Effect of Transverse and Longitudinal Surface Waviness on the Operation of Journal Bearings

An analysis is made to evaluate the effect of surface finish produced by the two final machining processes of high speed aero boring and broaching. A finite difference method of solution is used in which the number of waves superimposed on the basic geometry is successively increased. A strong asymptotic trend was found for all bearing characteristics beyond a relatively small number of waves. It is found that the load capacity compared to a smooth bearing is reduced for both processes if the surface waviness is included as an addition to the film height. If the film thickness is assumed to extend to the mean wave height, the load capacity is increased. The effect of surface waviness becomes more pronounced at higher eccentricities or as the amplitude of the waviness is increased. The variation of bearing friction and oil flow is shown. It is concluded that neither finishing process would have a serious deleterious effect on journal bearing performance.