挖掘机工作装置为大型焊接件，因在作业过程中承受各种复杂载荷而易在焊缝处发生疲劳破坏，其疲劳强度直接关系着整机的使用寿命和性能。为了更有效地对焊缝处的疲劳寿命进行评估，文中基于等效结构应力法提出一种挖掘机工作装置焊缝疲劳寿命评估方法，即基于焊线上的节点力和节点力矩对网格不敏感的结构应力进行计算，通过把不同接头形式、板厚、加载模式的焊接接头统一起来的主S-N曲线，并结合疲劳累计损伤准则进行疲劳寿命评估。通过建立包括焊缝细节的工作装置动臂、斗杆的有限元模型，利用等效结构应力法对动臂、斗杆上的6条关键焊缝进行疲劳寿命评估，并与疲劳台架试验和其他分析方法进行对比分析。结果表明：采用名义应力法得到的动臂和斗杆的疲劳寿命评估结果与疲劳试验值的偏差分别为9.2%和14.2%，采用热点应力法得到的疲劳寿命评估结果与疲劳试验值的偏差分别为24.4%和23.4%，采用等效结构应力法得到的疲劳寿命评估结果与疲劳试验值的偏差分别为6.6%和9.5%，因此与名义应力法和热点应力法相比，等效结构应力法的评估结果与疲劳试验结果最为接近，名义应力法的评估结果偏于危险，热点应力法的评估结果偏于保守，说明等效结构应力法对于挖掘机工作装置的疲劳寿命评估是十分有效和可靠的。文中方法可为其他焊接结构的疲劳寿命评估提供思路。

The working device of the excavator is a large welded structure, which is prone to damage at the weld due to various complex loads during the operation, and its fatigue strength is directly related to the service life and performance of the whole machine. In order to evaluate the fatigue life of its welds more effectively, an evaluation method of weld fatigue life of excavator working device was proposed based on the equivalent stress method in this paper. That is, based on the node force and node moment on the welding line, the structural stress that is not sensitive to the grid is calculated. The fatigue life is evaluated by the fatigue cumulative damage criterion and the main S-N curve of welded joints, which can unify with different joint types, plate thicknesses, and loading modes. By building the finite element models with detail information of the welding seam for the boom and bucket, the fatigue damage assessment was carried out for six key welds on the boom and the bucket by the equivalent structural stress method. The fatigue assessment accuracy of the boom and the bucket is comparatively studied with the fatigue experiment results in this study, the results indicate that the deviations obtained through the nominal stress method are 9.2% and 14.2%, and they reach to 24.4% and 23.4% by employing the hot spot stress method and decrease to 6.6% and 9.5% in the approach with equivalent structural stress analysis. Therefore, compared with the nominal stress method and the hot spot stress method, the evaluation results of the equivalent structural stress method are the closest to the fatigue test results. The evaluation results of the nominal stress method tend to be bold, while the evaluation results of the hot spot stress method tend to be conservative, which means that the equivalent structural stress method is very effective and reliable for the fatigue life assessment of excavator working device. The proposed method can provide ideas for the fatigue life assessment of other welded structures.