A method called modified modal superposition method (MMSM) for calculating the vibration fatigue dynamic stress of carbody under shaking condition is proposed. In MMSM, each external load is divided into low frequency component and high frequency component according to critical frequency (CF), which is used to separate whether the external load causes resonance effect of the structure, then traditional quasi-static method (QSM) and modal superposition method (MSM) are adopted to deal with the two load components respectively. During the simulation, QSM is used to ensure the integrity and accuracy of the structural stiffness under quasi-static condition, while MSM can consider the dynamic characteristics of the structure in resonance state. At last, the fatigue strength of the carbody was carried out based on the stress calculated according to cumulative damage method. The calculation results show that the fatigue life of carbody under shaking condition is significantly reduced to 81,450 km, far less than the design life. The damage of the stress obtained by MMSM is far greater than that from traditional QSM, even in the new wheel condition, the damage obtained by QSM is too dangerous. For the stress obtained by MSM, generally in the low-frequency region, the stress level is higher than that obtained by QSM due to mode truncation, especially for the average stress. So QSM and MSM are not recommended to evaluate the fatigue strength of railway vehicle carbody.

提出了一种计算振动条件下车体振动疲劳动应力的修正模态叠加法（MMSM）。在MMSM中，每个外荷载按临界频率（CF）分为低频分量和高频分量，用来区分外荷载是否引起结构的共振效应，然后是传统的准静态法（QSM）和采用模态叠加法（MSM）分别处理两个荷载分量。在仿真过程中，QSM用于保证准静态条件下结构刚度的完整性和准确性，而MSM可以考虑结构在共振状态下的动态特性。最后，车体的疲劳强度是根据累积损伤法计算的应力进行的。计算结果表明，振动工况下车体疲劳寿命显着降低至81450公里，远低于设计寿命。MMSM所获得的应力损伤远大于传统QSM，即使在新的车轮工况下，QSM所获得的损伤也太危险了。对于MSM得到的应力，一般在低频区，由于模态截断，应力水平高于QSM得到的，尤其是平均应力。所以不推荐用QSM和MSM来评价铁路车辆车体的疲劳强度。计算结果表明，振动工况下车体疲劳寿命显着降低至81450公里，远低于设计寿命。MMSM所获得的应力损伤远大于传统QSM，即使在新的车轮工况下，QSM所获得的损伤也太危险了。对于MSM得到的应力，一般在低频区，由于模态截断，应力水平高于QSM得到的，尤其是平均应力。所以不推荐用QSM和MSM来评价铁路车辆车体的疲劳强度。计算结果表明，振动工况下车体疲劳寿命显着降低至81450公里，远低于设计寿命。MMSM所获得的应力损伤远大于传统QSM，即使在新的车轮工况下，QSM所获得的损伤也太危险了。对于MSM得到的应力，一般在低频区，由于模态截断，应力水平高于QSM得到的，尤其是平均应力。所以不推荐用QSM和MSM来评价铁路车辆车体的疲劳强度。一般在低频区域，由于模态截断，应力水平高于 QSM 获得的水平，特别是对于平均应力。所以不推荐用QSM和MSM来评价铁路车辆车体的疲劳强度。一般在低频区域，由于模态截断，应力水平高于 QSM 获得的水平，特别是对于平均应力。所以不推荐用QSM和MSM来评价铁路车辆车体的疲劳强度。