Influence Of Local T-Joint Of Waistrail On Rollover Safety Of Closed Ring Of The Body Structure Of Coach

The plastic hinges are the main factor which influencing the deformation of the busbody when it happens rollover crash. And these plastic hinges distribute throughout all theconnecting regions of the body structure. These connecting regions are: the unions of theside wall and the cover; the unions of waistrail beam and window pillars or door pillars; theunions of the vertical beam and floor. How these plastic hinges deforming and how thestress distributing, Finding the rules can help to reveal the internal relationship of theseplastic hinges and the bus body, and can help enhancing the bearing capacity of these plastichinges, also can help improving the safety of bus body when it happens rollover crash. Andit has important theoretical significance.The studying subject is the T-union of the waistrail beam and window pillars or doorwindow. We use the statistical method to analyze and process the acquired data. By usingthe reduction ratio of the displacement and the stress, we can compare the four kinds ofunions and know which union is favor to enhance the ability of anti-deformation. And alsocan compare the variation of stiffness and strength between the eight experiments of model2. By the differential ratio of displacement and stress, we can discover the changes betweenthe adjacent experiments of the eight experiments. Using the increment ratio of the usedarea by square root and quality. Througth the deformation index which called DI, themaximum displacement called△D_max, the ultimate displacement called△D_ult, the peakacceleration and the time corresponding, the maximum internal energy and the ultimateinternal energy and the time corresponding, the application of model2in the closed rings ofbus body can help enhance the safety of rollover crash.The result reveals that, there are significant differences in different unions of the abilityof anti-displacement, the main conlusions of the study are:（1）The window pillar or door pillar and the vertical beam meet the dimensionalcharacteristics of thin-walled bar, they only beare bending load when rollover crash, so itcan use the theory of thin-walled beam to analyze the stress characteristics of the side wall of bus body, because the maximum bending moment happens in the connection regions ofthe waistrail beam and window pillars, the stress at these regions are maximum, as toovercome the weakness of the unions we need use changing cross section design;（2）The deformation index called DI and the method of penetration of contact can betterreflect the deformation characteristics, and can quantitatively evaluate the degree ofinvasion of the survival space;（3）Model2compared to the other three unions, it can bear greater load;（4） When the height of the arc of the union increase from70mm to143.5mm, theability of anti-deformation can enhance as the size increasing of the structure of the union,when the height of the arc of the union increase10.5mm, the displacement decrease0.302857mm, and the stress reducing2.32857MPa;（5）When the height of arc of the union changes from70mm to143.5mm, the squareroot of the increment of the area which used increase from76mm to147mm, and incrementof quality increase from0.0908Kg to0.3396Kg, comparing to the total consumption of areaof material and the total weight of the bus body, these increments are very small, and can beneglected;（6）The thickness of the material has very little effect on the ability of theanti-deformation of the T-union, between the thickness of1.5mm and2mm, the change ofthe stiffness only is3.13%and the change of strength only is1.41%;（7）The application of model2in the closed rings in the bus body can significantlyenhance the rollover safety.This research was sponsored by the Shaanxi Province Natural Science Fund Project.