地铁扣件Ⅲ型弹条的弹塑性疲劳性能分析

Analysis on Elastoplastic Fatigue Performance of TypeⅢClip in Metro Fastener

地铁Ⅲ型扣件系统主要是通过弹条趾端变形产生的扣压力来紧固铁轨,扣件系统弹条处于复杂的应力状态,在服役过程中往往达不到预期寿命过早断裂。为了研究弹条的弹塑性疲劳性能,根据扣件系统实物尺寸建立了有限元模型,进行了静力学分析,得到了弹条的弹性系数为1.06 kN/mm,验证了模型的可行性。在此基础上建立了两种弹塑性疲劳模型对弹条的寿命进行了预测和分析,其中模型1采用Neuber塑性修正的弹性有限元法,模型2采用弹塑性有限元法。结果表明,为避免弹条与铁垫板插孔由线接触变为点接触而产生应力集中,弹条小圆弧内侧与铁垫板距离D应不小于7 mm;在钢轨位移循环荷载下,两种模型计算得到的弹条疲劳寿命分别为2.449×10^(9)次和6.081×10^(8)次;随着钢轨位移差的增大,弹条的寿命急剧下降,为满足500万次不破坏的标准,钢轨位移差应不超过4 mm,危险点处应力比应大于0.6;在相同次数的疲劳荷载循环下,随着初始安装扣压力的增大,危险点处的损伤值也越大,当扣压力超过13 kN后,最大损伤值增长速率明显增大。

Subway typeⅢfastener system is mainly to tighten the rail through the clamping force provided by the deformation of the toe end of the clip,in which the clip of the fastener system is subjected to the complex stress state and often fails to meet the expected life and breaks prematurely during service.To study the elastoplastic fatigue performance of the clip,the finite element model was established according to the real size of the fastening system,and the static analysis was carried out.The elastic coefficient of the spring bar is 1.06 kN/mm,which verifies the feasibility of the model.On this basis,two kinds of elastoplastic fatigue models were established to predict and compare the clip s life,the Neuber plastic modified elastic finite element method was used in model 1,and the elastic-plastic finite element method was used in model 2.The results show that,to avoid stress concentration from line contact to point contact between the spring bar and the iron cushion plate,the distance D between the inner circle of the clip and the iron cushion plate should not be less than 7mm.Under the displacement cyclic load of rail,the fatigue life of the two models is 2.449×10^(9)times and 6.081×10^(8)times.With the increase of the displacement difference of the rail,the fatigue life of clip drops sharply.To meet the standard of 5 million times without failure,the displacement difference of the rail should not exceed 4 mm and the stress ratio at the danger point should be greater than 0.6.With the increase of the initial clamping force,the damage value at the danger points increases under the same number of fatigue load cycles.When the buckle pressure exceeds 13 kN,the growth rate of the maximum damage value increases significantly.