ABSTRACT
A large variety of instrumental techniques exists that allow the deter-mination of rheological and fracture properties. In rheology, the two main classes are tube or capillary viscometers and rotational instruments. For determining fracture behavior, the so-called tension compression apparatuses are often used. Rotational instruments can be equipped with a range of different measuring geometries such as coaxial cylinders, cone and plate, parallel plates, or a spindle with thin vanes. Capillary instruments are well suited for determining accurately the viscosity of Newtonian liquids, and rotational instruments for studying rheological properties of non-Newtonian liquids and materials that can solidify in the rheometer (e.g., gels). Rotational instruments equipped with parallel plate geometry can also be used for studying solid materials. Tension compression apparatuses consist essentially of a fixed bottom plate and a moving bar, each of which has a part of the measuring geometry fixed to it. A load cell is placed in the moving bar or bottom plate, by which the forces, required to deform the test piece, can be registered. Because they are very popular in the food industry, in addition, several empirical test methods will be discussed in Section 8.4.
