【作者】 王方；

【导师】 杨济匡；

【作者基本信息】 湖南大学 ， 车辆工程， 2014， 博士

【摘要】 人体胸部损伤在车辆交通事故中的发生非常普遍,研究表明在车辆交通事故造成的人员死亡中,有30%是由胸部损伤导致,而在所有车辆交通事故导致的乘员致命和严重伤害中胸部损伤位居第二,仅次于头部损伤。同时行人碰撞事故数据也表明,在行人碰撞事故尤其是行人与微型客车的碰撞事故中,经常被忽视的胸部和上腹部损伤也占据了较大的比例,其发生概率仅次于头部和下肢损伤,特别是在碰撞速度较高的严重事故中,行人胸部损伤发生的概率更为明显。因此,深入的了解人体胸部损伤生物力学对降低车辆碰撞事故中的人体胸部损伤风险具有重要的现实意义。人体胸部结构复杂,内部包含了心、肺、肝、脾、肾等重要内脏器官,而人体胸腔则起到保护这些重要器官的关键作用。在过去的几十年中,研究者们在胸部损伤生物力学领域做了大量的研究工作,但是在包括肋骨失效和胸部损伤准则等诸多问题上还有待进一步的研究。本文基于人体解剖学结构建立和验证了胸部有限元模型；进而利用开发的模型,选择三种基于von Mises应力和/或塑性应变的肋骨骨折失效模型,进行了不同载荷条件下的人体肋骨损伤分析；研究了胸部受到侧面冲击载荷时损伤评价准则的有效性；最后结合选取的失效模型和损伤评价准则将模型应用于行人与微型车碰撞中的胸部损伤分析和防护研究。文中建立了一个基于中等身材的中国男性人体解剖学结构的三维胸部有限元模型。模型描述了主要的胸部解剖学结构,包括人体胸椎、腰椎、肋骨、胸骨、肋间软骨、胸腹部器官和其他的软组织等等。整个模型由87000余个单元,63000余个节点组成。胸部骨骼和软组织的材料特性都来自于国内外文献资料。首先用肋骨三点弯曲实验对模型进行验证,对比分析了肋骨力-变形响应；然后借助肋骨前后方向加载结构实验验证了模型,比较分析的损伤参数包括准静态和动态加载条件下的肋骨力-变形响应、肋骨断裂位置、肋骨断裂时刻及该时刻的肋骨响应力；进而分别模拟胸部正面碰撞志愿者实验和尸体实验对模型进行了验证,主要分析参数是胸部力-变形响应；最后根据尸体实验对胸部模型进行了纯侧面碰撞和斜碰撞下的有效性验证,验证损伤参数包括碰撞力、胸部变形模式和力-变形响应。选取了三种分别基于von Mises应力和/或塑性应变分析的肋骨骨折失效模型：T1,T2和T3,将其运用到本文所建立并验证的人体胸部有限元模型中,模拟分析了实验中所记载不同载荷形式下的肋骨骨折,并对比研究了三个肋骨骨折失效模型与不同载荷形式下的损伤参数。模拟肋骨三点弯曲载荷中的肋骨力-变形响应发现,运用T3的模拟结果与实验数据吻合得较好；模拟肋骨前后方向加载实验,分析了肋骨力-变形响应、肋骨断裂时刻及该时刻的肋骨响应力,并对肋骨断裂位置截面进行了应力应变分析,运用T2的响应好于另外两种失效模型的结果；最后模拟了胸部正面碰撞块冲击载荷条件下的肋骨骨折,分析了不同碰撞速度下的肋骨骨折数及骨折位置的应力分布,运用T1所得到的肋骨骨折响应与实验结果更为接近。使用该胸部模型分析了人体胸部在侧面碰撞载荷下的损伤响应。首先进行了人体胸部在纯侧面碰撞和斜碰撞中不同碰撞角度下的碰撞块冲击仿真分析,得到了每个碰撞角度下的肋骨骨折数,以及与各个损伤评价准则相关的损伤参数响应峰值,包括碰撞力、胸部变形量、压缩比例、胸部侵入速度及脊柱加速度。基于肋骨骨折数和损伤评价准则的损伤响应,建立了相关性评价函数,对比分析了不同的损伤评价准则对胸部损伤预测和评价的有效性。最后,采用三个已有的微型车有限元模型和基于本文胸部模型所建立的行人模型,模拟分析了不同速度下行人与微型车发生碰撞时的胸部动力学响应和损伤参数,对比研究了不同的微型车前部结构和车辆碰撞速度对行人动力学响应和损伤参数的影响,这些损伤参数包括行人胸部碰撞速度、胸部变形量、基于TTI(Thorax Trauma Index)准则的胸部损伤等级(Abbreviated Injury Scale) AIS3+和AIS4+级损伤风险和肋骨骨折数。基于本文的研究可以得出如下结论：胸部有限元模型的仿真计算结果与实验验证数据吻合较好；在肋骨失效模型分析中,失效模型T1更适用于胸腔碰撞块冲击载荷分析；与其他的胸部损伤准则相比,TTI准则对人体受到侧面碰撞时的胸部损伤预测和评价最为有效；微型车与行人发生碰撞时会导致较高的行人胸部AIS3+和AIS4+级损伤风险,微型车前部结构和车辆碰撞速度对行人胸部损伤风险影响显著,在高速碰撞时,车辆前部结构对损伤风险的影响更大。更多还原

【Abstract】 Human thoracic injury could be observed frequently in vehicle traffic accidents. It was reported that about30%of all the reported deaths in road traffic accidents were related with thoracic injuries. Thoracic injuries of the occupants ranked second in number of fatalities and serious injuries recorded in passenger vehicle collisions, only secondary to head injuries. Traffic accident data have also indicated that thoracic and upper abdominal injuries are frequently occurred in Minicar-pedestrian collisions, which was only lower than those of head and lower extremity injuries, especially in high speed accidents the incidence of the pedestrian thorax injuries is rather high. It is therefore necessary to have a good understanding of the thoracic injury mechanisms in order to reduce the injury risk in automobile accidents. The human thorax has an extremely complex structure that includes the most vital chest internal organs:the heart, lung, liver, spleen and kidney. The thorax rib-cage plays a key role of protect the organs from external attack. During the past several decades, many studies have been presented on human thoracic injury in vehicle collisions, but there is still long to get better understanding of thoracic injury biomechanics, such as rib fracture failure and injury criteria.In this study, an FE thorax model was developed and validated based on the human anatomical data. The thorax FE model was then used for analysis of rib fracture in different loading conditions and it was also used to analyze the effectiveness of the rib failure models and the thoracic injury assessment criteria, according to the three selected rib fracture failure models. Finally thoracic injury prevention in Minicar-to-pedestrian impacts was analyzed by using the FE model in combination with the selected failure models and injury assessment criteria.A new3D finite element thoracic model was developed based on the anatomical structure of a real Chinese human body of average size. The main structures of the model include thoracic and lumbar vertebrae and intervertebral discs, ribs, a sternum, costal cartilages, internal organs and other soft tissues. The entire model consisted of more than87,000elements and63,000nodes. The material properties of the thoracic model were defined based on the biomechanical data from literature. For the purpose of the model validation, the force-displacement responses of rib from simulations were compared with the test results of three-point bending tests; The isolated rib anterior-posterior loading structural tests were reconstructed by the FE model, and the calculated results were compared with experimental data in terms of the rib force-displacement responses, rib fracture locations, rib fracture timing and the resultant forces under static and dynamic loading conditions. In addition, using the volunteer tests and cadaver tests, the entire thorax force-displacement responses were simulated in frontal impactor loading, and the thorax model was also validated against the human thorax impactor loading tests in both pure lateral and oblique impacts by comparing the impact force, chest deformation mode, and the force-displacement responses.Three selected rib failure models of T1, T2, and T3based on either von Mises stress and/or plastic failure strain were utilized in the current study, in order to simulate and analyze the rib fractures under various loading conditions by using the thorax FE model. According to the failure models and the loading conditions, the simulated injury data were compared and analyzed. The results from simulations indicated that the rib fracture responses obtained using failure model T3exhibit the best agreement with the three-point bending experimental data; the rib fracture responses using failure model T2demonstrate the best agreement between the simulations and the isolated rib anterior-posterior loading structural tests in terms of both force magnitude and time of rib fracture occurrence. The cross sectional stress&strain at the fracture location were analyzed as well and the relationship between the Number of Rib Fracture (NRF) and impact speed obtained from the simulations using failure model T1exhibited the best agreement with the observations in the thorax frontal impactor loading tests.The current thorax model was used to analyze human thorax injury responses in side impact. For this purpose, the thorax impacts were simulated in pure lateral and oblique impactor loading conditions at a range of different impact angles. The calculated NRF and the injury parameters related to the thoracic injury assessment criteria were obtained from simulations, including the impact force, chest deflection, compression, deflection rate and spine acceleration. A correlation evaluation function between NRF and the injury criteria was built up for a comparative analysis of effectiveness in prediction and assessment of thorax injuries.Finally the FE model was used to study the human thorax dynamic and injury responses in pedestrian impacting by Minicars with different frontal structures at different impact velocities. The influences of Minicar frontal structures and vehicle impact velocities on pedestrian dynamic response were analyzed in terms of the chest impact velocity, chest deflection, both chest AIS3+(Abbreviated Injury Scale-AIS) and AIS4+injury risks based on injury criterion of Thorax Trauma Index (TTI), and the NRF.Based on the present study the conclusions can be drawn as follows. The results of validation simulations fit well with those of previous tests recorded in literature. Rib fracture failure model T1is the most appropriate for the thoracic responses analysis in impactor loading. The TTI criterion has the best effectiveness in prediction and assessment of thorax injuries according to the evaluation analysis. The pedestrian would suffer high AIS3+and AIS4+thoracic injury risk when impacting a Minicar. The frontal structure of Minicar and the vehicle impact velocity has significant influence on pedestrian dynamic responses and thoracic injury, and the frontal structure of Minicar has a greater effect on pedestrian thoracic injury risk than vehicle impact velocity.更多还原