Relation of tangential force and pitting limit at rolling-sliding contact surface under mixed lubrication condition

Abstract

Design for pitting (surface crack initiated rolling fatigue wear) at rolling-sliding contact surface under mixed lubrication condition is based on the combination of maximum contact pressure (Hertzian stress) and lubrication condition (ratio of surface roughness value and oil film thickness value). However there is indirect relationship in the combination of contact pressure and lubrication condition to the pitting phenomena. The origins of rolling fatigue pit are the micro cracks at contact surface due to tangential force. In this paper, the pitting test results are re-examined from a standpoint of influence of the tangential force on pitting. The new parameter f·(pH/HB)2 based on the friction coefficient estimation formula by Matsumoto for pitting design is introduced. And it is cleared that the new parameter has same value in pitting limit to every different contact pressure and lubrication condition. In conclusion, it is necessary to reconsider the pitting design method for power transmission gears excepted tangential force from consideration.

Keywords

• rolling-sliding contact surface
• rolling fatigue
• pitting
• tangential force
• coefficient of friction
• mixed lubrication
• elastohydrdynamic oil film thickness
• surface roughness in maximum height