Skjuvförtjockande

Skjuvförtjockande, often translated as shear thickening or dilatant behavior, refers to a non-Newtonian fluid property where the viscosity of the fluid increases with increasing shear rate. This means that the faster you try to move or agitate the fluid, the more resistant it becomes to that movement.

This phenomenon is the opposite of shear thinning, where viscosity decreases with shear rate. Skjuvförtjockande fluids appear to behave like a liquid under normal conditions, flowing relatively easily. However, when subjected to sudden stress, such as a quick impact or rapid stirring, they can temporarily become as rigid as a solid.

A common example of a skjuvförtjockande fluid is a mixture of cornstarch and water, often referred to as oobleck. When you gently dip your hand into oobleck, it feels liquid. But if you punch it or try to stir it quickly, your hand meets resistance, and the mixture feels solid.

The mechanism behind skjuvförtjockande behavior typically involves the microscopic particles within the fluid. In a shear-thickening fluid, these particles are usually suspended in a liquid medium. At low shear rates, the particles can move past each other relatively freely. However, at high shear rates, the particles become jammed or interlocked, creating a more viscous structure that resists flow. This jamming can be due to hydrodynamic interactions, particle collisions, or elastic forces between particles.

Skjuvförtjockande fluids have practical applications in areas such as protective gear (like bulletproof vests or sports padding), industrial processes for controlling fluid flow, and even in some specialized ink formulations.