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A dilatant (/ d aɪ ˈ l eɪ t ə n t /, / d ɪ-/) (also termed shear thickening [1]) material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the initialism STF, is an example of a non-Newtonian fluid. This behaviour is usually not observed in pure materials, but can occur in ...
Rheopecty: The longer the fluid is subjected to a shear strain, the higher the viscosity. Time-dependent shear thickening behavior. Thixotropy: The longer a fluid is subjected to a shear strain, the lower its viscosity. It is a time-dependent shear thinning behavior. Shear thickening: Similar to rheopecty, but independent of the passage of time.
The viscosity of a shear thickening – i.e. dilatant – fluid appears to increase when the shear rate increases. Corn starch suspended in water ("oobleck", see below ) is a common example: when stirred slowly it looks milky, when stirred vigorously it feels like a very viscous liquid.
Dilatant, or shear-thickening fluids increase in apparent viscosity at higher shear rates. They are in common use in viscous couplings in automobiles. When both ends of the coupling are spinning at the same rotational speed, the viscosity of the dilatant fluid is minimal, but if the ends of the coupling differ in speed, the coupling fluid ...
Time-dependent shear thickening behavior. Thixotropy: The longer a fluid is subjected to a shear force, the lower its viscosity. It is a time-dependent shear thinning behavior. Shear thickening: Similar to rheopecty, but independent of the passage of time. Shear thinning: Similar to thixotropy, but independent of the passage of time.
Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick or viscous under static conditions will flow (become thinner, less viscous) over time when shaken, agitated, shear-stressed, or otherwise stressed (time-dependent viscosity). They then take a fixed time to return to a more viscous state. [1]
Nonlinear viscoelasticity also elucidates observed phenomena such as normal stresses, shear thinning, and extensional thickening in viscoelastic fluids. [ 3 ] An anelastic material is a special case of a viscoelastic material: an anelastic material will fully recover to its original state on the removal of load.
Shear yielding involves the material undergoing shear flow with minimal or no change in density. In contrast, craze yielding, is highly localized and the macroscopic behaviors of shear and craze yielding differ significantly. [43] [44] Crazing and shear yielding are the two principal deformation mechanisms inherent to polymers.