【作者】 刘吉明；

【导师】 雷刚；

【作者基本信息】 重庆理工大学 ， 机械设计及理论， 2010， 硕士

【摘要】 承受交变载荷的结构都会产生疲劳,由此带来的疲劳破坏会带来巨大的损失。因此,承受交变载荷的结构都需进行疲劳强度设计。车身作为车辆的主要承载构件,也要承受交变载荷的作用,因此也要进行疲劳强度设计。目前,车身疲劳寿命的评价主要靠台架试验和道路试验。试验周期长,费用高。随着计算机技术的发展,有限元技术在现代汽车产品开发中发挥着越来越重要的作用,几乎贯穿了汽车设计的全过程。采用CAE技术,可以大大缩短车辆的开发周期,降低开发成本,提高设计质量。本文即利用有限元法,分析了某款轿车车身的疲劳寿命。首先,本文建立了白车身的有限元模型,并通过实验模态对模型进行了修正。对修正后的白车身模型进行了弯曲刚度和扭转刚度分析,并做了系统的评价。在白车身有限元模型的基础上,建立整个车身的有限元模型。进而进行了车身强度的分析。在MSC.Nastran中,对整车车身进行模态分析,生成了车身模态中性文件,进而在Adams中建立了刚柔耦合的多体动力学模型。通过多体动力学分析,得到了车身的DAC文件。利用模态结果文件和DAC文件对车身进行了疲劳寿命分析。分析发现,车身底板疲劳强度不足,需要加强。最后,通过结构改进,使得车身的各项性能得以提高,为结构的设计改进提供了有力的支持。更多还原

【Abstract】 Structural fatigue occurs by alternating loads, and the resulting fracture will cause huge losses. Structure bearing alternating loads needed to make fatigue design. As the main bearing component of the vehicle, body bears alternating load. Therefore fatigue design must be implemented. At present, the estimate methods of the car body fatigue are bench test and road test. Test cycle is long, and it`s expensive. With the development of computer technology, finite element technology plays an increasingly important role in the modern automotive product development. Using CAE technology, it can greatly reduce the vehicle’s development cycle, reduce development costs and improve design quality. Using the finite element method, fatigue life analysis is executed in a certain type of car.First, the finite element model of the BIW is established. The model is modified by modal experiments. Then, bend stiffness and torsion stiffness analysis are executed, and systematic evaluation of the results is executed. On the basis of the BIW`s finite element model, the finite element model of the whole body is created. And then, the strength analysis is executed.Modal Neutral File of the body is generated through modal analysis in Nastran. And then a Rigid-flexible coupling multibody dynamics model is created in Adams. DAC files of the body are generated after multi-body dynamics analysis. In MSC.Fatigue, the fatigue life analysis of the body is executed using the results file of the model analysis and the DAC mode file. It shows insufficient fatigue strength in the back floor of the car body. These places need to be strengthened.Finally, the performances of the car body are enhanced by structural improvements. This provides a strong support for the structural design improvements.更多还原