Masayoshi Muraki

Synergistic effect on frictional characteristics under rolling-sliding conditions due to a combination of molybdenum dialkyldithiocarbamate and zinc dialkyldithiophosphate

Abstract The frictional characteristics of molybdenum dialkyldithiocarbamate (MoDTC) and/or zinc dialkyldithiophosphate (ZnDTP) in a paraffinic mineral oil were studied using a two-roller machine, in which the synergistic effect for reducing friction was found for the oil containing ZnDTP together with MoDTC. Variation in chemical composition of the surface film over time indicated preferential formation of the products through decomposition of ZnDTP. The reduction in friction was mainly due to MoS 2 derived from MoDTC, while ZnDTP had a role in enhancing the wear resistance and promoting the formation of MoS 2 . More severe conditions such as an increase in sliding speed tended to more significantly decrease friction.

Molecular structure of synthetic hydrocarbon oils and their rheological properties governing traction characteristics

Abstract Correlations between rheological properties governing traction and the molecular volume or structure of synthetic hydrocarbon oils are presented. A simplified thermal theory is applied to the traction curves experimentally determined on a four-roller machine, and characteristic parameters are obtained. It is shown that effects of molecular volume on the parameters are small and that the parameters are primarily related to the molecular structures. Further, the maximum traction coefficients of the oils are critically dependent on the effective viscosity—pressure coefficient among the parameters.

Evaluation of some traction fluids with a four roller machine

Abstract Traction characteristics of eight fluids of various compositions are evaluated with a four-roller machine, in which rotational speeds of mating rollers are positively controlled. The fluids tested are paraffinic and naphthenic mineral oils, liquid paraffin, polyisobutylene, and synthetic branched hydrocarbons. When the coefficient of traction is determined as a function of slide/roll ratio all fluids show essentially similar behaviour. However, different compositions have a marked effect on the values of the coefficient. These values are found to show a reasonable correlation with the estimated viscosity of each fluid at the average Hertzian pressures in the contacts

Rheological properties of polyolester under an EHD contact in some refrigerant environments

EHD traction of polyol ester in some refrigerants is analyzed using the non-Newtonian theory, from which available rheological parameters are determined. Then the rheological parameters are studied in elation to refrigerant concentration, As a result, the viscosity pressure coefficient of the mixtures is inversely correlated with refrigerant concentration in terms of mole per volume, while the representative stress characterizing the non-Newtonian is positively correlated. When the viscous volume relating to the unit of viscous flow is plotted as a function of molecular volume of refrigerant/POE mixture. the relation between them is well described by a single line independent of kinds of refrigerants.

Determination of Film Thickness and Traction of Polyol Ester under an EHD Contact in Some Refrigerant Environments

Oil film thickness and traction characteristics of a polyol ester in some hydrofluoro carbon and hydrochlorofluoro carbon refrigerants are determined with an EHD tester, where increase in refrigerant gas pressure decreases film thickness as well as traction in each refrigerant. When compared under an identical gas pressure, the film thickness with refrigerant is R-125 > R-134a > R-22, while that for the coefficient of traction at a certain slide-roll ratio is the same as film thickness. Oil film formability and traction performance are inversely correlated with solubility of refrigerant in POE in mole concentration.

Frictional properties of some additives for sliding guide way lubricants in a sliding speed range between 0.002 and 1.5 m/s with a thrust collar friction tester

Abstract Frictional properties of some additives used in sliding guide way lubricants were studied for a pair of mild steels under sliding speeds ranging from 0.002 to 1.5 m/s with a thrust collar type friction tester. As the sliding speed was decreased, the coefficient of friction first decreased, then after reaching the minimum value, it increased. The minimum friction coefficient μ min and the transition sliding speed V min showing μ min depended upon the additive. That is, μ min for the oil containing sulfurized lard was lower than those for the other oils tested and its V min was as low as 0.005–0.1 m/s compared with the transition speeds of 0.2–0.5 m/s for the other oils tested. Observations of the surface profile and surface analyses of the test specimen after the tests indicated that the unique phenomena for sulfurized lard were due to the formation of a boundary film containing a long carbon chain with a chemical bond between the sulfur and carbon.