On the role of viscoelasticity in polymer rolling element bearings: Load distribution and hysteretic losses

In this paper, we present a Boundary Element methodology to numerically investigate the operation of a viscoelastic rolling element bearing in steady-state conditions. The methodology is fully general, able to deal with any real linear viscoelastic material, and relies on the ad hoc definition of steady-state viscoelastic Green's functions that intrinsically take into account the circular geometry of the domain. From an applicative point of view, the assessment of this contact problem is crucial: we show that the distribution of the load among the rollers is really different from what is predicted in purely elastic conditions, with some rollers eventually losing the contact with the raceways for some speed values. This has dramatic consequences not only on the rolling element bearing durability but may impact the rotor dynamics of the system supported by the bearing. Furthermore, our analysis assesses the viscoelastic torque pointing out the sources of hysteretic dissipation. Finally, to corroborate our model, numerical predictions for a rolling element bearing with the outer ring made of Polytetrafluoroethylene (PTFE) are compared, with good agreement, to experimental outcomes.