For analysis and validation of results, three methods of predicting bending stress– ISO standard, 3D-TCA (tooth contact analysis) method and Finite Element Analysis are applied and discussed. This paper investigates the influence of pressure angle of spur gears on bending stress considering the variation of root fillet radius, and provides a recommendation on how to optimize the pressure angle for high bending strength gears. The maximum tool tip radius will vary with the pressure angle changing due to the geometrical relationship of basic rack. Because the critical section occurs in the gear root fillet, the root fillet radius largely affected by tool (hob) tip radius also has a great significance for improving the bending strength. Formula of spur gearsCircular PitchPitch circular diameterAddendum circle diameterDedendum circle diameterAddendumDedendumClearanceTooth thicknessFillet radi. Gear pressure angle is an important parameter affecting tooth bending stress. There should be no relative sliding (abrasion) as this will cause excessive wear. It is imperative to understand the effect of gear parameters on bending stress in the initial stage of designing gears. As pinion and gear rotate, their teeth should ‘roll over’ each other. With increasing demand for high power density gear applications, the need to optimize gears for minimum stress becomes increasingly important. Many efforts have been made to increase gear bending strength including improving gear material property.
Tooth breakage will end the gear life, so gear bending stress has to be accurately calculated for reliable operation. Tooth breakage from excessive bending stress and surface pitting from excessive contact stress are the two primary fatigue failure modes for gears.
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