The bending and contact stress analysis of spur gears

With the developing of science and technology the use of gears has become more common in all the upcoming industries. Accessory units used in aircraft provide the power for hydraulic, pneumatic and electrical systems in addition to providing various pumps and control systems for efficient engine operation. The design of an effective and reliable gearing system is governed, amongst other factors, by its ability to withstand high root bending stress (RBS) and surface contact stress(SCS). A number of authors have utilized thefmite element method to predict RBS and SCS in gears. This paper presents the utilization of a three-dimensional (3D), finite element method (FEM) to conduct RBS and SCS calculations of a pair ofspur gears. Firstly a pair of parallel spur gears without errors and tooth modifications is defined in a CAD system. Then, MES analysis is conducted. Using FEM to calculate the RBS the load is applied as a force to the tip of the gear, it is modeled as a linear force uniformly distributed along the face width and perpendicular to the tooth surface. The SCS is considered as nonlinear contact analysis, where the contact of the pair of gears is assumed on teeth flanks. The tooth RBS and SCS of the same pair of gears are calculated and presented. Gears with wrought alloy steel are considered. The results are compared with the ISO standards, Levis formula and Hertz equation. The analysis was made for applied moment equal: 600[Nm], 1200[Nm] and 1600[Nm]. It was found that the calculated results are comparable. Finally, an example of calculating a pair of spur gears is given in the paper.