Wear data from friction pairs for microscale piezoelectric actuators

This paper presents friction and wear data from a series of physical tests on numerous friction pairs. The tests were designed to simulate the loads, motions, and conditions typical in microscale piezoelectric actuator applications. The friction pairs tested included various combinations of steels, ceramics, and surface‐treated steels. Both high‐cycle tests and low‐endurance tests were performed and the optimum friction pairs for these applications were identified based on high friction, low wear, and low roughness.     

The friction and wear behavior of 2-(n-alkyldithio)-benzimidazole as additives in liquid paraffin

Three 2-(n-alkyldithio)-benzimidazoles were synthesized. The friction and wear behavior of the synthetic compounds as additives in liquid paraffin were examined with a four-ball machine, with emphasis on revealing the relationship between the chain length of the additive and the friction-reducing ability and lubricating mechanism of the additives. The film formed by the additive during the sliding process was investigated by using X-ray photoelectron spectroscopy. It was found that the synthetic compounds as additives in liquid paraffin had good antiwear performance. The longer the chain length of the synthetic compound, the more stable or less volatile is the compound and the more effective it is in improving wear resistance. This revised version was published online in July 2006 with corrections to the Cover Date.     

箱形结构焊缝声发射源定位技术

研究了声波在典型箱形结构中的传播特点,比较了2种布置方式下的线性定位方法,分析了其在焊缝声源定位时的误差,讨论了基于平面定位法的箱形结构声源定位。试验结果表明,箱形结构的准确定位影响因素很多,需要将平面定位方法与线性定位方法等结合起来去实现焊缝处裂纹的定位。     

高分子固体润滑耐磨涂层研究进展

在阐明高分子固体润滑耐磨涂层的主要类型和减摩耐磨机理的基础上，总结评述了常用的几种高分子树脂基体固体润滑耐磨涂层的摩擦学特性，分析讨论了高分子涂层固体润滑耐磨性能的影响因素，并且展望了高分子固体润滑耐磨涂层的发展趋势和研究方向。     

A predictive analytical friction model from basic theories of interfaces, contacts and dislocations

Friction between crystalline bodies is described in a model that unifies elements of dislocation drag, contact mechanics, and interface theory. An analytic expression for the friction force between solids suggests that dislocation drag accounts for many of the observed phenomena related to solid–solid sliding. Included in this approach are strong arguments for agreement with friction dependence on temperature, velocity, orientation, and more general materials selection effects. It is shown that calculations of friction coefficients for sliding contacts are in good agreement with available experimental values reported from ultrahigh vacuum experiments. Extensions of this model include solutions for common types of dislocation barriers or defects. The effects of third-body solid lubricants, superplasticity, superconductivity, the Aubry transition, and supersonic dislocation motion are all discussed in the framework of dislocation-mediated friction.     

Wear studies using acoustic emission techniques

This paper describes measurements of acoustic emission RMS signals obtained from sliding metallic contacts. The results show that RMS measurements are able to differentiate between different wear mechanisms occurring in both dry and lubricated contacts. Further, for the test conditions studied there is a direct empirical relationship between the integrated RMS signal and the wear volume removed from the test ball.     

Acoustic emission of rolling bearings lubricated with contaminated grease

In elastohydrodynamic lubrication (EHL), an extreme smoothness of the contacting surfaces is essential for the formation of a thin lubricant film, which separates the moving surfaces from each other. Sharp asperities, in particular, are very detrimental for the sliding surfaces. Because of the limited thickness of the lubricating film, the contact zone is very vulnerable if the lubricant contains contaminants, especially if hard particles are present in the lubricant.The present paper focuses on the acoustic emission (AE) measurement method for the monitoring of the lubrication situation in a grease lubricated rolling bearing. The aim of the investigation was to clarify how the contaminants in the grease influence the acoustic emission of the rolling bearing. In the paper, the results of tests with clean greases and with deliberately contaminated greases, and the influence of the cleaning and re-greasing of the bearing are discussed. The results showed that the AE measurement indicated very clearly the lowest contaminant concentration included in the study that was as low as 0.02 weight-%. Small size contaminant particles generated a higher AE pulse count level than large size particles. The AE time signal analysis method proved to be a suitable method to indicate the hardness of the contaminant particles. Cleaning the bearing of contaminants and re-greasing with a clean grease reduced the AE level of the bearing.     

PTFE基固体润滑涂层的摩擦学和力学性能试验

为了探讨PTFE基固体润滑涂层的摩擦学和力学性能,采用HSR-2M型高速往复式摩擦磨损试验机、INSTRON5944拉压试验机和DDL-300电子万能试验机分别对PTTE基固体润滑涂层的摩擦学性能、粘结性能和抗压性能进行研究.结果表明:A配方涂层的粘结性能较优,其粘结强度是B配方和C配方涂层的4倍左右;B涂层的力学性能最差;C涂层的摩擦学性能和抗压性能最优,其抗压强度是A和B涂层的2倍左右,并且其韧性也较好.     

Analysis of the nonlinear behavior of gear pairs considering hydrodynamic lubrication and sliding friction

This paper describes an analysis of the nonlinear behavior of gear pairs according to the direct contact elastic deformation model over a wide range of speeds, considering the hydrodynamic effects and friction force. The inclusion of the hydrodynamic effect facilitates nonlinearity by increasing the overlap range (i.e., multiple solution regimes) and damping, as well as decreasing elastic deformation and tooth reaction forces. The effects of various lubrication parameters, such as viscosity and film width, on the nonlinear dynamic behavior were analyzed. While the viscosity has a strong effect on the behavior of gear pair systems, friction has very little effect on torsional behavior. Although the model of direct contact without friction has overall nonlinear behavior similar to the model including hydrodynamic effects with friction, the time data of these models are different due to the squeeze effect. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Cheon Gill-Jeong received his B.S. in Mechanical Engineering from Seoul National University (SNU), Korea, in 1981. He then received his M.S. and Ph.D. degrees from SNU in 1983 and 1988, respectively. He served as a senior research engineer at Seoul National University Hospital and Daewoo Heavy Industry for several years. Dr. Cheon is currently a Professor at the Division of Mechanical Engineering at Wonkwang University in Iksan, Korea. His research interests include dynamics, tribology, and design engineering.     

Effect of applied voltage on friction and wear characteristics in mixed lubrication

The effect of an electric field applied between rubbing surfaces on friction and wear characteristics was examined using a ballon-disc testing apparatus under different lubrication conditions. The lubrication conditions were changed by changing the viscosity of the lubricants. By applying an electric field between the rubbing surfaces, the oxidation of the rubbing surface at the anode side is enhanced, and suppressed on the cathode side surface. The oxide film formed on the anode surface being harder than the bulk steel, the rubbing surface at the anode side was little worn, but that at the cathode side was abrasively worn. This wear characteristic could be utilised to attain favourable running-in. The application of an electric field, however, is considered to promote the breakdown of any EHL film formed. Therefore the effect of the application of an electric field between rubbing surfaces is influenced by the lubrication condition that is being tested.     

Comparative Investigation on Tribological Properties of Ion-Sulfuration Layers Under Dry Friction

Four kinds of steel, including high-speed steel (M2), die steel (L6), stainless steel (420) and plain carbon steel (1045), were treated by low-temperature ion sulfuration. Sulfide layers, dominated by the FeS phase, were produced on the surfaces of the four steels. The tribological properties of sulfide layers were investigated on a block-on-ring test rig under dry friction conditions. The results showed that the tribological properties of all sulfurized steels were remarkably improved. The tribological properties decreased in the order of high-speed steel—die steel—1045 steel—stainless steel. The hardness, microstructure and corrosion resistance of the substrate determined the differences in the tribological properties of different steels.     

Application of acoustic emissions for mass wear analysis

An experimental method is considered for measuring the mass wear of friction pairs during operation. The method is based on the analysis of acoustic emission characteristics. The conditions for creation of the experimental data array are discussed. A formula for computing the mass wear as a function of the total energy of the acoustic emission signals was derived.     

石墨含量对石墨固体润滑涂层摩擦学性能的影响

利用简便的刷涂法在钢基体表面制备了石墨固体润滑涂层。利用MM-200型摩擦磨损试验机对不同石墨含量的固体润滑涂层进行了详细的摩擦学性能对比试验。结果发现．石墨固体润滑涂层的摩擦学性能与石墨含量之间呈“马鞍形”变化规律，当石墨的质量分数为28％时，固体润滑涂层的减摩、耐磨性能最佳。     

基于声发射技术的金属动态塑性摩擦研究

利用声发射技术研究了凸模胀形过程中有油润滑和干摩擦2种不同摩擦条件下的动态摩擦过程,得到了凸模胀形声发射特性曲线,并对声发射特性曲线进行了分析。结果表明：凸模胀形过程中的声发射信号是由凸模胀形过程中的摩擦产生;摩擦力随胀形深度而变化,是胀形深度的函数;凸模胀形过程中的声发射信号证明凸模胀形过程中的摩擦是一个动态过程;声发射信能动态地反映这一摩擦变化过程。     

溅射沉积MoS_2/Sb_2O_3复合润滑膜的摩擦磨损过程与失效分析

采用UMT-2型球-盘摩擦磨损试验机研究溅射沉积MoS2/Sb2O3复合固体润滑膜的滑动摩擦磨损寿命,采用显微镜分析球-盘摩擦副在不同磨损阶段的磨损形貌与磨损状况,并对磨痕位置S、Mo元素进行XPS分析。结果表明:在摩擦磨损寿命试验过程中,摩擦副的接触方式最开始的点接触逐步过渡到面接触;MoS2固体润滑膜对滑动摩擦副的延寿作用是基底材料表面的有效厚度润滑膜及MoS2对摩擦偶件(钢球)的转移;机械磨损的剪切剥离效应是润滑失效的主要原因,MoS2的氧化在一定程度上加剧了润滑失效的进程。     

切削刀具摩擦磨损的研究方法综述

从切削试验、常规摩擦试验及特殊摩擦试验三个方面概述了国内外有关刀具材料摩擦磨损的研究方法,分析了各种方法的优缺点,最后对这一问题的重点研究方向进行了展望。     

Adhesion and friction studies of silicon surfaces processed using a microparticle-based method

A surface processing method that combines electrostatic deposition of microparticles and dry etching is utilized to modify the surface topography of silicon surfaces to reduce adhesion and friction force. Microscale adhesion and friction tests were conducted on flat (smooth) and processed silicon surfaces with a low elastic modulus thermoplastic rubber (Santoprene) probe that allowed a large enough contact area to observe the feature size effect. Both adhesion and friction force of the processed surfaces were reduced comparing to that of the flat surfaces.     

Influence of protein conformation on frictional properties of poly (vinyl alcohol) hydrogel for artificial cartilage

Poly (vinyl alcohol) (PVA) hydrogel is one of the anticipated materials for artificial cartilage. In our previous studies, wear of PVA hydrogel depended on content of proteins in lubricants. The secondary structures of bovine serum albumin (BSA) and human gamma globulin (HGG) were investigated in circular dichroism spectroscopy to clarify the influence of the proteins on frictional properties. BSA and HGG were mainly composed of the α-helix and the β-sheet, respectively. BSA containing the α-helix structure showed low friction compared to HGG composed of the β-sheet structure in mixed or boundary lubrication mode. The α-helix structure forms low shear layer because the α-helix structure is easily released from surfaces and low cohesive strength. HGG forms uniform adsorption layer, but showed higher friction than BSA in the rubbing with single protein. In the repeated rubbing with changing of lubricants from HGG to BSA, however, the final friction was reduced, because an optimum layered structure of proteins was formed. Hence, layered structure of proteins appears to play an important role to protect rubbing surfaces and to reduce friction. In heat treatment tests, heat-induced BSA showed very low friction because of reduction of the α-helix structure. Heat-induced HGG did not show large differences from native HGG, but could not bring low friction with heat-induced BSA. Thus it was shown that the protein conformation has effective influences on friction.     

运用声发射技术监测金属塑性成型过程中润滑状态的研究

为监测金属塑性成型过程中的润滑状态,采用运用声发射技术,通过对无润滑和有润滑时金属塑性变形过程和摩擦过程的监测及对比,分别研究了金属摩擦声发射信号和塑性变形声发射信号.结果表明,不同材料摩擦产生的声发射信号数值上大小不同,同种材料摩擦声发射信号数值上小于塑性变形声发射信号;采用声发射技术,基于实时波形和声发射信号参数的平均值都能监测金属塑性成型时的润滑状态.     

Triboemission as a basic part of the boundary friction regime: A review

This paper reviews selected phenomena related to the boundary friction process. The central thrust is on triboemission, defined as emission of electrons, charged particles, photons, etc., under conditions of boundary friction and/or surface damage caused by fracture processes. Low‐energy electrons are one of the most important particle components in triboemission. Accordingly, the triboemission process is of particular significance for (i) the boundary friction process as such, and (ii) the tribochemistry of the boundary lubrication process. This review considers all the major issues of triboemission and related phenomena/processes. It is shown that, in the boundary lubrication regime with hydrocarbon lubricants, charge intensities decrease with an increase in lubricant molecular weight. The paper also includes some recent information concerning research on triboemission along with a newly developed apparatus.