1. Fluids and solids
  2. What rheology allows us:

Rheology is a scientific discipline dedicated to the study of the deformation and flow of matter or, more precisely, of fluids. The word rheology comes from the Greek ρειν which means to flow.

Although Rheology could cover everything that has to do with flow behavior in aeronautics, fluid mechanics and even solid mechanics, the objective of Rheology is restricted to observing the behavior of materials subjected to very high deformations. simple. By means of observation and knowledge of the applied strain field, the rheologist can in many cases develop a constitutive relationship or mathematical model that allows, in principle, to obtain the material functions or properties that characterize the material.

Material functions and constitutive relationships have various uses in practice, depending on the objective of the study of each type of material. In this sense, two main objectives can be distinguished:

• Predict the macroscopic behavior of the fluid under process conditions, for which use is made of the constitutive relationships and material functions.
• Study indirectly the microstructure of the fluid and evaluate the effect of various factors on said microstructure. For this, the material functions or rheological properties are compared.

The fluids that are of interest to Rheology present a range of behaviors that go from the viscous Newtonian to the elastic solid of Hooke, which will be defined later. Within this category you can get innumerable materials such as yogurt, mayonnaise, blood, paints, fats and many more.

Fluids and solids

Fluid is understood as any portion of matter capable of continuously deforming when subjected to a force or deformation, unlike solids, which either do not deform or only deform to a certain extent. Fluids are all liquids, gases and other fluids with a more complex composition such as emulsions and suspensions, pastes and molten polymers, among others. Chewing gum, putty, bread dough could also be classified as fluids, although some might argue that they are deformable solids.

In reality, the classification of fluid or deformable solid is not very clear in many cases; frequently one can only speak of the degree to which a fluid approaches one or another type of behavior.

In this sense, the behavior of fluids can be bounded between two extremes, being the Newtonian viscous behavior one extreme and the Hookean elastic behavior the other extreme. It is precisely within this range of behavior that the interest of Rheology is found.

What rheology allows us:

• Characterize matter and define its rheological parameters such as viscosity, consistency, elastic properties, etc.
• Design sophisticated equipment for industrial processing, previously knowing the characterization of the material to be processed.
• Design new materials with very specific and well-defined mechanical responses, among many other actions. As a product formulation tool.
• Describes how a material will respond to the application of a given stress or strain. It foresees the behavior during the handling of the material.


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