正面偏置碰撞载荷中儿童乘员损伤机理与自适应约束系统研究

Vehicle front small overlap crash is one of the most severe accident scenarios，which causes injuries and deaths of the child occupants. Moreover, the usage of the child restraint system （CRS） is very low in China and the rate of misuse is high. Therefore child occupant safety in small overlap crash become a novel and important research topic. In the existing regulations the assessment of child occupant safety is carried out only by using sled test in crash condition of a single forward acceleration load pulse. It is quite different from the 3-dimensional dynamic loads to the child occupants in a real world small overlap crash. There thus exist notable limitations for the current assessment method to evaluate child occupant safety in real world front offset impacts. In the proposed project, a new finite element (FE) model for a 6-year old child is developed by scaling the THUMS AM50 based on biomechanical similarity theory and scaling laws, the anthropometry parameters are based on the characteristics of Chinese 6-year old children. The new 6-year old FE model and an existed 3-year old FE model are used to investigate the child occupant dynamic response and injury mechanism in the 25% overlap and 40% offset impacts. Furthermore, the influence of design parameters of the children restraint system on the protective performance for the 3- and 6- years old children is analyzed by defining different child posture, as well as the operating conditions of proper use and misuse. A weighted evaluation criterion of child injuries in front offset impact is developed based on the injury related physical parameters of head and chest. A methodology for an adaptive optimization design of the restraint system is developed based on the multi-objective genetic algorithm. Development a new porotype of adaptive protection child restraint system. The results from proposed project can be served as fundamental knowledge in CRS design for child occupant protection from vehicle frontal offset impact.

汽车小偏置碰撞是导致儿童伤亡的重要交通事故形态之一。我国儿童安全约束系统的使用率低，误用率高，儿童乘员安全已成为一个新的重要研究课题。现有法规中的台车试验动态评价方法仅采用单一加速度，与实际偏置碰撞中儿童乘员的三维动力学载荷相比有显著差异，因此现有评价方法存在明显的局限性。本项目应用生物力学相似原理和比例缩放法，基于已验证的50%分位人体数值模型，缩放成具有6岁儿童特征参数的人体模型。利用该模型和已有的3岁儿童模型研究在25%和40%偏置率碰撞条件下的儿童乘员动力学响应和损伤机理，并分析3岁和6岁儿童约束系统在不同的初始姿态及正确和误用工况下的设计参数对防护性能的影响。基于儿童头部、胸部等损伤参数构建偏置碰撞损伤加权评价准则。基于回归近似模型和多目标遗传算法的约束系统自适应优化方法，研制一款新型的自适应儿童乘员约束系统样品。研究成果可为儿童乘员在偏置碰撞中的损伤防护提供理论基础和设计依据。

汽车小偏置碰撞是导致儿童伤亡的重要交通事故形态之一。我国儿童安全约束系统（CRS）的使用率低，误用率高，儿童乘员安全已成为一个新的重要研究课题。现有法规中的台车试验动态评价方法仅采用单一加速度，这与实际偏置碰撞中儿童乘员的三维动力学载荷有显著差异。.项目首先综合有效地运用动物实验、假人碰撞测试和有限元数值仿真方法研究了不同约束载荷下3岁儿童胸腹部的损伤风险和机理。结果表明前置护体型CRS中儿童胸腹部的损伤风险比普通五点式CRS更大。当采用THUMS儿童人体模型进行数值仿真时，前置护体型CRS中儿童的胸部压缩率达到了39.25%， AIS 4级的损伤风险为50%。相比于普通五点式CRS，前置护体型CRS约束的小猪还出现了肋骨无骨折但冠状动脉撕裂、肺挫伤等胸腹部损伤。.进一步地，采用Hybrid III 3岁和6岁儿童假人建立了不同儿童约束系统载荷下正面碰撞台车数值分析模型，通过建立假人胸部运动力学方程，分析了胸部加速度和胸部所受内外力的相互关系。研究表明假人胸部加速度与胸部所受的外力和内力都相关，其中外力是胸部加速度的最重要的影响因素，其主要来自前置护板、五点式安全带和汽车安全带。.基于整车有限元仿真分析，研究了儿童乘员在40%和25%重叠率碰撞条件下的动力学响应和损伤机理。研究表明：偏置碰撞会导致儿童乘员遭受横向载荷而偏转并可能与车门发生接触。对于3岁儿童，普通五点式CRS中儿童乘员的前向位移均超过了600 mm，远大于法规值550 mm。对于6岁儿童，无靠背增高垫CRS中儿童乘员出现了下潜现象且头部和胸部损伤较高。基于此，提出了具有限力作用和可充气的安全带，发现二者均能降低乘员损伤，而限力式安全带更有效。.本项目厘清了儿童乘员在不同约束载荷下损伤风险以及胸腹部损伤机理，推动了儿童乘员腹部法规准则的建立；研究了儿童乘员在不同偏置率碰撞下的动力学响应和损伤风险，提出具有可温控调节和五点式安全带预警的智能儿童约束系统。本研究成果将为儿童乘员在偏置碰撞中的损伤防护提供理论基础和设计依据。