Shearratefügg

Shearratefügg is a term used in rheology to denote a material property that varies with the shear rate. The word is a compound inspired by the English phrase "shear rate" and the Hungarian verb függ, meaning "depends," and is found in Hungarian-language scientific writing to express the idea of shear-rate dependence.

In rheological terms, many fluids are non-Newtonian, meaning their viscosity is not constant but changes as a function of the applied shear rate (gamma_dot). A common way to model this dependence is through constitutive equations such as the Ostwald–de Waele power-law: tau = K (gamma_dot)^n, where tau is shear stress, gamma_dot is shear rate, and K and n are material constants. The apparent viscosity eta = tau / gamma_dot = K (gamma_dot)^(n-1). If n < 1, the fluid is shear-thinning; if n > 1, it is shear-thickening. Other cases include yield-stress behavior (Bingham plastics) where flow occurs only above a critical shear rate.

Practically, recognizing a property as shearratefügg informs measurement and modeling choices. Rheometers operating under controlled shear rate or controlled stress regimes are used to obtain the gamma_dot dependence. Such data underpin material classification, formulation, and process design in industries ranging from polymer processing to food science.

See also: non-Newtonian fluid, shear-thinning, shear-thickening, viscosity, rheology, constitutive model.