钢桥面横隔板与U肋焊接处残余应力场分析

Analysis of Residual Stress Field in Welding Joints Between Diaphragms and U Ribs of Steel Bridge Deck

为了解正交异性钢桥面板横隔板与U肋焊接处残余应力分布特征,明确横隔板弧形切口疲劳开裂机理,采用热-结构耦合方法建立横隔板-U肋焊接连接的热弹塑性有限元模型,通过“生死单元”技术模拟焊缝的填充过程,得到焊接温度场与应力场,分析横隔板焊缝和弧形切口处残余应力的分布规律。结果表明:横隔板焊趾处纵向残余应力为拉应力,峰值为345 MPa,横向残余应力在焊缝开始位置和尾部区域为拉应力,在焊缝中间应力水平较低;横隔板弧形切口附近残余应力变化剧烈,且沿切口弧线长度和钢板厚度分布不均匀;从切口顶点到起弧点位置,残余应力从压应力变化为拉应力,起弧点处应力峰值为231 MPa;焊接引起的焊缝尾部高水平残余应力是导致横隔板弧形切口疲劳开裂的关键因素。

To examine the characteristics of residual stress distribution in the welding joints between diaphragms and U ribs of the orthotropic steel bridge deck and make clear the fatigue cracking mechanism of the arc gap of the diaphragm,the thermal-structure coupling method was used to establish the thermal elastic-plastic finite element model of the welding joints,and the filling process of the welding joints was simulated by the"Element Birth-and-Death"technique to obtain the welding temperature field and stress field and to analyze the distribution law of residual stresses in the welding joints and arc gaps of diaphragms.The results show that the longitudinal residual stress at the welding toe of the diaphragm is the tensile stress,with a peak value of 345 MPa.While the transverse residual stress is the tensile stress at the starting point and end of the welding joints,and is lower in the middle of the welding joint.The variation of residual stress near the arc gap of the diaphragm is dramatic,and the distribution of residual stress along the arc length of the arc gap and the thickness of the steel plate is not uniform.The residual stress changes from compressive stress to tensile stress from the top point of the gap to the starting point of the arc,and the peak value of the stress at the starting point of the arch is 231 MPa.The high-level residual stress induced by welding is the key trigger of fatigue cracking at the arc gap of the diaphragm.