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针对疲劳载荷造成的不同应力比和频率对船舶与海洋结构中裂纹扩展速率的影响,本文在分析了疲劳裂纹扩展速率几种经验公式的基础上,考虑了不同应力比与不同加载频率的疲劳载荷作用对直线裂纹和弯曲裂纹扩展速率的影响,提出了相应的计算公式;并与经验公式和现有实验数据进行了比较,验证了所提公式的正确性,研究结果可以直接应用于对不同频率、应力比条件下疲劳裂纹扩展速率的预测。结果表明:在同等应力强度因子变化幅值条件下,疲劳裂纹扩展速率随着疲劳载荷应力比和加载频率的增大而增大,在第一阶段增加比较缓慢、在第二和第三阶段增加非常迅速。本文给出的新型Irving公式适用于疲劳载荷作用下线弹性直线、弯曲裂纹扩展的第一、第二、第三阶段,计算结果比原Irving公式的结果更接近实验数据。该新型Irving公式更具有实用性和准确性。
In view of the influence of different stress ratio and frequency caused by fatigue load on the crack propagation rate in ship and offshore structures, this paper analyzes several fatigue fatigue crack growth rate empirical formulas, considering the different stress ratio and different loading frequency fatigue load The corresponding calculation formulas are put forward. Compared with the empirical formula and the existing experimental data, the correctness of the formula is verified. The research results can be directly applied to different frequencies , Prediction of fatigue crack growth rate under stress ratio conditions. The results show that the fatigue crack growth rate increases with the increase of fatigue load-stress ratio and loading frequency under the same magnitude of change of stress intensity factor, and increases slowly in the first stage and increases in the second and third stages Very fast. The new Irving formula given in this paper is suitable for the first, second and third stages of the linear elastic bending and crack propagation under the fatigue load. The calculated results are closer to the experimental data than the original Irving’s formula. The new Irving formula is more practical and accurate.