Hydrodynamic effects of tailored inlet roughnesses: extended theory

In a recent paper (STLE/ASME, Tribology Conference, 1999), the author introduced the idea of generating hydrodynamic pressure in bearings and other devices by means of an inlet zone having tailored roughness. The latter implies removal of material and therefore eases the ingress of fluid into the device. The inlet microstructure thus replaces the macrostructure—steps, inclined surfaces, etc.—of standard devices, and can operate with a nominally parallel film. ew subsequent papers (JSME ITC, 2000, 1549; Tribology International, 34, 2002, 847; NORDTRIB’02, Intnl Tribology Conference), this concept was developed, resulting in the prediction of very desirable properties. Compared to values of standard devices, film stiffness and damping may be strongly enhanced. ne family of surface structure has been investigated, namely that of parallel striations running along the direction of motion or at right angles to it. In the present paper two more structure patterns have been studied, i.e. checkerboard and sinusoidal dimples. st typical hydrodynamic parameters of sliders have been calculated for a wide variety of cases and the results are compared with step profile sliders of similar dimensions. ilored surfaces show a consistent improvement in performance compared to the smooth ones. The effects are, however, less marked than those of the best combinations of striations and macro-geometries. y, a thorough discussion of various aspects of the new devices is given.