Residual Stress Relaxation Behaviors and Fatigue Strength of Micro-Shot Peened EA4T Axle Steel under Constant and Variable Loading.

To investigate the residual stress relaxation behaviors and fatigue strength, EA4T steel specimens are subjected to micro-shot peening (MSP), and part of them are isothermally annealed at 250 °C for 2 hours. Fatigue experiments are conducted on a four-point rotating bending machine under constant and variable loads. Surface compressive residual stress (CRS) and full width at half maximum (FWHM) before the experiment and during fatigue loading are analyzed using the x-ray diffraction method. The results indicate that the CRS of the MSP specimens are relaxed after the isothermal annealing, leading to a decrease in their fatigue strengths. Variable loading slightly increased the fatigue life of the un-peened specimen, but significantly reduced that of the MSP specimens. The effect of CRS relaxation on fatigue strength is analyzed, and the relationship between CRS and FWHM is also discussed. [ABSTRACT FROM AUTHOR]