The rheology is the specialty of physical centered on analysis of the beginning that determine how fluids move. The concept was proposed by the American scientist Eugene Cook Bingham (1878–[1945) in the first half of twentieth century.
What rheology does is study the link between the strength that is exerted on a material and the deformation that it experiences when flowing. Through constitutive equations, it is possible to establish a model about the way these substances behave.
In this context, deformation is a change that occurs in the shape or size of a body due to the production of internal forces that arise as a result of the application of one or more forces, or of thermal expansion. To carry out the measurement of the deformation, the magnitude called strain or axial, that engineering defined as the modification of the length of a body for each unit.
The branch of physics in which the concept of rheology is studied is the continuous media mechanics, also known as streaming media physics, which relies on a single model to treat fluids, rigid solids and deformable solids. Fluids can be classified as gases or liquids.
On the other hand, the notion of internal effort refers to a set of forces and moments that are applied on a section of a structural element and that present a static equivalence relation with respect to the distribution of internal stresses, that is, they result in a force and their moments are equal.
The properties that are responsible for studying rheology are analyzed with an instrument known as rheometer, which makes it possible to carry out deformations under control, measuring the forces. So you can determine the viscosity and the normal stress coefficient of each substance, among other properties.
The concept of viscosity should be understood as the endurance that a given fluid offers before deforming when subjected to stress. It is important to note that all fluids discovered by humans are viscous to some degree; Therefore, when you want to simulate the zero viscosity, you must make use of the assumption of ideal fluid.
Another point to keep in mind regarding viscosity is that it is only appreciated when the liquid is in movement; in fact, a definition of viscosity proposes it as the relationship that exists between the shear stress (explained in the next paragraph) and the velocity gradient.
It is known by the name of normal effort, on the other hand, to that which takes place as a result of normal stresses (in other words, perpendicular) to surface for which it is intended to determine the magnitude of effort. The stress arising from shear stresses (that is, tangential) the plane in question is called cutting.
Thanks to rheology, it is possible to know precisely how fluids and solids react to stress. In the case of ideal fluids, its deformation is irreversible: the energy takes the form of hot and it dissipates in the material, without being able to recover despite the end of the effort. In the ideal solidsOn the other hand, the energy that drives the elastic deformation is recovered when the stress is withdrawn.
Rheology provides information, for example, about the process that food undergoes when it is chewed and swallowed. This matter, through chewing and the action of saliva, it deforms and becomes a paste that flows into the body.