Analytical approach for low and high cycle bending fatigue life prediction of carburized gear steel specimens

Bending fatigue is one of the most common failure modes in spur gears. In carburized spur gears, subsurface failure initiation is characteristic for the high cycle fatigue regime, which is ratherhard to detect and may cause rapid crack growth and complete failure of the tooth. Experimentaltesting of specimens made of the same material under comparable loading conditions is oftenused to gain insight into actual fatigue behavior of the component. Furthermore, in the absence ofdefinite fatigue data of the specimens, various methods are used for estimating fatigue para-meters. In this paper, analytical model for bending fatigue life prediction of carburized gear steelspecimens based on strain- life approach is proposed. Multilayer method and hardness method areused for estimating strain-life fatigue properties. Rule of mixture is employed tofind averagecyclic stress-strain curves of carburized specimens. An approach for conversion of axial tobending fatigue data by utilizing Neuber’s rule and modifying factors is suggested. Initial vali-dation of the analytical model is carried out against experimental results from the literature oftwo types of specimens with different carburizing depths. Good correlation between the pre-dicted and experimental data is observed for both types of specimens, with nearly all data pointsfalling within the scatter factor of three.