摘要:

AbstractTin coatings are used as a final protection for cuprous substrates involved in low‐level electrical contacts. High friction forces and fretting phenomena remain a cause of electrical failure of connector terminals, and so should be minimised. A lubricant layer can improve the life and reliability of connector terminals but such a layer must ensure low and stable resistance values even under severe temperature conditions. Work has been undertaken to investigate the lubricant layer most suitable for the protection of tinned electrical contacts. Perfluorinated polyethers (PFPEs) were chosen for their inertness. The aim was to correlate various physico‐chemical properties of branched or linear PFPEs, with their frictional and electrical properties. The long‐term electrical properties of a contact are shown to be linked to the initial wear mode in the co

ISSN:0265-6582    

DOI:10.1002/jsl.3000190302

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractTheoretical work has underlined the importance of squeeze effects in non‐steady‐state elastohydrodynamic (EHD) lubrication when parameters such as load, speed, or geometry vary cyclically. The present paper reports on the results of an experimental investigation into EHD film thickness under start‐stop, ball‐on‐flat contact conditions for four liquid lubricants used in space applications. The conditions studied are representative of those occurring in stepper motor bearing contacts. The lubricants investigated included a multiply alkylated cyclopentane (Pennzane™ SHF 2000), a branched perfluoropolyether (Krytox™ 143 AC), a polyalphaolefin (Nye™ 182), and a linear perfluoropolyether (Braycote™ BXL 413). Measurements were made at two frequencies (2 and 50 Hz) and two temperatures (25 and 80°C). At 50 Hz, corresponding to stop‐start time intervals of 10 ms, there was insufficient time during the stationary periods between motion for any significant collapse of the central film thickness to occur. However, partial collapse did take place at the contact peripheries. Since this collapse occurred in the inlet, it often produced a pronounced reduction in central film thickness during start‐up. It was also found that, during start‐up, a series of film thickness oscillations occurred, resulting in the film thickness becoming successively greater and less than the steady‐state value. This may have a significant effect on the pressure experienced by the contact. Although the four lubricants exhibited similar overall patterns of behaviour, there were considerable differences in the rate of film collapse and in the details of the film thickness

ISSN:0265-6582    

DOI:10.1002/jsl.3000190303

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractVegetable‐based oils are not only biodegradable but also environmentally advantageous, and the range of lubrication applications offered by them continues to grow. Recently, vegetable‐based oils have been combined with synthetic esters to produce modified vegetable‐based oils.This paper presents an investigation of the theoretical characteristics of hydrodynamic journal bearings lubricated with non‐Newtonian soybean‐based oil. The soybean‐based oil was mixed with synthetic esters and silicone oil. The relationship between the shear stress and shear strain rate of the oil was obtained experimentally. The time‐dependent modified Reynolds equation including non‐Newtonian effects was formulated for short circular journal bearings. The perturbation technique was applied to the Reynolds equation to obtain zero‐ and first‐order pressure equations. The finite difference method was used to calculate the pressure distribution numerically. The static and dynamic characteristics, such as pressure distribution, Sommerfeld number, attitude angle, and spring and damping coefficients, were obtained numerically. It was found that the nonlinear factors of the non‐Newtonian soybean‐based oil strongly affected the performance characteristics

ISSN:0265-6582    

DOI:10.1002/jsl.3000190304

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractTotal vegetable oil greases are those in which both the lubricant and gellant are formed from vegetable oil. Vegetable oil may be used as a lubricant as such or, with appropriate structural modification, as an ester or alkylated ester. Total vegetable oil greases have the advantage of good biodegradability and conform to the requirements for high performance.Total vegetable‐oil based greases can be formed by mixing preformed soap and lubricant in the required proportions to form a grease with the desired properties. Alternatively, a grease can be formed from the same vegetable oil by simultaneous alcoholysis and saponification of the oil to form the lubricant and soap. The alkali used as a catalyst for the alcoholysis reaction serves as a reactant for the saponification reaction. The use of the appropriate proportion of oil, alcohol, and alkali will thus form a grease of the desired composition.A simultaneous reaction scheme to form sodium and lithium grease using castor oil has been studied. The alcoholysis reaction is separately studied for its kinetics, and the kinetics of the alcoholysis and saponification reaction are reported. Greases with 20% soap have been formed and their properties evaluate

ISSN:0265-6582    

DOI:10.1002/jsl.3000190305

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThere is an increasing move towards the use of environmentally safe lubricants. However, the development of a common biodegradable base stock that could replace conventional ones is a big challenge. Synthetic lubricants, whether synthetic hydrocarbons, organic esters, or others, all have problems associated with their use. However, in general terms synthetic lubricants protect better, last longer, and outperform their conventional mineral‐based counterparts in certain applications. Future lubricant specifications in view of the demand for improved performance to meet stringent environmental regulations are the main drivers for new technological developments. As part of a study to produce polyol ester lubricant base stocks from C5polyols and C6‐C14carboxylic acids in the presence of eco‐friendly catalysts, a series of products has been synthesised. A biodegradable lubricant formulation for automotive transmission fluids has been developed based on a synthesised product as a base fluid. This paper reports on the physico‐chemical characteristics and performance evaluation results of this formulation, which is a promising base stock for automotive transmission

ISSN:0265-6582    

DOI:10.1002/jsl.3000190306

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000190307

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000190308

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000190301

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY