Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 4 Articles
Lubricant additives, based on inorganic nanoparticles coated with organic outer\nlayer, can reduce wear and increase load-carrying capacity of base oil remarkably, indicating\nthe great potential of hybrid nanoparticles as anti-wear and extreme-pressure additives with\nexcellent levels of performance. The organic part in the hybrid materials improves their\nflexibility and stability, while the inorganic part is responsible for hardness. The relationship\nbetween the design parameters of the organic coatings, such as molecular architecture\nand the lubrication performance, however, remains to be fully elucidated. A survey of\ncurrent understanding of hybrid nanoparticles as lubricant additives is presented in this review....
Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard\ndisk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly\ndesign have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand\nthe touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very\ndifferent touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as\nwell as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing\nsliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal flyheight\ncontrol slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters,\nand air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported....
The role of surface protective additives becomes vital when operating conditions\nbecome severe and moving components operate in a boundary lubrication regime. After\nprotecting film is slowly removed by rubbing, it can regenerate through the tribochemical\nreaction of the additives at the contact. However, there are limitations about the\nregeneration of the protecting film when additives are totally consumed. On the other hand,\nthere are a lot of hard coatings to protect the steel surface from wear. These can enable the\nfunctioning of tribological systems, even in adverse lubrication conditions. However, hard\ncoatings usually make the friction coefficient higher, because of their high interfacial shear\nstrength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its\nrelatively low friction and superior wear resistance. In practice, conventional lubricants\nthat are essentially formulated for a steel/steel surface are still used for lubricating machine\ncomponent surfaces provided with protective coatings, such as DLCs, despite the fact that\nthe surface properties of coatings are quite different from those of steel. It is therefore\nimportant that the design of additive molecules and their interaction with coatings\nshould be re-considered. The main aim of this paper is to discuss the DLC and the\nadditive combination that enable tribofilm formation and effective lubrication of\ntribological systems....
Tribofilms are dynamic structures that form at the interface during frictional\nsliding. These films play a significant role in friction control, particularly under heavy\nloaded/high temperature conditions, such as those found at the cutting tool/chip interface.\nThe thermodynamic aspects of tribofilm formation are discussed here. Thermodynamic\nanalysis of entropy production during friction shows that there are two types of tribofilms\nthat affect the wear behavior of a cutting tool: (1) tribofilms forming as a result of the\nsurface modification of the cutting tools with further tribo-oxidation; and (2) tribofilms that\nform as a result of material transfer from the contacting frictional body (the workpiece)\nduring the tool/chip interaction. Experimental examples are presented, outlining the\nbeneficial role of both types of tribofilms....
Loading....