Optimization Design Of The Monocoque Bus Body Structure

The Monocoque bus body structure consists of profile steel, with the advantages of superior carrying capacity, structural safety, structural stability, comfortableness, energy efficiency and environmental protection, which is widely used in public transportation. Combined withoptimal design method and finite element method,lightweight design is applied to Monocoque bus body structure. Firstly, in order to determineforms of layout,topology optimization design is applied; then, based on the result of topology optimization,size optimization design is applied;lastly, according to assessment criteria of bus body structure,the new bus body structureis verified by finite element statics analysis in typical working conditions.Thespecific contents are as follows:(1) Elucidate research status of the Monocoque bus body structure; summarizefinite element method and structural optimum design method, whichincludesize optimization,shape optimization and topology optimization.For the purpose oflightweight,the design scheme is made by reference to detailed design, basic design and conceptual design in the design process of mechanical product.(2)Mathematic model of topology optimization is built in bending condition, whoseobjective functionis minimum weight.According to interpretation of topology optimization and the force transferring path, basic layout of bus body structure is ascertained.Refer to common profile steel, the preliminary design is done.Therequirements of strength and stiffness are verified byfinite element statics, which lay the foundation of size optimization.(3)Based on sensitivity analysisofthe section dimensionof profile steel, theinfluence of design variable on structural mass is verified. Then, astratifiedsize optimizationmethod is raised. The section sizes of profile steel are established after three times size optimization. The lightweight design of Monocoque bus body structure is done.(4)Finite element statics analysis is applied to verifying the strength and stiffness of bus body structure in four typical conditions. Stress concentration occursin limited torsion condition, so that the structureof stress concentrationarea should be enhanced.Lastly,the total mass of new bus body structure is1313 Kg.