Purpose -The purpose of this paper is to study the dispersion and tribological properties of liquid paraffin with aluminum nanoparticles as additive, which are prepared by the surface-modification method using oleic acid (OA). Design/methodology/approach -The dispersion stability of aluminum nanoparticles in liquid paraffin is measured by spectrophotometry, which can be optimization by Taguchi method. The tribological properties are evaluated by using a ball-on-ring wear tester. Findings -The results show that few concentrations of aluminum nanoparticles as additives in liquid paraffin have better antiwear and antifriction properties than the pure paraffin oil. Scanning electron microscopy and energy dispersive spectrometer analyses can show that the thin films on the rubbing surfaces can be formed by these aluminum nanoparticles, which not only bear the load but also separate the both interfaces, thus the wear and friction can be reduced. Originality/value -Machine components and mechanism pairs rely on high-quality lubricants to withstand high temperature and extreme pressure. Extreme pressure and antiwear additives are typically adopted to improve the tribological performance of a fluid lubricant in reducing friction and surface damage under severe conditions.
Purpose -This paper is the third part of a serial studies for constant and variable compensations of the closed-type hydrostatic thrust bearings which has face-to-face recesses couple. The static stiffness of closed-type hydrostatic thrust bearings can then be obtained from the differentiation of recess pressure with respect to worktable displacement. The paper aims to discuss these issues. Design/methodology/approach -In this paper, the double-action restrictors of cylindrical-spool-type and tapered-spool-type are taken into consideration for variable compensation of hydrostatic bearings. Findings -The static stiffness in thrust direction of hydrostatic bearing is determined by the flow continuity equations that are formulated by film flow and compensation flow for each recess, respectively. The type selection and parameter determination of the double-action spool-type restrictors can be obtained from finding results of this study for maximum stiffness in design of hydrostatic bearings. Originality/value -This study reveals that the appropriate range of recess pressure ratio and design parameters of restrictors for the maximum stiffness can be obtained, the avoidance of negative stiffness is also provided.
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