Discussion: "An Analysis of Stress Relaxation in Elastico-Viscous Fluid Lubrication of Journal Bearings" (Harnoy, A., 1978, ASME J. Lubr. Technol., 100, pp. 287–294)

R. C. Rosenberg
1978 Journal of Lubrication Technology  
The behavior of journal bearings lubricated by non-Newtonian fluids is a complex subject. In this paper the author's basic premise is that a non-Newtonian lubricant exhibits superior performance as compared to an equivalent Newtonian lubricant in steadily loaded journal bearings. I question if this is true. Polymer-containing oils may provide certain performance advantages in the areas of engine cold starting and oil consumption. However, data supporting improved load earring capacity for these
more » ... lubricants in steadily loaded bearings is sparce and in my opinion questionable. The only realistic data that the author has cited to support his premise is that of Dubois, Ocvirk, and Wehe [5]. Careful examination of this reference shows that the limit of accuracy of the experiment is such that any differences between Newtonian and non-Newtonian fluids cannot be supported. As the author points out, other experimental studies [6, 7] involved either low speed simulated bearings or fluids with viscoelastic properties vastly different than those of commercial lubricants. In recent experimental studies at General Motors Research Laboratories [21], 3 we have examined the performance of a large number of polymer additives. These materials were evaluated in a high load, high speed journal bearing. Commercial additives from five chemical classes were used in concentrations which are typical of modern miltigraded engine lubricants. Some of our results are shown in Fig. 5 where the friction and film thickness data for both Newtonian and non-Newtonian oils are presented. These data have been normalized so that the performance of the base oil (an SAE 20) is equal to 1.0. Four Newtonian oils define the classical behavior of the bearing. The 13 polymer-containing oils lie scattered to either side of the line defined by the Newtonian oils. The author's results (Table 2) predict a 10 percent improvement in load capacity for a non-Newtonian lubricant in bearings operating at an eccentricity ratio of 0.95. Our results, which were obtained for eccentricity ratios of 0.93 to 0.97, show that there is no statictically significant increase in the load capacity of non-Newtonian oils as measured by changes in film thickness.
doi:10.1115/1.3453168 fatcat:2ggku7gbdnfd3aznpspnv54yaa