Shear Thickening

While most suspensions and polymer structured mate­rials are Shear ThinningThe most common type of non-Newtonian behavior is shear thinning or pseudoplastic flow, where the fluid vis­cosity decreases with increasing shear.shear thinning, some materials can also show shear thickening behavior where viscosity increases with increasing shear rate or shear StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress.

This phenomenon is also called dilatancy and although this refers to a specific mechanism for shear thickening associated with a vol­ume increase, the terms are often used interchangeably.

In most cases, shear thickening occurs at higher shear rates and there can be a region of shear thin­ning at lower shear rates. Usually, dispersions or particulate suspensions with a high concentration of solid particles exhibit shear thickening when the particles can no longer freely flow at increasing shear rates and hence start to “jam” together increasing its resistance to flow.

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