【作者】 安琪；

【导师】 李芾；

【作者基本信息】 西南交通大学 ， 车辆工程， 2013， 博士

【摘要】 随着列车运行速度的提高,线路对车辆的激扰频率范围更为宽广。在车辆运行时,轻量化承载结构的动态特性问题日渐突出。论文以高速动车组转向架焊接构架为对象,研究其结构刚度特性与车辆系统动力学行为和构架疲劳强度之间的关系,提出了柔性构架的结构强度和刚度设计方法。利用有限单元法建立动车组非动力转向架焊接构架的结构动力学分析模型,获得构架在较低频率范围内的振型。采用柔性体动力学理论,建立引入了构架结构刚度特性的车辆系统动力学研究模型,分析车辆在不同计算工况下的动力学响应。研究结果表明,构架扭转振型对车辆运行稳定性和平稳性没有影响。在引入该振型后,转向架系统的扭转刚度较刚体模型低,车辆在扭曲线路上的均载性提高,其轮重减载率和轮轨垂向力的数值降低。基于准静态方法进行分析时,车辆脱轨系数下降。构架弯曲和剪切等振型的振动能量较低,不会改变车辆系统的动力学行为。从简化转向架系统扭转刚度试验和计算方法的角度出发,将斜对称载荷与构架垂向变形的比值定义为结构扭转刚度。通过改变材料物理性能,构建了具有不同扭转刚度特性的构架模型,研究扭转刚度对车辆系统动力学行为的影响。分析结果表明,构架扭转刚度的降低将使转向架轮轨垂向作用重新分配,各车轮的均载性得到改善。因此,车辆在通过曲线时的轮轨垂向力和轮重减载率的数值随构架扭转刚度的降低而降低。构架扭转刚度的降低对车辆运行稳定性、平稳性、通过曲线时的脱轨系数和轮轨导向力之和的影响甚小。从提高车辆在扭曲线路上的运行安全性的角度出发,构架扭转刚度应选择低值。为克服现有方法的缺陷,采用德国机械工程学会推荐的基于材料利用度的方法(FKM方法)评估构架结构疲劳强度。结合高速动车组转向架焊接构架的制造工艺和服役环境,讨论了平均应力和载荷谱特性等因素对构架疲劳强度的影响。根据单元坐标系下的应力计算方法,确定了构架侧梁腹板与下盖板焊缝焊趾的分析应力谱,计算其材料利用度,并与基于传统方法的评估结果进行比较。在传统方法的框架下,车辆通过曲线这一准静态过程是结构疲劳强度的决定因素,浮沉运动所产生的垂向动态过程的影响较小。FKM方法考虑了准静态和动态过程载荷循环次数的影响,在接头抗疲劳特性一致时,基于该方法得到的结构疲劳强度评估结论较传统方法宽松。采用FKM方法评估结构疲劳强度有利于结构轻量化设计。为研究刚度特性对结构疲劳强度的影响,建立了变扭转刚度的构架模型,基于国际铁路联盟UIC515-4标准推荐的试验载荷谱,评估构架疲劳强度。研究结果表明,降低构架扭转刚度将导致斜对称载荷敏感区域变形增大,在较高的应力水平下,该区域的正应力材料利用度、剪应力材料利用度和材料综合利用度均有所上升。在斜对称载荷敏感区域选择应力水平较低的接头是扭转柔性构架强度设计的根本原则。对不同形式等截面直梁的弯曲和扭转刚度特性进行了分析。结果表明,在截面壁厚和壁厚中线所围面积相同时,与管截面横梁相比,箱形横梁具有较小的扭转刚度,但其弯曲刚度则较大。基于有限元方法的计算结果表明,构架扭转刚度受横梁弯曲刚度和扭转刚度的共同影响。在不同壁厚条件下,横梁弯曲刚度和扭转刚度对构架扭转刚度的影响程度存在差异。设计扭转柔性构架应着眼于合理协调横梁结构的不同刚度特性,通过提高该区域的柔性化水平降低构架结构扭转刚度。更多还原

【Abstract】 With the higher running speed of the train, the range of excitation frequency that the line gets to the vehicle is more extensive. While running, the dynamic behavior of light-weight structure is increasingly prominent. The thesis adopts the welded frame of high speed electric multiple unit (EMU) bogies as object, studies the relationship among its structural stiffness characteristic, vehicle system dynamic behavior and frame fatigue strength, and puts forward the designing method for the structural strength and stiffness of torsionally flexible bogie frame.The analyzing model for the structural dynamics of EMU trailer bogie welded frame is set up by finite element method, so the vibration mode of frame in the low frequency range is achieved. The flexible multibody dynamic theory is adopted to set up the vehicle system dynamic research model which introduced the stiffness characteristic of bogie frame, and analyze the dynamic response of vehicle under different calculated working condition. The study shows that the bogie distorting vibration has no effect on the stability and ride comfort of the train running. After adopting the frame distorting vibration mode, the distortion stiffness of bogie system is lower than rigid model; while the vehicle is on the warping line, the vertical load of the wheel is approaching to well-distributed, and its wheel unloading ratio and maximum vertical force between wheel and rail have dropped. While analyzing by using quasi-dynamic method, the derailment coefficient has dropped. The vibration power of frame bending and shear mode is low, and the vehicle system dynamic behavior would not be changed.To simplify the distortion stiffness experiment and calculating method of bogie system, the ratio of twist load to frame vertical deflection is defined as structural distortion stiffness. The physical properties of material is changed to set up the frame model for the different distortion stiffness characteristic, and to research the effect which distortion stiffness gives to the vehicle system dynamic behavior. The analyzing result shows that, the lowering frame distortion stiffness would let the vertical interaction between vehicle and rail re-allocate, the vertical load of the wheel is approaching to well-distributed. So the maximum vertical force between wheel and rail and the wheel unloading ratio low with the lowering frame distortion stiffness while passing through curve. The low frame distortion stiffness has very little effect on the running stability, ride comfort, derailment coefficient, and the sum of guiding force per axle. Starting from the running safety of vehicle on the warping line, the low figure would be chosen for the frame distortion stiffness.In order to overcome the defect of present method, the method based on the degree of utilization is recommended by FKM to evaluate the frame fatigue strength. Considering the manufacturing technology and service condition of high speed EMU welded frame, the effect which the average stress and load spectrum characteristic have given to the frame fatigue strength is illustrated. According to the stress calculating method under element coordinate, the analyzing stress spectrum of the weld toe which connect the web and the bottom cover plate of the side sill are fixed. The degree of utilization is calculated, and is compared with the evaluation result based on the traditional method. In the convention of traditional method, the vehicle passing through curve as a quasi-static process is the determined element for the structural fatigue strength, the effect which the dynamic vertical process made by the bounce movement is quite low. The effect of load cycle in the quasi-static and dynamic loads is considered by FKM method. When the fatigue resistance on the joint gets agreement, the evaluation result for the structural fatigue strength based on this method is looser than the traditional method. Evaluating the structural fatigue strength by FKM method is beneficial for the light-weight structure design.In order to study the effect which stiffness characteristic gives to structural fatigue strength, the frame model for variable distortion stiffness is set up. Based on the experimental load spectrum which is recommended by the leaflet UIC515-4, the frame fatigue strength is evaluated. The research result shows that, to low the frame distortion stiffness would make more deflection in twist load sensitive area. In the high stress condition, the normal stress degree of utilization, the shear stress degree of utilization and the overall degree of utilization in this area have all increased. The low stress joint in twist load sensitive area is the basic principle for the torsionally flexible bogie frame strength design.The bending and distortion stiffness characteristic of the beam with different section is analyzed. The result shows that, when the wall thickness and the area surround by neutral plane of tube transom and the wall thickness of box transom is equal in quantity, compared with tube transom, the box transom has low distortion stiffness, but its bending stiffness is high. The calculation result based on the finite element method shows that, the frame distortion stiffness has been influenced by both the bending stiffness and distortion stiffness on transom. In different wall thickness condition, the difference exists in the effect that bending stiffness and distortion stiffness on transom give to the distortion stiffness of the frame. The design for torsionally flexible frame should take in coordinating different stiffness characteristic of the transom structure as the basis, and low the distortion stiffness for the frame structure by improving the flexible standard in the transom.更多还原