Influence of Profile Modification on the Reduction of Root Fillet Stress in Spur Gear by Alternative Root Fillet Profile by using Finite Element Method

Mechanical Engineering

The working profile (involute) of a spur gear generated using a rack cutter produces a root fillet curve that is inherently trochoidal. However, this trochoidal fillet is not necessarily optimal with respect to the bending stresses experienced during gear operation. This study investigates stress distribution in the gear tooth by replacing the conventional trochoidal fillet with alternative polynomial-based curves. A circular root fillet is first constructed by drawing an arc tangent to both the working profile and the root circle, which serves as the reference fillet. This arc is then divided into six segments, and new fillet profiles are generated by radially displacing the intermediate points according to different mathematical relations while keeping the end points fixed. The modified fillet profiles demonstrate an improvement, reducing bending stress by approximately 9–12%. These results are based on two-dimensional finite element analysis (FEA).

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