Multiple semi-elliptical cracks frequently develop at the weld toes of welded joints. These interfering multiple cracks significantly accelerate crack growth rates and reduce the fatigue life of a welded joint compared to a single crack. This study proposes a method for predicting the fatigue life of a welded joint with multiple cracks, considering weld toe amplification effect, multiple crack interference amplification effect, and crack closure effect. The method is validated through fatigue tests on Q420qFNH weathering steel welded joints. The main factors influencing the interference amplification effect are investigated, and theoretical formulas for the interference amplification factor of the stress intensity factor are derived using the finite element method and the superposition principle. The initiation, aggregation, and morphological evolution during the propagation process of multiple cracks is accurately simulated, and the fatigue life of both cruciform-welded and butt-welded joints is predicted. Additionally, a quantitative analysis is conducted to assess the impact of the number of fatigue cracks on fatigue strength. The results indicate that the interference amplification effect of cracks depends on their distance and mainly affects the surface point where the crack front is closest. The proposed fatigue life prediction method can accurately estimate the fatigue life of Q420qFNH steel welded joints considering the effect of multi-cracks. The interference and coalescence of multiple cracks significantly reduce the fatigue life of welded joints. An increase in the number of fatigue cracks notably decreases the fatigue strength.

中文翻译：

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考虑多裂纹影响的Q420qFNH耐候钢焊接接头疲劳寿命预测


焊接接头的焊趾处经常出现多个半椭圆裂纹。与单个裂纹相比，这些干扰的多个裂纹会显著加快裂纹扩展速度并缩短焊接接头的疲劳寿命。本研究提出了一种预测多裂纹焊接接头疲劳寿命的方法，考虑了焊趾放大效应、多裂纹干涉放大效应和裂纹闭合效应。该方法通过对 Q420qFNH 耐候钢焊接接头的疲劳测试进行了验证。研究了影响干扰放大效果的主要因素，并利用有限元方法和叠加原理推导出了应力强度因子干扰放大因子的理论公式。精确模拟了多裂纹扩展过程中的萌生、聚集和形貌演变，并预测了十字形焊接和对焊接头的疲劳寿命。此外，还进行了定量分析，以评估疲劳裂纹数量对疲劳强度的影响。结果表明：裂纹的干扰放大效应取决于其距离，主要影响裂纹前沿最近的表面点。所提出的疲劳寿命预测方法可以准确估计考虑多裂纹影响的Q420qFNH钢焊接接头的疲劳寿命。多个裂纹的干涉和聚结显着降低了焊接接头的疲劳寿命。疲劳裂纹数量的增加会显著降低疲劳强度。