| Recently the increasing amount of rollover crash with “group death and group injury” threatened the personal safety seriously and caused huge property loss,and under the implement of regulations,the stricter requirement has been carried out on the intensity of coach superstructure.Taking a certain minibus as the research object,this paper mainly researches the conduct of roof crash resistance test and rollover crash test,establishing the corresponding finite element model(FEM),analyzes the deformation features of superstructure and influence factors of crashworthiness,thus carrying out the optimization plan which has been finished as the following steps:(1)Analyze the non-linear dynamic FE algorithm from the points including deformation and equation of controlling motion,time integration algorithm and step control,simulation algorithm of contact-rollover interface,shell elements,hourglass control and so on.Introduce the features and functions of simulation software LS-DYNA and HyperMesh.The procedure of establishing and checking FEM is analyzed from checking grid quality,setting material,property and contact.(2)Conduct the roof crash resistance test of the certain passenger car according to FMVSS 216,the results tell that when the load reaching as three times as mass force,the displacement of loading device is 60 mm which is less than 127 mm regulated by the law and the largest load is 40.12 KN leading to the shortage of load margin.Comparing the result of simulation and test,the car roof has been optimized with the compressive strength and energy absorption ability improved respectively by 17.04% and 12.23% based on the key deforming parts and the route of transforming force.(3)Conduct the coach rollover test of the certain passenger car according to GB17578-2013,by observing whether the deformation gauge has contacted with the car body,it comes to the conclusion that the residual space has been intruded.The mass center of rollover FEM is compared with the mass center of real car which can be measured by lifting method in order to validate the calculating precision of the critical angle.Two methods respectively improving simulation efficiency by 24.82% and 79.84% are carried out based on the motion feature of coach rollover.Comprehensively considering deformation,simulation time and velocity,finally the plan of rollover starting from touching the ground has been chosen.The simulation results tell that the largest intrusion amount at the point of the chute in the upper side beam is 45.9mm which don't meet the demand of the standard.The main absorption parts,bearing parts and deformation model can be known by analyzing the vehicle deformation,crash force,section force,acceleration.(4)The deformation of thin-walled beam is analyzed from three kinds of models including combined deformation of tension and bending,combined deformation of tension and torsion,buckling deformation of compression bar.The influence of thickness,section pattern and reinforced structure on the superstructure have been analyzed and validated by simulation.The key parts are A pillar,B pillar,cantrail,the roof beam ordered by their influence on quality,absorption and intrusion amount which can be weighted by orthogonal design.Finally based on the research results above,the optimal scheme is carried out through increasing thickness,using reinforced structure,corner plate and high strength steel,improving the section pattern.The simulation results tell that the largest deformation amount of the superstructure has changed from 128 mm to 75.6mm which means that the residual space has not been intruded.The crashworthiness of mini-bus superstructure has been improved. |
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