基于真实交通事故损伤及其数值再现的行人头部损伤动力学机制研究

Head injury is the main injury type in severely-injured and fatal pedestrian accident cases. Injury thresholds under head dynamic response are widely used as the criteria for vehicle safety assessment in many countries. However, characteristic dynamic responses for pedestrian head injuries are still not clear due to the complexity of pedestrian head injury mechanism in real-world vehicle collisions. Therefore, the current project aims at investigating characteristic dynamic responses for pedestrian head injuries by analyzing the dynamic mechanism of pedestrian head injuries based on real-world accident data and numerical reconstruction of real-world injuries. Firstly, pedestrian injury characteristics and parameters for impact boundary condition in accident cases are investigated based on the information directly extracted from real-world accident data. Secondly, a total human body finite element model which is satisfied for reconstruction study of real-world pedestrian injuries is developed with the purpose of high biofidelity and computationally time-effective, and then a reconstruction study for kinematics of real-world pedestrian injuries is conducted. Finally, characteristic dynamic responses for pedestrian head injuries in vehicle collisions are investigated based on comprehensive understanding of the dynamic mechanism of pedestrian head injuries, and evaluation functions of pedestrian injury risk are established based on these characteristic dynamic responses. The findings of this project could provide important technical references for the improvement of vehicle safety assessment criteria and vehicle safety design.

头部损伤是交通事故中行人重伤和死亡的主要损伤类型，世界各国普遍将组织损伤耐受极限对应的头部动力学特征响应作为车辆安全性评价的准则。但由于真实事故中的行人头部损伤机制高度复杂，现有表征头部损伤的动力学特征响应仍未被广泛认同。本项目拟采用“以真实事故数据为基础—以事故损伤数值再现为手段—以提取表征头部损伤的动力学特征响应为目标”的思路展开车辆碰撞中的行人头部损伤动力学机制研究。首先，提取真实事故信息，研究事故中的行人头部损伤特征，构建事故碰撞工况参数系统模型；然后，建立满足行人头部损伤再现逼真度和时效性要求的整人有限元模型，开展真实车辆碰撞中的行人头部损伤动力学数值再现研究；最后，结合真实事故头部损伤特征，深入研究行人头部损伤动力学机制，提取表征行人头部损伤的动力学特征响应，构建基于特征响应的行人头部损伤风险评估函数，为健全车辆安全性评价准则和改善车辆安全性设计提供科学依据。

道路交通事故每年在全球范围内造成多达数十万行人死亡和巨大经济损失，车辆-行人碰撞安全已成为关系到人们生命财产安全的重大社会问题。行人事故中多达64%的死亡案例和43%的重伤案例都源自头部损伤，头部损伤是值得重点关注的行人损伤类型。但是，在车辆安全评价体系中，一方面测试工况中对行人头部碰撞边界条件进行了较大简化，另一方面又仅仅将头部动力学响应中的线性加速度作为车辆行人头部防护性能的评价准则，因而一直受到学术界的质疑。本项目通过损伤生物力学与车辆工程学科交叉，基于真实交通事故数据及损伤过程再现，研究了车辆碰撞中的行人头部损伤特征、损伤再现方法及损伤动力学机制，具体包括：基于真实车辆-行人碰撞事故信息和原始资料，厘清了行人头部损伤类型及其分布规律，发现颅骨骨折和局灶性脑损伤是行人头部损伤主要类型，且两者存在强关联性，为行人头部损伤防护研究指明了方向；提出了基于肌肉和皮下脂肪等效机械力学镂空化模拟的人体有限元模型建模方法，建立并验证了兼具仿真时效性和生物逼真度的行人有限元模型，为行人损伤和防护研究提供了重要工具；通过典型车辆碰撞事故中的行人头部损伤数值再现，深入研究了车辆碰撞载荷下的行人头部-车辆碰撞边界条件特征和头部损伤动力学机制，发现：车辆碰撞中行人头部WAD在1.5m到2.3m之间浮动（均值1.84m），80%案例头部线性和旋转速度分别低于45km/h和40rad/s，77%案例的头部接触时刻在50-140ms之间，70%案例头部碰撞角在40°到70°之间浮动（均值53°），行人头部损伤跟其线性和旋转响应均密切相关，考虑线性加速度和耦合线性及旋转响应的损伤动力学准则对行人头部损伤具有较强表征能力，为车辆安全性设计和评价提供了理论基础和科学依据。