Modeling,Analysis And Software Development Of Thin-walled Frame With Complex Cross-section For Automotive Body

Nowadays,the main design scheme of the body structure is to repeatedly modify the detailed FEM(Finite Element Model)until its performance is satisfied in the design process.However,due to the complex modification process and long design cycle of the detailed FEM,it is not suitable to be applied to in the conceptual design process.It is noted that the structure of the beam FEM is simpler because it has fewer elements so that the modeling process is faster and the solution time can be remarkably reduced.It is of great significance to shorten the design cycle and improve the solution accuracy of car body by using the the frame FEM.In this paper,Firstly,the co-rotational technique and the large deformation Belytschko beam are introduced in chapter.Afterwards,three methods of coordinate transformation are deduced to describe beam element space position.Secondly,the processing methods of beam,joint and plate structure are detailedly introduced,and the solution methods of geometric properties and plastic hinge properties of cross-sectional shape and mass properties are derived.Thirdly,three complex cross-sectional shape optimization models are presented,including improvement model of geometric properties,improvement model of plastic hinge properties and calibration model of plastic hinge properties.The accuracy of the cross-sectional shape optimization models are verified through numerical examples.Fourthly,the bending stiffness,torsional stiffness and modal solution accuracy of the frame FEM is verified by comparing the whole body structure detailed FEM and simplified frame FEM of car body.Meanwhile,the crashworthiness solution accuracy of the frame FEM is also proved by comparing the detailed and simplified FEM of the thin-walled straight beam,the front longitudinal beam and the side structure of car body.Finally,the frame modeling and analysis software Car Frame is independently developed based on the above theory.Briefly,the main functions of the software include the pre-processing of the frame model,mass properties solution,bending and torsional stiffness analysis,modal analysis,crash analysis,geometric properties and the plastic hinge properties solution and the cross-sectional shape optimization design of thin-walled beam.From the result,it has been proved that the errors of bending stiffness and torsional stiffness solution are 3.94% and 6.12%,respectively,the maximal error of the modal and crashworthiness solution are 14.41% and 9.88% by adopting reasonable modeling method and considering plastic hinge properties of the beam element.In the conceptual design stage,the frame model of car body can be easily created and solved.And the design cycle of body structure can be greatly shortened by using the Car Frame software.