【作者】 李娅娜；

【导师】 兆文忠；

【作者基本信息】 大连交通大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 铁路车辆生产制造中不论是薄壁结构,还是箱型梁结构都具有结构复杂、尺寸大、焊接部位多等特点,它们的焊接残余变形直接影响了焊接产品的制造质量和服役使用,如何预测和控制焊接变形是铁路车辆工厂中迫切需要解决的研究课题。虽然焊接变形的预测与控制的数值模拟研究在国内外已经开展了许多年,但是对铁路车辆焊接结构残余变形数值模拟方面的研究工作还比较少,特别是在数值模型验证的基础上,研究多种因素对焊接变形的影响就更少。在对企业实际需求深入研究的基础上,针对铁路车辆三种典型的焊接结构——薄板结构、多道焊箱型结构、大尺寸箱型结构,提出了不同数值研究方法。在焊接变形模型得到验证的基础上,研究了焊接工艺参数、结构参数、多道焊及焊接顺序对焊接变形的影响,以掌握焊接变形预测与控制规律,从而为铁路车辆在焊接工艺设计、制定和工艺方法优化上提供技术支持。本文的主要研究内容包括：首先,对国内外关于焊接变形预测与控制方法和焊接数值模拟技术现状进行研究,了解焊接数值仿真算法的基本理论,包括焊接传热学、焊接热弹塑性理论知识,并对焊接过程中涉及的热源模型概念、分类和各自的优缺点进行了详细分析。其次,针对铁路车辆薄板类焊接结构特点,提出了基于固有应变等效热载荷的预测变形的方法。以货车侧墙薄板结构为研究对象,将固有应变等效为焊缝及热影响区的热载荷对其结构屈曲变形进行计算,结果表明仿真数值与实测数值基本一致。同时在此仿真模型的基础上,通过正交设计方法调整焊接工艺参数与结构参数,研究不同因素对焊接变形的影响程度,最后得出最优方案,为控制薄板侧墙的焊接变形提供理论根据。再次,针对铁路车辆多道焊箱型类焊接结构特点,提出了基于焊接过程热弹塑性的多道焊处理方法。以转向架构架侧梁为研究对象,使用SYSWELD焊接变形仿真软件,采用双椭球热源模型,利用热循环曲线,对构架侧梁多道焊焊接变形进行了研究,并给出了实验测量方法。仿真模拟计算结果与实测结果进行了比较,其一致性证明仿真模型的正确性。同时,研究了多道焊焊接顺序对变形的影响,实现了多道焊技术在铁道车辆产品设计中的应用。最后,针对铁路车辆大尺寸箱型类焊接结构特点,提出了基于“局部—整体”映射的预测焊接变形的方法和宏单元技术。以集装箱底架中梁为研究对象,使用Pam-Assembly焊接变形仿真软件,利用宏单元技术,计算了中梁在现有焊接工艺参数下的变形,研究了焊接顺序和结构参数对变形的影响,从而为结构大、焊缝长、有限元规模庞大、计算求解时间长这一类问题,寻求了一种快速有效解决大型复杂结构焊接变形的方法。本课题得到国家“863”高技术研究发展计划项目：《复杂产品协同设计、仿真、优化一体化平台研究开发及其应用》(项目编号：2006AA04Z160)的资助。更多还原

【Abstract】 The thin-plate structure and the box-beam structure are two typical welded structures in railway vehicles. Because of their structure complexity, bigger size and multi-seams, welding residual distortion which occur in welding process bring unfavorable effect on the quality of welding products manufacturing and service. As a result, welding distortion forecasting and control become an important and urgent research topic in railway vehicles. Although the numerical simulation studies on welding distortion have been conducted for many years at home and abroad, less research work for welding structures in railway vehicles is done, especially in considering multifactor influences for welding distortion based on numerical model validation. According to thorough investigation of enterprise requirements, three different numerical methods are presented corresponding to three typical types of welded structures of railway vehicles-thin-plate structure, multi-pass welded box structure and large size box structure. After the analysis of welding distortion and the validation of welding simulation model, influences of welding parameters, structure parameters, multi-pass welding and welding sequences on welding distortion are studied. It is helpful for mastering the regularity of welding distortion, so as to provide technical support for the design, making, and optimization of railway vehicle welding process.Research work of this dissertation mainly includes:Firstly, prediction and control methods and numerical simulation technologies of welding distortion are reviewed. Basic theories of welding numerical simulation including heat transfer theory and thermo-elastic-plastic theory are developed. At the same time, relative concepts, classifications, advantages and disadvantages of heat source models involving in welding processes are discussed in detail.Secondly, according to the characteristic of thin-plate welded structure in railway vehicles, an equivalent thermal load method based on inherent strain is put forward. Taking truck side-wall as research object, thin-plate buckling distortion is simulated by transforming inherent strain into equivalent thermal loads on the welded seams and heat affected zones. Compartments between numerical simulation results and experiments data show that both have great consistence. Based on the simulation model, influences of different factors include welding and structural parameters on welding distortion are investigated by using orthogonal design method to regulate the parameters, and the optimal design is concluded which provide reliable theoretical references for controlling thin-plate welding distortion of the truck side-walls.Thirdly, according to the characteristic of multi-pass box welded structure in railway vehicles, a heat treatment method of multi-pass welding based on thermo-elastic-plastic theory is put forward. Taking bogie side beams as research object, multi-pass welding distortion is studied by the use of thermal cycling curves as heat source with SYSWELD simulation software. Meanwhile, the experimental measurements are given and the consistence of simulation results with the measured results proves the correctness of the simulation model. The influence of welding sequences to welding distortion in multi-pass welding process is studied which promotes the application of multi-pass welding technology in railway vehicle product design.Finally, according to the characteristic of large size box welded structure in railway vehicles, a "local-global" project FEM method and mcroelements technology are put forward. Taking the middle beam of container underframe as research object, welding distortion using present welding process is simulated based on macro-elements technology with Pam-Assembly simulation software. Influences of welding sequences and structural parameters to the welding distortion are also studied, which provide a kind of fast and effective method to solve welding distortion of large-scale complex structure for solution problems such as large size, long seams, large scale finite element calculation and much solution time etc.This research is sponsored by the National "863" high-tech research and development project:"Coordinated design of complex product, simulation and optimization----integrated platform research, development and application" (Project Number:2006 AA04Z160).更多还原