ABSTRACT
This chapter is concerned with the rheology of a number of substances, an extensive and complex topic. It is necessary to restrict the treatment to substances that function as interface layers in tribological devices. In addition to being widely used as lubricants, greases are of special interest because, structurally and rheologically, they have much in common with powder films, as discussed. The science of rheology deals with the relationship between the applied force and the resulting flow or deformation. From a rheological standpoint, substances that are used in tribological applications can be divided into several categories. Of direct interest are viscous fluids, viscoelastic materials, and Bingham plastics. Not only do polymers have complex rheological properties, but under high pressure, they can undergo a change of phase from liquid to solid. The apparatus designed to establish the basic rheological quantity of the shear response to applied stress force.
