【作者】 彭倩；

【导师】 杨济匡；

【作者基本信息】 湖南大学 ， 车辆工程， 2012， 博士

【摘要】 车辆翻滚是一种伤亡风险极高的事故形态。据统计，美国每年翻滚事故中丧生人数达到近万人，约占机动车碰撞死亡总数的三分之一；在我国，乘员安全同样受到翻滚事故的严重威胁。车辆顶盖侵入是翻滚事故中乘员伤亡的主要原因，也是当前翻滚安全试验程序对车身结构强度的主要考察参数之一。美国联邦机动车辆安全标准FMVSS216是翻滚安全领域全球影响力最大的强制性法规，但其加载条件一直饱受争议；同时该试验在准静态条件下开展，难以反映真实事故的特点。轿车的JRS (Jordan Rollover System)试验在动态翻滚条件下开展，具有较高的代表性和可操作性；目前JRS的试验条件设置是相关试验开发研究的重要课题。此外，顶盖防护装置的开发也是该领域的研究热点。基于FMVSS216法规，开展双侧顶盖抗压性能虚拟试验研究。首先建立了车辆顶盖抗压有限元模型并通过准静态抗压试验进行验证。采用全因子正交试验方法按照顶盖准静态抗压试验条件对9组侧倾角以及4组俯仰角进行组合试验，研究加载角度对顶盖强度的影响，并对近侧及远侧顶盖抗压性能差异进行评估；然后对车身关键结构件以及挡风玻璃在顶盖抗压中的作用进行敏感性分析；最后分别建立近、远侧顶盖抵抗力的响应面模型，通过优化评估来确定最严格的顶盖加载角度。结果表明：近侧顶盖的强度整体上高于远侧；挡风玻璃在顶盖抗压中贡献强度的变化范围为18%~37%；此外，俯仰角和侧倾角的变化对顶盖抗压性能影响十分显著。俯仰角相同，侧倾角范围在10°~45°时，顶盖强度随着角度增加而持续下降。侧倾角相同，俯仰角范围在5°~10°时，顶盖强度均随着角度增大而明显降低。从顶盖强度变化范围来看，侧倾角对远侧强度的影响更大，而俯仰角对近侧强度影响更显著。综合优化评估来看，45°侧倾角以及10°俯仰角组合为最严格的顶盖加载角度。基于JRS试验程序，开展整车动态翻滚安全性能研究。建立整车JRS虚拟试验模型后通过顶盖冲击试验进行验证。在不同的初始侧倾、俯仰角度组合条件下，研究整车惯性响应以及顶盖抗压性能的变化。在既定初始角度下，分析车辆顶盖在准静态和动态试验条件下的性能差异。通过参数分析，研究JRS初始试验设置包括车辆跌落高度、翻滚速度以及移动路面初速度等对车辆翻滚响应特性的影响。试验结果表明，相同试验条件下，车辆远侧顶盖的侵入风险远高于近侧。初始侧倾角或初始俯仰角增加时，远侧顶盖侵入程度显著上升，而近侧侵入明显下降。从车辆在准静态和动态试验中顶盖性能差异来看，FMVSS216试验中近侧顶盖的加载距离标准过于宽松；在翻滚的惯性作用下，远侧顶盖抵抗力峰值的增加幅度为17%~72%。在不同初始跌落高度下，近侧顶盖侵入量、侵入速度峰值变化幅度分别为210%和92%，而远侧侵入程度无显著差异。在不同移动路面初速度下，远侧顶盖侵入量、侵入速度变化幅度分别为31%和63%，而近侧侵入程度无明显变化。在LS-DYNA模拟环境下，分别建立了沥青，水泥及泥土路面的有限元模型，基于JRS试验条件开展了道路路面对车辆翻滚响应特性的敏感性研究；分析不同道路刚度，摩擦系数对车辆惯性响应以及顶盖侵入特性的影响。结果显示，摩擦系数对车辆顶盖侵入的影响十分显著；而路面刚度对顶盖侵入特性影响很小。不同路面刚度下，远侧顶盖侵入量变化范围为2.2%~8.5%，侵入速度的变化范围为0.8%~4.8%。本论文分别采用加强型顶盖以及新型蛋盒式顶盖防护装置来提高车辆翻滚安全性。建立了蛋盒形结构的有限元模型，开展准静态抗压测试来研究蛋盒形的抗压变形特性并对有限元模型进行验证。在JRS基准试验条件下，分别对加强型顶盖以及蛋盒形盖板对翻滚过程中的防护性能进行研究。结果表明，在采用加强型顶盖、蛋盒式盖板的条件下，远侧顶盖侵入量分别减少31.4%和33%；而远侧顶盖侵入速度分别下降21.8%和26.6%；综合采用以上两种改进方法，远侧顶盖侵入量、侵入速度分别降低57%以及37.5%。更多还原

【Abstract】 Vehicle rollover crashes are complex events which result in relatively higher fa-tality rate than any other crash scenarios. In the United States, it’s indicated that therewere approximately10,000people killed as occupants involved in light vehicle roll-over crashes each year. This accounted for one third of occupant fatalities in crashes.In China, rollover crashes also critically threaten the occupant safety. It has been re-vealed that roof crush is a predominant factor accounting for fatalities and seriousinjuries of belted occupants in rollover crashes. Therefore the current test proceduresconcerning rollover have been particularly emphasizing on the roof mechanical beha-viors. As a unique compulsory legislation of rollover in the US, FMVSS216incurs alot of arguments due to the poor representative and its quasi-static loading manner.Jordan rollover system (JRS) is considered as a versatile test procedure that can wellrepresent the real world scenarios. It is also meaningful to develop some new me-chanisms to reduce the risks in rollover crashes.A study of double-sided roof crush was carried out by virtual testing in accor-dance with FMVSS216. A Ford Fiesta FE model was refined and validated against theroof crush test. A full factorial DOE (Design of Experiment) was then made based onvarying pitch and roll angles. Thereafter parametric analyses were conducted to in-vestigate the effects of body structure, windscreen, and the dynamic variables of rollangle and pitch angle on roof strength. Subsequently, the response functions con-cerning the resistance force of the double-sided roof were hence constructed with theresults from a series of virtual tests based on9levels of roll angle and4levels ofpitch angle. Finally, the worst loading conditions were evaluated using an optimiztionanalysis. The results show that roof strength is a function of the roll and pitch angles.In general, the roof on the near side performs stronger than the far side and greatlyinfluences the overall collapse behaviour. Within the127mm (5inch) crush, thestrength on both sides of the roof decrease as the roll angle varies from10°to45°.The variation of the pitch angle influences the resistance force. In addition, the con-tribution of the windscreen on the far side roof varies from18%to37%with differentloading angle combinations. From the virtual parametric analysis and optimisationcarried out, it further shows that the recommended stringent loading angle combina-tions in the newly updated FMVSS216roof crush test should be roll angle of45°and pitch angle of10°for both near and far side roof Load application.The dynamic behaviour of vehicle rollover was investigated based on JRS testprocedure. The Ford Fiesta FE model for rollover virtual testing was established andfurther validated against the roof impact test in dynamic condition. The mechanicalbehaviours including the roof intrusions and relevant resistance forces in the rolloverevents were investigated at varying combinations of initial pitch and roll angle. Af-terwards, the behaviour discrepancies on the roof were evaluated while the vehiclesubjected to quasi-static and dynamic test with fixed angle combinations. Then para-metric studies were carried out to assess the effect of JRS test setup involving dropheight, roll rate of the vehicle as well as the velocity of the moving roadbed. The re-sults reveal that the intrusion level on the far side is extremely greater than that on thenear side in the same test. As the initial pitch or roll angle rises, the intrusion on thefar side tremendously goes up, while it drops down sharply on the near side. Form thecomparisons between the quasi-static and dynamic test, it could be revealed that thecrush distance in FMVSS216is overestimated; in addition, the contribution of thedynamic inertia effect to the resistance forces on the far side varies from17%~72%.The initial drop height extensively results in an additional intrusion amount and in-trusion velocity by210%and92%on the near side respectively, whereas there is nosignificant difference to be found on the far side. With the varying velocity of movingroadbed, the maximum discrepancies are correspondingly31%and63%in terms ofroof intrusion and intrusion speed on the far side, while trivial differences could benoticed on the near side.Finite element models of road surface were established with regard to differenttypes of materials including bitumen, concrete as well as sandy soil in LS-DYNA. Asensitive study on the roof structural behaviour subjected to JRS test was then carriedout with different road types. Thereafter the effect of varying stiffness and the frictionfactors on the roof behaviour were conducted. The results indicate that roof intrusionis a function of the friction factor as shown in logistical regression equations; whilethe stiffness could hardly make any significant effect. With different stiffness of theroad surface, the discrepancies in intrusion amplitude and intruding speed vary from2.2%~8.5%and0.8%~4.8%correspondingly.Two approaches were proposed to enhance the crashworthiness of the vehicle inrollover crashes in this thesis. One is a strengthen roof and another an egg-box styleroof panel. A finite element model of egg-box panel was established and validatedagainst the relevant quasi-static crush tests which particularly focus on the collapse behavior of the egg-box. The strengthen roof and the egg-box panels were then re-spectively employed in the JRS test. As depicted in the results, the intrusion on the farside could be reduced by31.4%and33%respectively with the strength roof and theegg-box roof panel; while the intruding speed could be decreases by21.8%and26.6%correspondingly with the strength roof and the egg-box roof panel. Ultimately, theroof that incorporates the two approaches can considerably reduce the far side intru-sion amplitude and intrusion speed by57%and37.5%respectively.更多还原