Abstract: In the service process,welded structures often bear complex random dynamic load.When the dynamic load frequency is close to the natural modal frequency of the structure,fatigue failure may occur in the joint,at this point the traditional fatigue analysis method of uniaxial static load is no longer applicable.A multi-axis random vibration fatigue analysis method for welded structures was presented.In this method,the time-domain excitation signals were transformed into self-spectrum and cross-spectrum,the self-spectrum and cross-spectrum including normal stress and shear stress was obtained by combining modal decomposition and structural stress method,and gets the power spectrum of equivalent structural stress was got based on PDMR principle.The structural damage and vibration fatigue life were calculated by using the Dirlik model.At the same time,a high-speed freight car was taken as an example to analyze the fatigue life,and the timeliness and accuracy of fatigue life prediction of welded structures were verified.

Key words: welded structure, random vibration, fatigue failure, time domain, frequency domain, fatigue life

摘要： 针对焊接结构在服役过程中承受的随机动载荷频率与结构固有模态频率接近时,接头可能发生疲劳破坏,使传统单轴静载疲劳分析方法不再适用的问题,提出评估焊接结构的多轴随机振动疲劳分析方法。该方法将时域激励信号转化为自谱和互谱,并结合模态分解与结构应力方法,得到包括结构正应力与剪应力的自谱和互谱,基于路径依赖的最大范围法原理得到等效结构应力的功率谱,最后通过Dirlik模型计算出结构损伤和振动疲劳寿命。以某高速货车为例进行疲劳寿命分析与改进校核,验证了该方法可进一步提升焊接结构疲劳寿命预测的时效性和准确性。

关键词: 焊接结构, 随机振动, 疲劳破坏, 时域, 频域, 疲劳寿命