study of the deformation and flow of matter under the influence of an applied
which might be, for example, a shear
or extensional stress.
The experimental characterisation of a material's rheological behaviour is
known as rheometry, although the term rheology is frequently used
synonymously with rheometry, particularly by experimentalists. Theoretical
aspects of rheology are the relation of the flow/deformation behaviour of
material and its internal structure (e.g. The orientation and elongation of polymer molecules),
and the flow/deformation behaviour of materials that cannot be described by
classical fluid mechanics or elasticity. This is also often called
non-newtonian fluid mechanics in the case of fluids.