Experimental study of EHL film thickness behaviour at high speed in ball-on-ring contacts

To date few experimental studies of EHL film are at speed above 5 m/s, and most optical EHL experiment is based on classical ball-on-disc contact. This paper presents a newly developed optical EHL test rig in ball-on-ring contact for the investigation of film thickness at high speed. Tests are conducted under tractive rolling condition up to 52 m/s. Results show that, film thickness follows classical prediction at low speed, deviates but still increases at medium speed and finally decreases at very high speed; severe sliding occurs at high speed; the film thickness profile along motion direction changes from flat to wedge.