Viscoelasticity and Its Application to Lubrication

Abstract

Polymer solutions such as polymer-containing (VI-improved) oils show a variety of mechanical effects in flow that differ qualitatively from the ones observable under the same conditions in Newtonian liquids. This has, of course, been realized for a long time but the reason for their occurring has been traced to different sources. The point of view that the author has supported for a number of years, actually his idea for this happening, is that polymer solutions become elastic in steady flow. This thesis can be supported beginning with molecular theory through the mechanics of observable effects down to tests by a large variety of experimental methods. This point of view is by no means universally accepted in the rheological community. This elasticity causes “normal stresses” that may influence the load-carrying ability of journal bearings. However, the great problem is measuring their properties at the rates of shear occurring in practice (in the millions sec−1 ) and the existing eccentric geometry.