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 researc h to study the operating and lubrication conditions in highspeed, high -load rolling/sliding contacts with liquid oxygen (LO(2)). A cryogenic traction tester having a single rolling/sliding contact conjunction w as used in the experiments. Contact between two AISI 440C stainless st eel rolling elements was studied at a rolling velocity of 47 m/s and a t a load that generates a Hertzian peak pressure of 2.2 GPa. Tests wer e run with a slide-to-roll ratio up to one percent, and traction and s pecimen wear were measured. Experiments were also conducted at rolling velocities of 1.0 m/s and 11.7 m/s to provide evidence of LO(2) load support at high speeds and to deduce parameters for subsequent theoret ical analyses. The measured total traction and asperity friction were then used as inputs to an analytical model to determine the load-carry ing capacity and average film thickness of LO(2). The analyses show th at the traction is mainly due to asperity friction; however, LO(2) can support a large portion of the total load despite its extremely low v iscosity. This analytical result is also supported by the specimen wea r data. The analyses in conjunction with the experimental data also pr ovide a meaningful estimate of the average film thickness and LO(2) vi scosity in the contact nip.