Piezoviscous-Rigid Rolling and Sliding Traction Forces, Application: The Rolling Element–Cage Pocket Contact

Abstract

Piezoviscous Rigid (PVR) film thicknesses, rolling and sliding traction forces formulas for the line and point contact case have been derived. They have been used to study the Rolling Element (R.E.)–cage pocket contact mechanism. As the R.E. gets closer to the cage web, the lubrication regime change gradually from the PVR regime to Piezoviscous Elastic (PVE or EHD) regime when steel cages are used. If plastic cages are used, the lubrication regime moves from the Isoviscous Elastic (IVE) regime to EHD regime. For the conditions simulated herein, the transition occurs at typical film thickness values of the order of 0.5 micrometers and substantially large loads can be calculated in the R.E.–steel cage contact. They can be of the order of 100 N at the transition. In many circumstances, the PVR regime prevails and the braking moment due to hydrodynamic traction in the contact can be easily calculated. A tight osculation between the R.E. and the cage pocket will increase significantly the load and braking moment on the R.E. Starvation effects are also estimated and cause a reduction of the load, but not of the braking moment.