Experimental and Analytical Study of the Surface Texturing Enhanced Lubrication Elements

Abstract

Surface texturing is a method that modifies the frictional surface of a nominally flat tribocomponent by shallow patterns. It is found that with added patterns to the surface of a mechanical face seal or thrust bearing, their tribological performance improves, i.e. both friction and wear rate decrease. The current research concentrates on the analysis of hydrodynamic effect responsible for the performance enhancement of the spiral groove patterns and dimples on mechanical seal-like structures and the experimental evaluation of the tribological behavior of these structures. Surface textures considered are: dimple texture and spiral groove pattern. In the research on the dimple textures, the cavitation effect of the dimple enhanced friction pair is modeled using a mass-conservative theory – the Jakobsson-Floberg-Olsson (JFO) cavitation theory. Roughness effect is considered in the analysis of the dimple pattern performance. A thermohydrodynamic model is also developed to examine the influence of the temperature on the performance of the dimple textured frictional pair. The experiments on the dimple textured frictional pair are conducted on heat-treated 17-4 PH stainless steel specimens. The surface textures of the specimens are created by means of Nd:Ytterbium fiber laser. The laser surface textured specimens provide low coefficient of friction compared with plain (dimple free) surfaces. However, for the material used in the current experiments, the surface texture decreases the surface’s resistance to wear. In the research on the spiral groove pattern, the thermohydrodynamic model of the spiral groove surface seal is created. A commercially available CFD code – CFD-ACE+– is used for this purpose. The result shows that spiral grooves have significant influence on the seal’s thermal and load-carrying capacity behaviors. The experimental specimens on the spiral groove patterned friction pair research are made the same way as the dimple textured frictional pair. In this research spiral groove thrust bearings with variety of spiral angles subjected to different loads and speeds are tested. The frictional behaviors of the spiral groove thrust bearings are analyzed. In addition, a theoretical model is developed to gain further insight into the frictional characteristics of spiral grooves in both the hydrodynamic regime and the mixed lubrication regime.