基于SWT方法的钢绞线索微动疲劳特性分析

为得到钢绞线索丝间接触区的应力场分布并预测微动疲劳裂纹萌生位置和微动疲劳寿命,本文利用参数化方法建立了精细化的钢绞线拉索有限元模型,包括整索模型和不同层丝间接触区域的局部精细化子模型.分析了钢绞线索在两种交变荷载工况下的应力场变化情况,并基于多轴疲劳SWT(Smith-Watson-Topper)临界平面法进行了疲劳特性分析和疲劳寿命预测.主要结论如下:钢绞线索内接触区边缘处的微动幅值较大,中心处几乎没有相对滑动,微动疲劳的初始裂纹萌生点位于接触区域边缘;经不同区域子模型分析比较,在轴向循环荷载作用下,外层钢丝的接触区域比内层钢丝更易发生微动疲劳损伤;在横向位移循环荷载作用下,同层钢丝因位置角度不同而产生了较大的疲劳特性差异,且相比轴向循环拉伸,该工况下最不利单丝的微动疲劳寿命更低;与非接触区域相比,接触区的疲劳寿命大幅降低,微动现象对钢绞线索的抗疲劳性能有明显降低作用.

Analysis on Fretting Fatigue Characteristics of Steel Strand Cable Based on SWT Method

In order to get the contact stress distribution in contact areas between steel wires inner spiral strand cable and then predict the fretting fatigue life, refined finite element models were established by using a parametric method, including a whole cable model and local refined sub-models of the contact area. The stress field variation and fatigue characteristics were analyzed under two kinds of alternative loading conditions for bridge cables. The fretting fatigue life was also predicted by using SWT(Smith-Watson-Topper) critical plane method that is usually used to analyze the multiaxial fatigue. The conclusions are as follows: The fretting amplitude is larger at the edge than at the center of the contact area, and therefore the nucleation point of fretting fatigue in the contact area is generally located at the edge; According to comparison of the sub-models in different regions, fretting fatigue damage is more likely to occur in the contact area of the outer layer wires under axial alternative load; Under the cyclic load of lateral displacement, the fatigue characteristics of the same layer wires vary greatly due to different normal directions of contact surface. And under this loading condition, the fatigue life of the weakest wire is even lower than that under the axial loading condition. Compared with the non-contact area, the fatigue life of the contact area is significantly reduced.