Simulation of Microtextured Surfaces in Starved EHL Contacts Using Commercial FE Software

In order to improve the lubricating conditions and thus realize a reduction of friction and wear, the surfaces of contacting bodies in lubricated tribological contacts can be microtextured. Although this approach has already reached industrial applications for lower loaded contacts, it is still in basic research for higher loaded contacts, where elastic deformation plays a significant role. In the past, it was common in theoretical studies to assume a fully flooded condition for the inlet to the contact. However, in reality a lubricant contact may suffer from starvation due to high speeds, highly viscous lubricants, or limited lubricant supply. This article presents an efficient straightforward approach to compute starved microtextured elastohydrodynamic contacts based on a full-system approach and using commercial FE software. The numerical study on starvation is realized by shifting the position of the inlet meniscus toward the contact zone combined with the use of an appropriate cavitation model. Therefore, negative pressures are penalized by reducing the lubricant's density, respectively its volume or mass fraction, with a penalty term. First, the implementation for the steady-state smooth-surface problem as well as the impact of decreasing lubricant supply on the film thickness are discussed as a reference case. Special is paid to proving suitability and validity of the used cavitation model for starvation problems. Subsequently, the influence of different degrees of starvation on film thickness and pressure distribution for a microtextured time-dependent demonstrator case is illustrated.