Fatigue crack growth behavior in gradient microstructure of hardened surface layer for an axle steel

Abstract

A B S T R A C TThis paper experimentally investigated the behavior of fatigue crack growth of an axle steel with a surface strengthened gradient microstructure layer. First, the microstructure, residual stress and mechanical properties were examined as a function of depth from surface. Then the fatigue crack growth rate was measured via three point bending fatigue testing. The results indicated that fatigue crack growth rate decelerated first and then accelerated with the increase of crack length within the gradient layer. Especially, the fatigue crack was arrested in the gradient layer under relatively low stress amplitude due to the increase of threshold value for crack growth within the range of 3 mm from surface. Based on these results, the parameters of Paris equation and the threshold value of stress intensity factor range within the gradient layer were determined and a curved surface was constructed to correlate crack growth rate with stress intensity factor range and the depth from surface. The effects of microstructure, residual stress and surface notch on the crack growth behavior were also discussed.

The influence of combined gradient structure with residual stress on crack-growth behavior in medium carbon steel

“…Due to the combined effects of gradually decreasing residual compressive stress and the gradually increasing crack length, J Δ path starts to increase gradually when the crack propagates from 3.9 mm. This variation in J Δ path can be adopted to explain crack arrest at the crack length of 3 mm in high-cycle fatigue experiments on train axle steel [52]. Fig.…”

“…Many literatures [48][49][50][51] have shown that the residual compressive stress resulted from surface mechanical treatment could effectively improve the fatigue resistance. More recently, Zhang et al [52] studied experimentally the fatigue crack-growth behavior in gradient axle steel with residual stress. The authors reported crack arrest in the gradient layer under relatively low stress amplitude, which was a resultant of compressive residual stress.…”

Optimizing Fatigue Performance in Gradient Structural Steels by Manipulating Grain Size Gradient Rate

“…However, although existing studies have revealed the positive effect of gradient structure on fatigue performance, there is still insufficient understanding of how gradient rate precisely regulates the fatigue life, crack initiation threshold, and cyclic deformation behavior, which undoubtedly constitutes a technological bottleneck restricting the further optimization and industrialization of its application [35,36]. Furthermore, with no sophisticated methods for controlling gradient rates [34], researchers urgently need to conduct more systematic and in-depth research to reveal the intrinsic law between the gradient rate and the key properties of gradient structural steel, establish accurate performance prediction models, and explore efficient and economical preparation processes to achieve precise control of gradient structure [37].…”

Size and Shape Effects on Fatigue Behavior of G20Mn5QT Steel from Axle Box Bodies in High-Speed Trains

“…Wang et al [15] analyzed the fatigue strength of the CRH2 motor bogie frame through simulation and online tests. Zhang et al [16] studied the fatigue crack growth behavior in the gradient microstructure of the surface layer of S38C axle steel. The results indicated that the crack growth rate firstly decelerated and then accelerated with increasing the crack length in the gradient layer.…”