【作者】 卢耀辉；

【导师】 曾京；

【作者基本信息】 西南交通大学 ， 载运工具运用工程， 2011， 博士

【摘要】 我国铁道客车转向架构架均采用钢焊接结构,这样可大大降低车辆结构的白重。但是,运行速度的提高、载荷的增大、频率范围的扩大,尤其是复杂的焊接接头形式使得转向架构架的承载状况变得十分恶劣。由于焊接接头存在的焊接缺欠,如几何不平顺、空洞、夹杂、残余应力及变形、热影响区母体材料性质的变化等,导致焊接接头是结构失效的主要区域。在以往的铁道车辆运行中,焊接构架陆续暴露出许多疲劳可靠性方面的问题,随着列车速度的不断提高,对其安全可靠性提出了更高的要求。本文将以铁道客车转向架焊接构架作为研究对象,对其疲劳可靠性开展较深入的研究,主要开展以下的研究工作：(1)从设计-制造一体化的角度,研究构架焊接缺欠的形成机理。采用数值模拟的方法对T型焊接接头的焊接变形进行了热-弹塑性法和固有应变法对比分析,并应用固有应变法对构架焊接变形进行了数值模拟。提出了消除焊接缺欠的工艺措施,以确保构架的疲劳强度可靠性。(2)基于多轴疲劳强度的基本理论,对转向架构架在有限元分析中的建模方法和标准载荷下的应力状态进行了分析,基于3种将多轴应力转化为单轴应力的方法(最大主应力法、Mises等效平均应力法和Sines平均主应力法),分别应用ERRI B 12/RP 17和JIS E4207推荐的焊接结构Goodman曲线对构架进行了疲劳强度对比分析。得出结论认为,三种转化方法中,最大主应力方法适合于构架的多轴疲劳强度分析。(3)运用多刚-柔耦合系统动力学方法,首先在有限元分析软件中建立了转向架构架的柔性体模型,然后在多体动力学软件中建立完整的车辆系统动力学模型,考虑构架的柔性,其余主要部件如车体、轮对及轴箱等仍作为刚体处理。通过时域积分,计算出构架的振动响应。获得构架载荷谱的基础上,本文探讨了几种应力谱的分析方法,对瞬态动力学分析法和多项式耦合方法进行对比,通过随机抽取的载荷样本历程将载荷谱转换成应力谱,并将转换的应力谱与瞬态计算出来的应力时间历程作对比,分析了其误差。最后采用多项式耦合方法得到了构架疲劳寿命评估的应力历程样本。基于WAFO雨流技术和Miner损伤理论,以及ⅡW推荐的焊接接头的名义应力法S-N曲线和BS7910标准的裂纹扩展率曲线,对构架的疲劳寿命和裂纹扩展寿命进行了分析,其寿命满足设计要求。(4)基于结构动态设计的思想,应用模态分析的方法研究由于振动引起的疲劳强度问题是目前广泛采用的研究手段。采用模态叠加法,将构架模态对其疲劳强度的影响进行了分析,在此基础上可以改进构架的动态性能,提高构架的疲劳可靠性。(5)铁道车辆转向架构架的可靠性受诸多因素的影响,找到主要因素是保证设计高可靠性构架的前提。本文运用概率分析方法,建立了某转向架构架的参数化有限元模型,选取构架的材料属性、几何参数和载荷等作为随机变量,通过统计分析得到其分布参数；以构架母材和焊缝部位疲劳薄弱环节的最大主应力与其许用疲劳强度建立失效状态函数；基于蒙特卡罗数值模拟方法,计算了转向架构架的可靠性参数灵敏度,为构架的优化设计提供参考。(6)提出利用加速寿命试验方法解决高速列车关键部件的可靠性试验成本和时间问题,并用子系统的寿命预测整体系统的寿命,用构架试验验证。通过焊接接头的失效模型估计构架的疲劳寿命,对构架和几个焊接接头进行了疲劳试验,推断了构架疲劳试验的加速系数,计算了试验后的损伤值和寿命。更多还原

【Abstract】 In order to decrease the weight of railway passenger vehicles, the welded steel structures are used for the bogies in our country. However,with the raising of operation speed,and increasing of loads and frequency ranges, and especially the complicated types of weld joints, the load conditions of railway bogies become even worse. Because of the exsitence of weld imperfections of weld joints, such as geometry irregularity, porosity, welding cracks, residual stress, deformation and the changing of material characteristic in heat affected zones, the weld joints are turned to be the main areas of structure failure. In the previous vehicle operation, the fatigue problems of welded bogies have occurred as the increasing of speed.Therefore, higher safety and reliability of bogies in operation are required. In this paper, the fatigue relability of welded bogies are carefully studied and the work is as follows:(1) From the viewpoint of integration of design and manufacture, the formation mechanisms of weld imperfection have been studied. The thermo-elastic-plastic FEM and inherent strain methods have been applied to predict the welding deformation of T-joint, also the comparative analysis between two methods has been carried out. Meanwhile, the bogie welding deformation is simulatied by using the inherent strain method. To assure the bogie fatigue strength and relabiltiy, the measures of eliminating welding imperfection are proposed.(2) Based on the theory of multi-axial fatigue, the bogie stress states under standard loads are analyzed. Meanwhile, three methods (maximum principal stress, Mises equivalent average stress and Sines average principal stress) are used to transform the multi-axial stress to uniaxial stress. The fatigue strength is evaluated and compared based on the Goodman curves recommended in ERRI B 12/RP 17 and JIS E4207. It is concluded that the method of maximum principal stress is suitable to analyze the multiaxial fatigue strength of bogie frame.(3) Rigid-flexible coupling multi-body dynamics has been used to build the bogie frame model of a passenger car. Firstly the flexible model of bogie is built in FEM software, and then the entire vehicle dynamics model is established in multi-body dynamics software. In the rigid-flexible coupling model, the bogie frame is built as flexible body, and other parts are taken as rigid. The dynamical response of bogie is obtained by time integation calculation. Based on the load time history of bogie, several methods which convert the load spectrum to stress spectrum are investigated. Meanwhile, the stress results of transient kinetic analysis and polynomial fitting method are compared, and also their deviation is analzed. At last the polynomial fitting method is selected to calculate the stress spectrum of fatigue life. Based on WAFO rain flow skill, Miner damage theory, nomial stress S-N curve of welding joint recommended by IIW and crack propagation curve of BS7910 standard, the fatigue life and crack propagation life of bogie frame are analyzed. The results show that the life of bogie can satisfy the requirement of design.(4) Based on the dynamic design methodology, the modal analysis method is used to research the fatigue strength problems which caused by the vibration of structure. The modal superpostion method is applied to analyze the influence of structure modal on the fatigue life. According to the analysis, the dynamic performance and fatigue relablity of bogie can be improved.(5) The reliability of railway vehicle bogie is affected by lots of factors. Therefore, finding out the main factor is very important to assure the reliability of bogie. In this paper, the parametric finite element model of a bogie frame is established by using the probabilistic analysis method.The material properties, geometric parameters and loads of the bogie frames are taken as the random variables and their distributed parameter values are obtained through statistical analysis. The failure state functions of the fatigue strength reliability are established by the allowed fatigue strength value and the maximum principal stress of the parent material or weld in fatigue weak location of welded bogie frame. The reliability and parametic sensitivities of random variables are computed by Monte Carlo method, which provides the reference for the bogie design.(6) The accelerated life testing methods are proposed to solve the problems of large cost and long testing period for high-speed train reliability tests. Meanwhile, the whole system life is predicted by sub-system which is verified by bogie frame experiments. In addition, the fatigue life of bogie frame is predicted by failure model of welded joints. Finally the fatigue experiments of bogie and some welded joints are carried out, and the accleration factor of fatigue experiment is calculated.更多还原