Abstract
Surface-hadened gears are employed as the power transmission elements in many recent machines. The design for tooth surface durability of surface-hardened gears is empirically performed using the relation between tooth surface hardness and Hertzian stress for both pitting and spalling failures. However, the dominant mode of the tooth surface failures in surface-hardened gears is spalling, whose failure mechanism is different from that of pitting failure. For this spalling failure, neither a guide for the establishment of a designing method nor a design formula has yet been give. In this paper, the recent fundamental works on spalling in surface-hardened gears carried out mainly at Okayama University are reviewed, and simple equations for estimating the spalling fatigue life and strength, and a general design guide for the spalling strength considering the spalling failure mechanism are introduced. Some problems for future investigation are also pointed out.
