Evaluation of load capacity of gears with an asymmetric tooth profile

Abstract

Background: An ISO standard tooth profile has a symmetric pressure angle of 20°. However, the load capacity can be increased with respect to bending and contact pressure by increasing the pressure angle on the meshing side of an asymmetric tooth. Accordingly, we analyzed the torque transmission capacity of asymmetric gears with various pressure angles. Methods: We calculated the deflection and bending stress of teeth by the finite element method and found the root stress taking into account the load-sharing ratio. Hertzian contact stress was calculated with respect to contact pressure. Normal vector load was converted into a torque, and torque capacity was evaluated when the stress reached the allowable stress for each case. Results: Reduced bending stress because of an increase in tooth thickness and decreased transmission torque because of a reduction in the base circle radius work together to maximize the load capacity for bending at a pressure angle of around 30°. Maximum load capacity with respect to contact pressure is achieved when the pressure angle is made 45°by increasing the radius of the contact surface. Conclusions: Both strength with respect to bending and contact pressure are found, and the torque transmission capacity of the gear is determined by the lower value of the two. For low-strength materials such as flame-hardened steel, damage due to contact pressure is expected for all forms of gears and the greatest torque capacity was at a pressure angle of 45°. In the case of assuming 800 Hv and an inclusion size ffiffiffi A p ¼ 50 μm for a high-strength material, the greatest torque transmission capacity is obtained at a pressure angle of 30°. In the case of assuming a moderatestrength material such as case-hardened steel, an optimal form exists at which strength with respect to bending and strength with respect to contact pressure are equal.

Coefficient of friction behavior of gear oils and significance for the meshing process of spur gears

“…Coefficient of friction measurements were carried out with a force of 30 N. In the contact area between the ball and the plate there is a maximum Hertzian pressure of pH = 947.8 N/mm 2 . This contact pressure of the MTM specimen is equivalent to the maximum Hertzian contact stress of a loaded gear pair with approximately FN = 1000 N in the LPSTC and HPSTC zone along the line of action [16]. The oil to be examined was heated to 80 °C in all measurement series.…”

Gear manufacture process by using chilled ductile iron casting

“…In addition to material factors, there is also a production process, especially dimensional accuracy. Changes in the dimensions of the tooth flank are very high, which will affect to the tooth contact point to become out of focus, so wear resistance decreases, this is explained by M. Ristivojević et al [18] that Uniformity and intensity of tooth flank wear depend on pitch point position on the profiles of meshed teeth and will be very critical at maximum torque capacity [85].…”

Research on composite bending stress of asymmetric gear in consideration of friction

“…In the same year, Miyazaki et al. 24 took into account the load distribution ratio, calculated the deflection and bending stress of the gear by the finite element method and studied the torque transmission capacity of the asymmetric gear with different pressure angles; In 2017, Zhou C. J et al. 25 showed that the effect of friction on bending strength of spiral bevel gears was greater than that of contact strength, which was verified by theoretical calculation and finite element analysis.…”