Influence of root geometry on bending stress for involute spur gears

Abstract

Involute spur gears are subjected to bending stress on its root and surface stress where the contact occurs during the meshing process. This bending stress affects the bending fatigue life of tooth. The other side, with increasing demand for higher power and torque, the stress level increases. For this reason, designers have begun to investigate non-standard tooth root geometries to decrease it. In this study, different tooth root geometries were designed and analysed for comparing each other in view of bending stress. For this aim, first the mathematical equations of involute and root geometries are programmed in MATLAB, then point cloud of gear tooth were exported to CATIA for generating FEA model, finally the finite element analyses were conducted in ANSYS program for determined gear parameters. Tooth is loaded on highest point single tooth contact (HPSTC). It is seen that elliptical root geometry is more expedient choice for stress reduction. The fully rounded trochoid geometry and circular geometry follow it respectively.