【作者】 蔡志华；

【导师】 兰凤崇；

【作者基本信息】 华南理工大学 ， 车辆工程， 2013， 博士

【摘要】 近年来，随着汽车保有量的大幅增加、汽车动力性能的逐步提高以及高速公路的大量建设，交通事故中造成大量人员重伤与死亡。每年造成约15-60万人员受伤，约5-12万人员死亡，给国家造成巨大的经济财产损失，给家庭带来沉重的精神伤害。在交通事故所造成的损伤中胸部损伤的发生率仅次于颅脑损伤，在所有的损伤中胸部损伤AIS轻微到中度伤占13%，AIS严重与致命伤占29%，是交通事故造成重伤与死亡的主要原因之一。肋骨骨折是胸部损伤中最主要的损伤类型，肺、心脏、大动脉、肝在体内受到肋骨和胸骨的保护，但一旦受到损伤是很致命的。因此深入理解汽车碰撞过程中胸部的生物力学响应及影响损伤的相关因素，对于改善汽车安全性能，减小事故中人员的损伤具有十分重要的现实意义和工程应用价值。本论文利用生物力学有限元仿真分析方法对胸部在冲击作用下的力学响应与损伤进行仿真研究。对生物力学仿真过程中采用的非线性显式算法的基本原理、接触算法、时间步长控制、接触问题的迭代法进行了公式推导。对比了四面体单元与六面体单元在仿真计算中的优缺点，提出采用六面体单元对人体胸部主要组织进行建模的思路。概述了模型建立的方法与步骤。结合人体医学解剖结构，建立了肋骨、胸骨、椎骨、椎间盘、锁骨、肩胛骨、骨盆、皮肤、肌肉及上肢、下肢、头部等具有中国成年男性解剖特征的人体生物力学有限元模型。结合大量的国内外研究成果与文献资料对人体胸部组织所采用的材料参数与本构关系模型进行了定义与选取。模型验证参考了尸体实验(PHMS)数据与理论模型进行了前碰撞和侧面碰撞的仿真验证，通过对理论模型的计算与实验及仿真结果进行对比，碰撞中接触力、胸骨位移量、力-位移响应与实验吻合较好，同时模型在仿真过程中所表现出的胸部肋骨骨折与内脏的损伤情况与实验描述保持一致。本模型能模拟胸部肋骨骨折及软组织的损伤。可用于汽车碰撞安全中胸部的损伤机理、胸部肋骨骨折与内脏组织的损伤研究。通过材料实验与国内外在肋骨骨折生物力学领域已取得的研究成果，利用建立的有限元模型对肋骨皮质骨厚度、皮质骨弹性模量、极限应力、失效应变及不同年龄阶段肋骨参数进行了研究，深入探索了肋骨在冲击作用下胸部的整体响应与肋骨骨折损伤机理。揭示了汽车碰撞中影响老年阶段肋骨骨折严重性的主要原因与损伤规律。研究结果表明相同载荷作用下，皮质骨厚度越薄，肋骨骨折越严重，肋骨弹性模量对肋骨骨折影响不明显，肋骨极限应力、失效应变越小，骨折越严重。通过仿真分析可以看出汽车安全法规中用胸部变形量作为评估正面碰撞肋骨骨折的损伤非常有效，但是没有考虑年龄的影响，应完善老年阶段的胸部损伤法规标准，进一步提高汽车的安全性能，减少老年人在汽车碰撞过程中肋骨骨折的风险。利用建立与验证的人体生物力学有限元模型对胸部在不同冲击速度与不同冲击方向进行仿真分析，研究冲击载荷下人体胸部的生物力学响应并分析不同的损伤指数对胸部损伤的敏感性。结果表明冲击速度越大，胸部接触力、胸骨变形量、胸腔内部组织压力、椎骨加速度、胸部粘性指数VC等越大。通过对比各类损伤指数，相同速度下冲击位置的不同胸部产生的损伤不同，正面碰撞所产生的胸腔压力比侧面碰撞的压力大。侧面碰撞肋骨骨折比正面碰撞严重，不论正面还是侧面碰撞，胸部内脏组织中心脏处的压力最大，过大的心脏压力容易造成主动脉压力增加而产生主动脉破裂，是汽车碰撞事故中死亡的主要原因之一。通过对胸部正面与侧面碰撞中各参数与损伤评估指数进行比较，胸腔压力对于胸部内脏的损伤评估非常有效，可用于汽车碰撞法规中对内脏损伤的评估。最后，利用建立的有限元模型开展与方向盘碰撞的应用研究，研究不同转向管柱安装角与不同方向盘高度对胸部损伤的影响，得到了胸部碰撞方向盘产生的生物力学响应。结果表明，汽车碰撞事故中方向盘高度与人体头部与胸腹部的损伤严重性有直接关系，方向盘位置越高，造成头部、肋骨骨折、肺挫伤、心脏等胸部内脏组织的损伤越严重。当方向盘位置在胸部与腹部的中间位置对于肝脏、胃、膈肌的损伤比较严重而对胸部肋骨与内脏损伤较小。当方向盘位置在下腹部时肠、胃、腰椎产生的变形较大，而对胸骨肋骨与胸部内脏损伤较小。转向管柱安装角越大，接触力越小，变形量越大，胸腔压力越大，因此从满足法规的角度出发应增加转向管柱的安装角度减小接触力。但从内脏损伤的角度出发应在满足法规的前提下减小转向管柱的安装角，增加碰撞时胸部与方向盘的接触面积，减小内脏的损伤。本论文的研究成果表明人体生物力学有限元模型是一个非常有效的工具评估汽车碰撞安全中胸部损伤。对于改善汽车在正面与侧面的安全性具有重要的指导作用，本模型可用于现实世界的汽车碰撞中的胸部损伤评估与重构，汽车安全法规研究与假人的设计与开发。更多还原

【Abstract】 In recent years, with the increase in vehicle ownership, vehicle dynamic performancegradually improved, a large number of highway construction, and highly energetic,trauma-like traffic accidents result in a higher rate of morbidity and mortality. Every yearabout15-60million people who were injured, about5-12million deaths causing hugeeconomic losses and made the family heavy spiritual harm. Traffic accidents resulted insevere injuries to the head and thorax more frequently than injury to other body regions. Inparticular, thorax injuries are common in vehicular accidents and is second only to headinjuries, thorax injuries account for13%of minor to moderate injuries and29%of all seriousto fatal injuries. Rib fractures are the most frequent lesions in traumatic thorax injury. Whilerespiratory diseases such as pneumonia, flail chest, and pneumo/hemothorax are regarded asthe leading complications associated with sternum and multiple rib fractures. Therefore, it isvery practical significance and value in engineering to increase understanding thoraxbiomechanical response and the factors influencing thoracic trauma may lead to improvedsafety features and a decrease in fatalities and injuries. Improving safety to minimize or avoidfatalities and injuries is a primary field of research for automotive designers and legislators.The present study focuses on the dynamic response and injuries of the thorax by usingthe simulation analysis method. Elaboration and derives the basic theories and formulas usedin the simulation process. Especially for a non-linear calculation process using the explicitalgorithm basic principle, the contact algorithm, time step control, contact problems iterativemethod derivation of formulas. Comparing the advantages and disadvantages of thetetrahedral and hexahedral elements in the simulation, proposed the hexahedral elements formodeling the main tissue of the human body and method of establishing the human-bodybiomechanical model. An integrative medical Anatomical structure, a human bodybiomechanical model was developed. The model featured in great detail the main anatomicalcharacteristics of skeletal tissues, soft tissues, and internal organs, including the head, neck,shoulder, thoracic cage, abdomen, spine, pelvis, pleurae and lungs, heart, aorta, arms, legs,and other muscle tissues and skeletons. The material properties of all tissues in the humanbody model were obtained from literature. Material model can accurately simulate the rib fracture and soft tissue injury. Validations of the human body model have been made againstCadavers responses for frontal and side impact and for the mathematical lumped massmodel.The accuracy of the model response was investigated through experimental testing on(PMHS) during front thoracic and side pendulum impacts. The model well agreed with thefront thoracic and side pendulum impact tests and had a reasonable correlation during thefrontal thoracic pendulum impact test. The thorax response was excellent when theforce–time, compression–time, and force–compression were considered. The human bodymodel was validated for frontal and lateral impacts to the thorax. The responses well agreedwith those of human bodies sustaining impact loads. The model can also predict skeletalinjuries such as bone fractures and ligament ruptures. Overall, the predicted model responsereasonably well agreed with the experimental data and highlighted areas for futuredevelopments. The model can be used to further evaluate thoracic injury in real-worldcrashes.Through the in-depth analysis of material properties of the ribs, this paper uses theestablished and verified finite element (FE) model of the human thorax to investigate thesensitivity of structural responses and rib fractures to age-related rib material properties toprovide guidelines for the development of FE thorax models used in impact for biomechanicsand injury assessment. Age-related rib material properties were determined based on previousexperimental test results, research and age-related cortical bone material parameters (such ascortical bone thickness, elastic modulus, ultimate stress, failure strain rate), the cortical bonematerial parameters of young and elderly individuals, analysis of Sternal deformation underlow-speed frontal impact, and the number of fractured ribs. The results show that elasticmodulus changes under low-speed frontal impact, with less Sternal deformation resulting inless affected rib fractures. Lower ultimate stress corresponds with greater Sternal deformation,and more fractured ribs correspond with less failure strain. The degree of sternal deformationcorresponded with more fractured ribs. The older the patient, the greater was the sternaldeformation, the number of sternal fractures, and the number of fractured ribs.The simulationresults show that sternal deformation is a highly favorable index for assessing rib fractures. Incar crash safety regulations, the thorax deformation index for frontal crashes is76mm. Thisindex more accurately reflects rib fracture injury, and it can be adopted for different age groups. The evaluation criteria in this index should be changed to reduce rib fractures,thereby reducing the number of thorax injuries among the elderly in automobile collisions.This paper uses the established and verified finite element (FE) model of the humanthorax to investigate the sensitivity of different impact speeds and different impact directionto provide guidelines for the development of FE thorax models used in impact forbiomechanics and injury assessment. The results showed that the greater the impact velocity,the contact force of the chest, the deformation of the sternum, chest internal organizationpressure, the acceleration of the vertebrae, chest viscosity index VC greater. By comparingthe various types of damage, the same speed impacts the different position of the internaltissue damage different, frontal impact chest pressure greater than in side impacts. Ribfractures in the side impact more serious than Frontal Impact, whether front or side impact,the maximum pressure on the heart. Excessive heart pressures likely to cause increased aorticpressure and aortic rupture. Through parameters compared with indices of damageassessment on the front and side impact of thorax, thorax pressure is effective for the damageassessment of the internal organs in the thorax, can be used in automobile collisionregulations for the internal organs damage assessment.Finally, this paper uses the established and verified finite element (FE) model of thehuman thorax to investigate the sensitivity of different angles and different steering wheelheight in impact for biomechanics and injury assessment. The results showed that the higherthe steering wheel position, rib fractures, pulmonary contusion, heart and other internalorgans of the chest injury is more serious. When the steering wheel position in the middle ofthe chest and abdomen, the liver, stomach, diaphragm injury is more serious and ribs andinternal organs of the chest with less damage. When the steering wheel position in theabdomen, intestines, stomach produces large compressive deformation, while the Sternal ribsand the chest visceral injury are small. Steering column mounting angle, the contact force issmaller, the greater the deformation, the greater the pressure chest, Therefore, from the pointof view to meet regulations should increase the mounting angle of the steering columnreduces the contact force. But from the viewpoint of visceral injury shall meet the regulationsof the mounting angle of the steering column reducing the pleural pressure decrease,increasing the collision contact area between the chest and the steering wheel, reducing damage to the internal organs.The results from this study suggested that the numerical finite element model developedhere in could be used as a powerful tool for improving front and side impact automotivesafety. The model can be used to evaluate thoracic injury in real world crashes andautomotive safety regulations and dummy design and development.更多还原