An experimental/analytical study of high-speed, high-load rolling/sliding contacts with ultra-low viscosity fluids©

Experiments and theoretical analyses were carried out in this research to study the operating and lubrication conditions in highspeed, high-load rolling/sliding contacts with liquid oxygen (LO₂). A cryogenic traction tester having a single rolling/sliding contact conjunction was used in the experiments. Contact between two AISI 440C stainless steel rolling elements was studied at a rolling velocity of 47 m/s and at a load that generates a Hertzian peak pressure of 2.2 GPa. Tests were run with a slide-to-roll ratio up to one percent, and traction and specimen wear were measured. Experiments were also conducted at rolling velocities of 1.0 m/s and 11.7 m/s to provide evidence of LO₂ load support at high speeds and to deduce parameters for subsequent theoretical analyses. The measured total traction and asperity friction were then used as inputs to an analytical model to determine the load-carrying capacity and average film thickness of LO₂. The analyses show that the traction is mainly due to asperity friction; however, LO₂ can support a large portion of the total load despite its extremely low viscosity. This analytical result is also supported by the specimen wear data. The analyses in conjunction with the experimental data also provide a meaningful estimate of the average film thickness and LO₂ viscosity in the contact nip.