Reologie environmentálně akceptovatelných maziv

Abstract

This thesis investigates the viscosity and friction characteristics of environmentally acceptable oils at high shear rates. The theoretical section covers viscosity measurements, rheology, and discusses viscosity under high shear and Taylor vortices. The Stribeck curve and friction coefficient measurement methods are also explored. The experimental study focuses on measuring friction coefficients and viscosity at varying shear rates using a rotational viscometer with cylinder-cylinder geometry, tribocells, and cells with narrow slots. Results showed that higher viscosity grade oils maintained constant viscosity over a limited range of shear rates, with a tendency toward "shear thinning". The Stribeck curve analysis indicated that higher temperatures and pressures shifted the lubrication regime from mixed to hydrodynamic at increased rotational speeds. These findings have practical implications for applications like propeller lubrication, emphasizing the importance of considering temperature, pressure, and shear rate when selecting suitable oils.