钢轨铝热焊接接头性能的有限元分析

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Rail thermite welding joint is the weakest link in continuous welded rail（CWR）. In order to study the performance of welding joint, vehicle/track coupling dynamics theory based on Timoshenko beam model was used with the results of simulation on thermite welding process. The wheel/rail contact parameters under short wave irregularity of welding joint were figured out with this method. Finally, based on Hertz contact theory, the wheel/rail contact elastic-plastic finite element model was constructed and analyzed. The results indicate that under pure rolling working condition, the largest Mises stress and equivalent plastic strain （PEEQ）are both 4.1 mm beneath the rail head surface where cracks may probably form. While under pure sliding condition, they both move to the surface where the welding joint may be squashed or even break. Under pure rolling circumstances, the largest Mises stress, PEEQ and residual displacement are increasing with the increased vehicle speed and also increasing when the distance between welding center and nearer rail sleeper is minishing,but has no significant change if the width of heat affected zone（HAZ） of welding joint changes.钢轨铝热焊接接头是铁路无缝线路最薄弱的环节，为了研究焊接接头的性能，在钢轨铝热焊接过程数值模拟结果的基础上，采用基于Timoshenko梁的车辆一轨道耦合动力学方法，求解了带有焊接接头短波不平顺的轮轨接触参数，最后，基于Hertz接触理论，建立了轮轨接触弹塑性有限元模型，并对该模型进行了分析。研究结果表明：当轮轨处于纯滚动工况下，最大等效应力和等效塑性应变（PEEQ）均位于轨头表面以下约4．1mm深度处，裂纹容易从此处萌生；当轮轨处于全滑动接触时，最大等效应力和PEEQ均移动到轨头表面，很可能造成焊接接头表面压溃、剥离甚至断裂；而纯滚动工况下，最大等效应力、PEEQ以及残余变形随着车速的增加而增加，随着接头焊缝中心与较近的轨枕中心的距离的减小而增大，随焊接接头热影响区（HAZ）宽度的增加没有明显变化。