高铁声屏障连接螺栓松弛对疲劳寿命的影响

螺栓的疲劳寿命和松弛寿命影响着螺栓的使用寿命,在疲劳和松弛的共同作用下,柱脚处连接不断退化,为探究高铁声屏障连接螺栓松弛对疲劳寿命的影响,以某速度为400 km/h高铁声屏障非对称排布和对称排布螺栓为研究对象,利用ANSYS建立柱脚螺栓有限元模型,通过降温法施加预紧力,并施加正负单位弯矩荷载,计算柱脚最不利螺栓在不同预紧力作用下的应力幅,提出了应力幅随预紧力变化的拟合关系式;利用Midas建立声屏障整体模型,分析列车在400 km/h行驶速度下结构动力响应特性,提取柱脚螺栓弯矩时程结果,对仅考虑疲劳失效的螺栓寿命和考虑松弛疲劳共同影响下的螺栓寿命进行比较.研究结果表明：螺栓松弛会使预紧力下降,导致两种柱脚模型的螺栓应力幅增大;在已有的柱脚螺栓时程计算中,考虑松弛疲劳共同影响下的疲劳寿命比仅考虑疲劳作用时大大降低,当松弛导致预紧力下降至55%以后,将会产生疲劳效应,该结果可为连接结构领域设计人员定量评估螺栓寿命以及对螺栓的维修养护方面提供参考依据.

Influence of Bolt Relaxation of High-Speed Railway Sound Barrier on Fatigue Life

The fatigue life and relaxation life of bolts affect their service life. Under the joint action of fatigue and relaxation, the connection at the column base is deteriorating. In order to explore the influence of the relaxation of connecting bolts on the fatigue life of high-speed railway sound barrier, bolts with asymmetrical and symmetrical arrangements used for high-speed railway sound barrier at a train speed of 400 km/h are taken as the research objects, and the finite element models of column base bolts are established using ANSYS. The preload is applied by cooling method, positive and negative unit bending moment loads are applied to calculate the stress amplitude of the most unfavorable bolt at the column base under different preloads, and the fitting relationship between the stress amplitude and preload is proposed. Moreover, based on Midas, a whole model of noise barrier is established to analyze the dynamic response characteristics of the barrier structure at the train speed of 400 km/h. The bending moment time history results of column base bolts are extracted to compare the bolt life considering fatigue failure only and the bolt life considering relaxation and fatigue together. Results show that the bolt relaxation will reduce the preload and increase the bolt stress amplitude of bolt base models in both cases of asymmetrical and symmetrical arrangements. In the existing time history calculation of column base bolts, the fatigue life considering the combined effect of relaxation and fatigue is much lower than that only considering the fatigue effect. When the preload is reduced to 55% due to the relaxation, the fatigue effect will occur. The results can provide a reference for designers of connection structures to quantitatively evaluate the bolt life and the maintenance of bolts.