EHD film thickness in non-steady state contacts

This paper describes a study of EHD film thickness in non-steady state contact conditions. A modification of ultrathin film interferometry is employed which is able to measure both central film thickness and film thickness profiles 50 times a second. Film thickness with two perfiuoropolyethers and two mineral base oils are investigated in a number of different types of non-steady state motion, including acceleration/deceleration, stop/start and reciprocation. The results demonstrate a range of transient behaviors of EHD film whose thicknesses deviate from those in steady state conditions.