A development of simple analysis model on bumper barrier impact and new IIHS bumper impact using the dynamically equivalent beam approach

This paper presents a simple analysis model for bumper barrier impact and new IIHS (Insurance Institute for Highway Safety) bumper impact instead of a non-linear finite element impact analysis. A dynamically equivalent beam approach was introduced to simplify the non-linear dynamic bumper impact. For a bumper barrier impact, the equivalent curved-beam element was substituted for the bumper beam and the bumper foam. For a new IIHS bumper impact, a modified curved-beam element of bumper barrier impact considering the effect of contoured new IIHS impact barrier was used. The accuracy of this simple analysis model was tested by comparing its results with those of the non-linear finite element analysis. Tested bumper beam types were press type beam and roll forming beam used widely in the current car bumpers. The maximum displacement error between the two models did not exceed 1.95% for a barrier impact and 13.2% for a new IIHS bumper impact. This accuracy is good enough to be used in the early stage of bumper beam design process. This simple analysis model is expected to reduce the car development time and tests cost significantly.     

Design of pedestrian friendly vehicle bumper

Car-pedestrian accidents take thousands of lives worldwide annually. Therefore, pedestrian protection is an important issue in traffic safety. How to consider a pedestrian friendliness vehicle and then propose pedestrian protection methods are urgent works for minimizing pedestrian injury. For designing a pedestrian friendly vehicle bumper, this study adopts the European Enhanced Vehicle-safety Committee/ Working Group 17 (EEVC/WG17) regulations of legform impactor to bumper tests. Analyzing the pedestrian friendliness of a vehicle bumper by using LS-DYNA is described in detail. Simulation results were analyzed to identify the reasons for the unfriendliness. Furthermore, the analysis of the influence of bumper structure on pedestrian leg was performed and then some guideline was suggested. The analyzed models and results obtained could help evaluate pedestrian friendliness of a vehicle and guide the future development of pedestrian friendly vehicle technologies.     

The effect of leg fracture level and vehicle front-end geometry on pedestrian knee injury and response

In this study a MADYMO (mathematical dynamic modelling) model has been used to identify the influence of leg fracture on the injuries sustained by the pedestrian during front end impact with a vehicle. A factorial study of a MADYMO pedestrian and vehicle model are used to investigate the effect of different leg fracture tolerances, geometry, and vehicle compliance on the criteria measured in the European Enhanced Vehicle-safety Committee (EEVC) pedestrian safety tests. These criteria include knee bending, knee shear response, and lower leg bone (tibia) acceleration. The main study examines the spread of typical values of lower limb tolerance based on reported literature and contrasts the response of weaker, low-strength bones, normal tolerance, and limbs which do not fracture. Results show that knee bending angles and therefore ligament strains are significantly increased when fracture does not occur, and are decreased in bones exhibiting a low-strength response. Bone fracture tolerance is shown to be a significant parameter influencing knee bending. The parameters are compared to show that knee shear is significantly influenced by vehicle bumper compliance and that both criteria are heavily influenced by bumper height. Vehicles with more aggressive geometry, higher bumpers, and larger bumper lead were considered for comparative purposes.     

基于组合近似模型的可靠性优化方法在行人柔性腿型碰撞中应用研究

当行人与车辆发生碰撞时,车身最前端的部件将直接与行人下肢腿部发生接触,其设计是满足行人下肢保护要求的关键。然而针对传统要求的基于刚性腿型行人保护车辆前结构设计方法,在应对柔性腿型行人保护要求已呈现明显的局限性。为了提高保险杠结构的柔性腿型保护功能,结合试验设计技术、组合近似建模技术、多目标优化算法和可靠性分析方法,以行人腿部的伤害值最低为优化目标,对车辆前端结构参数进行可靠性优化设计并对优化结果进行试验验证。研究结果表明:优化后的车辆前端结构与原设计相比,行人柔性腿型保护功能得到明显提高,为车辆前端结构的设计与开发提供有效的参考。     

汽车前部与行人下肢的冲击实验评价方法研究

利用MADYMO软件数据库中的下肢冲击器模型进行了汽车碰撞计算机仿真，并利用一个生物逼真度较好的行人模型进行了汽车与行人碰撞计算机仿真。将仿真结果除以相应的技术要求值得到各自的风险系数。依照风险系数的综合评价，可对不同汽车前部结构对行人下肢的碰撞性能进行排序。排序结果表明，由下肢冲击器实验仿真得到的结果和由汽车与行人碰撞仿真得到的结果基本相符。将EEVC制订的下肢冲击器实验评价方法得到的实验结果按损伤风险系数进行排序的方法，可用来进行汽车前部结构对行人下肢碰撞安全性能好坏的评价，但下肢冲击器实验依然存在一些不足需要进行政进．     

基于行人下腿部与汽车保险杠的碰撞研究及优化设计

交通事故中当汽车与行人发生碰撞时,下腿部易受到骨折甚至更严重的伤害.所以行人保护受到越来越多的关注.各大汽车厂商和研究机构也在自身的产品开发中考虑对行人保护的改善.介绍了行人保护法规内容要求和实验要求,并采用仿真方法,建立了行人下腿部撞击器与保险杠碰撞的有限元模型,分析了腿部与保险杠的撞击响应,得到了行人腿部与保险杠相撞时的加速度、弯曲角度、剪切位移等参数,并通过调整保险杠的造型以及保险杠发泡和蒙皮刚度改善车辆前部对下腿部的影响,从而改进对行人腿部碰撞的伤害.     

Bumper shape design for pedestrian safety

The main cause of leg injuries is the bumper during car-pedestrian accidents. Bumper geometry and bumper material have the greatest effect on pedestrian leg injury. The first objective of this study is to evaluate the effects of bumper shape on pedestrian leg injuries. This study uses three bumper shapes on three car models to evaluate the effects of bumper geometry on pedestrian leg injury: A Ford Taurus, Dodge Intrepid, and Dodge-Neon. Then, based on the results of the impact between legform and bumper, this study chooses the best bumper shape that results in the least injury to the pedestrian’s leg. The second objective of this study is to design a new bumper. Using some conclusions regarding the effects of bumper shape on the pedestrian leg injuries, a new pedestrian-friendly bumper was designed. This bumper satisfies EEVC/WG17 safety requirements regarding pedestrian leg injuries. The analyzed models and results obtained could help evaluate pedestrian friendliness of a vehicle and guide the future designing and development of pedestrian friendly vehicle technologies.

     

Crumple zone design for pedestrian protection using impact analysis

This paper describes the design process for an automobile crumple zone for pedestrian protection. The impact load and bending moments predicted by impact analysis were used to design a plastic structure that may help reduce pedestrian injuries to the thigh area. The fracture effect was incorporated into the model by calculating the damage to the plastic material during impact, and the analysis was conducted under the European New Car Assessment Program (Euro NCAP) test conditions, using the upper legform developed by ESI Corporation. In addition, the values predicted by the analysis were validated by comparison with results of actual impact tests.     

基于加速度波形优化的行人头部保护设计

人车碰撞过程中头部保护是国内外研究的一个重点,在HIC值相同的情况下头部加速度曲线可能千差万别,从而导致碰撞深度也有差异,因此,通过合理的车身结构设计来控制加速度曲线,可以保证在相同的碰撞深度下使头部伤害程度降低到最小。首先分析了几种常见的加速度近似波形的不同特性,并找出最优化的加速度曲线,然后借助有限元软件的仿真分析,通过对头部碰撞区域内的结构进行改进,实现对头部加速度的优化,从而降低头部的伤害程度。     

基于行人保护的波纹式铝制发动机罩盖的结构设计

针对钢制发动机罩盖不能满足行人碰撞保护法规要求的问题,对钢制发动机罩盖进行了材料替换和结构设计.在ANSYS中建立了头块和发动机罩盖的有限元模型,通过有限元仿真分析结果与试验结果的对比,证明了有限元建模的可靠性.对新设计的波纹式铝制发动机罩盖和原来的梁式钢制发动机罩盖进行了有限元仿真分析与对比.研究结果表明,新设计的波纹式铝制发动机罩盖可以有效地减小人-车碰撞过程中行人头部伤害值,满足行人碰撞头部保护标准.     

计及二阶效应的大位移柔性梁杆系统动力学分析

结合小变形条件下梁杆单元精确有限元方法和大位移随动坐标法,建立了计及二阶效应的大位移运动柔性梁单元的动力学方程.首先从小变形结构入手,建立考虑二阶效应的柔性梁压弯力学模型,推导出二阶理论条件下平面压弯梁的精确有限元方程,进而获取二阶理论条件下梁单元精确刚度阵.运用大位移随动坐标法建立大位移几何非线性弹性梁杆单元平衡方程,使用柔性多体动力学的相对描述方法推导大位移梁单元在局部坐标系下的动力学方程.通过结点位移、速度和加速度在随动坐标系与整体坐标系间的相互关系得到梁单元在整体坐标系下的包含二阶效应的动力学方程.对某型港口起重机臂架系统的变幅工况进行了计及二阶效应的弹性动力分析.     

负泊松比蜂窝芯非线性等效弹性模量研究

设计并加工了一种负泊松比蜂窝结构,采用柔性悬臂梁模型,对蜂窝壁板大变形条件下的弯曲变形进行分析,给出了蜂窝芯面内等效弹性模量理论计算公式。通过有限元仿真和力学实验的对比分析,验证了非线性理论计算公式的正确性。得出了等效弹性模量的非线性特性及相同方向和不同方向弹性模量的变化特性。研究结果为柔性蜂窝芯层的工程实用化提供了参考。     

某扭转梁扭转疲劳工况应力分析以及结构优化

针对某扭转梁在扭转疲劳试验过程中出现的裂纹现象,采用有限元法对扭转梁进行应力分析,结合计算结果给出优化改进措施,对该扭转梁的横梁加强板进行结构优化,横梁加强板开裂问题得到解决。     

Modélisation de nœuds mixtes acier–béton soumis à des sollicitations sismiques

The paper deals with the three-dimensional finite element modelling of typical beam-to-column intersection zone of composite frames under earthquake horizontal loading. The modelling takes into account the non-linear material properties of the different components: column, longitudinal beam, transverse beam, reinforced concrete slab and shear connectors. The studied element is the longitudinal composite beam, which is chosen to dissipate the earthquake energy. The paper presents the basic modelling, its calibration on a subassembly tested experimentally and a part of the parametrical study performed with the model. The important results obtained for the behaviour of the beam subjected to sagging bending in an exterior node configuration and for the behaviour of the beam subjected to hogging bending at one side of the node and sagging bending at the other side in an interior node configuration are presented.     

轿车白车身有限元模型修正研究

有限元模型与实际结构的一致性影响着CAE分析的可靠性。以典型点焊薄板件为例,分别采用刚性梁单元和等效板两种方式对结合面连接刚度进行了修正方法研究,并将研究方法成功应用于某轿车白车身的有限元模型上。修正后有限元模型的分析结果与试验结果基本一致。     

基于ANSYS的金属软管的静态有限元分析

运用非线性有限元法，波纹管采用三维壳单元Shell93，网套采用空间梁单元Beam189，利用耦合和约束理论，在ANSYS中建立金属软管的有限元模型，对金属软管的拉伸、压缩、弯曲等特性分别进行有限元分析，得到金属软管的特性曲线，并将分析结果与试验结果进行比较，证明了有限元建模分析结果以及耦合和约束理论运用的合理性，为金属软管的力学性能和设计分析的进一步研究提供了参考。     

后悬架拖曳臂开裂有限元分析

基于有限元分析方法，对某SUV样车在道路实验过程中后悬架拖曳臂开裂的问题，进行了加速、转向、制动和垂直冲击四种工况分析。结果表明，在制动器支架、制动器支架与拖曳臂本体的焊缝处，出现应力大于强度极限现象，导致了后悬架拖曳臂的开裂。     

The effect of ‘material ratchetting’ on the incremental growth of beams subjected to steady axial loads and cyclic bending

An elastic-plastic material behaviour model capable of predicting material ratchetting, cyclic relaxation and cyclic hardening has been incorporated into finite element programs. The resulting programs have been used to predict the behaviour of beams subjected to the steady axial loads and cyclic bending. The results are compared with experimental data obtained from three tests performed on beams made from a model material. Overall, the predictions were found to be good; discrepancies in the results for the most highly loaded beam were attributed to creep effects in the experiment.The results indicate that an elastic-perfectly plastic material behaviour model, with an equivalent yield stress, does not allow acceptable prediction of the beam behaviour to be obtained.     

液压镦锻机下横梁结构的静态有限元分析

在对某液压机下横梁结构特点研究的基础上,以有限元软件ANSYS为工具,选用实体单元建立下横梁结构的有限元模型,并对模型进行了整体静态有限元分析,揭示下横梁结构的应力和应变的分布规律,获得了受力及变形危险点的位置,为其进行结构改进提供了重要的依据。