in Transmission Gearing
THIS PAPER is a discussion of compressive loading versus stress repetitions resulting in surface failures of transmission gears in laboratory tests. It is also an attempt to utilize data from such tests as a basis for future gear design.
A compressive loading failure is a breakdown of the gear tooth contacting surface by pitting until the surface becomes too rough for proper operation of the gear. This surface breakdown is caused by high compressive loading of the gear tooth surface for many tooth contacts or stress repetition. This surface failure is a surface fatiguing of the metal.
As the fatigue bending life of gears has been lengthened, the incidence of surface fatigue has increased. *