试验载荷谱作用下的焊接构架疲劳强度

Fatigue Strength Test of Welded Frame Under Load Spectrum

基于变幅循环的等效恒幅应力计算方法和非比例应力状态下的修正强度理论,提出谱载荷作用下的构架疲劳强度分析方法。根据节点在焊缝坐标系下的应力分量,基于EN 13749标准规定的试验载荷谱,生成节点各应力分量的时间历程和应力谱;依据焊接接头的S-N曲线和恒幅等效应力计算方法,结合接头抗疲劳设计等级,计算节点材料利用度分量和综合材料利用度,评估结构在指定寿命下的疲劳强度。基于ⅡW和DIN提供的S-N曲线,对构架典型焊缝的疲劳强度进行评估。对比研究基于不同S-N曲线获得的节点材料利用度特征,结果表明,较基于DIN提供的S-N曲线获得的结果,根据ⅡW提供的S-N曲线进行分析,将获得较大的节点材料利用度。DIN提供的S-N曲线具有较高的接头疲劳极限和较大的指数。根据该曲线进行分析,节点的材料利用度数值小于1.0,与构架疲劳试验结果间具有较好的一致性。

In this study,a method for analyzing the fatigue strength of a bogie frame under a spectrum load was proposed based on the calculation of the equivalent constant amplitude stress under a variable amplitude load and modified strength theory in a non-proportional stress state.According to the stress components of each node in the weld coordinate system,the time history and stress spectrum of each stress component of the joints were generated based on the fatigue test load spectrum specified in EN 13749.According to the S-N curve and the constant amplitude equivalent stress calculation method of the welded joint,combined with the anti-fatigue design grade of the joint,the degree of utilization components and the comprehensive degree of utilization were calculated,and the fatigue strength of the structure under the specified life is evaluated.The fatigue strength of typical welds in the frame was evaluated based on the S-N curves provided by IIW and DIN.The comparative study of nodes’degree of utilization characteristics based on different S-N curves shows that compared with the results obtained by the S-N curve provided by DIN,the analysis of the S-N curve provided by IIW will obtain a larger nodes’degree of utilization.The S-N curve provided by DIN has a higher joint fatigue limit and a larger index.According to the analysis of the curve,the degree of utilization value of each node is less than 1.0,and there is good consistency with the frame fatigue test results.