Relationship between occupant injury and the perturbation mark on the velocity indicator on a cluster panel

A perturbation mark is occasionally produced on the velocity indicator of the cluster panel of a vehicle during a vehicle collision. This mark can be used to estimate the velocity of the vehicle at the moment of the vehicle’s impact. In this study, the effect of the impact velocity and the deceleration of the vehicle on the perturbation mark were investigated, and an analysis of the driver’s injury was also conducted through a numerical pulse representation and computer simulations. Sled and pendulum tests were used to replicate the conditions that produce a perturbation mark on the velocity indicator of a cluster panel. It was verified that a higher peak acceleration is more likely than the impact velocity to cause a perturbation mark. According to the computer simulation results, a driver’s injury could be more severe at higher peak accelerations with a constant impact velocity. If a perturbation mark, which can be used to estimate the impact velocity, is found while investigating a vehicle accident, this mark reveals that the acceleration was higher than that listed in the related crash report. Therefore, the injuries of the occupants could be more serious than those expected at the reported impact velocity.     

Wave propagation in head on bonnet impact: Material and design issues

Head on bonnet impact is becoming more and more important in automotive design as regulations on pedestrian safety become more demanding. Despite the relatively low amount of energy involved, these impacts are truly dynamic phenomena as the event duration is comparable with the traveling time of the different wavefronts generated by the impact. In this paper, we show that we can build up a simplified model for the impact based on wave propagation analysis. Using this model, we can analyze head acceleration on existing bonnets or predict it on new ones. Head acceleration in a bonnet impact can thus be estimated over the whole area of the bonnet with a few minutes of CPU.     

有利于行人头保护的风挡玻璃下横梁结构优化设计与试验验证

基于某车型的风挡玻璃下横梁结构,针对提高行人头保护性能进行了优化设计.结果表明,优化后的风挡玻璃下横梁可以提供更大的变形吸能空间,降低加速度峰值和HIC值,提高行人保护性能,为车型行人保护性能评价和开发改进提供借鉴.     

Influence of the geometric parameters of the vehicle frontal profile on the pedestrian’s head accelerations in case of accidents

The goal of this paper is to determine how the geometry of the vehicle’s frontal profile is influencing the pedestrian’s head accelerations (linear and angular) in car-to-pedestrian accidents. In order to achieve this goal, a virtual multibody dummy of the pedestrian was developed and multiple simulations of accidents were performed using vehicles with different frontal profile geometry, from different classes. The type of accidents considered is characteristic for urban areas and occur at relatively low speed (around 30 km/h) when an adult pedestrian is struck from the rear and the head acceleration variation are the measurement of the accident severity. In the accident simulation 3D meshes were applied on the geometry of the vehicles, in order to define the contact surface with the virtual dummy, similar with real vehicles. The validation of the virtual pedestrian dummy was made by performing two crash-tests with a real dummy, using the same conditions as in the simulations. The measured accelerations in the tests were the linear and angular accelerations of the head during the impact, and these were compared with the ones from the simulations. After validating the virtual model of the car-to-pedestrian accident, we were able to perform multiple simulations with different vehicle shapes. These simulations are revealing how the geometric parameters of the vehicle’s frontal profile are influencing the head acceleration. This paper highlights the main geometric parameters of the frontal profile design that influence the head injury severity and the way that the vehicles can be improved by modifying these parameters. The paper presents an approach to determine the “friendliness” of the vehicle’s frontal profile in the car-to-pedestrian collision.     

基于E—NCAP行人碰撞保护的发动机罩设计

行人头部碰撞保护一直是汽车行人安全设计的难点,随着E—NCAP对行人保护要求的不断提高,头部保护的得分比重对于获得高星级评价至关重要。文章基于某车型E—NCAPV6．2五星性能开发,采用虚拟仿真与试验测试有效结合的方法,对发动机罩进行了优化设计,提出了一种有利于行人头部碰撞保护的发动机罩。改进前后测试成绩的对比分析表明,该结构可极大优化行人头部碰撞保护效果,使发动机罩头部测试区域得分总分提升至24．43分,满足E—NCAPV6．2五星行人保护性能要求。可为后续设计提供参考,具有很高的推广价值。     

儿童安全座椅中填充吸能泡沫对头部的保护效果分析

采用Pam-Crash仿真软件,在已验证的6岁儿童乘员有限元模型上,施加ECE R129法规中规定的减速度曲线,以模拟汽车在侧面碰撞事故中后排儿童乘员的头部损伤情况。通过头部质心合加速度、头部性能指标(HPC)、脑组织Von Mises应力、颅内压、剪切应力和泡沫与头部之间的接触力等评价指标,研究侧面碰撞时安全座椅侧翼结构中头枕部位填充吸能泡沫对儿童乘员头部的保护效果。结果表明:安全座椅中填充泡沫可有效降低侧面碰撞对头部的损伤,且填充PU泡沫的保护效果要优于EPS泡沫。     

发动机盖参数对行人头部伤害指标的影响

交通事故中行人的伤亡率较高,行人保护正日益受到重视。文章通过有限元分析的方法模拟GTR法规中的头部撞击试验,利用正交设计的方法总结各个参数对行人头部伤害的影响程度和影响趋势,表明发动机盖的弹性模量和厚度对行人头部伤害影响最大,通过改进车辆前端的设计,可以减轻碰撞中对行人的伤害。     

基于行人保护头部碰撞的空调进气格栅结构

研究了一种适用于行人保护头部碰撞的空调进气格栅结构.通过增加前板结构的高度、椭圆形的压溃槽、倾斜角度及悬臂梁结构,弱化头部碰撞区域,有效降低行人头部受到车辆撞击时的撞击速度,进一步减小碰撞伤害.     

行人被面包车碰撞的运动学规律

为了丰富人车碰撞事故运动学理论,同时为面包车碰撞行人事故的分析鉴定提供理论支撑,对20～110 km·h^-1车辆碰撞速度下行人被面包车碰撞后的运动规律进行研究。利用多刚体建模系统PC-Crash软件构建面包车与行人碰撞仿真模型,并通过仿真获得多种碰撞条件下行人碰撞后的纵向/横向抛距、抛射高度、抛射角度、空中旋转圈数、躯干合成速度和头部合成加速度等运动学数据。结合国家车辆事故深度调查体系（NAIS）中14例具有可靠数据的事故样本进行比较验证。定义并提出了行人被面包车碰撞后的拱推型运动形态,以区别于长头车碰撞的卷绕型和平头车碰撞的推掷型。结果表明：拱推型碰撞中行人会在瞬间被加速到车辆碰撞速度的111%～127%;在高速（110 km·h^-1）碰撞中,头部合成加速度值超过3 000 m·s^-2,头部损伤指标（HIC）值超过7 500;行人空中旋转不超过3圈,被抛高度不超过4.0 m,抛射角度介于6°～11°;行人抛距与车辆碰撞速度之间的关系可以用幂函数模型进行描述;碰撞接触位置、车型外廓参数、行人行走速度和行人碰撞姿势对行人被抛运动形态有一定程度的影响,相对标准碰撞的影响程度一般在5%以内,最大不超过10%（边翻型除外）;行人头部损伤安全界限（HIC值为1 000）对应的车辆碰撞速度约为55 km·h^-1;边翻型碰撞中行人的运动形态与拱推型差别较大,横向抛距最大可达12.0 m。     

交通事故中的行人头部伤害分析

简要分析了我国交通伤亡的发生情况及其分布,并与其他国家的相关数据进行对比。从行人头部损伤分析入手,对在交通事故中的头部损伤发生形式及严重程度做了简要介绍,并对影响车辆—行人碰撞中行人头部伤害严重程度的影响因素进行了详细的分析和阐述,以期为行人头部保护装置的研究提供思路。     

Automotive windshield — pedestrian head impact: Energy absorption capability of interlayer material

During accident, the interlayer of windshield plays an important role in the crash safety of automotive and protection of pedestrian or passenger. The understanding of its energy absorption capability is of fundamental importance. Conventional interlayer material of automotive windshield is made by Polyvinyl butyral (PVB). Recently, a new candidate of high-performance nanoporous energy absorption system (NEAS) has been suggested as a candidate for crashworthiness. For the model problem of pedestrian head impact with windshield, we compare the energy absorption capabilities of PVB and NEAS interlayers, in terms of the contact force, acceleration, velocity, head injury criteria, and energy absorption ratio, among which results obtained from PVB interlayers are validated by literature references. The impact speed is obtained from virtual test field in PC-CRASH, and the impact simulations are carried out using explicit finite element simulations. Both the accident speed and interlayer thickness are varied to explore their effects. The explicit relationships established among the energy absorption capabilities, impact speed, and interlayer material/thickness, are useful for safety evaluation as well as automotive design. It is shown that the NEAS interlayer may absorb more energy than PVB interlayer and it may be a competitive candidate for windshield interlayer.     

基于EuroNCAP的成人头部碰撞保护设计研究

成人头部碰撞保护一直是车辆行人安全设计的难点,随着ENCAP对行人保护的要求不断提高,成人头部保护的得分比重对于获得高星级评价至关重要。文章以SMTC某车型的行人保护开发为例,分别从造型、布置、结构等方面分析了成人头部碰撞保护的设计原则与改进方法,并通过试验与CAE仿真分析,验证了本文结论的对提高成人头部碰撞保护性能的有效性。     

人车相撞头部伤害影响因素仿真分析及试验

在汽车与行人碰撞事故中,行人头部伤害是造成行人重伤或死亡的主要原因。采用有限元三维实体建模技术,建立了发动机罩和包括头皮、头骨两层球体结构的行人头部有限元模型,分析了头部与发动机罩的瞬态大变形非线性撞击响应,得到了头部与发动机罩相撞时的速度、位置及头部质量、发动机罩的厚度、摩擦因数等因素对头部伤害的影响规律,并对铝质与钢质发动机罩作了比较,结果表明铝质发动机罩对行人头部具有更好的保护效果。     

轿车与6岁儿童行人不同方位碰撞中下肢损伤分析

Euro NCAP发布的行人模型认证技术公告TB024的最新版本对6岁儿童行人模型认证提出了单独要求,旨在加强对儿童行人的保护.本研究应用符合Euro NCAP技术公告(TB024)规定并且具有详细解剖学结构的6岁儿童行人有限元模型,设置了4组不同方位行人-汽车碰撞仿真试验,以探究不同碰撞方位下的儿童下肢损伤机理.结果...     

基于EuroNCAP V6．2行人保护小腿碰撞优化

为减小人车碰撞时对行人小腿的伤害,文章基于某车型E-NCAP星级性能提升,采用虚拟仿真与试验测试有效结合的方法,对失分点碰撞过程和失分原因进行分析,确定降低低速吸能盒刚度的优化方向。通过对该车型的优化,有效减轻了行人小腿伤害。优化后,胫骨加速度降低55．40％,膝部弯曲角度降低69．5％,膝部剪切位移降低3％,提升了该车型行人保护性能,为后续设计提供了参考。     

Development of Headform Impactor Finite Element Model Considering the Hyperelastic and Viscoelastic Responses of Rubber

To evaluate and analyze the pedestrian injury risk of automobiles, the finite element models of headform impactors are used. In this study, a modeling method that can accurately estimate the peak of the headform impactor impact pulse and head injury criterion (HIC) was developed. The headform impactor skin has the characteristics of both hyperelasticity and viscoelasticity. Therefore, compression tests, stress relaxation tests, and rheometer tests were conducted, and the hyperelastic and viscoelastic models were developed. The models were combined and used in the finite element analysis. The new headform impactor model was verified to accurately estimate the peak of impact pulse and HIC at the certification test of the headform impactor.     

复合材料车身对头部撞击损伤的模拟

利用三维有限元分析方法模拟了人体头部与复合材料层板发生柔性撞击时的整个动态响应过程。采用复合材料层板模拟了汽车的发动机罩板。分析了石墨环氧As-3501-6两种铺设类型的复合材料层板与人体头部撞击的动态响应特性，得到了铺设角度对头部HIC值、撞击速度和位移的影响。文中的模型为设计具有保护行人头部功能的复合材料车身结构提供了参考。     

Evaluation of idle stability through in-situ torque measurement in automatic transmission vehicles

Idle stability directly affects a vehicle’s NVH (Noise, Vibration and Harshness) and is closely related to driver satisfaction. The present study proposes a method of measuring an engine’s idle roughness, which is useful in quantifying the idle stability. Engine brake torque was measured directly using a torque sensor, which can be installed without modification of the engine’s mounting structure. In addition, angular acceleration was measured at the same position as the torque measurement, to compare dynamic characteristics of the angular acceleration with the torque variation. Both torque and angular acceleration oscillate between positive and negative values. In this study, torque data were divided into several regions, and each region starts from the point where the torque data changes its sign from negative to positive. The root mean square values of both torque and angular acceleration were calculated for each region. This calculation showed a very good correlation between the torques and the angular accelerations. The idle stability was evaluated with the standard deviation of the measured torque, and the cycle-to-cycle variation is a more dominant factor in the idle stability than is the cylinder-to-cylinder variation. Because it is easier to measure the angular acceleration than to measure the torque, the variations of angular accelerations are usually compared between engines. However, the present study showed that the moment of inertia of an engine and the angular acceleration should be considered together when comparing the idle stability between engines.     

汽车副仪表板多学科优化的CAE应用

基于汽车内饰件设计中的性能要求,需要对副仪表板同时进行模态和头碰CAE分析。一般情况下,一阶模态为Y方向横摆,提高模态需要加强副仪表板连接地板的支架;头碰反加速度往往偏高,需要减弱副仪表板连接地板支架。振动和碰撞安全的优化区域重合,优化方向相反。使用多学科CAE优化的方法,可以实现两个性能协同优化,同时满足性能目标。     

行人头型撞击前风挡玻璃区域的损伤风险分析

针对行人头部防护开展研究,建立了符合GTR要求的4.5kg成人头部模型.通过虚拟试验方法使用成人头部模型对轿车前风挡玻璃进行冲击分析,比较不同碰撞部位及相关结构对人体头部损伤评价指标的影响.结果表明,头部损伤风险表现出明显的区域分布趋势,针对特定结构进行设计,可以有效降低风挡玻璃导致头部损伤的风险.