Lubrication modes

Figure 2.6 Surface asperities and lubrication thin films determine tribological behavior and types of lubrication modes.

Reasonable Choice of Lubrication Mode, Grease and Galvanized, Effective Prevention of... 

Reasonable choice of wire rope lubrication mode, grease and galvanized thickness, should be a way to effective prevention of wire rope corrosion. For a vertical shaft friction hoist, the general choice of class B or class AB galvanized wire rope, fiber rope core with the lubrication... 

From an engineering standpoint, SF can be regarded as an aqueous electrolyte solution containing proteins, lipids and hyalnronic acid [12]. SF is also important for implants since a few weeks into the healing process, it surrounds the artificial joint. The predominant lubrication mode is in the mixed and boundary regimes [13]. In this study, we focus on the role of the most abundant protein in SF—human serum albumin (HSA). A screening study involving proteins and lipids was used... 

Fig. 10 Lubrication modes in natural synovial joint under walking condition (modified from Ref. 15)...

Hyilrodyrntmic lubrication is based on the formation of a thick lubricant film (typically of thickness from I to 100 pm) which inhibits contact between the moving surfaces. This lubrication mode is governed by the bulk physical properties of the lubricant, mainly the viscosity, and by the speed of the relative motion. 

Elastohydrodynamic lubrication (EHD) occurs when the extent of surface deformation is comparable with the lubricant film thickness, so that a heavy load causes local elastic deformation of the contacting surfaces, but without any significant a.sperity interaction. Taking into account the low lubricant thickness (typically from 0.01 to 10 pm) and the high contact pressures (typically in the GPa range), the lubricant properties differ from tho.se of a traditional bulk liquid. since a strong viscosity increase may occur, when the lubricant behaves more like a solid than a liquid. Moderate temperature rises may occur, thus inducing some thermochemical reactions between the surfaces and the lubricant additives, but no tribochemical phenomena are involved, unlike the next lubrication mode. 

This chapter is divided in two parts additives for motor fuels and additives for lubricants. Concerning additives for gasoline, one will find here in Chapter 9 some useful complements to Chapter 5, especially regarding the synthesis of additives and their modes of action. 

As with any analytical method, the ability to extract semiquantitative or quantitative information is the ultimate challenge. Generally, static SIMS is not used in this mode, but one application where static SIMS has been used successfully to provide quantitative data is in the accurate determination of the coverage of fluropolymer lubricants. These compounds provide the lubrication for Winchester-type hard disks and are direaly related to ultimate performance. If the lubricant is either too thick or too thin, catastrophic head crashes can occur. 

Another example is a safety valve in standby service. If demands occur very infrequently, time-related stresses such as external corrosion may have a significant influence. Repeated demands in very dirty service could easily lead to faster degradation and failure, whereas repeated demands in lubricated service might actually enhance performance if the failure mode of interest is failure to open. Failure data based on time or demands can also be skewed if the relief valve is initially damaged or installed incorrectly. 

Lubricating-film instability is the dominant failure mode for sleeve bearings. This instability is typically caused by eccentric, or off-center, rotation of the machine shaft resulting from imbalance, misalignment, or other machine or process-related problems. Figure 44.48 shows a Babbitt bearing that exhibits instability. 

Most of the failure modes associated with jackshafts and spindles are the result of lubrication problems or fatigue failure resulting from overloading. However, the actual failure mode generally depends on the configuration of the flexible drive. 

Spectrographic analysis allows accurate, rapid measurements of many of the elements present in lubricating oil. These elements are generally classified as wear metals, contaminates, or additives. Some elements can be listed in more than one of these classifications. Standard lubricating oil analysis does not attempt to determine the specific failure modes of developing machine-train problems. Therefore, additional techniques must be used as part of a comprehensive predictive maintenance program. 

Study on mechanisms of ordered molecular films as a model lubricant is of particular importance in the field of micro and nano-tribology, for it would help to understand how molecules contribute to the creation of friction and wear. The understanding has been much improved in recent years through MD simulations, performed by investigators around the world, to detect interactions between the molecular films in relative motion, and to reveal the process and specific mode of energy dissipation. 

In Felix s experiments conducted on the surfaces prepared with arrayed defects and in lubricated contact [54], the dependence of deformation on the slide-to-roll ratio was also observed, but in a more complex mode, as presented in Fig. 24. In pure rolling, the defects deform and entrap lubricant underneath during their passage through the inlet zone. For the same reason as discussed above in single defect case, the... 

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