乘用车前挡风玻璃角度对行人头部/颅脑损伤影响研究

头部/颅脑损伤在车辆与行人碰撞事故中频繁发生,而行人头部与挡风玻璃的碰撞是导致头部损伤的主要原因。旨在采用数值模拟方法研究乘用车挡风玻璃倾斜角度对行人头部/颅脑损伤的影响。采用TNO多刚体行人模型和THUMS4.0头颈部有限元模型耦合得到新的行人碰撞数值模型,并结合已有的多刚体乘用车模型,借助真实的行人碰撞交通事故案例对该耦合模型进行基于人车动力学响应的有效性验证。在此基础上,构建人车碰撞模型矩阵,其中挡风玻璃角度的变化范围设定为24°~50°(间隔为2°),车辆速度设置为45 km/h,行人与车辆碰撞位置时分别处于车辆前保险杠前端1/2和1/3处。分析结果表明,该耦合模型可以较准确地再现事故中的行人动力学响应;行人碰撞保险杠前端中间(即1/2处)位置时的头部损伤较1/3处更严重;头部损伤在本文所分析的变化范围内随挡风玻璃角度的增加呈先减小后增加的变化趋势,且当挡风玻璃角度位于32°~34°左右时损伤风险较低。     

考虑失效的非线性Burgers’海冰模型及其数值应用

该文以发表的海冰蠕变实验为基础,建立考虑损伤失效的非线性Burgers’海冰模型。此模型在Jordaan模型基础上考虑韧脆转变应变率影响,使原有模型应用范围扩展至较高应变率。在模型中引入经验损伤失效准则,以准确反映不同应变率、围压等工况下海冰损伤失效过程。应用FORTRAN语言,通过隐式积分中心法对此模型进行数值求解,并将其嵌入到有限元软件LS-DYNA中。对实验室尺度的柱状冰蠕变实验、真实尺度冰块-刚性板碰撞场景进行数值模拟,分析蠕变实验的轴向应变-时间曲线,讨论冰块碰撞得到的压力-面积曲线及碰撞力时历曲线。这些数值模拟结果与实验及真实碰撞结果吻合较好,验证此模型的正确性及其对工程实际进行模拟的可行性。     

基于小偏置碰的乘员二次碰撞分析及约束系统仿真优化

研究64 km/h小偏置碰的乘员动态响应及约束系统参数影响。通过建立50 km/h全正碰与64 km/h小偏置碰的约束系统模型,比对两种工况中的乘员二次碰撞运动姿态与损伤特点。仿真结果表明小偏置碰中乘员上躯干相对车体产生较大的横向加速度,导致头部和颈部等部位损伤加剧。基于上述损伤特点,导入侧气帘模块并分析其对乘员损伤的影响;优化驾驶员侧气囊袋形并通过代理模型方法匹配其参数。CAE优化结果显示小偏置碰中假人头部HIC 36和颈部N ij分别降低61.75%和31.3%,加权损伤指标(WIC)降低了47.22%。     

基于Sobol法的载人空降人体头-颈部损伤响应特性研究

建立了载人着陆冲击的"假人-座椅"数值模型,并进行数值模拟和实验验证。模型经验证后,其数值结果与实验数据非常接近,并基于Sobol法对人体不同部位角度对人体头-颈部损伤响应的影响进行了灵敏度分析。结果表明:人体头-颈部角度和体位角对人体损伤响应有着重要影响。根据分析结果,可为最佳人体着陆姿势的研究提供变量选取依据,在载人空降防护技术领域具有一定的实际工程意义。     

基于复合耗能假设的黏弹夹芯梁振动的有限元分析

建立了一种新的有限元模型用于研究黏弹夹芯梁的振动和阻尼特性。该模型同时考虑了黏弹性层的剪切和压缩阻尼。建模时将约束层和基梁层视作欧拉-伯努利(Euler-Bernoulli)梁,假定中间黏弹性层同时承受纵向剪切和横向压缩变形以耗散振动能量。应用该模型研究了不同边界条件和几何参数的黏弹夹芯梁结构的振动和阻尼特性。通过与精确解析法及其它常用数值法的对比,结果证明该模型具有良好的精度和适用性,在对夹芯梁结构固有频率和损耗因子的预测中,其精度要高于常规的几种数值模型。最后通过实验结果进一步地验证了该有限元模型的正确性。     

形状记忆合金-玻璃纤维/环氧树脂复合材料在振动边界条件下的低速冲击数值模拟

采用有限元方法（FEM）研究了振动边界条件对形状记忆合金（SMA）-玻璃纤维/环氧树脂复合材料的抗低速冲击性能的影响。在数值模拟过程中,将改进的三维Hashin失效准则和Brinson模型分别应用于玻璃纤维/环氧树脂复合材料层合板和SMA,以表征其本构关系。首先通过与固定边界条件下的SMA-玻璃纤维/环氧树脂复合材料板低速冲击实验进行比较,验证了数值模拟过程中所用模型及材料参数的准确性。其次,在模拟过程中,应用了包含不同振幅的一系列振动边界条件,对其进行模拟,揭示了振动边界条件对其抗低速冲击性能的影响。数值模拟结果表明,在大振幅条件下,无SMA复合材料的抗冲击性能比小振幅条件下弱;在相同振动边界条件下,SMA-玻璃纤维/环氧树脂复合材料与无SMA复合材料相比,其抗低速冲击性能提高。      

修正GTN模型及其在预测硅钢冷轧边裂中的应用

考虑剪应变对微孔洞损伤演化的影响, 对GTN损伤模型的损伤演化机制进行修正, 建立了适用于不同应力三轴度水平的损伤模型. 结合隐式应力更新算法和显式有限元计算, 采用VUMAT子程序实现了修正GTN模型在有限元软件ABAQUS中的数值计算. 通过模拟纯剪切和剪切-拉伸两组试样的损伤演化和断裂行为, 验证了修正GTN模型在不同应力三轴度承载条件下的有效性. 运用修正GTN损伤模型模拟含边部缺口的带钢在轧制过程中裂纹的萌生和扩展行为, 模拟结果与实验相一致, 表明该模型可有效地用于带钢缺陷在轧制过程中扩展行为的分析和预测. 模拟和实验结果表明, 带钢边部缺口在轧制过程中, 缺口前沿和后沿均会萌生裂纹, 且后沿裂纹扩展更为明显.     

SPH方法在剪切式碰撞能量吸收器中的应用

剪切式碰撞能量吸收器是提高汽车被动安全性的一种实用新型设计。建立了剪切式碰撞能量吸收器数值分析模型,采用SPH方法数值模拟了碰撞吸能器的碰撞过程,研究了其碰撞吸能特性,并通过不同碰撞速度的台车碰撞试验进行了试验验证研究。数值模拟结果同试验结果相符,表明SPH方法在碰撞吸能器性能研究中是行之有效的数值计算方法。同时分析了在碰撞吸能器的复杂碰撞情况下,SPH方法相比有限元法的优势。     

破冰船在冰层中连续破冰过程的数值模拟

介绍了一种用于模拟破冰船在冰层中连续破冰的冰材料数值模型。通过与冰锥受压实验数据进行对比,对该数值模型进行了验证。将该模型应用于破冰船在无限冰区与冰层碰撞的数值模拟,对破冰船的破冰阻力进行了计算,并将不同船首、不同冰层厚度下计算所得的破冰阻力与经验公式计算结果进行了对比。     

后碰撞中人体颈部动力学响应的有限元分析

为了得到人体颈部在后碰撞中的动力学响应数据,细化完善了先前建立并验证的符合中国人特征且具有较高逼真度的C1-T1全颈椎有限元生物力学模型,模型由椎骨、椎间盘(髓核、纤维环及软骨终板)、韧带和肌肉构成,用六面体实体单元、梁单元和索单元进行模拟,其材料分别定义为线弹性、粘弹性和索。用后碰撞志愿者实验数据对模型进行仿真,得到各椎骨间相对转角,软组织的等效应力曲线。后碰撞过程中颈部形成S形曲线、C形曲线,各软组织应力曲线峰值均发生于最大S形曲线、C形曲线出现阶段,最大相对转角及各软组织最大应力主要发生在C7-T1。后碰撞中过度伸展易导致颈部损伤。有限元仿真有助于理解颈部运动学及其损伤机制。     

Finite element modelling of helmeted head impact under frontal loading

Finite element models of the head and helmet were used to study contact forces during frontal impact of the head with a rigid surface. The finite element model of the head consists of skin, skull, cerebro-spinal fluid (CSF), brain, tentorium and falx. The finite element model of the helmet consists of shell and foam liner. The foam is taken as elasto-plastic, the brain is assumed to be viscoelastic and all other components are taken as elastic. The contact forces and coup pressures with helmet on the head are much lower than in the absence of the helmet. A parametric study was performed to investigate the effect of liner thickness and density on the contact forces, pressures and energy absorption during impact. For 4 ms⁻¹ velocity, expanded poly styrene (EPS) foam of density 24 kgm⁻³ gave the lowest contact forces and for the velocities considered, thickness of the foam did not affect the contact forces.     

Three-dimensional modal analysis of an idealized human head including fluid–structure interaction effects

A three-dimensional analytical and numerical method is presented in this article for the analysis of the acoustic fluid–structure interaction systems including, but not limited to, the brain, cerebro-spinal fluid (CSF), and skull. The model considers a three-dimensional acoustic fluid medium interacting with two solid domains. This article deals with the analytical and numerical computation of eigenproperties for an idealized human head model including fluid–structure interaction phenomena. We determine in the present work the natural frequencies and the modes shapes of the system of the brain, cerebro-spinal fluid (CSF), and skull. Two models are presented in this study: an elastic skull model and a rigid model. In the analysis, a potential technique is used to obtain in three-dimensional cylindrical coordinates a general solution for a solid problem. A finite element method analysis is also used to check the validity of the present method. The results from the proposed method are in good agreement with numerical solutions. The effects of the fluid thickness and compressibility on the natural frequencies are also investigated.     

Near-infrared light propagation in an adult head model. I. Modeling of low-level scattering in the cerebrospinal fluid layer

Adequate modeling of light propagation in a human head is important for quantitative near-infrared spectroscopy and optical imaging. The presence of a nonscattering cerebrospinal fluid (CSF) that surrounds the brain has been previously shown to have a strong effect on light propagation in the head. However, in reality, a small amount of scattering is caused by the arachnoid trabeculae in the CSF layer. In this study, light propagation in an adult head model with discrete scatterers distributed within the CSF layer has been predicted by Monte Carlo simulation to investigate the effect of the small amount of scattering caused by the arachnoid trabeculae in the CSF layer. This low scattering in the CSF layer is found to have little effect on the mean optical path length, a parameter that can be directly measured by a time-resolved experiment. However, the partial optical path length in brain tissue that relates the sensitivity of the detected signal to absorption changes in the brain is strongly affected by the presence of scattering within the CSF layer. The sensitivity of the near-infrared signal to hemoglobin changes induced by brain activation is improved by the effect of a low-scattering CSF layer.     

Study of a spherical head model. Analytical and numerical solutions in fluid–structure interaction approach

This paper deals with the analytical and the numerical computation of elastoacoustic vibration modes. We determine in the present study the eigenfrequencies and the modal shapes of the system of brain, cerebro-spinal fluid (CSF) and skull. Two models are presented in this work: an elastic-acoustic model assuming a rigid skull and an elastic-acoustic-elastic model assuming a deformable skull. The analytical results are compared with the numerical solution obtained using the software Comsol Multiphysics. It is shown that eigenfrequencies and more significantly the modal shapes are strongly influenced by the interaction between solid phases (brain and skull) and the cerebro-spinal fluid. Finally the influence of the CSF compressibility and thickness on the natural frequencies was investigated.     

内燃机气缸盖瞬态温度场数值模拟

分析了内燃机不稳工况的热负荷及测点在起动、突然加载工况的温度变化规律,进而得出边界条件的变化规律,由此用有限元法对缸盖温度场进行数值模拟,模拟结果与实测基本吻合．该分析方法具有通用性,温度场结果可为计算热负荷提供依据．     

The influence of heterogeneous meninges on the brain mechanics under primary blast loading

In the modeling of brain mechanics subjected to primary blast waves, there is currently no consensus on how many biological components to be used in the brain–meninges–skull complex, and what type of constitutive models to be adopted. The objective of this study is to determine the role of layered meninges in damping the dynamic response of the brain under primary blast loadings. A composite structures composed of eight solid relevant layers (including the pia, cerebrospinal fluid (CSF), dura maters) with different mechanical properties are constructed to mimic the heterogeneous human head. A hyper-viscoelastic material model is developed to better represent the mechanical response of the brain tissue over a large strain/high frequency range applicable for blast scenarios. The effect of meninges on the brain response is examined. Results show that heterogeneous composite structures of the head have a major influence on the intracranial pressure, maximum shear stress, and maximum principal strain in the brain, which is associated with traumatic brain injuries. The meninges serving as protective layers are revealed by mitigating the dynamic response of the brain. In addition, appreciable changes of the pressure and maximum shear stress are observed on the material interfaces between layers of tissues. This may be attributed to the alternation of shock wave speed caused by the impedance mismatch.     

The influence of heterogeneous meninges on the brain mechanics under primary blast loading

In the modeling of brain mechanics subjected to primary blast waves, there is currently no consensus on how many biological components to be used in the brain–meninges–skull complex, and what type of constitutive models to be adopted. The objective of this study is to determine the role of layered meninges in damping the dynamic response of the brain under primary blast loadings. A composite structures composed of eight solid relevant layers (including the pia, cerebrospinal fluid (CSF), dura maters) with different mechanical properties are constructed to mimic the heterogeneous human head. A hyper-viscoelastic material model is developed to better represent the mechanical response of the brain tissue over a large strain/high frequency range applicable for blast scenarios. The effect of meninges on the brain response is examined. Results show that heterogeneous composite structures of the head have a major influence on the intracranial pressure, maximum shear stress, and maximum principal strain in the brain, which is associated with traumatic brain injuries. The meninges serving as protective layers are revealed by mitigating the dynamic response of the brain. In addition, appreciable changes of the pressure and maximum shear stress are observed on the material interfaces between layers of tissues. This may be attributed to the alternation of shock wave speed caused by the impedance mismatch.     

爆炸作用下坑道头部结构毁伤试验研究与数值模拟

针对信息化条件下坑道头部结构战时生存面临的挑战,对爆炸冲击作用下坑道头部结构的毁伤情况进行了试验研究。通过动力有限元软件LS-DYNA模拟了爆炸冲击对坑道头部结构的作用过程,将得到的结构毁伤情况与试验结果进行对比分析,二者比较接近,可为坑道结构的设计及毁伤模式研究提供参考。     

爆炸作用下坑道头部结构毁伤试验研究与数值模拟

针对信息化条件下坑道头部结构战时生存面临的挑战,对爆炸冲击作用下坑道头部结构的毁伤情况进行了试验研究。通过动力有限元软件LS-DYNA模拟了爆炸冲击对坑道头部结构的作用过程,将得到的结构毁伤情况与试验结果进行对比分析,二者比较接近,可为坑道结构的设计及毁伤模式研究提供参考。     

Head injuries in lateral impact collisions

Individual non-minor injuries (Abbreviated Injury Scale (AIS) ≥ 2) to the head that occurred to belted and unbelted drivers and front seat passengers on the struck side of impacted vehicles were examined. Injury type, injury combination, collision severity in relation to type of injury as well as contact sources were assessed. Forty-eight percent of injuries were moderate in severity (AIS 2). The most common type of injury was the diffuse brain injury, typically marked by a short period of unconsciousness, which occurred in collisions of lower severity than focal brain and skull fracture injuries. One-hundred and five out of 216 (48.6%) of contact sources for all injury types originated from outside the vehicle and such exterior sources were more likely to result in high severity injuries. Thirty percent of injuries resulted from head contacts with other vehicles. The most frequent vehicle interior contact source was the side window glass. Diffuse injuries tended to occur independently of other injury types and were more likely to originate from an interior rather than exterior contact. Preventative measures for head injury reduction in lateral collisions are discussed. Overall, the data show that proposed and present European and U.S. lateral impact test methods do not address many head injury problems such as those included in this study.