Integrated Fatigue Analysis Of A Car Body

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.