【作者】 杨杏梅；

【导师】 杨济匡；

【作者基本信息】 湖南大学 ， 车辆工程， 2010， 博士

【摘要】 近几年来,道路交通事故每年导致约26万名儿童丧生,1,000万名儿童受伤。其中,车内儿童占有相当比重,汽车儿童乘员安全性问题受到世界各国的高度重视。由于汽车装备的常规座椅、安全带约束系统和安全气囊主要针对成人设计,在汽车碰撞事故中儿童乘员面临的伤亡风险远远高于成人。国外早在20世纪60年代就已经开展了儿童乘员安全方面的研究,欧、美、日等许多发达国家对儿童乘员约束系统已有专门的法规要求并已实施。我国有关儿童乘员安全方面的研究已经起步,首个《机动车儿童乘员用约束系统》(征询意见稿)已经通过网上公示阶段,有望近期出台。汽车儿童约束系统专为儿童乘车安全设计,但它在我国的实际使用情况存在两个问题:第一,使用率低;第二,误用率高。因此,开展儿童乘员损伤防护技术研究对于当前的中国具有重要的经济价值和社会意义。本文旨在研究儿童乘员交通伤流行病学特征;分析典型事故中儿童乘员的动力学响应;确定儿童乘员的损伤原因和损伤机理;评价不同碰撞条件下儿童约束系统的防护效率;改进儿童乘员的损伤防护技术;为提高儿童乘员安全性设计提供可靠的理论依据和有效的研究方法。为此目的,对美国CIREN数据库(1996-2005年)、FARS数据库(2000-2007年)及中国长沙市交警事故数据库(2001–2007年)中的儿童乘员事故数据进行了统计分析;采用多体动力学和有限元模型进行了事故重建分析,提出了一种基于多种软件(PC-Crash,LS-Dyna和MADYMO)相结合的儿童乘员两车碰撞事故重建方法,并将该重建方法应用到从德国GIDAS数据库中挑选的一起典型前碰撞和一起典型侧碰撞事故案例;进而采用多体动力学方法深入细致地研究了前碰撞条件下约束系统误用对防护效率的影响,构建了多项式回归(PRG)、Kriging及RBF神经网络代理模型,对儿童约束系统的设计参数进行了优化,并利用能量效率理论对儿童乘员碰撞过程中动能的耗散进行了深入分析;在侧面碰撞条件下,采用MADYMO软件中的PSM方法建立仿真模型,深入研究了不同碰撞角度下儿童增高座椅的防护效率和约束系统不同使用情况下侧面安全气囊的防护效率,并利用RBF神经网络构建代理模型,对影响儿童乘员和成人乘员损伤防护的侧面安全气囊的主要设计参数进行了优化研究。对国内外的儿童乘员事故数据进行统计分析发现,小型客车(轿车占较高比例)是主要事故车型;两车事故是主要事故类型;前碰撞和侧碰撞是主要事故形态;伤亡儿童乘员中,4-8岁儿童占有较高比例。与儿童乘员损伤风险密切相关的因素有碰撞类型、座椅位置、碰撞严重度、约束类型、儿童的年龄(体重)以及约束系统的使用情况等。使用的约束系统类型不同,儿童乘员的损伤部位也不尽相同。对典型儿童乘员事故进行重建的结果表明,使用提出的重建方法得到的事故车辆最终停止位置、运动轨迹、变形及儿童乘员损伤情况等都与事故案例记录基本吻合,这在一定程度上证明了该重建方法和模型的有效性。此外,从前碰撞事故重建结果可知,后倾的前排座椅靠背是导致儿童头部损伤的主要原因,头胸部运动的不同步导致了儿童颈部的损伤。从侧碰撞事故重建结果可知,侵入的车门是导致儿童乘员严重损伤甚至死亡的主要原因。前、侧碰撞事故重建结果都表明,安全带织带是导致儿童乘员胸、腹部软组织擦伤的主要原因。对前碰撞事故形态中儿童乘员的损伤防护技术进行研究的结果表明,与正确使用儿童约束系统情况相比,误用降低了儿童约束系统的防护效果,使得儿童乘员损伤风险增加;除Kriging模型外,PRG和RBF神经网络模型最优设计点对应的目标函数的仿真值都小于实验设计样本点中的最小值,PRG模型优化设计点处的目标函数的仿真值最小,比实验设计样本中的最小值降低了约14.7%,三个代理模型中,RBF神经网络模型的优化结果与仿真验证结果之间的误差最小,仅为2.6%,基于多个代理模型的优化方法有助于设计者鉴定设计空间不同区域内的其他优化结果;儿童乘员胸部加速度与缓冲能量效率并不直接相关,而是由安全带吸收的能量效率决定,安全带吸收能量效率越低,胸部加速度值也越低,安全带松弛会增加安全带吸收能量效率,与带定位式增高座椅相比,使用嵌入式增高座椅,安全带吸收能量效率也会增加。对侧碰撞事故形态中儿童乘员的损伤防护技术进行研究的结果表明,对于在车辆轴向方向上有运动分量的侧面碰撞,儿童增高座椅具有一定的保护效果,对于在车辆轴向方向上没有或有很小运动分量的侧面碰撞,儿童增高座椅的保护效果并不理想;对于误用增高座椅的儿童乘员,展开的侧面安全气囊不会明显增加其头、胸部损伤风险,对于正确使用增高座椅的儿童乘员,展开的侧面安全气囊能够降低其头、胸部损伤风险,无论误用或正确使用,颈部损伤风险都需视实际碰撞情况而定;优化后的侧面胸部气囊使得儿童乘员的头部合成加速度值和成人乘员的胸部VC值比初始模型中的相应值分别降低了约17.9%和49.7%,优化后的侧面胸部气囊既能有效保护儿童乘员又能有效保护成人乘员。随着轿车进入中国家庭步伐的加快,儿童乘员碰撞安全性问题越来越突出。本文从宏观角度对儿童乘员交通伤流行病学特征进行研究;从微观角度对典型儿童乘员事故进行重建研究;具体对发生频率较高的前、侧碰撞事故形态中儿童乘员的损伤防护技术进行了深入细致的研究。本论文可望对我国全面深入开展儿童乘车安全保护研究起到积极的推动作用。更多还原

【Abstract】 There are around 260,000 child fatalities and 10,000,000 injured in traffic accidents worldwide every year. The safety of children in cars is a significant issue in the world today. The vehicle seat, safety belt and airbags are designed for adults. The injury risk for children is higher than for adults in car collisions. Studies about child occupant safety were started from the 1960s around the world. The European countries as well as U.S. and Japan established regulations for child restraint systems. The child occupant safety researches have been begun in China. The to-be-commented draft of“Restraining Devices for Child Occupants of Power-Driven Vehicles”has been published and will come into effect in the near future. The child restraint systems (CRSs) are designed for children. Unfortunately, there are two major problems associated with the use of CRSs in China. First, the usage rate is rather low. Second, the CRSs are often misused for children in cars. It is very important to study the child occupant protection in China.This thesis aimed at study of the characteristics of child occupant traffic injury epidemiology; analysis of the dynamics responses of children in the accidents; determination of child occupant injury reasons and mechanisms; evaluation of the efficiency of child restraint system under different crashes; improvement of child restraint system design in reliable and effective ways. To this end, child occupant accident data from the CIREN database (from 1996 to 2005), FARS database (from 2000 to 2007) and Changsha traffic police database (from 2001 to 2007) were analyzed statistically, the descriptive statistics and multinomial logistic regression methods were used; the multi-body dynamics and the finite element models were utilized in the accident reconstruction analysis, proposed a method of combining PC-Crash, LS-Dyna and MADYMO softwares to reconstruct the child occupant accident cases, the method was used in the two cases (frontal and side impact cases) selected from the GIDAS database; then employed the multi-body dynamics methods in frontal impact to study the impact of CRSs misuse, constructed PRG, Kriging and RBF neutral network surrogate models to optimize the design parameters of CRS, and the energy efficiency theory was used to analyze the dissipated kinetic energy of child occupant in vehicle impacts. Finally, PSM method was used to construct simulation models in side impacts, the efficiency of protection of booster seat in different impact angles and of side airbag in different uses of restraint system were studied, and RBF neutral network was used to construct the surrogate model to optimize the parameters of side thorax airbag based on the injury protection of child occupant and adult occupant.The statistical results of child occupant accident data from U.S. and China indicated that the small passenger car is the main type of vehicle (the saloon cars are most) involving child occupants, the two vehicles collision is the main type of accident, frontal and side impacts are the most frequent accident configurations, and the children aged from 4 to 8 account for a high proportion among casualties. In addition, the factors associated with the injury risks of the child occupant are impact type, seat position, impact severity, restraint type, the child’s age and the use of the restraint system. The injury regions vary with the type of restraint system used.The accident reconstruction results indicated that the rest positions and wheel traces of two cars were comparable with ones in real world accident, the intrusions and deformations of door of the objective car were comparable with that of accident car, the dynamic responses of child dummy reflected well the injury risk of the objective child in crash accident, and the reconstruction method is feasible and effective. In addition, in frontal impact case, the head injury was mainly caused by the impact on the headrest of the reclined front seat, the nonsynchronous motion between head and thorax caused the neck injury. In side impact case, the head injury was mainly caused by the headrest of booster seat and intrusion of door, which resulted in the death of the child occupant. The results from two reconstructions (frontal and side impact cases) indicated that the thorax and abdominal soft tissue organ were injured by webbing of seat belt.The study results of child occupant injury protection in frontal impacts indicated that misuse will reduce the protective effects of CRS and increase the injury risks of child occupant comparing the correct use of CRS. Except for the Kriging model, the optimal values suggested by the surrogates for the objective function PCOMB were smaller than those obtained within the sample. The optimization using the PRG model resulted in the smallest objective function value (the best solution found), a 14.7% improvement over the minimum value of the sample. The RBF neural network model presents the smallest difference between the surrogate estimations for PCOMB and the corresponding values obtained using MADYMO. The use of multiple surrogates has helped identify alternative optimal solutions corresponding to different regions in the design space. In addition, it was concluded that the chest acceleration was not dependent on the ride down energy efficiency but dependent on the energy efficiency absorbed by the belt. The chest acceleration will decrease with the reduced energy efficiency absorbed by the belt. The belts having slack or using built-in booster seat will increase the energy efficiency absorbed by the belt.The study results of child occupant injury protection in side impacts indicated that booster seat will produce some benefits when an axial motion component exists in the objective vehicle. When the axial motion component does not exist or is very small, the booster seat may not provide enough protection for children. A misused child booster seat will not increase injury risks from the side airbag to the head and thorax. A child using the booster seat correctly may receive the protective benefits of the side airbag for head and thorax. Whether a child misuses or uses correctly booster seat, the injury risks of the neck depends on the actual impact situations. The optimal values suggested by the surrogate models for the objective functions were smaller than those obtained from the initial models. Compared to the head resultant acceleration of the child, a 17.9% improvement over the initial value of the initial model was found, and compared to the chest VC value of the adult, a 49.7% improvement over the initial value of the initial model was found. The thorax side airbag can protect not only the adult but also the child effectively after optimization.In recent years, the number of newly registrated passenger cars in China is increasing rapidly. Therefore, the issue of crash safety of child occupants is becoming more and more serious. The characteristics of child occupant traffic injury epidemiology were studied from the macro-perspective. The accident reconstruction was studied from the micro-perspective. The injury protection of child occupants in frontal and side impacts were studied further, in detail. The findings from this study may contribute to the child occupant protection research for passenger car impacts in China.更多还原