Effects of surface defects on rolling contact fatigue of heavily loaded lubricated contacts

Abstract

Surface-initiated fatigue caused by surface defects is one of the most dominant failure modes for bearing contacts. In this study, a damage mechanics-based Voronoi finite-element model (VFEM) is developed and used to investigate the effects of surface defects (such as dents and fretting wear) in elastohydrodynamic lubricated line contacts. A line contact elastohydrodynamic lubricated model is used to calculate the pressure distributions acting over the surface defects, which are then employed by Voronoi finite-element model to determine subsurface stresses. Continuum damage mechanics-based approach is used to incorporate cyclic damage accumulation and progressive degradation of material properties with rolling contact cycling. The model also takes into account the effects of residual stresses generated during the debris denting process. Using this methodology, the model is used to simulate microcrack initiation, coalescence, and propagation stages, finally a fatigue spall. The locations and patterns of dentinitiated spalls are found to be consistent with experimental observations. The fatigue model is used to study the effects of the topology of the material microstructure, dent sharpness, and material properties on rolling contact fatigue (RCF) life and Weibull slopes.

A novel approach for modeling retained austenite transformations during rolling contact fatigue

“…To reproduce RCF loading conditions in the area of interest, a Hertzian pressure profile was moved from left to right along the upper surface of the RVE from −3 b to 3 b in 81 discrete steps. The developed FEA model closely mirrors previous rolling contact models …”

“… τ r and m are material specific parameters established from torsional fatigue experimentation. This modified damage law has been implemented in multiple RCF modeling procedures . Equations and can be used to calculate the energy dissipation in the material microstructure as a function of stress cycles.…”

“…The developed FEA model closely mirrors previous rolling contact models. 37,[40][41][42]45 In order to incorporate material effects due to austenite concentration, a random function generator was used to assign an austenite volume fraction to each element within the RVE. The procedure further ensures that the aggregate volume fraction of austenite within the domain is comparable to reported levels in experimental data.…”

A Model for Rolling Bearing Life with Surface and Subsurface Survival—Tribological Effects

“…[24] it follows that Eq. [21] can be modified with a surface integral by replacing ln with the more general bearing notation, P, and introducing a fatigue limit load-life modifying factor, as described in Ioannides, et al (12), here it will be named a u . Notice that this function becomes b A in case of zero fatigue limit.…”

“…Because of this, there is an increased need for more versatile or generalized rolling bearing life models, able to adapt and incorporate new developed knowledge about the tribology of surface initiated failures of the rolling contact. Despite the progress achieved in the last few years in the numerical modeling of the tribology and surface performance of rolling contacts (e.g., Epstein,et al (16), (17); Morales-Espejel and Brizmer (18); Morales-Espejel and Gabelli (19); Brizmer, et al (20); Warhadpande and Sadeghi (21)), the integration of this new knowledge into an engineering model for bearing life estimation is, to some extent, hindered by the simplicity of present standardized life rating formulation (ISO 281:2007 (15)), which only relies on averaged global de-rating factors. This approach, although sufficient for most common situations, is not designed to give an account and differentiate among surface/subsurface competing failure modes that may occur in a bearing when exposed to a hostile environment and tough operating conditions.…”