基于车人碰撞事故重建的行人头部动力学响应

目的 研究行人交通事故中,不同碰撞速度、不同车型及行人不同受撞击部位与行人头部损伤严重度的关系。方法 通过MADYMO多刚体动力学软件对一起有视频的行人交通事故进行事故重建,获得初始和边界条件,然后通过获得的边界和初始条件进行不同车速(20、30、40、50、60 km/h)、不同车型(轿车、SUV型车、面包车)、行人不同受撞击部位(正面、侧面、背面)的模拟碰撞实验,对模拟碰撞实验中行人头部损伤情况进行分析,并利用两例真实行人交通事故对部分结果进行验证。结果 不仅车辆碰撞速度、车辆前置结构影响行人头部损伤严重度,行人受撞击部位也是影响行人头部损伤严重度的重要原因。在碰撞速度≤30 km/h时,行人与地面接触造成的损伤可能比与车辆造成的损伤严重;碰撞速度≥40 km/h时,行人头部损伤主要是与车辆接触所致。结论 利用监控录像能比较准确地开展行人交通事故重建,从而对行人动力学响应进行分析。在行人交通事故频发路段,对不同车型进行不同限速,能有效减小行人头部损伤的严重程度。     

6岁儿童行人-汽车碰撞中碰撞角度对头部损伤的影响

目的应用符合欧洲新车安全评鉴协会(the European New Car Assessment Programme,Euro NCAP)要求的6岁儿童行人有限元模型,探究不同碰撞角度对儿童头部损伤的影响。方法应用符合Euro NCAP技术公告(TB024)并且具有详细解剖学结构的6岁儿童行人有限元模型,设置4组行人-汽车碰撞仿真试验,探究不同碰撞角度下儿童头部损伤情况。人体头部质心初始位置在车的纵向中心线上,轿车初速度为40 km/h,轿车分别与人体右侧、前侧、左侧、后侧碰撞(即0°、90°、180°、270°)。比较不同碰撞角度下运动学差异和头部碰撞响应,同时分析面骨和颅骨的损伤情况。结果通过分析儿童行人头部接触力、头部质心合加速度、头部质心相对于车的合速度、头部损伤标准(head injury criterion,HIC_(15))、面骨骨折情况以及颅骨应力分布发现,背面、正面碰撞下儿童头部骨折及发生脑组织损伤的风险大于侧面碰撞,其中背面碰撞下儿童行人头部损伤风险最高,侧面碰撞下儿童行人头部损伤风险最低。结论背面碰撞下儿童行人头部损伤风险最大,研究结果对行人-汽车碰撞评估和防护装置研发具有重要的应用价值。     

10岁儿童头部有限元模型的建立及验证

运用ANSYS ICEM CFD以及HYPERMESH软件对10岁儿童头部几何模型进行合理的网格划分,获得具有高度解剖学细节的10岁儿童头部有限元模型。利用MADYMO软件自带的假人,模拟一起典型跌落事故中,受伤儿童从3个不同高度跌落时人体的动力学响应过程,并计算头部与地面碰撞接触瞬间的方位和速度等运动学参数。然后将这些参数输入到10岁儿童头部有限元模型中,模拟头部与地面的碰撞过程,并分析与损伤相关的生物力学参数。结果表明,颅骨的最大应力和最大应变分布在枕骨右侧,与碰撞点的位置较为吻合,但均未超过颅骨的耐受极限。利用颅内压力可较好地预测脑组织的损伤程度,而利用脑组织的von mises应力可较好地判断脑组织的损伤位置。事故重建的结果表明,该模型具有较好的生物逼真度,可以用于儿童头部损伤生物力学的研究。     

汽车后碰撞时人体头颈部的动力学响应及损伤分析

目的建立基于人体解剖学结构的精细化头颈部有限元模型,研究不同后碰撞速度下颈部损伤。方法该模型以人体头颈部CT扫描图像为基础,利用Mimics进行三维骨重建,通过Hyper Mesh完善颈部三维实体韧带、小关节等组织,并进行网格划分。生成的模型包括头部、8节椎骨(C1～T1)、6个椎间盘(包括纤维环、髓核和上下软骨终板)、小关节(包括软骨和关节囊韧带)、韧带、肌肉等结构,最后在有限元后处理软件中完成模型验证与后碰撞计算。结果分别对模型进行轴向冲击、前后屈伸和侧屈模拟并与实验数据对比,验证模型的有效性,并进行速度为20、40、60、80 km/h后碰撞计算。在20 km/h速度下,颈部无损伤出现,在40、60、80 km/h速度下,最早出现损伤的都是韧带。随着速度增加,颈部各组织受力不断增大。速度为80 km/h时,颈椎的密质骨、松质骨和纤维环最大应力分别为226. 4、11. 5、162. 8 MPa,当韧带应变达到极限时,开始出现撕裂。结论所建头颈部有限元模型具有较高的生物仿真度和有效性,可用于交通事故中颈部损伤分析的研究,在一定程度上有助于颈椎损伤的诊断、治疗和预防。     

国人第 5 百分位女性行人下肢生物力学计算模型开发及应用

目的 预测与评估行人-汽车碰撞中小身材女性行人下肢的生物力学响应及损伤机制。 方法 基于符合国 人第 5 百分位女性特征的志愿者 CT 影像数据,重构具有详细解剖学结构的下肢几何模型,进行表面处理和网格化 后,构建下肢有限元计算模型。 重构动态三点弯曲尸体试验以及高速载荷下膝关节横向弯曲和剪切尸体试验,对 模型进行有效性验证。 应用该模型参照 Euro NCAP 技术公告 TB024 设置 4 组行人下肢-汽车碰撞仿真试验,探究 第 5 百分位女性行人下肢损伤机制。 结果 通过对比仿真试验与尸体试验结果,验证该模型具有较高的生物仿真 度。 在 4 种不同车型仿真试验结果中,SUV 车型对下肢损伤最轻。 小身材女性下肢股骨最易发生骨折,长骨最先 骨折,使得膝关节韧带未见损伤。 结论 本文所建下肢有限元模型作为国人第 5 百分位整人模型开发的一个重 要组成部分,为模型研发奠定基础。 研究结果对小身材女性行人损伤机制研究和行人保护装置研发有重要的应 用价值。     

6岁儿童头部有限元模型的构建与验证

借助6岁儿童医用头部CT扫描图片,通过图像分析处理,提取几何参数,重构生成三维几何模型。对几何模型进行有限元前处理,构建了一个6岁儿童头部有限元模型。模型中包含颅骨、骨缝、脑脊液、大脑、小脑、脑干、脑室等各个器官,共有44 886个节点,11 675个壳单元,37 482个六面体单元。.各器官材料属性采用来自参考文献的数据。仿真分析计算中,力加载时窗为11 ms时,模型的CPU计算时长低于1 h。采用Nahum尸体实验数据与仿真结果进行对比。仿真分析结果显示:成人头部撞击时撞击压与对撞压的形成规律同样适用于儿童头部碰撞。在7 900 N力作用下,尸体头部撞击侧最大压应力为140 kPa,对撞侧最大压应力为-60 kPa,而儿童头部的值分别为220.2 kPa和-135.2 kPa;在HIC值均为775的作用下,成人头部撞击侧和对撞侧最大压应力分别为140 kPa和-60 kPa,而儿童头部的值分别为160 kPa和-89 kPa。这表明,在相同作用力或HIC值下与成人相比,儿童头部更容易受到损伤。     

基于多种优化算法的交通事故精准化重建与颅脑损伤风险评估

目的 探究不同优化算法对精准化重建交通事故的影响。方法 应用非支配排序遗传算法(non-dominated sorting genetic algorithm-II, NSGA-II)、邻域培养遗传算法(neighborhood cultivation genetic algorithm, NCGA)以及多目标粒子群优化算法(multi-objective particle swarm optimization, MOPSO)对1例真实案件的多刚体动力学重建进行优化,研究不同优化算法对收敛速度与最优近似解的影响,并将优化所得的最优初始碰撞参数作为有限元模拟的边界条件,将仿真得到的颅脑损伤预测结果与实际损伤进行比较。结果 NCGA算法在优化过程中收敛速度更快,结果更优,最优近似解重建所得行人-车辆碰撞的运动学响应与监控视频相符,颅脑损伤预测情况与尸体检验基本一致。结论 通过优化算法和多刚体、有限元方法结合可以完成交通事故精确化重建,减少人为因素的影响。     

自动紧急制动对公交车内儿童乘员颅脑损伤影响

目的 研究自动紧急制动(autonomous emergency braking,AEB)对公交车内儿童乘员的颅脑损伤影响。 方法 使用 Prescan 软件搭建公交车 AEB 测试场景,通过仿真得到 60 km/ h 初速度下公交车 AEB 制动工况下的减速度曲线。 基于已经验证的公交车模型和具有详细解剖学头部结构的 6 岁儿童混合有限元模型,选取车内儿童乘员典型的 4 个乘坐位置,使用 LS-DYNA 软件对公交车有、无 AEB 制动工况下儿童乘员头部损伤进行仿真。 以儿童乘员头部损伤指标 HIC15 、大脑灰质处压力、脑组织 von Mises 应力及剪切应力等生物力学响应为损伤评价指标,对儿童乘员的颅脑损伤进行分析。 结果 各组仿真试验中,位置 1 和 2 前方设置挡板时,儿童乘员大脑灰质处压力超过其损伤阈值,其余各位置儿童乘员的各项损伤指标均远小于对应的损伤阈值。 结论 AEB 能有效降低公交车内儿童乘员头部碰撞损伤,公交车内位置 3 处的儿童容易发生碰撞损伤风险,位置 1、2 处设置广告牌挡板会增加儿童乘员的颅脑损伤风险。     

面部碰撞对行人创伤性脑损伤影响的生物力学研究

为预测和评判行人面部碰撞对创伤性脑损伤机理及生物力学响应,结合计算机断层扫描（CT）和磁共振（MRI）医学成像技术,建立符合中国人体特征的50百分位头颈部几何模型和有限元模型。有限元模型中颅骨与脑之间的相对运动采用切向滑动边界条件,摩擦系数定义为0.2,模拟鼻骨斜碰撞、鼻外侧软骨正面碰撞、牙齿正面碰撞、下颌骨碰撞和颧骨外侧斜碰撞等5种典型面部碰撞交通事故场景,探讨应力波在颅骨和脑内传播路径,得到颅内压力、von Mises等效应力和剪切应力等生物力学响应参数分布规律。结果显示,鼻骨斜碰撞颅内压力峰值为236.7 kPa,von Mises应力为25.97 kPa,超过了大脑耐受阈值;颧骨外侧斜碰撞最大横向剪切应力分别为14.56 kPa和-18.07 kPa,促使脑组织产生了较大的剪切变形,存在严重脑损伤风险。结论表明：面部碰撞的位置和方向是导致面部骨折严重程度的关键因素,面骨骨折的位置决定创伤性脑损伤的部位,面骨骨折都带有一定程度的创伤性脑损伤;头部受到冲击时,面部结构能够吸收大量的冲击能量来保护大脑,降低颅脑损伤的风险。     

不同载荷作用下头部生物力学响应仿真分析

目的建立符合解剖结构的人颅骨三维有限元模型,研究多种载荷作用下头部生物力学响应。方法通过建立具有解剖结构的高精度头部有限元模型,颅骨采用能模拟骨折的弹塑性材料本构模型,结合已发表的正面冲击颅内压实验、动态颅骨骨折实验、头部跌落实验结果,仿真再现实验过程中头部受冲击载荷作用下的生物力学响应、颅骨骨折及头部不同速度下的跌落响应。结果前碰撞表现出冲击与对冲侧正-负颅内压分布,相近载荷下枕骨变形比前额、顶骨严重,跌落中速度越快损伤越大。结论建立精确解剖结构的头部有限元模型可以较好模拟头部在冲击、跌落等载荷下的生物力学响应。通过量化接触力、颅内压力等参数来评价头部损伤风险,为防护系统的设计提供科学依据。     

Progress in reducing road-related deaths and injuries in Irish children

The aim was to study road-related injuries and fatalities in under 15 year olds in two time periods (1996-2000 and 2004-2008 inclusive) to assess whether progress has been made via cross-sectoral efforts to reduce this injury toll in Ireland. For pedestrian and car-related accidents, police assistance is required and at the time a detailed CT 68 form is completed by the attending officer and sent to the Road Safety Authority for analysis. Details re the severity of injury, light and road conditions and safety measures such as seat belt or car restraint use, seat position and helmet use if a cyclist were recorded. Injuries were sub-classified as fatalities, serious (detained in hospital, fractures, severe head injury, severe internal injuries or shock requiring treatment) or minor. All data for the two time periods was entered onto an SPSS database. A concerted national campaign re road safety media campaign allied to random breath testing, penalty points for driving offences, on the spot fines for speeding and far greater police enforcement took place between the two time frames and continues to this day. When looked at as most likely estimates of death ratios the results were found to be statistically significant with an overall p value of < 0.0001 CI [0.39, 0.69]. When broken down into specific age ranges all were significant apart from the 0-3 age range with a p value of 0.69 CI [0.26, 1.1]. The most significant changes were found in the 7-9 years, 10-12 and 13-15 year age ranges with p values of < 0.0001, 0.0002 and 0.0007 respectively. When results were compared between the two cohorts, car occupant fatalities between both groups dropped by 36%. Pedestrian injuries dropped from 1719 to 1232, pedestrian fatalities decreased by almost 50% as did serious pedestrian injuries from 261 down to 129. Cyclist fatalities saw the most significant fall (76%) with a dramatic reduction in cyclist injuries from 25 down to 6 (63%). The 13-15 year old age group had the highest mortality and morbidity in both cohorts. Documented restraint use was less than 70% in both cohorts. A national road safety campaign, greater police enforcement and a cultural change has seen road-related injuries in children drop very significantly (by 50%) over the two time periods and this campaign should continue.     

颅脑有限元模型演化规律及其生物力学研究进展

交通事故中头颈部损伤因其较高的致命性,已成为最严重的损伤类型。有限元模型在创伤性脑损伤生物力学机理研究中得到日益广泛应用。回顾头颈部有限元模型的生物力学研究历史和现状,并阐述车辆碰撞交通事故中人体颅脑典型交通伤演化规律和生物力学研究进展,探索头颈部损伤安全防护的方法,以期为车辆碰撞事故中人体颅脑损伤生物力学研究和相应的汽车安全防护装置研制提供理论依据。     

Intracranial diffuse axonal injury at autopsy

An illustrative case of diffuse axonal injury (DAI) emphasizes features that help to separate focal outer head trauma owing to blows and/or falls from angular acceleration head injuries associated with diffuse inner brain lesions. In the past, explaining significant neurological deficits and death as the result of diffuse closed head trauma received from high-speed automobile accidents has been difficult as well as confusing. The long-term consequences from such diffuse inner cerebral trauma are still poorly defined. Head injuries sustained in automobile accidents have been associated with diffuse brain damage characterized by axonal injury at the moment of impact. The reported victim of a motor vehicle accident showed post-mortem findings for both inner cerebral trauma and focal outer cerebral damage. The diffuse degeneration of cerebral white matter is associated with sagittal and lateral acceleration with centroaxial trauma and has a different pathogenesis from outer focal head trauma, typified by subdural hematomas and coup injuries. Unlike outer cerebral injury, over 50 percent of victims with diffuse axonal injury die within two weeks. These individuals characteristically have no lucid interval and remain unconscious, vegetative, or severely disabled until death. Compared to head trauma victims without diffuse axonal injury, there is a lower incidence of skull fractures, subdural hemorrhages, or other intracranial mass effect as well as outer brain contusions. Primary brainstem injuries often demonstrated at autopsy are seen in the reported victim. Diffuse axonal injury is produced by various angles of acceleration with prolonged acceleration/deceleration usually accompanying traffic accidents. Less severe diffuse axonal injury causes concussion.     

A case-control study of the effectiveness of bicycle safety helmets

Bicycling accidents cause many serious injuries and, in the United States, about 1300 deaths per year, mainly from head injuries. Safety helmets are widely recommended for cyclists, but convincing evidence of their effectiveness is lacking. Over one year we conducted a case-control study in which the case patients were 235 persons with head injuries received while bicycling, who sought emergency care at one of five hospitals. One control group consisted of 433 persons who received emergency care at the same hospitals for bicycling injuries not involving the head. A second control group consisted of 558 members of a large health maintenance organization who had had bicycling accidents during the previous year. Seven percent of the case patients were wearing helmets at the time of their head injuries, as compared with 24 percent of the emergency room controls and 23 percent of the second control group. Of the 99 cyclists with serious brain injury only 4 percent wore helmets. In regression analyses to control for age, sex, income, education, cycling experience, and the severity of the accident, we found that riders with helmets had an 85 percent reduction in their risk of head injury (odds ratio, 0.15; 95 percent confidence interval, 0.07 to 0.29) and an 88 percent reduction in their risk of brain injury (odds ratio, 0.12; 95 percent confidence interval, 0.04 to 0.40). We conclude that bicycle safety helmets are highly effective in preventing head injury. Helmets are particularly important for children, since they suffer the majority of serious head injuries from bicycling accidents.     

车-人碰撞事故中行人胫骨撞击响应的二维数值分析

目的基于两相多孔弹性胫骨模型,建立一种车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法。方法选用健康成年男性胫骨行CT分层扫描,结合数值插值方法获得胫骨的结构参数;在两相饱和多孔弹性理论的框架内,建立胫骨动力学控制方程组;采用自行开发的流-固耦合两相多孔介质有限元数值分析程序,数值模拟小汽车车头从侧向撞击行人下肢的动力学过程,并计算撞击载荷作用下0-200ms内行人胫骨的动力学响应。结果胫骨的弯曲变形主要集中在撞击载荷作用的区域;胫骨骨干上节点107处的侧向位移响应,约在75ms时刻出现峰值位移（-6mm）,对撞击载荷有明显的时间滞后;胫骨骨干上单元E77中心处的轴向应力响应,约在30ms时刻出现峰值应力（140MPa）,对撞击载荷也有明显的时间滞后。结论本研究所建立的对车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法,能够近似地模拟胫骨撞击区的弯曲变形、侧向位移响应和轴向应力响应以及胫骨中骨髓流体组分对骨架固体组分动力学特性的影响。下一步研究将在现有初步结果的基础上提高胫骨动力学模型的生物仿真性。     

Air weapon fatalities.

AIMS: To describe characteristics of a series of people accidentally and deliberately killed by air powered weapons. METHODS: Five cases of fatal airgun injury were identified by forensic pathologists and histopathologists. The circumstances surrounding the case, radiological examination, and pathological findings are described. The weapon characteristics are also reported. RESULTS: Three of the victims were adult men, one was a 16 year old boy, and one an eight year old child. Four of the airguns were .22 air rifles, the other a .177 air rifle. Two committed suicide, one person shooting himself in the head, the other in the chest. In both cases the guns were fired at contact range. Three of the cases were classified as accidents: in two the pellet penetrated into the head and in one the chest. CONCLUSIONS: One person each year dies from an air powered weapon injury in the United Kingdom. In addition there is considerable morbidity from airgun injuries. Fatalities and injuries are most commonly accidents, but deliberately inflicted injuries occur. Airguns are dangerous weapons when inappropriately handled and should not be considered as toys. Children should not play with airguns unsupervised.