The Impact of Pressure Angle and Tooth Root on the Modified Elliptical Gears Bending Stress and Fatigue Life

Abstract

Noncircular gears are receiving growing attention due to their ability to deliver variable transmission ratios and to optimize motions in specialized mechanical and industrial applications. Unlike circular gears, noncircular gears experience continuous variation in pressure angle and load distribution throughout the meshing cycle, leading to non-uniform stress states among teeth. This study explores the impact of pressure angle and tooth root radius on the bending stress and fatigue life of modified elliptical gears. Finite Element Analysis (FEA) is conducted on three representative teeth positioned at varying distances from the gear centre, highlighting the asymmetric loading characteristic of specific profiles. The tooth root radius is varied, showing a clear reduction in maximum stress with the increased fillet radius size. Then, by varying the rack cutter angle, it is shown that higher angles reduce stress concentration. The results reveal the critical influence of tooth position and geometry on the fatigue vulnerability in noncircular gear design.