【作者】 张斌；

【导师】 钟志华； 杨济匡；

【作者基本信息】 湖南大学 ， 车辆工程， 2010， 博士

【摘要】 在高度工业化国家,汽车设计和道路交通的改善直接减少了交通事故发生率和人员的伤亡。但是,车辆碰撞事故仍然是交通伤亡的首要原因,据世界卫生组织最近一次的全球统计,2004年全世界约有120万人死于车辆交通事故。而车辆交通事故中轿车侧面碰撞是非常危险的一种碰撞形式。由于没有足够的缓冲吸能区间,侧面碰撞相比正面碰撞更容易引起严重的人员伤亡。头部损伤和胸部损伤是车辆侧面碰撞中常见的损伤类型,并且是造成重伤和死亡的主要原因。由此导致的伤亡、治疗和赔偿给社会带来了大量的经济损失。因此开展头部和胸部损伤形式、损伤机理、耐受限度和防护方法的研究具有重要的社会意义和现实意义。本论文主要目标为:研究车辆侧碰撞事故中乘员的生物力学响应;侧面碰撞事故中乘员头部及胸部的损伤机理;头部各种物理参数与损伤风险的关系;探索了乘员侧面碰撞中头部及胸部的保护方法;降低胸部损伤参数的方法;胸部安全气囊的防护效率。为实现以上目标,采用了多刚体动力学与有限元相结合的研究方法对侧碰撞中的损伤生物力学问题和人体防护技术进行了深入的分析研究。主要研究内容如下。首先基于人体解剖学结构进行了有限元头部模型(HBM-Head Brain FE Model)的改进和验证工作,利用该颅脑模型评估了侧碰撞安全气帘对乘员头部的保护效果。而后,采用ES2(Euro Side 2)侧面碰撞假人模型评估了车门内饰板优化对提高乘员胸部保护的效果,进而评估了胸部安全气囊对乘员胸部的保护效果。改进了湖南大学开发的头部有限元模型的整个网格结构,细化了部分解剖学组织结构,比如胼胝体、脑桥和第三脑室,同时提高了脑脊液的生物逼真度。改进的头部模型基于成年男子头部的主要解剖学结构,包括由坚质骨组织和松质骨组织组成的颅骨骨骼、硬脑膜、软脑膜、大脑镰、大脑皮层、脑脊液、大脑、小脑和脑干。该模型的质量为4.36kg,共有57043个节点、51728个实体单元和11984个壳单元。模型的材料参数来自文献资料。将头部模型对照Nahum实验数据进行了验证。结果表明,颅脑模型具有良好的生物逼真度,可用于脑损伤研究,尤其适用于颅内应力应变分布、颅内压力等损伤相关参数的研究和约束系统参数的评估研究。利用有限元仿真对侧碰撞安全气帘的保护效率进行了分析研究。建立了驾驶员头部模型与轿车B柱碰撞的有限元模型。通过与侧面碰撞试验结果对比验证了该有限元模型的有效性。进而分析了头部模型与安全气帘的碰撞响应,计算得到损伤相关的碰撞响应物理参数,包括von-Mises应力、剪应力、冲击压力、对冲压力及相关损伤风险曲线。通过实验设计对安全气帘的气体质量流率和泄气系数进行了优化,结果表明,安全气帘的防护效率得到了改善。有限元颅脑模型是一个有效的工具,可以用来研究乘员头部损伤,评估保护装置的保护效果。乘员胸部也是侧碰撞中容易造成较严重损伤的部位。为了提高侧碰撞中乘员胸部的保护效果,利用有限元技术和优化方法进行了胸部损伤的研究,主要研究内容为车门内饰板的优化。建立了整车侧面碰撞有限元模型,通过与试验结果对比验证了该模型的可靠性。考虑汽车侧围结构的碰撞安全性,由整车侧撞有限元模型导出了轿车侧围子结构模型。计算得到胸部损伤参数RDC(Rib Deflection Criterion)值,采用响应面法进行了车身侧围结构仿真优化。将胸部损伤参数RDC值从52.66mm降低到41.02mm。仿真结果表明:基于响应面法的子结构模型可将汽车侧撞安全性优化时间缩短至传统整车模型方法的五分之一。优化后的胸部损伤参数明显降低,满足侧撞乘员保护法规要求。轿车侧面结构优化后,通过加装侧碰撞胸部安全气囊,进一步提高轿车侧碰撞中对乘员胸部的保护效果。胸部安全气囊安装于座椅内,结合变量筛选技术和二阶响应面法进行轿车侧碰撞安全气囊的优化研究。整个优化研究的过程包括:整车有限元模型的建立及验证,耦合侧碰撞安全气囊模型,筛选匹配敏感因子和优化设计等步骤。最终以胸部损伤参数为依据,分析出影响侧气囊保护效率的关键匹配设计变量,即侧碰撞安全气囊的安装高度和与人体的距离,通过对关键变量进行优化设计,可将胸部压缩参数RDC值降低23.1%。通过以上研究,分析了侧碰撞事故中乘员的生物力学响应、头部及胸部的损伤机理、损伤相关的物理参数与损伤风险。探索了乘员侧面碰撞中头部及胸部的保护方法。为头部及胸部侧面碰撞损伤生物力学研究和汽车被动安全性开发设计提供了重要的手段和参考依据。更多还原

【Abstract】 Improvements in roads and automobile design have steadily reduced injury and death rates in traffic accidents in all industrialized countries. Nevertheless, automobile collisions are the leading cause of traffic injuries, with an estimated total of 1.2 million cases around the world in 2004 according to world health organization’s latest record. The side collisions of passenger cars are a particularly dangerous form of vehicle accident, because there is not enough space for padding that can absorb energy. Compared to frontal collisions, side ones are more likely to cause casualties. Head and chest injuries in side impacts are very common. Moreover, these types of injuries are usually serious and can lead to death. Such fatalities and the treatment of head and chest trauma from road accidents result in a lot of social and economic costs. Therefore, it is vital to conduct research on the types of injuries, injury mechanisms, injury tolerance, and protective measures.This thesis aims at the study of occupant biomechanical responses in vehicle side impacts, investigation of the head and chest injury mechanics, identification of the relationship between physical parameters and injury, development of protective solutions for reduction of the head and chest injury risks from side impacts. To achieve the objectives mentioned above, the multi-body dynamic method and the finite element (FE) method were used to study the injury biomechanics problem and human protection techniques. The conducted researches is summarized as follows. Firstly, the modeling and validation of an FE head model were carried out based on human anatomical structures. The effect of protective devices in side impacts such as the air curtain was evaluated by using this model. Also the effect of an optimized inner panel as well as the thorax airbag was evaluated with the ES-2 dummy model for improving thorax protection.The entire mesh of the finite element head model, developed previously in Hunan University was improved. Several structures as the corpus callosum, pons, and 3rd ventricle as well as the representation of cerebral spinal fluid (CSF) were improved. The improved FE model of the head was based on anatomical structures of a male adult head. This model consists of the skull with representation of compact and trabecular bones, brain with dura and pia mater, falx cerebri, cerebral cortex, cerebral spinal fluid, cerebellum and brain stem. The model includes 57,043 nodes, 51,728 solid elements and 11,984 shell elements, with an effective mass of 4.36 kilograms. Material parameters of the model mainly come from literature. Based on experimental data from Nahum’s study, the HBM head model was validated regarding force and stress distribution. The results showed that the simulation and experimental results agree well. The model has high biofidelity and can be used in studies on brain injury, particularly once involving investigation of intracranial stress and strain distribution, intracranial pressure and other injury related parameters, as well as in the assessment studies of restraint systems.An FE approach was applied to evaluate the protective efficiency of the air curtain. An occupant head impacting a B-pillar was simulated using the HBM head model and a car model. The validity of this car model was evaluated by using the results from a side crash test performed within C-NCAP. The impact responses of the HBM head impacting an air-curtain were analyzed using calculated injury parameters, including the distribution of von Mises stress, shear stress, coup and contrecoup pressure. These parameters were used for assessment of the injury risk to occupants. Furthermore, an optimization of the safety air-curtain was conducted in terms of the mass flow rate and permeability coefficient by using the DOE procedure. The results show that the HBM is an effective tool for the analysis of the brain injury risk and for the evaluation of the performance of the protective devices.The human chest is also likely to be exposed to serious injuries in side collisions. In the study the FE simulation and optimization methods were used to improve the protection level of the chest in side impacts. The main effort was placed on the optimization of the response of the door trim panel. An FE model of a full scale vehicle to simulate side impacts was developed. The validity of the model was evaluated through a comparison with a side crash test performed within C-NCAP. Considering the crash safety of the car side structure, a sub-structure model of the car side assembly was derived based on the FE model mentioned above. Simulation and optimization of the car side structure were carried out using the response surface method (RSM). The chest injury parameters were calculated in terms of rib deflection criterion (RDC), which was reduced from 52.66mm to 41.02mm. The results of the simulation demonstrated that the duration of optimization using sub-structure model and RSM can be reduced to one fifth, compared with the traditional method of using a full scale model. The injury related parameters such as the RDC were lowered to a level that meets the C-NCAP requirements of occupant protection in side impacts. After optimization of the side structure of the car, enhancements of the chest protection through an additional thorax airbag was further evaluated. The airbag was mounted in the seat and optimization of the thorax airbag was done by a combination of the variable screening technique and the quadratic response surface method. The study was carried out through the following steps: development and validation of a full-scaled car finite element model; coupling of a thorax airbag model; screening sensitive variables and optimizing design. Finally, based on the RDC, the key parameters affecting the thorax airbag’s efficiency were analyzed. It was found that the level where the airbag is installed and the distance between the airbag and passenger are two crucial parameters influencing the safety level. The results from optimizations showed that the RDC could be reduced by 23.1%.Based on the research mentioned above, the multi-body dynamic models and the finite element method are valuable approaches for study impact responses and injury biomechanics of the occupant head and chest in side impact accidents. The developed HBM head model is helpful in development of new protective system, which provided means for assessment of safety performance in new car design.更多还原