Study On The Beam-shell Hybrid Finite Element Modeling Method For BIW

In general, the body structure design is divided into the conceptual design stage anddetailed design stage. In the conceptual design stage for BIW，domestic and foreignautomobile manufacturers will establish different analytical models based on certainconsiderations. Based on the characteristics of the conceptual design stage， carmanufacturers generally tend to create a simplified model which contains one or moreelement of beam element, shell element,spring element and mass element. It tries toapproximately reflect the mechanical properties of the detailed model from the whole，andmodify the analysis model easily. So we can reduce the model computing time at the utmost,and eventually reduce the development cost.We can see that the simplified analytical model is the carrier of all CAE analysis ofthe conceptual phase. For the current car manufacture, hybrid simplified models with one ormore element（especially more) are widely used. We make a study on the hybrid elementmodeling method for BIW and a practical application on the new hybrid modelingmethod.Finally we make the modeling method step by step.All of this have a very importantpractical significance in the conceptual design stage. In this paper，we study on thebeam-shell hybrid modeling method which is extensively used and the most promising. Thisis the background of this study.Specific work as follows:1) Firstly, the hybrid model idea is introduced then the beam theory and relatedcalculation method are introduced, including the calculation of the beam section and themiddle beam element inertia properties, connection elements between the beam elementsand shell elements.Then explain the establishment and validation of beam-shell hybridmodel taking B column as examples. And the influential factors of torsion constantJawhich affect the precision of hybrid models are studied.2) Firstly, according to the mentioned method in the third chapter，we establishbeam-shell hybrid model for BIW. Then we make a comparison between the beam-shellhybrid model and detailed model for BIW form the torsion stiffness, bending stiffness, majoropening deformation, the lower modes including first-order integral torsion mode and the first bending mode, etc. It verify the validity of beam-shell hybrid model for BIW.3)The application on the beam-shell hybrid model for BIW are mainly introduced inthis chapter. As the outer layer of the beam-shell hybrid model is still shell element whosecoupling relations between the fluid and structure are unchanged, the beam-shell hybridmodel for BIW can be used for noise analysis directly, including acoustics mode analysis ofcab cavity, frequency response analysis of cab cavity, noise transfer function(NTF) analysisand so on.This paper researched an effective finite element modeling method, then necessaryverification and reasonable application are executed for this modeling method. This provethe feasibility of this modeling approach. In addition, the designer can appropriatelyextended the modeling method according to the different emphasis in the conceptual designstage in order to increase the generality and flexibility of modeling method. This is thesignificance of this research.