A study into the impact of tooth root transition curve morphology on the bending fatigue life of gears

Tooth fracture is a prevalent failure mode that is intimately related to the bending strength of gears. Among the myriad factors influencing gear bending fatigue life, the morphology of the tooth root transition curve stands out as a crucial one, intricately tied to the gear’s resistance to bending fatigue. However, despite its significance, related research efforts, particularly experimental studies that consider cost factors, are relatively scarce in the current research landscape. Therefore, this paper first theoretically examines the influence of the tooth root transition curve morphology on the bending stress of gear teeth. Subsequently, bending fatigue experiments are conducted on gears featuring three typical tooth root transition curve morphologies, and the S-N curves for gears with these different morphologies are summarized. The findings reveal that adopting the digging-root type tooth root transition curve processing method, coupled with appropriately increasing the radius of the tooth top transition curve on the rack cutter, suitably reducing the distance between the rack tooth profile line and the tangent of the tooth root transition curve, and meticulously controlling the roughness of the tooth root transition curve, will significantly enhance the bending fatigue strength and prolong the bending fatigue life of the gear.