Abstract (EN):
Experimental gear scuffing results were obtained in the FZG test rig for wide ranges of the applied torque, tangential speed, base oil viscosity and bath oil temperature, and for FZG type A and type C gears. For restricted and particular operating conditions all scuffing criteria seem to be valid, however no one seemed appropriated for the wide ranges of operating conditions considered. A preliminary analysis of the experimental results shows that the oil bath temperature and the friction coefficient between gear teeth have a very significant influence on the scuffing load carrying capacity of the FZG gears. An expression for the friction coefficient in mixed film lubrication, generally occurring between FZG gear teeth, was developed, taking into account the results published by Hohn et al [1] obtained from experimental measurements of the power loss in FZG type C gears lubricated with mineral oils. A scuffing criterion for FZG gears lubricated with base oils is proposed taking into account the following considerations: the traditional PVT scuffing criterion (Alman criteria) is adequate when the aim is to compare the performance of different gear geometries; the FPI (Friction Power Intensity) scuffing criterion, together with the friction coefficient developed, is adequate to evaluate the influence of the torque (or contact pressure) and of the tangential velocity in gear scuffing [2]; Critical oil temperatures were determined, above which the lubricant has no longer the ability to generate an hydrodynamic film and scuffing may occur for any conditions. The scuffing load carrying capacity of the FZG gears is proportional to the difference between this oil critical temperature and the actual oil bath temperature. The scuffing criterion proposed fully agrees with the experimental results.
Language:
English
Type (Professor's evaluation):
Scientific
No. of pages:
20