正交异性钢桥面板纵、横肋焊接残余应力数值模拟

发布时间：2018-02-16 02:22

本文关键词： 正交异性钢桥面板残余应力温度场应力场焊接数值模拟　出处：《西南交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：正交异性钢桥面板由于各方面具有的独特优势,于现代桥梁建设中得到越来越广泛地认可与使用。然而随着服役时间的增加,许多桥面板上已经涌现出不同程度的疲劳问题,对结构的使用性和安全性造成了非常严重的影响。正交异性钢桥面板结构复杂,纵肋、横肋等焊接到桥面板上,焊接所产生的残余应力以及应力集中对疲劳强度有着极为不利的影响。本文针对此特殊构造,模拟其焊接加工过程并计算焊后残余应力值,得出该结构残余应力整体分布情况,重点关注极易出现裂纹处的焊接残余应力分布状况。论文主要工作如下：首先,介绍了正交异性钢桥面板及其由焊接引发的疲劳问题,再分别概括了焊接残余应力的定义、分类、产生的原因和对结构的影响,总结归纳了有哪些实验测试方法以及简要叙述了它的消除方式,并结合实验所用测试方法以及残余应力消除措施做了进一步说明。其次,有针对性地论述了有限元分析理论在焊接中的应用及其特点,并总结了有限元模拟焊接过程涉及的关键技术。列出了焊接热过程中传热基本形式、有限元方法分析的基本方程,进一步阐述了对于涉及非线性瞬态问题时,分析所用离散方法。同时,简要说明了在有限元分析焊接应力场时所用基本理论与准则。然后,对基于ANSYS软件的热分析方法进行概述。详细总结了模拟焊接温度场、应力场的步骤及方法,其中待解决的关键问题有：模型的建立、网格的划分、单元的选择、热源的选择、边界条件的确定、荷载的施加、温度场与应力场之间的耦合、模拟热源的移动、焊缝逐步成形的关键技术以及荷载步的确定。最后,依据上述理论研究并参照实验模型建立计算模型。确立采用三维有限元数值方法模拟其温度场及应力场,针对问题选取形状规则的无中间节点的六面体实体单元以及一定温度范围内的材料热物理参数,合理规划网格划分密度,边界条件选择室温且结合实际情况确定采用双椭球热源模型,并对热源参数的选取进行评定,采用参数化设计语言编写程序实现热源移动；应力场计算时,施加边界条件限制刚体位移并读入计算所得的温度荷载,再利用生死单元法模拟焊缝的逐步填充。首先计算得到U肋焊于桥面板的温度场和应力场分布；在此基础上拼装横隔板,继而研究两种不同横隔板构造下各自残余应力分布状况,主要对两种结果进行对比分析,综合评判哪种构造细节应力分布对结构整体疲劳强度更为有利；再对加焊横隔板前后U肋焊缝残余应力分布变化做了简单分析；最后用实验所测数据对计算结果进行校核验证计算值的可靠性,为优化焊接结构、选择更合理的焊接形式提供重要依据。同时,本文数值模拟所得的残余应力大小和分布情况为今后评价结构的疲劳强度做好了铺垫。
[Abstract]:Due to the unique advantages of orthotropic steel bridge panels, they are more and more widely recognized and used in modern bridge construction. However, with the increase of service time, fatigue problems of various degrees have emerged on many deck panels. The structure of orthotropic steel bridge is complicated, longitudinal rib and transverse rib are welded to the deck of the bridge. The residual stress and stress concentration produced by welding have a very adverse effect on the fatigue strength. In this paper, the welding process of the structure is simulated and the residual stress value after welding is calculated, and the overall distribution of residual stress in the structure is obtained. The main work of this paper is as follows: firstly, this paper introduces orthotropic steel bridge face and fatigue caused by welding, and then generalizes the definition of welding residual stress. Classification, causes and effects on structures, summarizes and summarizes the experimental test methods and briefly describes its elimination methods, and further explains the test methods and residual stress relief measures used in the experiments. In this paper, the application and characteristics of finite element analysis theory in welding are discussed, and the key technologies involved in simulating welding process by finite element method are summarized. The basic forms of heat transfer in welding heat process and the basic equations of finite element method analysis are listed. The discrete method used in the analysis of nonlinear transient problems is further expounded. At the same time, the basic theory and criteria used in finite element analysis of welding stress field are briefly explained. The method of thermal analysis based on ANSYS software is summarized. The steps and methods of simulating welding temperature field and stress field are summarized in detail. The key problems to be solved are the establishment of model, the division of grid, the selection of element, the selection of heat source, and so on. The determination of boundary condition, the application of load, the coupling of temperature field and stress field, the movement of simulated heat source, the key technology of weld forming step by step and the determination of load step. According to the above theoretical research and referring to the experimental model, the calculation model is established. The three-dimensional finite element numerical method is used to simulate the temperature field and stress field. In order to solve the problem, the hexahedron solid element without intermediate node and the material thermophysical parameters in a certain temperature range are selected, and the density of mesh is reasonably planned. The boundary conditions are chosen at room temperature and combined with the actual conditions. The double ellipsoid heat source model is adopted, and the selection of the heat source parameters is evaluated. The program is written by parametric design language to realize the heat source movement. When the stress field is calculated, The boundary condition is applied to limit the rigid body displacement and read the calculated temperature load. Then the progressive filling of the weld is simulated by the birth and death element method. Firstly, the distribution of temperature field and stress field of the U-rib welding on the bridge slab is calculated. On this basis, the transverse diaphragm is assembled, and then the distribution of residual stress under two different structures is studied, and the two results are compared and analyzed. The variation of residual stress distribution of U-ribbed weld before and after welding is analyzed simply by synthetically judging which structural detail stress distribution is more favorable to the overall fatigue strength of the structure. Finally, the reliability of the calculated results is verified by the experimental data, which provides an important basis for optimizing the welding structure and selecting a more reasonable welding form. The magnitude and distribution of residual stress obtained by numerical simulation in this paper provide a good basis for evaluating the fatigue strength of structures in the future.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.4;U445.7

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