Study On Lightweight And Life Cycle Assessment Of Bus Body Structure

At present,energy-saving,environmental protection and safety,which have been concerned for a long time,have become the three major problems that must be solved for the sustainable development of the automobile industry.For buses,the frame of the bus bears all the loads during the driving,and its weight can account for about two-fifths of the bus gross weight.The weight of its body frame contributes about one-third of the fuel economy and pollutant emissions during the use phase alone.As an important way to save energy and reduce emissions,the structural optimization technology of the bus body frame has been promoted in the industry and has gradually matured.However,there are few studies on the combination of lightweight technology and life cycle energy-saving and emission reduction quantitative evaluation.Therefore,the 12-meter full-load hybrid city bus with air suspension was selected as the research object,and the finite element model of its body frame and air suspension was established respectively in this study.Under the bending condition and extreme torsion condition which are the worst conditions of bus operation,the finite element analysis was carried out to obtain the static strength and stiffness of the body frame,and to verified whether its body frame meets the strength and stiffness requirements and whether there is design margin.Then,modal analysis was carried out to determine whether the natural vibration characteristics of the structure are good or not.On the basis of good nature vibration characteristics and the static working condition of the structure has design margin,the structural optimization was carried out.The design variables were the crosswise and longitudinal beams with large overall mass and insensitive to the structural performances of the body frame,the maximum stress was the constraint condition,and the minimum volume fraction was the constraint objective.After the optimization was completed,finite element analysis and modal analysis were performed again to verify whether the structural performances meet the requirements.After it was confirmed that the structural optimization meets the structural performance requirements,life cycle assessment of underframe before and after lightweight was carried out.The life cycle stages were divided,and the evaluation models of each stage were established.The quantitative effect of energy saving and emission reduction of its body frame by structural optimization was further studied through calculation and analysis.The research results show that compared with the original body frame,the structural weight of the body frame is reduced by 52.5kg and the strength and stiffness requirements are met under both conditions.The first ten natural frequencies are slightly reduced.However,the resonance frequency is avoided and the mode shape is smooth and no mutation.In terms of whole life cycle,the mineral resource consumption is reduced by 0.4E-04 kg Sb-eq.,the fossil energy consumption is reduced by 0.7E04 MJ,and the comprehensive environmental impact value is reduced by 0.42E-11.The reduction ratios are: 3.81%,4.46%,4.56%.The research results have important reference significance for the optimization design method of bus structure and the exploration of energy-saving and emission-reducing potential.