Influence of Radius Fillet on the Fatigue Life Behavior of an AISI 1040 Steel Transmission Shaft

Abstract

Shafts are crucial components in mechanical transmission systems that transfer power between moving machine elements. In high-speed applications, shafts experience dynamic and cyclic loads that can trigger material failure due to fatigue, especially in cross-sectional areas such as stepped shafts. Stress concentrations that occur in diameter transition areas can be the starting point for cracking that leads to structural failure. One method to reduce these stress concentrations is by applying a radius fillet to the diameter change area. This study aims to analyze the effect of radius fillet on torsional and bending loads on a transmission shaft made of AISI 1040 steel. The method used is a numerical simulation based on Finite Element Analysis (FEA). It was found that the application of an 11 mm radius fillet on the stepped shaft provided better performance compared to a 1 mm radius fillet for a diameter transition from 190 mm to 150 mm. The use of an 11 mm radius fillet on the stepped shaft made of AISI 1040 material resulted in a reduction of total deformation by 1.8% and improvement of 74% in the safety factor was also observed for the 11 mm radius fillet configuration. In the previous design without a radius fillet, the shaft operated up to 9,066 loading cycles before failure occurred. With the implementation of an 11 mm radius fillet, a significant improvement in fatigue performance was observed, with the shaft sustaining up to 66,425 loading cycles.