Analysis And Optimization Of Skeleton Structure Of Medium-sized Coach Body Based On Rollover Safety

Based on the great advantage of low cost and large passenger capacity,coach plays a great role on casing traffic congestion as an important urban and intercity public transportation tool.With the rapid development of passenger transport industry,the coach fleet increases year by year.Event of many passengers deaths have occurred because of coach rollover accidents,which have caused the government and enterprises’ attention.So,the research of the structural strength during coach rollover crash has became a hot spot in the automotive field,which was great importance for protecting the passengers and reducing the casualties caused by traffic accidents.In this paper,some research work has been done to improve coach rollover safety.The main research contents are as follows:(1)The finite element model of medium-sized coach is established,and the static characteristics and modal analysis were carried out.In the study of static characteristics,the vertical bending and ultimate torsion are used to analyze the two typical working conditions.The results show that the maximum stress of the vehicle body skeleton under the two conditions is within the allowable stress range of the vehicle body Q235,the maximum displacement is smaller,which met the requirement.In the modal studies,the free modal forms are analyzed,the results show that the low order frequency of the most destructive,the free modal of coach body frame is not in the frequency range that may cause resonance,met the requirements,which met the requirement.(2)Based on the relevant requirements of Rollover national standard,the finite element model of medium-sized coach was established.A new evaluation method of living space combined with observation method,evaluation angle θ method and collision force method is proposed.Based on the analysis of the model,the advantages and disadvantages of evaluation methods about occupant’s living space were discussed.Using the combination of various evaluation methods in this paper can determine the invasion time and the maximum amount of intrusion time and define the accuracy of the simulation process by comparing with each other.(3)Aiming at the problem of excessive deformation in the process of rollover,the structural improvement program and material improvement program was proposed.In the structural improvement scheme,the main force of the skeleton is improved by the method of closed loop design and cross section size transformation.The improved body skeleton deformation was reduced,the living space has not been invaded,and the side gap between the column and the living space was about 32mm,which met the requirements.In the material improvement scheme,the foamed aluminum filling method was analyzed by static analysis.The results show that the effect of foam aluminum filling on the bending resistance of thin-walled tube is better than that of thickening member in the case of increasing the mass.(4)Based on the improved coach model,multi-objective optimization were carried out.The objective of the multi-objective optimization was as follows:the thickness of the left and right side frame and the roof beam was variable,the quality of the component and the minimum spacing of the column space were taken as the goal.Selected a set of optimal solutions under the premise of satisfying the requirement,which can achieve the purpose of lightweight design and intensity matching.