Design And Research On The Lightweight Of Automotive Body Based On Multi-material Construction

Reduction of automobile weight will greatly improve fuel economy of the vehicle, save energy and reduce engine emission. Method for design of lightweight automotive body based on multi-material construction is discussed. The main idea for design lightweight body construction by multi-material is the right material in the right place. Taking example for an automotive body, finite element analysis and structure optimal design techniques are used. Taking account of body weight and material cost, different materials for the appropriate parts of the body are analyzed and a synthesis method for designing lightweight automotive body using multi-material construction is obtained. The main points of the thesis are listed below.The parametric finite element analysis modal for the body is built based on the features of the period of body structure concept design. Analysis of deformation of body structure under the working load states including static bending and static twisting is conducted. The dynamic characteristic of the body structure is analyzed with the modal analysis technique.The optimization model of body structure is built with weight as objective function, the section size of body beams as design variables, and the overall body bending stiffness and torsion stiffness as state variables. The design variables are chosen with DOE techniques. The structural optimal designs of the steel body and the aluminous body are completed.A method for body structural and material optimization of trusses is proposed. Each candidate material type has been assigned an ID number, and then materials used for components and cross-sectional sizes are introduced as design variables. Two objectives involving the weight and the cost are considered under stiffness constraints. A mathematical model of the optimization problem is developed. The problem is solved using a multi-objective genetic algorithm. The optimal design of multi-material body structure is completed, furthermore, the two results is compared and analyzed.It is observed that several multi-material structures in the example achieved lower cost penalties associated with unit decrease in weight than single material structures. A lightweight, good structure performances and low cost car body can be acquired with the proposed method.