Theoretical characteristics of hydrodynamic journal bearings lubricated with soybean-based oil

Vegetable-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 of the journal bearings.