods and it can affect friction and wear properties. In this study, DLC-coating was prepared using a multi-cathode unbalanced magnetron sputtering (UBMS) system. The surface was polished with diamond slurry solution and aero lap to remove droplets. DLC-coatings were evaluated by tribo-tests before and after polishing. It is considered that some surface modification occurred. Moreover, the results of tribo-tests show that friction coefficients became lower and more stable than before polishing. Although partial delamination was observed after tribo-tests without polishing, no appreciable wear was observed after polishing.     

Influence of non-smooth surface on tribological properties of glass fiber-epoxy resin composite sliding against stainless steel under natural seawater lubrication

With the development of bionics, the bionic non-smooth surfaces are introduced to the field of tribology. Although non-smooth surface has been studied widely, the studies of non-smooth surface under the natural seawater lubrication are still very fewer, especially experimental research. The influences of smooth and non-smooth surface on the frictional properties of the glass fiber-epoxy resin composite(GF/EPR) coupled with stainless steel 316 L are investigated under natural seawater lubrication in this paper. The tested non-smooth surfaces include the surfaces with semi-spherical pits, the conical pits, the cone-cylinder combined pits, the cylindrical pits and through holes. The friction and wear tests are performed using a ring-on-disc test rig under 60 N load and 1000 r/min rotational speed. The tests results show that GF/EPR with bionic non-smooth surface has quite lower friction coefficient and better wear resistance than GF/EPR with smooth surface without pits. The average friction coefficient of GF/EPR with semi-spherical pits is 0.088, which shows the largest reduction is approximately 63.18% of GF/EPR with smooth surface. In addition, the wear debris on the worn surfaces of GF/EPR are observed by a confocal scanning laser microscope. It is shown that the primary wear mechanism is the abrasive wear. The research results provide some design parameters for non-smooth surface, and the experiment results can serve as a beneficial supplement to non-smooth surface study.     

The effect of surface chemistry in lubrication on the tribological behaviour of steel rollers under rolling-sliding contacts

Experiments were carried out on a wear test machine utilising a gearcam adapter to simulate line-contact lubrication. Due to the formation of a surface adsorption layer on the steel substrate, the tribological performance was detected by measuring the voltage for a lubricant with various additive concentrations. The roller wear rate was found to be strongly dependent upon both the rising rate of voltage in the wear process and the time period needed to create a positive voltage. The antiwear effect of differing additive concentrations was evaluated using the measurements of voltage for various operating conditions. An increase in rotational speed, with a lubricating oil with a low additive concentration, decreases the wear rate. A lubricating oil with a high additive concentration does little to decrease the wear rate at low rotational speeds.