Study of Rheological Properties of Industrial Lubricants

Abstract

The most important rheological parameter for lubricants is viscosity as it also affects the tribological properties like friction between interacting surfaces and wear. This research intends to study the relationship between viscosity and temperature at different shear rates for multiple grades of three different categories of lubricants used for different applications viz. L1: MG20W50 (engine oil), L2: SAE20W50 (engine oil), L3: MC20W50 (mineral engine oil), L4: EP90 (gear oil), and L5: DXTIII (steering fluid). Constant high dynamic viscosity, shear stress, and low compressibility at different temperatures in multigrade as well as single grade industrial oil will help to maintain the surface film over the period of time and hence the reduction in wear. The dynamic viscosity of these chosen samples has been measured experimentally in temperature range of 20 to 50°C. The measurements have been extended to observe the dependence of shear rate, time, and temperature on the dynamic viscosity. All the samples are observed to behave like Newtonian fluids in the entire temperature range of study. Further, all samples seem to obey the Arrhenius relationship with temperature. Shear stress shows linear variation with shear rate exhibiting uniform viscosity which is substantiated by almost no variation in dynamic viscosity with shear rate for value above 5 per second.