Numerical Model for the Critical Stress Determination in Spur Gears

 

Daniela Ristić

 

Gear carrying capacity and stress state depends to a large extent on main gear profile configuration parameters. To support this analysis, gear kinematics, carrying capacity, strength, production and some other characteristics are being actively investigated a tooth root form and the fillet radius. Great influence on gear tooth root strength that is one of the primary subjects of this paper. A special attention is given to the analysis of the impact of the gear tooth fillet radius at the critical cross section on stress value and distribution. The stress intensity factor and the gear working life depend directly on the tooth root stress. Real gears are statically undetermined systems and tooth root stress concentration depends on many parameters. Determining an optimal gear form relative to stress concentration is one of the main problems of gears design. It is well known that a first initial crack appears at the gear tooth affected the most by root stress concentration. Hence, this paper’s research topic is focused on finding the optimal fillet tooth root radius to minimize the root stress intensity. This paper provides the results achieved by the application of numerical methods: finite element method (FEM) and real working conditions simulation. The results are analyzed in order to form an effective numerical model for tooth root geometrical discontinuity phenomena at static loading. The results of this analysis are presented in this paper as figures and tables of Von Mises stresses as well as charts against different values of tooth root fillet radius ρ_F.

Key words: gear, spur gear, critical stress, stress concentration, finite element method.