Residual stress relaxation and low- and high-cycle fatigue behavior of shot-peened medium-carbon steel

• Residual stress relaxation of shot-peened carbon steel was investigated.
• Quantitative residual stress analysis was conducted by XRD method.
• Relaxation of residual stress was estimated by empirical equation.
• Fatigue limit criterion of shot-peened carbon steel was suggested.
• Quantitative analysis supports the stress concept of fatigue limit.

The objective of this study was to analyze the induced compressive residual stress (CRS) relaxation and redistribution during bending fatigue at low-cycle fatigue (LCF) and high-cycle fatigue (HCF) testing regimes of shot-peened 0.45% (annealed) carbon steel. First, the near-surface residual stress was measured by the X-ray diffraction method. After that, rotating bending fatigue tests were conducted to introduce the mechanical loadings, and quantitative measurements of the residual stress were made during the fatigue tests.The results showed that degradation of induced CRS under all loading conditions was found under the relaxation rates for residual stress depended on the applied strain. Moreover, it was found that the critical condition of the threshold-residual stress relaxation boundary that had a significant influence on the fatigue limit criterion for shot-peened medium-carbon steel. The empirical test results for the relaxation of induced CRS under the LCF and HCF regimes are discussed in detail and a new interpretation of the fatigue limit of shot-peened carbon steel is suggested based on the residual stress concept.