针对Q355B低合金钢T形接头承载角焊缝根部疲劳失效的扩展路径问题，提出了一种基于受力分析计算的等效应力强度因子法(KEQ法)预测根部裂纹的扩展角度. 经有限元模拟验证，其求解应力强度因子的最大误差小于5%. 与基于有限元分析计算的最大周向应力法(MCS法)和有效结构应力法(ETS法)相比较，并结合3种不同应力水平下弯曲疲劳试验结果发现，基于等效应力强度因子法、最大周向应力法与有效结构应力法求解的裂纹扩展角度分别为25.6°，25.9°和32.2°，相较于实际疲劳试验的根部裂纹扩展角度24°，误差分别为6.67%，7.92%和34.17%. 结果表明，基于KEQ法求解裂纹扩展角度准确度最高，更适于预测承受弯曲疲劳载荷下T形接头角焊缝根部裂纹的扩展角度.
Aimed at the root fatigue failure propagation path problem of T-joints in Q355B low alloy steel, an equivalent stress intensity factor (KEQ) method based on force analysis and calculation was proposed to predict the root crack propagation angle. The maximum error of solving the stress intensity factor is less than 5% verified by finite element simulation. Compared with the maximum circumferential stress method (MCS method) and the effective structural stress method (ETS method) based on finite element analysis, and combined with the bending fatigue test results of three different stress levels, it is found that: The crack propagation angles calculated by equivalent stress intensity factor method, maximum circumferential stress method and effective structural stress method are 25.6°, 25.9° and 32.2°, respectively. Compared with the root crack propagation angle of 24° in the actual fatigue test, the errors are 6.67%, 7.92% and 34.17%, respectively. The results show that KEQ method has the highest accuracy in solving crack propagation angle, which is more suitable for predicting the root crack propagation angle of T-joint fillet weld under bending fatigue loading.
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