Simulated Gear-Tooth Contacts: Some Experiments upon Their Lubrication and Subsurface Deformations

Abstract

This paper describes some experiments with disk machines in which the electrical resistance between the disks was measured at various stages of running. It also describes some experiments with mild steel disks run at such loads that considerable plastic deformation occurred. The resistance measurements illustrate the process of ‘running-in’ and show that a state of almost complete hydrodynamic lubrication is eventually reached. It has also been found that the surface temperatures of the disks have a very considerable influence upon the hydrodynamic film. The flow of material in the plastically deformed disks is described and its bearing upon the mutual accommodation of engaging tooth surfaces and their subsequent pitting is discussed. An explanation of the greater propensity to pit of surfaces with the lower peripheral speeds may be provided by one unexpected feature of the flow. It was also found that even at the high loads, which produce gross plastic distortion, the mild steel disks did not scuff, and this is attributed to the persistence of hydrodynamic lubrication even under such extreme conditions.