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<p>In this paper, the effect of load ratios and pre-strain levels on fatigue crack growth rate of 4130X steel under different load amplitudes is researched by experiment and finite element method. The investigation of load ratios and pre-strain on hysteretic curves, strain energy and plastic zone’s size near crack tip of 4130X steel are illustrated. The progression of crack tip stress under load ratios and pre-strain is clarified. This study establishes that the transition of fatigue crack growth (FCG) to the rapid propagation stage in 4130X steel is controlled by K<sub>max</sub>. The experimental evidences demonstrate that increasing both load ratio (R) and pre-strain level (ε<sub>p</sub>) accelerates FCG through two synergistic mechanisms, namely the expansion of plastic zones and initiation of secondary cracks, as conclusively verified by scanning electron microscopy (SEM) analysis. Furthermore, we develop an enhanced Jones model incorporating the newly identified K<sub>max</sub> dominance effect, which has superior predictive accuracy compared to conventional models. These findings establish new guidelines for the safety design of high-pressure gas cylinders.</p>

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Synergistic effects of load ratio and pre-strain on fatigue crack propagation of 4130X steel with a modified fatigue crack propagation rate model

  • 期刊论文

  • 发表日期：

    2026年3月18日

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  • Wen-wen Jin,
  • Wen-Jie Bao,
  • Feng-Lin Yu,
  • Long Chao,
  • Xiao-Hua He,
  • Chang-Yu Zhou

摘要

In this paper, the effect of load ratios and pre-strain levels on fatigue crack growth rate of 4130X steel under different load amplitudes is researched by experiment and finite element method. The investigation of load ratios and pre-strain on hysteretic curves, strain energy and plastic zone’s size near crack tip of 4130X steel are illustrated. The progression of crack tip stress under load ratios and pre-strain is clarified. This study establishes that the transition of fatigue crack growth (FCG) to the rapid propagation stage in 4130X steel is controlled by Kmax. The experimental evidences demonstrate that increasing both load ratio (R) and pre-strain level (εp) accelerates FCG through two synergistic mechanisms, namely the expansion of plastic zones and initiation of secondary cracks, as conclusively verified by scanning electron microscopy (SEM) analysis. Furthermore, we develop an enhanced Jones model incorporating the newly identified Kmax dominance effect, which has superior predictive accuracy compared to conventional models. These findings establish new guidelines for the safety design of high-pressure gas cylinders.