ALBERT

Notes: Purpose - The paper presents the results of research carried out on esters of carbonic, adipic, and sebacic acids with respect to their use as components of fully synthetic lubricating oil produced from a polyalphaolefin base. Straight dicarboxylic acid esters were synthesized in a transesterification reaction of dimethyl carbonate, dimethyl adipate, and dimethyl sebacate with 2-ethylhexanol and 3,5,5-trimethylhexanol. Design/methodology/approach - Oligomeric esters of adipic acid and sebacic acid were synthesized using neopentyl glycol, appropriate dimethyl adipate or dimethyl sebacate and 2-ethylhexanol as the starting material. The basic physicochemical properties of esters were determined and their compatibility with synthetic oils were defined. They were also evaluated with respect to resistance under the influence of thermo-oxidative factors, evaporation and susceptibility to hydrolytic decomposition. The selected esters were complemented with commercial additives to make up a fully synthetic lubricating oil with a polialphaolefin base. A special attention was paid to the effect of ester compounds on the physicochemical properties of the formulated oil. Findings - The obtained results show that straight adipates and sebacates of 2-ethylhexanol and 3,5,5-trimethylhexanol as well as oligomeric esters in which molecules are terminated with 2-ethylhexyl group can be used as component of lubricating oils. The addition of these esters reduced the pour point by a few degrees in comparison with the tested base oil. The temperature fell below 40°C. The presence of esters significantly improved the viscosity index. A positive influence of esters on the lubricating properties of the formulated oil was also observed. On the contrary, dialkyl carbonates show too low boiling point, which is indicated by the high amount of volatile components, 19-22 percent, in final product. Adipic and sebacic oligomers containing methoxyl groups in their structures proved to be immiscible with polyalphaolefins. Originality/value - The achievement of this work is the synthesis of new oligomeric esters of dicarboxylic acids, which can be excellent additives for improving properties of synthetic oils. Further studies will be focused on the use of esters as components of engine oils. This requires real motor tests.

Notes: Purpose - To study the combined effects of permeability and couplestresses on the performance characteristics of a secant-shaped porous slider bearing lubricated with Stokes couplestress fluid. Design/methodology/approach - The modified Reynolds type equation governing the fluid film pressure is derived on the basis of Stokes microcontinuum theory of couplestress fluids by using Beavers-Joshep slip boundary conditions at the fluid-porous interface. The modified Reynolds equation is solved analytically and closed form expressions are obtained for the fluid film pressure, load carrying capacity, frictional force and centre of pressure. Findings - The bearing characteristics are computed for various values of the couple stress parameter, slip parameter and the permeability parameters. It is found that, the effect of couple stress is to increase the load carrying capacity and to decrease the coefficient of friction as compared to the Newtonian case. However, the effect of permeability parameter is to decrease the load carrying capacity. It is also found that, the effect of couple stresses is to shift the center of pressure towards the outlet edge. Research limitations/implications - The end effects are neglected in the analysis and these can be included in the study by considering full three-dimensional problem. Practical implications - Reduction in the load carrying capacity due to the presence of porous facing can be compensated by the use of lubricants containing additives of proper size. As a result the bearing performance can be improved. Originality/value - This paper provides closed form expressions for the bearing characteristics and are analyzed with respect to non-dimensional parameters, viz. couplestress parameter, slip parameter and permeability parameter. This paper offers help to design engineers to design efficient bearing systems.

Notes: Purpose - To form and develop a new mode of mixed elastohydrodynamic lubrication (mixed EHL) which is more realistic and of more application values to a practical elastohydrodynamic contact on gears, cams and roller bearings than the previous and current existing mixed EHL models. Design/methodology/approach - The representative theoretical and experimental studies on elastohydrodynamic lubrication (EHL) and mixed EHL carried out in the previous and recent time, including those of the author, are reviewed. The obtained results on EHL and mixed EHL in those studies and the viewpoints on the mode of mixed EHL based on those results developed in those studies are compared and evaluated. Strong proves are formed on the new mode of mixed EHL proposed in the present paper based on these comparisons and evaluations. Findings - Strong viewpoints are formed on the mode of the occurrence of dry contact in EHL in a practical concentrated contact. A new mode of mixed EHL is proposed by incorporating this mode of the occurrence of dry contact in EHL. Also, comments and evaluations on the previous researches on mixed EHL are made. Practical implications - A very useful material for the engineers who are engaged in the design of EHL on gears, cams and roller bearings, and for the tribology scientists who thrust efforts in studying EHL and mixed EHL both by theoretical modeling and by experiments. Originality/value - A new mode of mixed EHL is originally proposed by incorporating the finding of a more realistic mode of the occurrence of dry contact in EHL. This new mode of mixed EHL should become the direction of the theoretical research of mixed EHL in the future time. It provides a clearer way to this research.

Notes: Purpose - Nowadays, green cutting has become the focus because of its ecological problem and the necessary environment protection, so that the research on experimentation of green cutting with water vapor as coolant and lubricant is studied because water vapor has many benefits of cheapness, no pollution, no harm and no recycling and handling. Design/methodology/approach - The vapor generator and the vapor feed system are manufactured, the distribution of temperature and velocity of vapor jet flow are simulated by MATLAB program, and under the conditions of compress air, oil water emulsion, water vapor as coolant and lubricant and dry cutting, respectively, the turning experimentation of comparison which the tool is YT15, and the working material is steel 45. Findings - Water vapor, as coolant and lubricant, the cutting force is reduced, respectively about 30-40, 20-30 and 10-15 percent by comparing to dry cutting, compressed air and oil water emulsion. The cutting temperature is, respectively about 30, 40 and 50 percent with the other conditions of dry cutting, compressed air and oil water emulsion. The friction coefficient and the chip deformation coefficient are correspondingly decreased and the surface roughness value has been diminished too. Through analysis of the experimental results, water vapor as coolant and lubricant possesses better lubricating action because of the excellent penetration performance and the low lubrication layer shearing strength of water vapor. Originality/value - Water vapor as coolant and lubricant provides a novel method for realizing no contamination green cutting.

Notes: Purpose - To prevent damages of machinery elements and enhancing life lubrication by using new surface engineering techniques. Design/methodology/approach - A new "wet" coating technique offers an easy and promising route to modify steel surfaces. The design of surface coatings and the results of an official bearing test are presented. Findings - Based on common bearing tests (e.g. DIN 51819), wear behaviour and tribological properties of modified surfaces are verified. Research limitations/implications - Our actual research proves an enhanced tribological behaviour in the case of improving surface properties. In contrast, to the common vapour deposition techniques the "wet" coating method seems to offer an alternative route to get surfaces with enhanced tribological properties. Practical implications - The technique of "wet" coating offers an easy route to modify steel surfaces of all kinds of bearings. Originality/value - Pre-polymer coating provides a promising future technique for surface engineering.

Notes: Purpose - Oil-in-water (O/W) emulsion has been used in industrial rolling mills for many decades, but its lubrication mechanism is still not adequately understood. There is a need to understand the role of chemical ingredients and emulsifier in lubrication and tribological characteristics of rolling oil. With this purpose, the authors selected three commercially available O/W emulsions of different generations and of known industrial performance. The aim is to understand the lubrication mechanism of these rolling oils and to correlate the laboratory findings with that of industrial rolling mills. Design/methodology/approach - The lubrication mechanism has been studied with the help of an ultra thin film interferometry EHD test rig, an advanced experimental rolling mill and a Coulter LS 230 instrument. Film thickness, rolling parameters and droplet size were measured. The coefficient of friction was computed with the help of the measured values of rolling parameters. Emulsion stability and saponification value (SAP) of the selected emulsions were also determined. The results of film thickness, rolling parameters and droplet size have been presented. The lubrication mechanism of the emulsions has been explained on the basis of film thickness, droplet size, emulsion stability, SAP value and coefficient of friction. Findings - Results of the present study reveal that chemistry of O/W emulsions plays an important role in their film forming and tribological behavior. Rolling emulsions of relatively low stability, higher droplet size and high SAP value are found to provide better lubrication and lower coefficient of friction. The results of the present study correlate well with the actual industrial experience except those obtained on EHD test rig. Research limitations/implications - Coulter LS 230 instrument was available with M/s LUBRIZOL CORP., USA. Only limited study on droplet size was carried. Although the study carried out has given good information but it would have been more practical if the emulsion samples taken from the experimental mill stand would have been studied for droplet size. Practical implications - From understanding point of view of lubrication mechanism of O/W emulsion, it will be useful for oil technologists, tribologists and rolling mill users. Originality/value - The study is original in nature and gives information on lubrication mechanism of O/W emulsions in steel cold rolling of steel strips.

Notes: Purpose - Provide tribological information about the applicability of multi-layer carbon-chromium composite coatings to gears. Discuss the protection provided against scuffing failures, wear and the influence on gear power losses. Design/methodology/approach - Several screening tests, such as Rockwell indentations, ball cratering, pin-on-disc and reciprocating wear tests, were performed in order to evaluate the adhesion to the substrate and the tribological performance of the carbon/chromium composite coating. Afterwards, twin-disc tests were performed at high contact pressure and high slide-to-roll ratios to confirm the good adhesive and tribological properties of the coating under operating conditions similar to those found in gears. Gear tests were performed in the FZG machine in order to evaluate the anti-scuffing performance of the carbon/chromium coating using additive free gear oils. Finally, the carbon/chromium composite coating was also applied to the gearing in a gearbox and its influence on the gearbox efficiency was analysed. Findings - The C/Cr has got very good adhesion to the steel substrate, provides low friction coefficients between contacting solids in relative movement, gives excellent protection against scuffing and wear reduction in gears, and promotes a slight improvement of the gears efficiency. Research limitations/implications - The protection of this carbon/chromium coating against gear micro-pitting should be investigated. Practical implications - This study confirms the applicability of this coating to industrial gear applications, especially in two particular applications: severe applications involving high contact pressures and high sliding, frequent start-ups and inefficient lubrication; and acting as tribo-reactive material and substituting non-biodegradable and toxic additives in environmental lubricants. Originality/value - This work validates and quantifies the influence of this C/Cr multi-layer composite coating in gear applications in terms of adhesion to the substrate, anti-scuffing performance and efficiency.

Notes: Purpose - To provide a suitable useful mixing ration of nano-sized molybdenum disulfide and commercial common molybdenum sulfide (MoS2) particles (approximately 1.5?µm in diameter) in liquid paraffin, which can lead to a better tribological performance. Design/methodology/approach - The MoS2 nanoparticles and commercial common MoS2 particles (approximately 1.5?µm in diameter) were dispersed in liquid paraffin with different concentrations and ratios by means of ultrasonic in order to study their lubrication capacity, friction reduction and wear resistance. The tribological experiments were carried out by MQ-800 four-ball tribometer, in which extreme pressure, wear scan diameter and friction coefficient were measured. It was analyzed that the chemical status of elements on the rubbed surface by X-ray photoelectron spectroscopy (XPS), and it was observed that the surface topography of wear scan by scanning electron microscope (SEM). Findings - The results showed that the loading capacity of liquid paraffin with different kinds of MoS2 particles were increased with their contents. The liquid paraffin containing the mixture of MoS2 nanoparticles and common MoS2 particles has a better wear resistance, friction-reducing performance and extreme pressure property than the liquid paraffin containing pure common MoS2 or pure nano-MoS2 particles. The optimal mixing ratio of nano-MoS2 and common MoS2 is 20?wt percent, the loading capacity reaches the highest value. By XPS and SEM it was suggested that the difference in the tribological performance between MoS2 nanoparticles and MoS2 common particles was attributed to the surface and interfacial size-effect of nanoparticles and the formation of molybdenum trioxide thin film on the rubbed surface. Research limitations/implications - It is not studied that the effects of mixing of common MoS2 and nano-MoS2 in the actual lubricating oil with various additives. Practical implications - It provided a basic research results and data for the application of nano-MoS2 particles. Originality/value - The mixing of nanoparticles and non-nano-sized particles will lead to new tribological results, which is different from results obtained from other nanoparticles before.

Notes: Deals with the development of aerostatic-cum-aerodynamic hybrid conical bearings, running at 70,000 r.p.m., suitable for supports of high speed spindles. Conical bearing bush is designed for two plane admission, with eight holes in each plane, with a semi cone angle of 108. In case of static response, the interactions between the major parameters, are projected on 3D response surface curve. The results give the magnitude of radial load to get the benefit of optimally minimum eccentricity ratio. Experimental results show close agreement with the theoretical work in regard to "no-rotation" cases. The exponential relationship existing between eccentricity ratio, radial load and supply pressure is generalised. Rigidity for the bearings developed, as seen from the response surface, supports the observations of previous researchers. For the use of designers, vital operational parameters have been tabulated. Estimated and experimental values of these parameters compare reasonably.

Notes: Scheduled rejection of lubricants in central lubrication systems often leads to loss of lubricants as these could be used for a further long period. To avoid such loss, periodic monitoring of lubricants is suggested so as to forecast the time when the lubricant in a particular system of equipment loses its properties and requires to be drained-off and charged afresh. To assess the remaining useful life of lubricant (RULL) in use, a new method by fourier transform infrared (FTIR) spectroscopy is used. The work is supplemented by a case study on heavy earth moving machinery (HEMM) deployed in Indian mines.