Investigation of lubricant supply in rolling point contacts under starved conditions using CFD simulations

Abstract

High friction and wear in rolling bearings are prevented by a lubricating film, which separates the contacting surfaces. In rolling contacts with limited lubricant supply, the film thickness decreases at high rolling speeds, as more lubricant is displaced than replenished. This lubricant depletion is known as starvation and may induce mixed lubrication due to a low film thickness. When estimating the bearing lifetime, a fully flooded lubrication, i.e. an unlimited lubricant supply, is usually assumed. This leads to an overestimation of film thickness in operating ranges where starvation occurs. Thus, considering the onset of starvation is crucial to reduce the risk of premature bearing failures due to high friction and wear in the mixed lubrication regime. Therefore, this contribution presents a method, based on computational fluid dynamics (CFD) simulations, to calculate the onset of starvation in oil lubricated point contacts.

CFD investigation of starvation behaviors in a grease lubricated EHL rolling contact

“…This flow is referred to as in-contact replenishment from side bands, which results in a concave meniscus in front of the contact. This oil distribution field agrees well with the simulation results by Fischer et al [22,23], in which the film thickness is assumed as a fixed value. The meniscus (indicated by green dotted lines) and the film thickness profiles are plotted together in Fig.…”

“…The oil distribution around a rolling contact is represented by its phase fraction α [17,22,23]. To avoid the discontinuous and non-differentiable nature around the interface, the isoAdvector method proposed by Roenby et al [24] is used, in which α at each mesh cell i between two time steps can be determined by:…”

“…The critical meniscus distance m is a value to determine the onset of starvation [21,22], which is proposed by Hamrock and Dowson [37], and can be calculated by Eq. 12:…”

“…Therefore, it is required to know the pressure distribution and surface deformation of the contacts under starved conditions. However, this correlation is not considered in the numerical investigations of starved contacts by Nogi [20,21] and Fishcer et al [22,23].…”

Research on the friction, lubrication and temperature rise characteristics of silicon nitride full ceramic ball bearing at low temperature

“…This is because when the ambient temperature is −80°C, the liquid nitrogen content in the working environment is less and the bearing is in an “oil-poor” lubrication state. The flow field area near the contact point is shaped like a “butterfly” (Fischer et al , 2021). The maximum stress in the fluid area is mainly distributed on both sides of the bearing raceway, and the maximum fluid stress is small.…”