Multi-objective Optimization Design For Electric Bus Body Skeleton Structure Lightweight

In recent years, safety, energy saving and environmental protection has been the mainproblems faced by automotive industries in sustainable development. A large number ofstudies have shown that automotive lightweight design is one of the principal ways toachieve energy conservation and emissions reduction. As the main bearing weight parts ofbus, body skeleton accounts for about30%~40%of the bus total weight. So the lightweightdesign of body skeleton has very important significance.To seek an effective method for bus body skeleton lightweight, this thesis performedstructure optimization designs on it, and made a lightweight plan, Combined with theproject. Under the premise of meeting bus performance requirements，the designs havereduced weight significantly.First of all, the FEM (Finite Element Model) of bus body skeleton was built, accordingto Finite element modeling principles. Then statics analysis and modal analysis were carriedout to obtain body skeleton structure stiffness, strength and lower frequencies. Analysisresults indicated that the FEM was built correctly and provided the basis for comparisonanalysis of subsequent optimization scheme.Secondly, topology optimization design for bus body skeleton was performed.Considering the complexity of bus body skeleton structure, the thesis adopted localtopology optimization combined with iterative algorithm to analyze roof skeleton, chassisskeleton and side wall skeleton in turn. Based on the optimization result and the designprinciples of bus, the bus body skeleton structure was extracted.Thirdly, size optimization design for bus body skeleton, based on sensitivity analysis,was carried out. The size parameters, that are not sensitive to structural performance ofbody skeleton but weight reduction, were confirmed. Then the efficiency of sizeoptimization analysis was improved significantly by making the parameters as design variables. Minimized the weight, the first torsion and bend frequency as the objectivefunction, and treated the statics compliance as the constraints in torsional and bendingconditions. Based on GRSM algorithm got the best value.Finally, the structural performance of bus body skeleton before and after optimizationwas compared. The result shows that the bus body skeleton, compared with the original one,has not only got11.07%weight reduction, but also met the performance requirements. Alightweight optimization method for bus body skeleton structure has been obtained throughthis thesis.