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。     

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。     

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。     

Mild Traumatic Brain Injury Predictors Based on Angular Accelerations During Impacts

Although Head Injury Criterion (HIC) is an effective criterion for head injuries caused by linear acceleration such as skull fractures, no criteria for head injuries caused by rotational kinematics has been accepted as effective so far. This study proposed two criteria based on angular accelerations for Traumatic Brain Injury (TBI), which we call Rotational Injury Criterion (RIC) and Power Rotational Head Injury Criterion (PRHIC). Concussive and non-concussive head acceleration data obtained from football head impacts were utilized to develop new injury criteria. A well-validated human brain Finite Element (FE) model was employed to find out effective injury criteria for TBI. Correlation analyses were performed between the proposed criteria and FE-based brain injury predictors such as Cumulative Strain Damage Measure (CSDM), which is defined as the percent volume of the brain that exceeds a specified first principal strain threshold, proposed to predict Diffuse Axonal Injury (DAI) which is one of TBI. The RIC was significantly correlated with the CSDMs with the strain thresholds of less than 15% (R > 0.89), which might predict mild TBI. In addition, PRHIC was also strongly correlated with the CSDMs with the strain thresholds equal to or greater than 20% (R > 0.90), which might predict more severe TBI.     

头部钝器损伤实验与仿真分析

目的　为了研究头部在钝器作用下的生物力学响应及损伤机理。 方法　利用CT图像数据和MRI图像数据对头部骨骼与内部软组织进行几何重建,然后画分网格,构建颅脑有限元模型。另一方面,对连于躯干的头部标本进行10 m/s的低速冲击,测试冲击部位接触力、顶部应变及冲击的对侧（枕部）加速度。把构建的有限元模型导入MADYMO软件进行相同条件下模拟仿真,从输出模块里输出相应部位的结果。 结果　仿真结果表明模型的头部接触力、顶部应变、对撞侧加速度与头部标本冲击实验测得值能较好吻合。 结论　建立的头部有限元模型及采用的仿真方法可满足头部钝器损伤的仿真研究需要。     

颅脑撞击伤的生物力学机制研究进展

颅脑撞击伤威胁着人类生命安全和生活质量，而未能从根本上揭示颅脑撞击伤的致伤机理，正是造成其预后较差的原因所在。国内外学者对此进行了大量研究，其中对撞击过控中的生物力学作用进行模拟实验和理论分析，积累了不少资料。现将颅脑撞击伤的生物力学研究情况综述如下：亚历史发展过程自1960年国际第一届仿生学讨论会起，生物力学作为一门学科还不到40年历史。然而早在半个多世纪以前，生物力学的有关理论和技术就已应用于颅脑撞击伤的研究。Gurdjian在四十年代便用脆漆法研究外力作用下颅骨的应力分布和应变”’。后来的研究者为了仿…     

对头部损伤判断准则适用性和可用性的新探索

头部损伤判断准则(Headinjury criterion,HIC)是目前较为广泛被接受的、用来衡量头部在外来载荷下安全性的一种损伤判断准则。它被应用于各国的汽车安全法规中,也是头部损伤防护装置(如头盔)设计的参考标准。然而对它的适用性和可用性也存在着不少的争议。本研究应用人类头部有限元的计算模型,通过分析两个不同大小、不同质量的头部模型在三种不同载荷下所产生的脑组织的应力和相应引出的"头部损伤判断准则"的计算值,识别影响"头部损伤判断准则"的适用性和可用性的因素,为如何更科学地评判头部受载安全性提供新的见解和结论。     

Development,Validation, and Application of a Parametric Pediatric Head Finite Element Model for Impact Simulations

In this study, a statistical model of cranium geometry for 0- to 3-month-old children was developed by analyzing 11 CT scans using a combination of principal component analysis and multivariate regression analysis. Radial basis function was used to morph the geometry of a baseline child head finite element (FE) model into models with geometries representing a newborn, a 1.5-month-old, and a 3-month-old infant head. These three FE models were used in a parametric study of near-vertex impact conditions to quantify the sensitivity of different material parameters. Finally, model validation was conducted against peak head accelerations in cadaver tests under different impact conditions, and optimization techniques were used to determine the material properties. The results showed that the statistical model of cranium geometry produced realistic cranium size and shape, suture size, and skull/suture thickness, for 0- to 3-month-old children. The three pediatric head models generated by morphing had mesh quality comparable to the baseline model. The elastic modulus of skull had a greater effect on most head impact response measurements than other parameters. Head geometry was a significant factor affecting the maximal principal stress of the skull (p = 0.002) and maximal principal strain of the suture (p = 0.021) after controlling for the skull material. Compared with the newborn head, the 3-month-old head model produced 6.5% higher peak head acceleration, 64.8% higher maximal principal stress, and 66.3% higher strain in the suture. However, in the skull, the 3-month-old model produced 25.7% lower maximal principal stress and 11.5% lower strain than the newborn head. Material properties of the brain had little effects on head acceleration and strain/stress within the skull and suture. Elastic moduli of the skull, suture, dura, and scalp determined using optimization techniques were within reported literature ranges and produced impact response that closely matched those measured in previous cadaver tests. The method developed in this study made it possible to investigate the age effects from geometry changes on pediatric head impact responses. The parametric study demonstrated that it is important to consider the material properties and geometric variations together when estimating pediatric head responses and predicting head injury risks.     

Skull Flexure as a Contributing Factor in the Mechanism of Injury in the Rat when Exposed to a Shock Wave

The manner in which energy from an explosion is transmitted into the brain is currently a highly debated topic within the blast injury community. This study was conducted to investigate the injury biomechanics causing blast-related neurotrauma in the rat. Biomechanical responses of the rat head under shock wave loading were measured using strain gauges on the skull surface and a fiber optic pressure sensor placed within the cortex. MicroCT imaging techniques were applied to quantify skull bone thickness. The strain gauge results indicated that the response of the rat skull is dependent on the intensity of the incident shock wave; greater intensity shock waves cause greater deflections of the skull. The intracranial pressure (ICP) sensors indicated that the peak pressure developed within the brain was greater than the peak side-on external pressure and correlated with surface strain. The bone plates between the lambda, bregma, and midline sutures are probable regions for the greatest flexure to occur. The data provides evidence that skull flexure is a likely candidate for the development of ICP gradients within the rat brain. This dependency of transmitted stress on particular skull dynamics for a given species should be considered by those investigating blast-related neurotrauma using animal models.     

Importance of partitioning membranes of the brain and the influence of the neck in head injury modelling

A head injury model consisting of the skull, the CSF, the brain and its partitioning membranes and the neck region is simulated by considering its near actual geometry. Three-dimensional finite-element analysis is carried out to investigate the influence of the partitioning membranes of the brain and the neck in head injury analysis through free-vibration analysis and transient analysis. In free-vibration analysis, the first five modal frequencies are calculated, and in transient analysis intracranial pressure and maximum shear stress in the brain are determined for a given occipital impact load.     

利用物质点法研究不同头部模型对头部碰撞动态响应的影响

目的 探讨头部肌肉及边界条件对头部碰撞动态响应的影响。方法 通过人体扫描CT图片构建3种人体头部三维物质点碰撞模型,第1种为简化的自由头部模型（SHFr）,包括头骨、膜层、脑组织,头部自由;第2种为带肌肉的自由头部模型(MHFr),包括头部肌肉、头骨、膜层、脑组织,头部自由;第3种为带肌肉的肩部固定的模型(MHSFi),包括头部肌肉、头骨、膜层、脑组织、肩部肌肉、肩颈部骨骼,肩部下缘固定。一铅质圆柱体锤以6.4 m/s初始速度垂直撞击前额部位,通过物质点法模拟计算3种模型的动态响应。结果 在本数值模拟条件下,SHFr、MHFr、MHSFi 3种模型的头部加速度峰值分别为6.018×103、4.69×103、4.76×103 m/s2。结论 头部肌肉的存在会分散头部的受力分布,扩大头部受力面积,减小受伤程度;在短时间冲击过程中,头部自由与肩部固定对头部动态响应的影响不大。     

Finite element analysis of brain contusion: An indirect impact study

The mechanism of brain contusion has been investigated using a series of three-dimensional (3D) finite element analyses. A head injury model was used to simulate forward and backward rotation around the upper cervical vertebra. Intracranial pressure and shear stress responses were calculated and compared. The results obtained with this model support the predictions of cavitation theory that a pressure gradient develops in the brain during indirect impact. Contrecoup pressure-time histories in the parasagittal plane demonstrated that an indirect impact induced a smaller intracranial pressure (−53.7 kPa for backward rotation, and −65.5 kPa for forward rotation) than that caused by a direct impact. In addition, negative pressures induced by indirect impact to the head were not high enough to form cavitation bubbles, which can damage the brain tissue. Simulations predicted that a decrease in skull deformation had a large effect in reducing the intracranial pressure. However, the areas of high shear stress concentration were consistent with those of clinical observations. The findings of this study suggest that shear strain theory appears to better account for the clinical findings in head injury when the head is subjected to an indirect impact.     

Dynamic Response and Residual Helmet Liner Crush Using Cadaver Heads and Standard Headforms

Biomechanical headforms are used for helmet certification testing and reconstructing helmeted head impacts; however, their biofidelity and direct applicability to human head and helmet responses remain unclear. Dynamic responses of cadaver heads and three headforms and residual foam liner deformations were compared during motorcycle helmet impacts. Instrumented, helmeted heads/headforms were dropped onto the forehead region against an instrumented flat anvil at 75, 150, and 195 J. Helmets were CT scanned to quantify maximum liner crush depth and crush volume. General linear models were used to quantify the effect of head type and impact energy on linear acceleration, head injury criterion (HIC), force, maximum liner crush depth, and liner crush volume and regression models were used to quantify the relationship between acceleration and both maximum crush depth and crush volume. The cadaver heads generated larger peak accelerations than all three headforms, larger HICs than the International Organization for Standardization (ISO), larger forces than the Hybrid III and ISO, larger maximum crush depth than the ISO, and larger crush volumes than the DOT. These significant differences between the cadaver heads and headforms need to be accounted for when attempting to estimate an impact exposure using a helmet’s residual crush depth or volume.     

建立人体头颈动力学有限元模型和验证

目的建立符合解剖结构的头颈三维动力学有限元模型,研究冲击力作用下头颈部动力学响应。方法采用中国成年男性志愿者颈部CT扫描图像,获取颈椎三维点云数据,通过有限元前处理软件ICEM-CFD和Hyper Mesh建立颈部有限元模型。模型包括椎骨、椎间盘、小关节、韧带和软骨等组织,结合已建立并验证的头部有限元模型,装配成具有详细解剖结构的人体头颈部有限元模型。结果模型参考公开发表的头颈部轴向冲击实验数据进行验证,其颈部变形、头部加速度、接触力曲线以及损伤部位与实验数据吻合较好。结论动力学三维有限元模型可用于汽车安全、运动学损伤等领域人体头颈部的动态响应和损伤机制研究。     

颅脑组织材料参数对儿童头部冲击响应的影响

目的针对目前对儿童颅脑组织材料参数的不确定性,研究直接冲击载荷条件下颅脑组织材料参数对儿童头部冲击响应的影响。方法应用已验证的3岁儿童头部有限元模型进行冲击仿真实验,采用正交实验设计和方差分析对儿童颅脑组织材料进行参数分析。结果颅骨弹性模量对儿童头部冲击响应具有显著性影响,随着颅骨弹性模量的增加,头部撞击侧颅内压力显著减小(P=0.000),对撞侧颅内压力显著增大(P=0.000),颅骨最大Von Mises应力显著增大(P=0.000)。脑组织的线性黏弹性材料参数对儿童头部冲击响应同样具有显著性影响,随着脑组织短效剪切模量的增加,脑组织最大主应变显著减小(P=0.000),脑组织最大剪应力则显著增加(P=0.000)。结论参数分析结果可为今后儿童头部有限元模型的材料选取提供参考依据,进而提升模型在预测临床上无法通过脑CT影像确诊的脑震荡等脑损伤时的准确性。     

Influence of wet surfaces and fall height on pediatric injury risk in feet-first freefalls as predicted using a test dummy

INTRODUCTION: Falls are a major cause of morbidity and mortality in children, but are also reported falsely in child abuse. Therefore, it is of interest to understand those factors which may lead to a higher likelihood of injury in a feet-first freefall. METHODS: We used laboratory freefall experiments and a 3-year-old Hybrid III anthropomorphic test dummy (ATD) to assess head and femur injury risk. Wet and dry linoleum impact surfaces were used from three fall heights: 22, 35 and 47 in. RESULTS: For a given fall height, dry surfaces were associated with higher head injury criteria (HIC) values than wet surfaces. Changes in fall height 22-47 in. did not significantly affect HIC values for falls onto either surface. Generally, compressive and bending femur loading increased significantly for wet as compared to dry linoleum. CONCLUSIONS: In simulated feet first freefall experiments up to 47 in. using a 3-year-old test dummy, a low risk of contact type head injury and femur fracture was found. However, both fall height and surface conditions influenced femur loading and head injury measures. Future efforts should explore the risk of head injury associated with angular acceleration in freefalls.     

1.5岁儿童头部有限元模型的建立及验证

利用1.5岁儿童头部MRI和CT扫描数据,通过医学扫描断层图像三维重构和有限元前处理,建立一个具有高度解剖学细节的1.5岁儿童头部有限元模型并赋予其最新公布的儿童颅骨材料参数。利用这个头部模型重构Loyd开展的儿童尸体头部跌落试验(17个样本),将仿真输出的加速度历程曲线和尸体试验曲线的加速度峰值、脉冲持续时间等进行对比。结果表明,该模型能够反映跌落工况中儿童头部的受载情况,具有良好的生物逼真度。30 cm跌落高度下,枕部撞击时得到最大HIC值357;不同跌落工况的头部颅内压力分析显示,儿童头部遭受撞击时,颅内压的分布满足经典的撞击压-对撞压产生理论;相比前额撞击和枕部撞击,颅顶撞击和侧向顶骨撞击的撞击侧正压力峰值较大,最大值分别为241.6 和157.3 kPa,遭受同侧脑挫裂伤的风险较高;枕部撞击工况下,撞击对侧的负压力峰值大于其他撞击工况,最大值为-74.4 kPa,遭受对侧脑挫裂伤的风险较高。跌落高度增加时,HIC和颅内压力峰值增大,损伤风险随之增加。     

关于头部组织材料性能敏感性对颅内压力响应的研究

应用有限元法 (finiteelementmethod)和试验设计技术 (design of experimentDOE)研究人头部颅骨(skull)、脑脊液 (cerebral spinal fluidCSF)和脑髓 (brain)材料性能的敏感性对颅内因撞击而产生的压力响应。该研究采用头部的有限元模型 ,用三因子、三层次的因子试验设计对影响颅内因撞击而引起的压力的颅骨、脑脊液和脑髓的材料性质的敏感性进行分析。研究结果进一步证实了颅骨、脑脊液、脑髓的材料性能对颅内因撞击而引起的压力的重要影响。本研究为进一步的头部的有限元分析提供了新的见解 ,并提出了对头部组织的材料性能作更进一步的探索。     

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.     

弥漫性轴索损伤的生物力学机理

弥漫性轴索损伤（DAI）作为原发脑损伤的一种类型，有其特有的损伤机理，荷载性质，施载方式，颅脑颈各组织结构特性均与DAI发生密切相关，本文从生物力学角度综述了荷载量，荷载波形，荷载作用时间，直线加速，旋转加速，直线／旋转复合加速，脑组织，大脑镰小脑幕，颅骨、颈部对应力应变产生及分布的影响，及与DAI发生的关系。