Research Article Open Access

Increasing the Strength of Standard Involute Gear Teeth with Novel Circular Root Fillet Design

V. Spitas1, Th. Costopoulos1 and C. Spitas1
  • 1 Laboratory of Machine Elements, Mechanical Engineering Department National Technical University of Athens, Iroon Politechniou 9, 15780, Athens, Greece


In this study the idea of spur gear teeth with circular instead of the standard trochoidal root fillet is introduced and investigated numerically using BEM. The strength of these new teeth is studied in comparison with the standard design by discretizing the tooth boundary using isoparametric Boundary Elements. In order to facilitate the analysis the teeth are treated as non-dimensional assuming unitary loading normal to the profile at their Highest Point of Single Tooth Contact (HPSTC), so that non-dimensional stress vs. Contact ratio diagrams are plotted. The analysis demonstrates that the novel teeth exhibit higher bending strength (up to 70%) in certain cases without affecting the pitting resistance since the geometry of the load carrying involute is not changed. The circular fillet design is particularly suitable in gear with a small number of teeth (pinions) and these novels gears can replace their existing counterparts in any mechanism without any alterations. Finally the geometry of the generating tool (i.e. rack) is determined in order to be able to cut these teeth using a generating method (i.e. hobbing).

American Journal of Applied Sciences
Volume 2 No. 6, 2005, 1058-1064


Submitted On: 7 May 2005 Published On: 30 June 2005

How to Cite: Spitas, V., Costopoulos, T. & Spitas, C. (2005). Increasing the Strength of Standard Involute Gear Teeth with Novel Circular Root Fillet Design. American Journal of Applied Sciences, 2(6), 1058-1064.

  • 38 Citations



  • Spur gears
  • circular fillet
  • root stress
  • generating rack
  • BEM