Generally, the fatigue failure of reinforced concrete beams under the coupled action of fatigue and corrosion is mainly controlled by the brittle fracture of the steel bar, confirming the significance of the fatigue crack growth (FCG) behavior of the steel bar. In this regard, FCG tests of opening mode I were conducted based on standard compact specimens manufactured from HRB400E steel bar. Meanwhile, the weak magnetic field, including the piezomagnetic field throughout the FCG process and the residual magnetic field (RMF) at certain crack lengths were both recorded. Piezomagnetic hysteretic curves and RMF distribution were analyzed separately, and the characteristic parameters of them were both determined. The evolution mechanism of the weak magnetic field was then comprehensively explored. Finally, the quantitative relationships between the FCG parameters and the characteristic parameters of weak magnetic field were separately established. The proposed relationships were applied in a prediction model of crack length, FCG rate and the FCG life, which were validated through the experimental results. The results showed that the prediction accuracy of stress intensity factor using PE method, and the prediction accuracy of crack length using PE and MMM methods all reached 90%. The errors between the FCG life predicted by PE and MMM methods and the experimental results were both within 20%.

通常，钢筋混凝土梁在疲劳与腐蚀的耦合作用下的疲劳破坏主要受钢筋的脆性断裂控制，这证实了钢筋疲劳裂纹扩展（FCG）行为的重要性。在这方面，基于由HRB400E钢筋制造的标准紧凑型试样进行了打开模式I的FCG测试。同时，还记录了弱磁场，包括整个FCG过程中的压电磁场和一定裂纹长度处的残余磁场（RMF）。分别分析了压电磁滞曲线和RMF分布，并确定了它们的特征参数。然后全面探讨了弱磁场的演化机理。最后，分别建立了FCG参数与弱磁场特征参数之间的定量关系。通过实验结果验证了所提出的关系在裂纹长度，FCG速率和FCG寿命的预测模型中的有效性。结果表明，采用PE法对应力强度因子的预测精度以及采用PE和MMM法对裂纹长度的预测精度均达到90％。PE和MMM方法预测的FCG寿命与实验结果之间的误差均在20％以内。结果表明，采用PE法对应力强度因子的预测精度以及采用PE和MMM法对裂纹长度的预测精度均达到90％。PE和MMM方法预测的FCG寿命与实验结果之间的误差均在20％以内。结果表明，采用PE法对应力强度因子的预测精度以及采用PE和MMM法对裂纹长度的预测精度均达到90％。PE和MMM方法预测的FCG寿命与实验结果之间的误差均在20％以内。