【作者】 陈跃；

【导师】 韩建民；

【作者基本信息】 北京交通大学 ， 载运工具运用工程， 2014， 博士

【摘要】 转向架构架是轨道车辆的关键承载和传力构件,对行车安全起着至关重要的作用。目前地铁构架属于复杂结构焊接构件,焊缝数量多,且采用多层多道焊焊接。由于焊接过程中不可避免地产生残余应力和变形,影响构架的尺寸稳定性及疲劳寿命。因此开发有效地预测构架焊接残余应力和变形的数值模拟技术,剖析多道焊应力和变形的演变机制及其调控方法,开展复杂结构焊接顺序优化设计研究,对促进构架精密焊接成形技术发展、提高质量及服役安全可靠性具有重要的学术意义和工程应用价值。本文研究了焊接数值模拟热源模型参数快速准确求解问题,提出了基于熔池轮廓形状拟合的焊接热源模型参数求解及误差评估方法。该方法采用伪彩色技术和差影法,获得接头熔池轮廓照片和温度场模拟的熔池图像间的色彩分布差值矩阵,构建熔池轮廓形状误差函数,采用模式搜索法反演求解出热源模型参数值。该方法应用于MAG焊T型接头焊接温度场模拟,分别获得了单一双椭球热源模型和高斯+双椭球组合热源模型参数的优化值。计算结果表明,组合热源模型比单一双椭球热源模型更适合T型接头焊接温度场模拟,模拟与试验熔池轮廓形状的误差为17.8%,相比单一双椭球热源模型准确度提高了11.5%。本文开展了多道焊残余应力分布影响因素及演变机制研究,提出调控残余应力的方法。对Q345C板材进行了表面堆焊两道焊试验,在焊道问覆盖率为0%和50%两种情况下,测量了先焊焊道的焊趾附近点温度循环曲线和焊后残余应力。利用瞬态三维热弹塑性有限元法并结合试验测试,分析了板材表面堆焊两道焊的焊接温度、应力和应变的变化规律。研究表明：塑性应变不变的位置残余应力会随着弹性应变的降低而降低,利用后焊焊道产生的压缩弹性应变可以影响先焊焊道的拉伸弹性应变,由此调控多道焊的残余应力分布。通过分析焊接热循环峰值温度与残余应力关系、后焊焊道对先焊焊道焊趾附近的热力作用,确定了先焊焊道焊趾附近残余应力因后焊焊道热循环作用而降低的条件,推导出了将先焊焊道的焊趾残余应力转变为压应力的后焊焊道焊接线能量估算公式。基于以上研究,本文开展了焊道数量、焊接线能量和焊接顺序对多道焊残余应力的影响研究,提出了调控残余应力的盖面焊工艺设计原则。基于该原则进行构架吊座管板接头盖面焊的焊接工艺多目标优化设计,优化工艺比原始工艺的焊后变形减小7%,焊趾附近残余应力转变为压应力,实现了多道焊残余应力调控的目的。考虑到构架焊接装配过程的工位变换与焊接顺序之间的关联与制约,本文开展了考虑焊接装配工位变换次数约束的焊接顺序优化问题研究,提出了含有工位约束的基因修复算子遗传优化算法。该方法采用反映焊缝所在工位号、接头组号及其组内序号的多参数级联编码方式,通过个体中的基因排序反映工位约束的要求,对遗传算法的种群产生引入基因修复算子,可剔除种群中无法采用的焊接顺序个体,优化并求解合理的焊接顺序。将该方法应用于转向架构架横梁和侧梁的环形焊缝焊接顺序设计,以焊后结构变形量最小为优化目标,结合焊接变形有限元仿真计算进行优化设计。在工位变换次数最少的情况下,获得了优化的环形焊缝焊接顺序,焊后最大垂向变形差为2.6mm,低于原始工艺,仿真与实测结果相比误差为18%。更多还原

【Abstract】 Bogie frame is a key bearing and load transmission component of vehicles, and it plays an important role on traffic safety. Usually, a subway bogie frame is a complex welded structure made of several parts using multi-pass welding. The welding process is inevitable due to the residual stress and deformation, has an affect on the size stability and fatigue life of the structure. Therefore, the establishment of the accurate welding residual stress and deformation numerical simulation techniques can be used to analyze the evolution and regulation methods of stress and deformation, and further study on the optimal design of welding sequence. It will promote the development of precision welding forming technology and improve the quality and reliability of service security, which will have important academic significance and application value.A welding simulation error quantitative assessment method based on weld bead contour shape was proposed to search for heat source model parameters of welding numerical simulation fast and accurately. Image enhancement processing of tested welded joint photo and simulated temperature field was conducted by pseudo color method and difference image method. A function was constructed to evaluate contour shape error between simulated and tested weld beads quantitatively. Based on the error, an inversion method was established using pattern search method for solving the heat source function parameters. Using this method, the value of the single double ellipsoid heat source function and the Gaussian+double ellipsoid combined heat source function parameters of the T-joint were optimized. Results show that combined heat source function is more suitable than a double ellipsoid heat source function for T-joint welding temperature simulation. The minimum error between simulated and tested weld bead contour shape is17.8%when simulated using the combined heat source function. The accuracy was improved by11.5%compared to the single heat source function.In order to study regulation mechanism and factors of welding residual stress distribution by the multi-pass welding, Q345C plates surfacing weld experiments were conducted with coverage were0%and50%respectively. Temperature cycling curve and residual stress were measured near the first weld toe. Based on the measurement results, three-dimensional transient thermal elastic-plastic finite element method was used to simulate and analyze the temperature, stress and strain fields during flat surfacing welding process. Study results have shown that the residual stress will decrease with the elastic strain decrease while plastic strain can remain constant. For multi-pass welding, the elastic compressive strain generated by the following weld bead offsets the initial elastic tensile strain result in the decrease of the initial residual stress. The conditions of reducing the initial residual stress near by the yield strength were studied by analyzing the relationship between welding peak temperature and the residual stress. The welding conditions to reduce the residual stress of the first weld toe to be compressive stress were studied and the weld heat input estimation formula was established.According to conditions of the first weld toe generated compressive residual stress, considering the number of weld beads, the heat input and the welding sequence of the weld beads, design principles of capping multi-pass welding to regulate residual stress was proposed. It is applied to capping welding process design of tube-sheet welded joint of the frame bracket. The welding deformation of the optimization process obtained decreases7%compared to the original process and the residual stress at all the weld toes turned into compressive stress. It has achieved the purpose of residual stress regulation.In this paper, considering the relationship and constraint of weld position and weld sequence during the welding assembly process, the welding sequence optimization problem was studied with the constraint of change times of weld positions in a complex welded structure. An advanced genetic algorithm optimization method with weld position constraint gene repair operation is proposed. A multi-parameter cascade encoding method is presented to reflect the weld position number, welded joint group number and weld seam number. Based on gene rank adjustment, the constraint optimal problem was solved. Gene repair operator can exclude the unusable welding sequence, so that a more satisfactory initial population becomes possible. The proposed method has been applied for welding sequence optimization in a bogie frame welding assembly process. In order to minimize the deformation after welding, a constrained multi-parametric optimization model was established, combined with welding distortion simulation to optimize the welding sequence. With the least change times of welding position, the optimized welding sequence of the girth weld seams of the bogie frame was obtained. The maximum vertical deformation difference using the optimized welding sequence is2.6mm. The error is18%compared with experimental results.更多还原