Abstract: In this paper, the idea of “CAE driven design” is introduced in the conceptdesign phase of bodyinwhite (BIW), an implicit parametric model for the BIW of a car is built by using SFECONCEPT, and the effectiveness of the model is validated by performance comparison with finite element model verified. A stepbystep optimization technique is adopted, combining with BIW performance matching and supplemented by the idea of light weigh design, to find the light weight design scheme of BIW on the premise of meeting all the static and dynamic performances of BIW to the maximum extent. The results of comparison between BIW performances before and after optimization show that with the little changes in bending stiffness and torsional stiffness (lowering by 02% and 06% respectively), the length, width and height of car body increase by 15mm, 13mm and 9mm respectively, the first order bending and torsional mode frequencies rise by 56% and 92% respectively, and the mass of car body reduces by 199kg with a lightweighting rate of 576%, achieving an apparent lightweighting results.

Key words: BIW, implicit parametric model, beam cross section optimization, lightweight design