Постоји блиска веза између вискозитета и брзине смицања, which is the rate at which a liquid deforms under shear force.

Shear rate is a physical quantity that describes the deformation rate of a liquid. It represents the deformation velocity per unit time. It is the ratio between the Shear velocity and the geometric constraint on the liquid. The shear rate is usually expressed as the ratio of the displacement difference per unit time (брзина смицања) на растојање између два паралелна слоја (растојање смицања). The unit is usually the reciprocal of the second (с^(-1)).

Viscosity is the internal viscous resistance of a liquid, which measures the degree of stickiness or fluidity of a liquid. The greater the viscosity, the stickier the liquid and the more difficult it is to flow. Viscosity is usually expressed as the ratio of force per unit area to the difference in velocity per unit time (брзина смицања). The unit is usually PASCAL seconds (Па·с) or millipascal seconds (мПа·с).

Viscosity versus shear rate

The relationship between viscosity and shear rate can be described by Newton’s laws of fluid. A Newtonian fluid is an idealized fluid with a constant viscosity that is independent of the shear rate. According to Newtonian fluid laws, вискозност је једнака односу напона и брзине смицања.

У њутновским течностима, changes in the shear rate do not affect the magnitude of the viscosity, да ли је брзина смицања мала или велика. The viscosity of a Newton fluid remains the same, no matter how fast or how it is cut. Међутим, за нењутнове течности, such as shear-thinning and shear-thickening fluids, вискозитет ће се мењати како се мења брзина смицања. То значи да је вискозност нењутновске течности функција брзине смицања, which can increase or decrease as the shear rate increases. Однос између вискозитета и брзине смицања нењутновских течности може се описати и предвидети реолошким тестовима и одговарајућим реолошким моделима.