What is meant by shear thinning?
In rheology, shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain. It is sometimes considered synonymous for pseudoplastic behaviour, and is usually defined as excluding time-dependent effects, such as thixotropy.
How do you quantify shear thinning?
Shear thinning index can be calculated by dividing apparent viscosity at the lowest speed by the value of apparent viscosity at the highest speed (typically at 2 and 20 or 5 and 50 rpm). The resultant ratio is an index of shear thinning.
What happens during shear thinning?
Overview. Shear-thinning is the pseudo-plastic rheological behavior of non-Newtonian liquids. It decreases the thickness of film and friction in EHD conjunction that is usually lubricated by orthodox fluid. Their flow resistance decreases in shear strain.
What makes a material shear thinning?
Shear thinning occurs because of rearrangements in the fluid microstructure in the plane of the applied shear. It is frequently seen in dispersions such as suspensions and emulsions, including melts and solutions of polymers.
Is shear thinning permanent?
Permanent shear thinning increases with the number of cycles in an approximately linear fashion, although it starts to level out after 20 cycles at the highest shear rate.
What is an example of shear thinning?
Shear thinning fluids, also known as pseudo-plastics, are ubiquitous in industrial and biological processes. Common examples include ketchup, paints and blood. Non-Newtonian behavior of fluids can be caused by several factors, all of them related to structural reorganization of the fluid molecules due to flow.
Why does shear thinning happen?
Why Does Shear Thinning Occur? Shear thinning occurs because of rearrangements in the fluid microstructure in the plane of the applied shear. It is frequently seen in dispersions such as suspensions and emulsions, including melts and solutions of polymers.
What is shear yield stress?
This theory asserts that yielding occurs when the largest difference of shear stress equals the shear yield strength. According to this theory, yielding will start at a point when the maximum shear stress at that point reaches one-half of the uniaxial yield strength, Fy.
Is shear rate the same as strain rate?
Strain rate is the change in strain (deformation) of a material with respect to time. It comprises both the rate at which the material is expanding or shrinking (expansion rate), and also the rate at which it is being deformed by progressive shearing without changing its volume (shear rate).