车桥强度与含损伤裂纹的剩余寿命预测方法的研究

发布时间：2018-03-07 06:15

本文选题：前桥　切入点：强度分析　出处：《山东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：转向桥作为汽车底盘的重要部件之一,所受载荷大,应力状况复杂,是决定汽车安全性能的关键部件之一。目前,车桥的疲劳损伤问题日益突出,疲劳破坏已经成为前桥的主要失效形式之一。因此,前桥的强度和疲劳对汽车安全行驶具有重要影响。本文对某重型载货汽车的前桥进行了有限元分析,检验其强度和寿命是否满足要求,为其设计生产和结构改进提供参考;还针对含损伤裂纹的前桥疲劳进行了分析。主要的研究工作如下:(1)对前桥进行多种工况的强度分析。依据前桥的结构和受力特点,对其进行合理简化,建立有限元模型,分析前桥处于满载弯曲、制动和转弯三种工况时的受力情况,确定不同工况下的载荷和约束,对前梁进行强度分析。结果表明,三种工况下的最大应力均没有超过材料的屈服极限,该前桥满足强度方面的要求。(2)建立S-N曲线,选取第一主应力为应力分量对前梁进行疲劳寿命分析,并采用Gerber平均应力修正法对其进行修正,得到前梁的疲劳寿命低于标准JB/T50109-1998规定的80万次;并将计算结果与试验结果进行比较,进一步验证有限元分析的可靠性。(3)针对前桥的结构和应力分布对前桥进行结构改进,再进行疲劳计算。改进后前梁的疲劳寿命满足了标准要求,并且各工况下的应力都有所减小;然后对优化后的模型进行模态分析,得到前梁前6阶模态的固有频率和振型。经过分析,前梁不会由于不平路面的激振而发生共振,显示了结构改进的合理性。(4)在强度和疲劳分析的基础上,研究裂纹的各种参数对前桥疲劳寿命的影响规律。根据应力计算划定前桥的危险区,在危险区域对裂纹进行参数化建模,建立椭圆形表面裂纹;调整裂纹的方向、尺寸等参数,对含不同裂纹的前梁进行疲劳分析,统计前梁的疲劳寿命。对统计的数据进行处理,分析前梁疲劳寿命随着裂纹各个参数的变化趋势,总结其对前梁疲劳寿命的影响。还对前梁含有多裂纹的情况进行了研究,分析裂纹间的间距对疲劳寿命的影响。上述研究不仅得到了该型号前桥的强度和疲劳情况,而且还得到了裂纹损伤对前桥疲劳寿命的影响情况。这为企业的实际生产提供了一定的理论依据,并且对预测车桥疲劳故障减少疲劳事故,起到一定的指导作用,而且也为其它含损伤裂纹结构的疲劳分析提供了一种值得借鉴的方法。
[Abstract]:As one of the important parts of automobile chassis, steering bridge is one of the key parts of automobile safety performance, which is subjected to heavy load and complicated stress condition. At present, the fatigue damage problem of vehicle bridge is becoming more and more serious. Fatigue failure has become one of the main failure forms of the front axle. Therefore, the strength and fatigue of the front axle have an important effect on the safe driving of the vehicle. In this paper, the finite element analysis of the front axle of a heavy-duty truck is carried out. Test its strength and life to meet the requirements, for its design and production and structural improvement to provide a reference; The fatigue of front axle with damage crack is analyzed. The main research work is as follows: 1) the strength of front axle under various working conditions is analyzed. According to the structure and stress characteristics of front axle, the fatigue of front axle is reasonably simplified, and the finite element model is established. The stress of front axle under three conditions of full load bending, braking and turning is analyzed, the load and constraint under different working conditions are determined, and the strength of front girder is analyzed. The maximum stress of the front axle does not exceed the yield limit of the material under three working conditions. The front axle satisfies the strength requirement. The S-N curve is established. The first principal stress is selected as the stress component to analyze the fatigue life of the front beam. The fatigue life of the front beam is 800,000 times lower than that of the standard JB/T50109-1998, and the calculated results are compared with the test results. Further verify the reliability of finite element analysis. 3) improve the front axle structure and stress distribution, and then carry out fatigue calculation. The improved fatigue life of the front beam meets the standard requirements. Then the modal analysis of the optimized model is carried out to get the natural frequency and mode shape of the first six modes of the front beam. After analysis, the front beam will not resonate because of the vibration induced by the uneven road surface. The rationality of structural improvement is shown. (4) on the basis of strength and fatigue analysis, the influence of crack parameters on fatigue life of front axle is studied, and the dangerous zone of front axle is determined according to stress calculation. In the dangerous area, the crack is parameterized, the elliptical surface crack is established, the direction and size of the crack are adjusted, the fatigue life of the front beam with different cracks is analyzed, and the fatigue life of the front beam is calculated. The change trend of fatigue life of front beam with each parameter of crack is analyzed, and the influence of fatigue life of front beam on fatigue life of front beam is summarized. The influence of crack spacing on fatigue life is analyzed. Moreover, the influence of crack damage on fatigue life of front axle is obtained, which provides a theoretical basis for the actual production of enterprises, and plays a certain guiding role in predicting the fatigue failure of vehicle and bridge to reduce fatigue accidents. It also provides a useful method for fatigue analysis of other structures with damaged cracks.
【学位授予单位】：山东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.4

【参考文献】