Chapter 17
The Influence of Pressure Angle of Spur
Gears on Bending Stress Considering
the Effect of Root Fillet Radius
Layue Zhao, Minggang Du, and Yang Yang
Abstract Tooth breakage from excessive bending stress and surface pitting from
excessive contact stress are the two primary fatigue failure modes for gears. Tooth
breakage will end the gear life, so gear bending stress has to be accurately calculated
for reliable operation. Many efforts have been made to increase gear bending strength
including improving gear material property. With increasing demand for high power
density gear applications, the need to optimize gears for minimum stress becomes
increasingly important. It is imperative to understand the effect of gear parameters
on bending stress in the initial stage of designing gears. Gear pressure angle is
an important parameter affecting tooth bending stress. Because the critical section
occurs in the gear root fillet, the root fillet radius largely affected by tool (hob) tip
radius also has a great significance for improving the bending strength. The maximum
tool tip radius will vary with the pressure angle changing due to the geometrical
relationship of basic rack. This paper investigates the influence of pressure angle
of spur gears on bending stress considering the variation of root fillet radius, and
provides a recommendation on how to optimize the pressure angle for high bending
strength gears. For analysis and validation of results, three methods of predicting
bending stress– ISO standard, 3D-TCA (tooth contact analysis) method and Finite
Element Analysis are applied and discussed.
Keywords Gear bending stress · Gear pressure angle · Root fillet radius · Gear
material property
17.1 Introduction
Gears are commonly used in automotive, mechanical engineering and other industries. Nowadays, high power density gear applications are increasingly in demand,
it is critical to design gears with improved load capacity. Gear tooth pitting due
L. Zhao · M. Du (B) · Y. Yang
Science and Technology on Vehicle Transmission Laboratory, China North Vehicle Research
Institute, Beijing, China
e-mail: mgdu@noveri.com.cn
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
J. Xu and K. M. Pandey (eds.), Mechanical Engineering and Materials,
Mechanisms and Machine Science 100,
https://doi.org/10.1007/978-3-030-68303-0_17
209
The Influence of Pressure Angle of Spur
Gears on Bending Stress Considering
the Effect of Root Fillet Radius
Layue Zhao, Minggang Du, and Yang Yang
Abstract Tooth breakage from excessive bending stress and surface pitting from
excessive contact stress are the two primary fatigue failure modes for gears. Tooth
breakage will end the gear life, so gear bending stress has to be accurately calculated
for reliable operation. Many efforts have been made to increase gear bending strength
including improving gear material property. With increasing demand for high power
density gear applications, the need to optimize gears for minimum stress becomes
increasingly important. It is imperative to understand the effect of gear parameters
on bending stress in the initial stage of designing gears. Gear pressure angle is
an important parameter affecting tooth bending stress. Because the critical section
occurs in the gear root fillet, the root fillet radius largely affected by tool (hob) tip
radius also has a great significance for improving the bending strength. The maximum
tool tip radius will vary with the pressure angle changing due to the geometrical
relationship of basic rack. This paper investigates the influence of pressure angle
of spur gears on bending stress considering the variation of root fillet radius, and
provides a recommendation on how to optimize the pressure angle for high bending
strength gears. For analysis and validation of results, three methods of predicting
bending stress– ISO standard, 3D-TCA (tooth contact analysis) method and Finite
Element Analysis are applied and discussed.
Keywords Gear bending stress · Gear pressure angle · Root fillet radius · Gear
material property
17.1 Introduction
Gears are commonly used in automotive, mechanical engineering and other industries. Nowadays, high power density gear applications are increasingly in demand,
it is critical to design gears with improved load capacity. Gear tooth pitting due
L. Zhao · M. Du (B) · Y. Yang
Science and Technology on Vehicle Transmission Laboratory, China North Vehicle Research
Institute, Beijing, China
e-mail: mgdu@noveri.com.cn
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
J. Xu and K. M. Pandey (eds.), Mechanical Engineering and Materials,
Mechanisms and Machine Science 100,
https://doi.org/10.1007/978-3-030-68303-0_17
209