Reaserch On Minibus Stiffness Analysis And Optimization

The continuous development of CAE（Computer Aided Engineering）technology,changed the traditional automotive design methods and abandonedthe traditional car development process of testing prototype car to modify itsperformance,making it possible to effectively design structural acorrding tothe performance requirements.CAE technology can timely validate designengineers’ programs, improve design programs and increase design efficiency.Bsed on topology optimization、sensitivity analysis method, optimizationtechniques can be used to optimize structure，and targeted improve structuredefects,find design problem before prototype was made,gain the mostoptimized body structure.Depend on CAE technology,modern CAD/CAE/CAM integration of digital design and development tools, has became a mainmeasure of capability of automobile manufacturing companies of vechilebody design.Adopting finite element technology-based CAE designoptimization method can effectively shorten the vehicle development cycle,improve design efficiency and reduce design costs.Body stiffness as the fundamental and the most important performanceindicators，which is needed to take consideration in car body design and is thecore indicator to evaluate the disadvantages and advantages of body structure.Body stiffness directly affect the body’s fatigue strength performance, passivesafety performance, NVH properties and so on.Thus, in the body designprocess, we must ensure that the stiffness properties of body structure to meetthe requirements, then accroding to optimize other properties such as fatiguestrength、collision safety、NVH and so on,to design a safe and reliable auto body. Body mass greatly influence the fuel economy and dynamicperformance of automobile, and the lightweight design of body caneffectively save fuel and improve vehicle dynamic performance. Automotivelightweight design including vehicle structure optimization, materials andadvanced manufacturing process,structural optimization is endless, thusaccording to optimize the body structures to ensure the stiffness performanceof vehicle body while minimizing the body quality, has been becaming acurrent research focus.In this paper, the author takes a mini-bus as the research object, analyzesthe influence of its assembly connection, the main cross-section geometriccharacteristics,overlapping forms of the frame beams to stiffness performance.Finite element analysis technology was used to build the structure of the bodyin white of the minibus, its free modal and stiffness properties was analysisedon the finite element model, and researches the loading method to analysis themini-bus body stiffness performance, evaluates stiffness properties of thiskind of minibus. Through analysis and calculation, the author found that themodal and stiffness performance do not meet design objectives, it’s need toimprove the performance of the original stiffness of the body by structuraloptimization, due to the specificity of minibus structure, its white body wasdivided into frame and body to separatly optimize and analysis.Used topology optimization to optimize the layout of frame beams todetermine suitable beam shape and position.biult a wire-frame model of theframe, used sensitivity analysis method to analysis the affection of the framecross-section shape and location on frame stiffness properties, optimized theframe cross-section shape and improved the performance of the framestiffness.Through lightweight design of the frame to maximize reduction theoverall quality of the frame,at the same time ensuring the modal and stiffnesspreperties of the frame. Established a wireframe model of minibus bodystructure, the analysis obtained that the affection of cross-section geometry onbody structure stiffness was non-linear, improving body cross-section areaand moment of inertia, does not mean that will enhance the body bending and torsional rigidity.Finally,the sensitivity analysis was used to comprehensiveoptimize key parts thickness, improving vehicle performance, while reducingthe body’s overall quality.Through complex optimization, the author comprehensive increases thestiffness performance of the original body and reduces the overall quality ofthe body,reflecting the advantages of CAE technology in the body design,andsupplys methods and theoretical for the design and optimization of suchmini-buses.