Effects of Drive Side Pressure Angle on Gear Fatigue Crack Propagation Life for Spur Gears With Symmetric and Asymmetric Teeth

Abstract

Today gears are one of the most crucial machine elements in the industry. They are used in every area of the industry. Due to the high performances of the gears, they are also used in aerospace and wind applications. In these areas due to the high torques, unstable conditions, high impact forces, etc. cracks can be seen on the gear surface. During the service life, these cracks can be propagated and gear damages can be seen due to the initial cracks. The aim of this study is to increase the fatigue crack propagation life of the spur gears by using asymmetric tooth profile. Nowadays asymmetric gears have a very important and huge usage area in the industry. In this study, the effects of drive side pressure angle on the fatigue crack propagation life are studied by using the finite element method. The initial starting points of the cracks are defined by static stress analysis. The starting angles of the cracks are defined constant at 45°. The crack propagation analyses are performed in ANSYS SMART Crack-Growth module by using Paris Law. Four different drive side pressure angles (20°-20°, 20°-25°, 20°-30° and 20°-35°) are investigated in this study. As a result of the study the fatigue crack propagation life of the gears is increased dramatically when the drive side pressure angle increase. This results show that the asymmetric tooth profile not only decrease the bending stress but also increase the fatigue crack propagation life strongly.

Influence of tooth root cracks on the mesh stiffness of asymmetric spur gear pair with different backup ratios

“…Figure 7 illustrates an example of the different crack levels (25%-50%-75%-100%) obtained for standard (a c /a d = 20°/20°) gear samples based on the previous studies. 7,50,53 Table 2 represents the maximum crack lengths (i.e. the stress at the crack tip exceeds the yield strength) obtained from crack propagation analyses carried out for 16 (4 3 4) gear geometries.…”

“…As mentioned above, the crack paths introduced to the created 3D CAD models (Table 1) within the scope of this study were also validated with the available literature 49 in our previous studies. 7,50,53 The single tooth stiffness results obtained for m b = 0.5 and m b = 3.3 are denoted in Figures 9 and 10, respectively. Here, an example of single tooth stiffness results for healthy and cracked (25%-50%-75%-100%) gears is presented for two backup ratios and four DSPA.…”

“…We have presented detailed information regarding static structural and crack propagation analyses (for instance, boundary conditions, mesh convergence, and validation) in our previous studies. 7,50,53 From this standpoint, this study acquired the crack propagation paths for 16 gear geometries (Table 1) based on the previous studies.…”

“…In our previous studies, we have solved the numerical crack propagation analyses step by step and increased the crack amount as much as the element size in the region of interest at each step. 7,50,53 In addition, the stress values at the crack tip were compared with the material properties of the created gear geometries. Suppose that the bending stress obtained was below the gear material’s (AISI 9310) yield strength.…”

Circumferential spatial tooth profile modification of flexspline for harmonic drive: A novel method and a case study

“…Doğan et al[13] point out that the pressure angle affects the root stress and crack propagation directly, and the maximum pressure angle and optimum rim thickness can increase the fatigue propagation life by 15 times. Karpat et al[14] show that when the pressure angle increased, the fatigue crack growth life of gear increased dramatically. Hong et al[15] study the fatigue failure with radial cracks in gears of aero-engines.In order to solve the problem that the meshing pointand pressure angle vary largely in RM, the concept of circumferential modification (CM) of FS is put forward in this paper.…”