Influence of surface velocity directions on lubricant film formation in EHL point contacts

Gear failures like wear, scuffing and micropitting strongly depend on lubrication conditions between gear tooth flanks. Many formulae have been developed to predict the EHL film thickness under various operating conditions. However, these methods are only valid if the surface velocities of the sliding partners are orientated in the same direction, like e.g. in spur gears. For bevel gears with hypoid offset the surface velocities of the contacting partners are orientated in different directions. For a reliable prediction of lubrication film thickness under conditions of different surface velocity directions film thickness measurements in a twin disc machine are performed.

► EHL-film-thickness measurements in a twin-disc test rig using the capacitance measuring method. ► Experimental examination of the influence of different surface velocity directions of two contacting partners. ► For constant absolute values of sum velocity an increasing skew angle leads to an increasing film thickness.