NUMERICAL-ANALYSIS OF THE INFLUENCE OF WAVINESS ON THE FILM THICKNESSOF A CIRCULAR EHL CONTACT

Surface roughness and/or surface imperfections are well known to signi ficantly affect the performance of concentrated contacts. Any deviatio n from the smooth surface will act as a stress raiser for itself(bump) or of its neighborhood (dent), and will therefore reduce the fatigue life of the component it is part of These imperfections can also act a s initiation sites of other types of contact failure such as scuffing, when contact conditions such as load, speed and film thickness become more and move severe. With the help of increasing computer speeds and more efficient numerical techniques, a theoretical analysis of the fa ilure of concentrated contacts becomes possible. The full answer will involve many aspects of the contact, including the generation of heat, thermal response of the lubricant and solids, non-Newtonian as well a s surface chemistry effects. This paper concentrates on the way the lu bricant film thickness is affected by waviness and tries to identify t he locations and the conditions where the film thickness is minimal. T he lubrication of nonsmooth surfaces is a transient two-dimensional pr oblem, which will be treated without any geometrical simplification. M ore precisely, this paper focuses on the influence of rolling speed an d the slide-to-roll ratio on the film thickness separating a smooth su rface and one with transverse waviness.