动车水箱焊缝随机振动疲劳寿命的时域法研究

Study on Random Vibration Fatigue Life of Weld Seam in Water Tank of Electric Multiple Unit Based on Time Domain Method

动车车载设备较多采用焊接结构,在列车高速行驶过程中,焊缝处易发生疲劳失效。以往的分析对象多数主要是简单焊接结构,而对于复杂焊接结构,特别是随机振动时焊缝的疲劳寿命预测比较欠缺。为此,针对某包含焊缝及水的动车水箱有限元模型,采用模态叠加瞬态响应分析法,获得该焊接结构中各节点的应力-时间、加速度-时间响应曲线。结合焊缝S-N曲线、Miner线性累积损伤理论和雨流循环计数法,基于时域法估算母材及焊缝的随机振动疲劳寿命。结果表明:连接水箱上盖板和下箱体的焊缝处疲劳寿命最低,仅为17 min,根据预测结果给出了水箱的结构优化方案。通过与台架试验数据对比,表明该种焊缝疲劳寿命数值模拟算法具有正确性和有效性。

Welded structures are widely used in railway vehicle equipment. Fatigue failure is easy to occur at the weld seam due to the high-speed running of trains. In this study,a finite element model of water tank of electric multiple unit(EMU) with weld seams and water was established,and the stress and acceleration curves of each node of the structure with time were obtained by modal superposition transient response analysis. The fatigue life of this structure was calculated based on time domain method,combined with S-N curves,Miner linear cumulative damage theory and rain-flow counting method. Results showed that the lowest fatigue life of the water tank was at the weld joint between the upper cover plate and the lower body of the inner tank,and the the fatigue life was about 17 minutes. The structural optimization scheme of the water tank was given based on the simulation results. By comparing with the results of the experimental tests,the validity and correctness of this numerical simulation method for predicting the fatigue life of weld seam in this paper were verified.