Thin-Film Properties of Some Functionalized Perfluoropolyether Boundary Lubricants Based on the n-Perfluoropropylene Oxide Monomer Unit

The thin-film properties of some perfluoropolyether boundary lubricants based on hydroxyl-termination of the n-perfluoropropylene oxide monomer units are investigated as a function of molecular polarity. The n-perfluoropropylene oxide monomer units provide a stiffer main chain than perfluoropolyethers comprised of a copolymer of perfluoro-methylene oxide and -ethylene oxide monomer units. Terraced flow and bonding kinetics show that the stiffer main chain reduces lubricant mobility on the disk surface but provides a lower profile lubricant film. The lack of mobility attributed to the main chain can be compensated for by decreasing the number of OH end groups. The Hamaker constants, derived from surface energy vs. thickness measurements are larger than the corresponding flexible main chains, suggesting an increased adhesion to the underlying carbon surface.     

A Combined Molecular Dynamics and Finite Element Analysis of Contact and Adhesion of a Rough Sphere and a Flat Surface

A combined molecular dynamics and finite element model and simulation of contact and adhesion between a rough sphere and a flat surface has been developed. This model uses the results of molecular dynamics (MD) simulations, obtained using an embedded atom potential, of a nanoscale Ru-Ru asperity contact. A continuum finite element model of an elastic–plastic microscale Ru-Ru contact bump is then created. In this model, the surface roughness is represented by a system of nanoscale asperities, each of which is represented by a nonlinear hysteretic force vs. distance relationship. The nonlinear hysteretic character of these relations is determined from curve-fits of the MD results. Load vs. interference and contact area vs. interference are determined using this two-scale model for loading and unloading. Comparisons with a single-scale continuum model show that the effect of the nanoscale asperities is to reduce both the adhesion and the real area of contact. The choice of Ru as the material for this work is due to its relevance in microswitches.     

A Computational Study of Contact Mechanics between Magnetic Recording Heads and Thin-Film Disks

The tribological phenomena between magnetic head sliders and thin-film disks are studied during rest, during start-up and shutdown, and during regular operation using numerical simulations. A theoretical model of stiction is first derived based on the surface tension of liquid and capillary condensation. Next, a hybrid method of FEM and BEM is developed in order to carry out high-precision microscopic contact stress analysis of a disk covered by multilayer thin films. An impact simulator based on FEM is then presented which considers the air lubricant film to be an elastic spring system determined from the solution of a compressible Reynolds equation, ft is found, that these simulators can be used to effectively study the tribology of slider/disk interactions and that the results can be used to establish qualitative design criteria for slider/disk mechanisms.     

Accurate Measurements of Pressure-Viscosity Behavior in Lubricants

The piezoviscous effect is accurately characterized for a number of representative lubricating oil base stocks and a simple, well-defined hydrocarbon. Procedures for the generation of accurate pressure-viscosity coefficients are outlined. The reciprocal asymptotic isoviscous pressure may be measured to within perhaps 1%. The piezoviscous effect may be important to automotive fuel economy. The departure from exponential behavior at very low pressure becomes more pronounced at high temperature.     

Compressibility of Lubricants at High Pressures

Results from a high pressure chamber, recently developed at Lund Institute of Technology, are presented. The compressibility variation with the pressure of five different lubricants is investigated for pressures up to 2.7 GPa. The density variation for each lubricant is presented as a curve fit. The results show that at high pressures when the lubricant has solidified, the density varies linearly with the pressure. It is also concluded that the Dowson-Higginson relationship may be inaccurate when describing the density variation for some lubricants, especially at higher pressures.     

Oxidation Characteristics of MoS2 and Other Solid Lubricants

Thermogravimetric oxidation data are presented for fifteen refractory metal dichalcogenides. Interpretation of these data is supported by oxidation thermograms of the chalcogens and the refractory metals and by X-ray diffraction analysis of the oxidized products. The effects of humidity, heating rate, and particle size on oxidation of the dichalcogenides are presented. Thermogravimetric analysis is shown to be helpful in detecting impurities, such as unreacted elements, in commercial samples. Some dichalcogenides are shown to retain the same relative oxidation stability, when bonded in thin films with a ceramic, as for pure powder samples. A table is presented summarizing these oxidation characteristics together with information from the literature on crystal structures, electrical resistivities, and densities.     

Slider Wear on Disks Lubricated by Ultra-Thin Perfluoropolyether Lubricants with Different Molecular Weights

In this study, the wear properties of a magnetic head slider on disks lubricated by ultra-thin perfluoropolyether (PFPE) lubricants with different molecular weights were evaluated by the continuous sliding of magnetic head sliders using the slider contact by the dynamic flying height control. Two types of PFPE lubricants (Z-tetraol and D-4OH) with different molecular weights were evaluated. Results show that the slider wear depended on the coverage of the lubricant film; i.e., the lubricant film with sufficient coverage reduced slider wear. The lubricant film with a low molecular weight (low-Mw), including a lubricant material with a Fomblin and Demnum main chain, exhibited better coverage on a diamond-like carbon surface. Sliders with a low-Mw lubricant film showed less wear than those of a high molecular weight (high-Mw), and the depletion of the low-Mw lubricant film was less than that of the high-Mw lubricant film.     

Dynamic Adhesion Characteristics of Spherical Sliders Colliding with Stationary Magnetic Disks with a Thin Lubricant Layer

The dynamic indentation characteristics of 1- and 2-mm-radius hemispherical glass sliders when colliding with stationary magnetic disks under various lubricant conditions were investigated to clarify the dynamic interfacial forces between flying head sliders and magnetic disks. The collision times were ~15 and ~30 μs, respectively, and independent of the impact velocity. For a 1-mm-radius slider (Ra roughness = 1.71 nm), a clear adhesion force nearly equal to the static pull-off force was observed at the instant of separation when the lubricant thickness was from 1 nm without UV (0.69 nm mobile lubricant thickness) to 3 nm with UV (1.89 nm mobile lubricant thickness). The dynamic adhesion force was maximum when the slider had separated from the disk surface by about 2 nm and dropped from the maximum to zero when the separation reached more than 5 nm. When the mobile lubricant thickness was 0.43 nm, a clear adhesion force was not observed. For a 2-mm-radius slider (Ra roughness = 0.34 nm), a clear adhesion force, similar to the static pull-off force, was observed at the instant of separation at almost all lubricant thicknesses and impact velocities tested except at a small mobile lubricant thickness of 0.43 nm with impact velocities greater than 1.1 mm/s. The dynamic adhesion force dropped from the maximum to zero when the distance traveled from the maximum reached more than 5 nm. These results suggest that the dynamic adhesion force of 1- and 2-mm-radius sliders originates from meniscus formation rather than van der Waals force.     

拉深润滑剂的摩擦特性及其影响因素

本文采用自行设计的探地法测定摩擦系数，模拟板粒拉深变形条件下所测得的润滑剂润滑性能与传统的测试方法进行比较，能起初的反应塑料为形工况条件，其结果与生产实际情况十分吻合。     

Thin-Film Lubrication of Dented Surfaces

Surface microfeatures introduced to conformal surfaces have been proved in the last decade to provide beneficial tribological performances. They were found to significantly improve load capacity, wear resistance, or friction coefficient in applications that involve mechanical seals, piston rings, thrust bearings, or ultra-high-density magnetic disc drives. Recent studies have suggested that such an approach could be used to improve the lubrication capabilities under thin-film lubrication of highly loaded non-conformal contacts. However, surface micro-features influence the film thickness and pressure distribution within concentrated contacts that could result in surface failures. In this paper, thin-film colorimetric interferometry has been used to study the effects of an artificially produced micro-dent on film thickness distribution within thin-film lubricated contacts. Obtained results have shown that the behavior of dented surfaces significantly depends on the slide-to-roll ratio. An increase in the lubricant film thickness has been observed just upstream of the trailing edge of the micro-dent when the disc is moving slower than the ball with the micro-dent. In the reverse conditions, for a positive slide-to-roll ratio, the presence of the micro-dent within the concentrated contact results in the film thickness reduction located downstream of the leading edge of the micro-dent. This reduction can cause the local film breakdown of very thin films. Nevertheless, it has been observed that highly viscous boundary films can avoid it and rubbing surfaces have been completely separated using the formulated oil even under very thin lubrication conditions.     

润滑添加剂性能的电负性判据

本文运用电负性的判据，计算不同润滑添加剂分子基团电负性的大小，分析了不同结构的极性基与非极性基对添加剂吸附性能的影响。     

生物摩擦磨损润滑剂的润滑特性

关节转换已广泛应用于关节炎晚期治疗,外伤致残和滑瘤切除手术中。关节转换材料的耐磨性能会直接影响转换关节的使用寿命和使用质量。蒸馏水、盐水、血浆、血清等均被用作生物摩擦磨损研究的润滑剂,但是对这些润滑剂的润滑特性并未认真考察。本文应用ＴＬＴ－１型弹流试验台对血浆在内的几种生物摩擦磨损润滑剂的润滑特性进行了研究,结果表明血浆的润滑性能最好。     

光盘中使用的光学薄膜

介绍了用于ＣＤ系列光盘,磁光光盘,相变光盘和ＤＶＤ系列光盘的信息记录膜,光学介质膜和反射膜材料的原理,性能要求,制膜技术以及膜层之间的匹配问题。     

A study of the effect of palm oil as MQL lubricant on high speed drilling of titanium alloys

The main objective was to study the potency of MQL palm oil (MQLPO) as a lubricant in the high speed drilling of Ti-6Al-4V. For the comparison, MQL synthetic ester (MQLSE), air blow and flood conditions were selected. Uniform flank wear, micro-chipping, thermal cracking and flaking were the dominant tool failure modes. It was found that MQLSE and MQLPO gave comparable performance with the flood conditions. In addition, MQLPO outperformed MQLSE on the cutting forces, temperature, power and specific cutting energy. This shows that palm oil can be used as a viable alternative to synthetic ester for MQL lubricant.     

Dynamic and Static Irradiation of Nuclear Power Plant Lubricants

Proper choice of lubricating greases for use in machinery exposed to high energy radiation requires not only a sound estimate of the service the radiation dose, but also careful consideration of the normal lubrication variables. Interaction of all the variables may be complex. Static and dynamic test results are given which illustrate this point, and which reveal utility of some commercial mineral oil greases and a new high temperature radiation resistant grease.

Irradiation tests of turbine oils show that maximum expected radiation dose in current and projected power plants over a twenty year period does not change the physical properties of the oil. Oxidation stability and other properties are therefore still of most importance in turbine oil selection. Some experimental radiation-resistant fluids are discussed which have potential for fluid lubricant use where radiation resistance may be required.     

干膜润滑剂附着性能评价方法的试验探讨

本文对润滑涂层附着力的测定方法进行了全面的评价,通过干膜润滑剂多项性能试验测定结果的讨论,认为评价润滑涂层真地着力应考虑其它性能测定结果。     

Boundary Lubrication,Wear-in and Hydrodynamic Behavior of Bearings for Liquid Metals and Other Fluids

Various material combinations are investigated in the form of thrust bearings in such fluids as sodium-potassium eutectic, xylene and spindle oil. It is found that with these fluids certain material combinations can be made to perform satisfactorily as hydrodynamic bearings by a process of wearing-in. With these unique combinations it is possible to obtain film thicknesses of the order of 10 × 10^?6 inches by extreme wear-in. The characteristics of bearings worn in to this degree are reported and mechanisms for the observed effects discussed.     

Application of Solid Lubricants in Grinding: Investigations on Graphite Sandwiched Grinding Wheels

The intense heat generated in grinding process, if not controlled, will lead to major quality defects. Conventional liquid coolants, employed in flood form, have many limitations from technical, environmental and economic angles. Minimization or possible elimination of cutting fluids by substituting their functions by some other means is emerging as a thrust area of research in grinding. The authors have reported the feasibility of application of solid lubricants in grinding. This paper deals with the detailed investigations on solid lubricant integrated grinding wheels, by providing peripheral graphite sandwiching. Improvement in process results has been observed with this concept.     

Tribological Behavior of Some Candidate Advanced Space Lubricants

Performance of a variety of space lubricants was compared under boundary and elastohydrodynamic lubrication (EHL). The types of fluids studied were naphthenic mineral oil, paraffinic mineral oil, polyalphaolefin, and silahydrocarbon. The silahydrocarbon and the polyalphaolefin lubricants exhibited lower traction under similar conditions. A specific additive package increased the traction of the polyalphaolefin. Volatility characteristics of some of these fluids were also studied.     

The Effect of Shear-Thinning on Film Thickness for Space Lubricants

The authors show that the difference between effective pressure-viscosity coefficients, obtained from film thickness, and coefficients obtained from viscometers for a PFPE space lubricant is substantially the result of shear thinning in the inlet zone of concentrated contact. Flow curves for the PFPE and a multialkylated cyclopentane are presented along with film calculations based on the Carreau model.