2019 年 14 巻 5 号 p. 422-427
Expecting to obtain a temperature-independent curve, pressure temperature superposition graph of lubricant high-pressure viscosity was tentatively constructed by adapting P/(T-Ts) as the horizontal axis, where P, T and Ts are pressure, temperature and the solidification temperature at atmospheric pressure, respectively. Published high-pressure viscosity data of mainly synthetic oils compiled in ASME pressure-viscosity report at different temperature could be plotted only on one curve named "master curve" depending on the kinds of oils with few data scattering up to 3 GPa or up to 220°C. The master curves were almost linear, but showed slightly nonlinear tendencies and convex in semi-logarithmic scale. Slope δ of the graph at the ambient point on the master curve is equivalent to α/(T-Ts), where α is the pressure-viscosity coefficient, so that α at the ambient temperature T can be easily obtained from δ determined by published or measured data (temperature). Employing this graph and its slope, high-pressure viscosity and α at 0°C and -18°C were estimated and they roughly agreed with the published data.
