Design and application of lightweight multi-objective collaborative optimization for a parametric body-in-white structure

The static bending and torsional stiffnesses, the lower-order modal frequencies of a body-in-white structure and the full frontal-crash and side-impact passive safety performances are simulated with finite element models which are generated on the basis of the implicit parametric model. The implicit parametric model is established through SFE CONCEPT software. The simulation results are compared with tests to validate the simulation analysis results. It is proposed that the multi-objective optimization is divided into non-safety parts optimization, frontal-crash safety parts optimization and side-impact safety parts optimization, which is computationally more efficient than optimizing the non-safety parts, the frontal-crash safety parts and the side-impact safety parts simultaneously. In this paper, the lightweight multi-objective collaborative optimization design of the body-in-white structure is conducted for a passenger car by optimizing the thickness, the beam section shape and the size; while maintaining the performances of the static bending and torsional stiffnesses, the lower-order modal frequency decreases to less than 5% of the initial value, and the full-frontal-crash and side-impact passive safety performances remain almost the same. Structural modifications are applied by means of implicit parametric technology, providing changes in the geometry in a fully controllable manner. After comparison between the optimized body-in-white structure and the initial structure, the mass decreased in total by 32.41 kg (i.e. by as high as 7.63%). The decreases in the performances of the bending and torsional stiffnesses are less than 2.54%; the bending and torsional frequencies increased a little, and the frontal-crash and side-impact passive safety performances underwent almost no change.