【作者】 姚小波；

【导师】 瞿伟廉；

【作者基本信息】 武汉理工大学 ， 结构工程， 2008， 硕士

【摘要】 由于焊接结构的诸多优点,焊接结构已日益广泛地应用于工业,船舶,建筑,桥梁建设中。近年来,随着焊接材料的发展,焊接技术和焊接工艺的不断进步和完善,焊接结构日趋大型化。特别是在高层建筑和大跨桥梁领域,大型和超大型的焊接结构日渐增多,但是由于焊接残余应力的存在经常会导致焊接结构性能的下降,例如使结构的抗疲劳、抗脆断、抗应力腐蚀的能力降低,使构件的稳定性下降,增大压杆的失稳性等。因而对重大焊接结构,从经济和消除应力的可能性方面考虑,有必要准确地了解焊接结构的残余应力分布规律,以便采取相应的措施进行控制消除。焊接是一个局部快速加热到高温,并随后快速冷却的过程。随着热源的移动,整个焊件的温度随时间和空间急剧变化,材料的物理性能参数也随温度剧烈变化,同时还存在熔化和相变时的潜热现象。因此,焊接温度场的分析属于典型的非线性瞬态热传导问题。因为焊接温度场分布十分不均匀,在焊接过程中和焊后将产生相当大的焊接应力和变形。焊接应力和变形的计算中既有大应变、大变形等几何非线性问题又有弹塑性变形等材料非线性问题。焊接温度场与应力场是双向耦合的,由于应力应变场对温度场的影响比较小,加上计算条件的限制,本文只考虑温度场对应力场的影响这一单向耦合。本文首先对焊接过程中的温度场和应力场的基本理论和数值模拟分析方法进行了阐述。在数值模拟计算过程中,本文采用ANSYS软件的热—结构耦合功能,利用间接耦合法,考虑了焊接温度场对应力应变场的单向耦合,对K型桥梁节点焊接过程中以及焊后的温度场进行模拟计算。为了提高收敛速度,本文对高温时的材料物理性能参数进行了适当的选取和处理,对焊缝处网格进行细化,选取高斯函数分布的热源模型,并利用ANSYS软件的APDL语言编写程序实现焊接热源的移动加载。最后通过后处理,给出了焊接温度场的动态变化图,不同时刻焊缝处各点的温度分布曲线,并描述了焊缝中心线及其热响应区各点的热循环。在温度场计算准确的基础上,将相应的热单元转换为结构单元,进行焊接残余应力的计算。通过后处理,给出了桥梁节点上各部位的热应力分布曲线以及焊缝部位残余应力的分布趋势。更多还原

【Abstract】 Due to welding structure’s many advantages, it is widely used in industry、boats、buildings and bridges. In recent years, with the development of welding material and technology, the welding structures become larger and larger. Especially in tall buildings and large span bridges, big even super structures stand out in our visions more and more.. But because of the existing of residual stress, it will leads to the decrease of structure’s function. For example, the reduction of fatigue resistance, brittle fracture resistance, erosion resistance and stability .Welding process is that parts of an area is quickly heated to high temperature and then rapidly cooled. With the heat source moving, the whole welding temperature sharply changes, and the material’s physical property parameters also sharply change. At the same time, there is latent heat of melt and phase-change. Therefore, the analysis of welding temperature field is a typical nonlinear transient heat conduction problem. Because of non-uniform temperature distribution, at the course of welding and post weld, welding takes on serious welding stress and deformation. Calculation of welding stress and deformation includes geometrical nonlinear problem and material nonlinear problem. Welding temperature field and stress, strain field are bi-directional couple, but the influence of stress and strain field on temperature is not so much,So this paper only considers the single couple which temperature field effects on stress and strain field.The paper firstly describes the basic theories and numerical analysis methods of the temperature field and residual stress field. In the process of numerical simulated calculating, with the thermal-structure coupling function of ANSYS software and indirect coupling this paper deals with the single coupling whose temperature field effects on stress and strain field and calculates the temperature field for the K-section welding line of bridge node. In order to improve the solution accuracy, it selects suitable material properties, refines the girding, chooses the Gauss function moving heat source model and uses ANSYS APDL language to compile program to apply moving heat source load in the process of numerical simulated calculating .Finally dynamic pictures of welding temperature field and temperature distribution curve of each point in welding line are shown, as well as heat circulation in heat response areas and welding centre line is described by post-solution.Based on accurate temperature field results, welding residual stress are also calculated by changing thermal elements into structural elements. A curve of regularity on transverse and longitudinal welding residual stresses and tendency of their distribution is presented by post-solution.更多还原