护栏碰撞中车体加速度敏感性分析

碰撞参数在试验组织中会产生误差,为了解车体冲击加速度指标对碰撞参数的敏感程度,建立车辆碰撞某组合式护栏有限元仿真模型,运用碰撞试验对有限元模型的可靠性进行验证后,进行敏感性分析。结果表明,仿真与碰撞试验结果相符,验证了仿真方法的可靠性;车体冲击加速度指标对车辆质量、碰撞角度与碰撞速度参数的敏感度系数分别为-0.58、1.63、4.18,碰撞速度是影响车体冲击加速度的最敏感因素。研究成果为制定碰撞试验误差范围有指导意义。     

新型柔性护栏碰撞安全性仿真分析及实车验证

为研究新型柔性护栏碰撞安全性,据国内现有评价标准,通过建立车辆、护栏有限元仿真模型,结合多次实车碰撞试验,对新型柔性护栏碰撞安全性进行综合分析。基于VPG前处理软件,对所建“汽车-护栏”模型从车辆运动轨迹、车体加速度及护栏最大横向位移等方面分析车辆撞击新型柔性护栏的碰撞安全性;通过实车碰撞试验验证护栏对车辆的导向性。结果表明,仿真计算所得车辆运行轨迹、车体加速度等护栏安全评价指标与试验结果一致,满足法规评定标准要求。     

组合式消能减速护栏实车碰撞试验研究

为了提高高速公路连续长大下坡路段的行车安全性,基于钢管构件变形吸能机理,设计出一种具有防撞和减速双重功能的组合式桥梁护栏。结合依托工程现场桥梁翼缘板情况,进行护栏基础锚固强度验算,通过在桥面现浇层增设钢筋的方式进行翼缘板加强,采用实车碰撞试验方法进行护栏安全性能检验。根据试验结果可知：护栏防撞等级可达到SS级（520kJ）;车辆贴靠碰撞减速护栏时吸能钢管变形吸能,有效降低车速;吸能钢管的设置使护栏横梁几乎没有变形,减小了碰撞后的维护工作量;吸能钢管的设置没有对车辆碰撞护栏过程的行驶姿态造成不利影响;根据钢筋应变测试数据可知,护栏迎撞面根部对应的钢筋应变值最大,桥面现浇层加强钢筋可以有效分担碰撞荷载,护栏基础锚固强度满足受力要求。     

卷板式护栏端头脱钩约束装置的改进

常用护栏端头易引发恶性事故,卷板式护栏端头吸收车辆动能效果不佳且车体碰撞方向加速度不满足要求,运用碰撞试验和有限元仿真分析相结合的方法,对卷板式护栏端头进行碰撞分析和结构优化研究。通过分析研究,得出改进的脱钩约束装置,应用该装置后的端头能够完全吸收车辆动能,且使车辆碰撞方向加速度最大值为由38g降低为11.9g,卷板吸能效果显著增强,各项指标均满足评价标准要求;仿真与碰撞试验结果相符,验证了仿真方法的可靠性。开发的端头优化结构可有效降低事故严重程度,保护乘员安全。     

直升机抗坠毁试验假人下肢动力学性能的计算机仿真研究

下肢动力学性能研究是直升机抗坠毁试验假人研制过程中的重要课题。在对直升机坠撞事故中飞行员下肢损伤分析的基础上,通过建立具有我国50 th百分位飞行员参数特征的假人下肢有限元模型,按试验要求对下肢动力学性能进行仿真分析;将仿真结果分别与假人下肢动力学性能参考指标及试验结果比较,发现该下肢模型具有较好的生物拟合性,表明采用有限元法对假人下肢动力学性能分析的有效性和可行性。由于直升机坠撞事故中人体下肢损伤形式较复杂,该研究对将来能实现多方位碰撞损伤评价的假人下肢动力学性能研究具有一定指导意义,对假人其他部位动力学性能的仿真研究也具有重要参考价值。     

弯道混凝土护栏碰撞特性的优化设计

摘要：平曲线半径不足400米的弯道是交通事故率最高的路段,由于缺乏对弯道护栏的研究,人们不得不在弯道上长期使用直道护栏。要改变目前这种无论弯道、直道,均一律使用直道护栏的不合理现象,就必须获得弯道半径为400米时的混凝土护栏最佳尺寸参数。为此,本文以NJ型混凝土护栏尺寸参数为参考基础,以防撞等级为SS级的护栏为研究目标,以大型客车总质量为18t、碰撞速度为80km/h、碰撞角度为20°的碰撞条件为研究工况,基于eta/VPG及Ls-dyna软件平台及“汽车-护栏-弯道”一体化车-路系统动力学模型,联合应用正交试验设计方法及动态显式有限元方法,以客车后轮抬高量为考核指标,对控制弯道混凝土护栏截面形状的6个设计变量,应用L25(56)正交试验表安排仿真试验,借助SPSS统计软件包,对仿真试验结果进行了方差分析,找出了各因素对结果的影响程度,并据此确定了弯道混凝土护栏的最佳尺寸参数。对25组仿真试验结果的分析发现,大型客车撞击弯道半径为400米的混凝土护栏时,发生的弯道事故全是翻车事故,且主要表现为客车翻越混凝土护栏而坠向护栏外侧悬崖的事故模式。优化设计结果表明,增加混凝土护栏的高度是抑制大型客车翻越护栏的重要途径,合理的弯道混凝土护栏尺寸参数,可以将翻车事故控制在护栏内侧,以避免重大恶性事故的发生,且控制弯道混凝土护栏截面形状的6个设计变量对弯道事故的影响,存在如下优先级关系：下斜坡高度>底部凸缘高度>上斜坡高度>顶部宽度>下斜坡宽度>上斜坡宽度,即高度的影响较宽度的影响要显著,下斜坡高度的影响又较上斜坡高度的影响显著。     

运输车辆碰撞事故对在建隧道影响的数值模拟

利用显式非线性有限元法对在建狭长隧道施工中运输车辆碰撞事故进行数值模拟,并研究事故对周围隧道产生的影响。为准确的模拟运输车辆碰撞时对周围隧道的影响,基于拟实建模方法,建立了大型输水工程青草沙隧道及运输车辆的三维有限元模型。通过三维动态接触方法来模拟轮轨之间的动力相互作用,能够模拟打滑、脱轨等实际接触情况。采用了基于罚函数的接触算法和基于段分类的搜索方式,对该大型输水工程隧道在运输车辆发生碰撞时的动态响应进行仿真计算。分析了运输车辆发生碰撞后车与管片的运动规律,以及在建隧道的动态响应,这对事故的防范及处理有指导作用。利用上海超级计算机曙光5000A进行并行计算,分析了对于大型工程问题的模拟仿真采用并行计算的加速效果。     

汽车碰撞护栏事故再现方法

为了应对大量的汽车碰撞护栏事故,提出了基于CRASH3碰撞模型的事故再现方法。该方法根据护栏的刚度特性,以车辆和护栏的残余变形量为输入,计算车辆的碰撞前速度,因此具有很强的可操作性。研究主要针对一款常见的高速公路波形梁护栏,通过对汽车冲击作用下的护栏进行有限元分析,研究了该款高速公路护栏的动力特征。研究发现在大多数情况下,随着变形量的增加,护栏受力几乎呈线性上升,基本符合CRASH3的线性假设。最后,应用上述方法,再现一起真实的汽车-护栏碰撞事故,将得到的碰撞前车速与PC-CRASH结果进行比较,初步证明了该方法的可行性。     

乘用车-载货汽车追尾碰撞相容性结构优化设计

对一种已获得专利的新型货车后防护结构进行碰撞相容性优化设计,建立了该结构的乘用车-货车追尾碰撞有限元模型,并通过实车碰撞试验验证了模型有效性。为提高碰撞相容性,制定了防护架最大的吸能和乘用车前部最小的变形量两个优化目标函数,并设计了优化设计参数变量及其变化范围,采用正交化试验方法对16组参数进行了有限元仿真,并对优化目标的影响因素进行了显著性分析,最后,对得到最优的设计方案进行了实车碰撞试验     

基于混合模型的超大规模隧道结构非线性动态有限元分析

提出了一种用于对超大规模隧道结构进行有限元分析的混合模型建模方法,弥补了以往仿真计算中宏观与微观不能同时兼顾的不足。利用并行算法,并对整体混合模型的计算时间步进行了有效的控制,使超级计算机能完成此类超大规模整体混合模型的计算。用混合模型建模法对青草沙水源地原水工程输水隧道进行非线性动态有限元仿真,得到的结果既反映了宏观的响应规律,又反映了局部精细结构的具体变化,证明了此种混合模型建模方法的可行性。     

Dynamic responses of connections in road safety barriers

Bolted road safety barrier connections utilise slotted holes that are perpendicular to the direction of the safety barrier beam. Due to the clearance between the slotted holes and the bolts, a varying amount of slippage is seen before contact with the edge of the slot is made. The stiffness characteristics of bolted road safety barrier connections have been examined with a representative test coupon that incorporates a full size safety barrier connection slot to industry standard dimensions.Previous research work has successfully determined the stiffness characteristics of the bolted connections at quasi-static strain rates. Representative non-linear finite element models of the bolted test coupons have been constructed. When compared to the laboratory results the initial stiffness, maximum force and displacement of the bolted connections are similar to the finite element model predictions.Current investigations have moved onto strain rates comparable to those observed in actual vehicle crash tests. Explicit dynamic finite element (FE) models have been constructed and validated, using experimental data produced using a series of high strain rate laboratory tests for a number of bolt configurations.     

Computational and experimental crash analysis of the road safety barrier

The paper describes the computational analysis and experimental crash tests of a new road safety barrier. The purpose of this research was to develop and evaluate a full-scale computational model of the road safety barrier for use in crash simulations and to further compare the computational results with real crash test data. The impact severity and stiffness of the new design have been evaluated with the dynamic nonlinear elasto-plastic analysis of the three-dimensional road safety barrier within the framework of the finite element method with LS-DYNA code. Comparison of computational and experimental results proved the correctness of the computational model. The tests have also shown that the new safety barrier assures controllable crash energy absorption which in turn increases the safety of vehicle occupants.     

Simulation of crash tests for high containment levels of road safety barriers

This paper presents the results of computer simulations of road safety barrier behaviour under vehicle crash conditions for high containment levels as mandated by the European standard EN 1317. Simulations were performed with the explicit finite element code LS-DYNA, running on a multiprocessor computational platform. A very good agreement of simulation and real crash tests results was observed, which in turn justifies the use of computer simulations in the process of development and certification of road safety barriers.     

多用途汽车正面碰撞特性的数值模拟

为保证驾驶员和乘员的安全性,综合运用多种有限元分析软件,建立多用途汽车的有限元正面碰撞模型。通过对正面碰撞模型进行数值模拟、分析碰撞仿真结果,得出整车动能、内能和沙漏能在碰撞瞬间的转换关系,获得碰撞过程中车身前围关键零件的能量吸收程度和变形形式,由此提出提高整车正面抗撞性的方法和措施。仿真结果表明：该方法可用于乘用车的正面碰撞等仿真分析,能达到降低研发周期、提高分析精度的目的。     

Improving the crashworthiness of reinforced wooden road safety barrier using simulations of pre-stressed bolt connections with failure

During the development process of a new type of steel reinforced wooden road safety barrier parametric computational simulations were used to simulate the experimental vehicle impact certification tests as prescribed by the standard EN 1317. First a detailed study of pre-stressed bolt connection behavior between the guardrail and the guardrail connector was performed using parametric computational simulations of which results were later used in a large scale vehicle impact simulations. A novel, simplified approach to the modeling of barrier wooden parts was introduced to achieve reasonable simulation times in parametric study of the barrier behavior under vehicle impact. The wooden parts of the road safety barrier were modeled indirectly through a modified contact definition. The developed safety barrier design was later successfully experimentally certified in a full scale crash test according to the standard EN 1317. Experimental results were in a good agreement with the results of the full scale crash test simulations, which validates the proposed computational safety barrier model and thus justifies the use of the simplified modeling approach of the wooden safety barrier parts.     

Design of an aluminium-based vehicle platform for front impact safety

The current paper examines the design of an aluminium-intensive small car platform for desirable front impact safety performance. A space frame-type architecture comprised of extruded aluminium members with welded joints is considered for inherent structural rigidity, and low investment in terms of tooling. A finite element model of the vehicle is employed for crash analysis using the explicit code LS-DYNA. Confidence in analysis is established at the component level by benchmarking finite element models of welded joints against experimental data, and axial crushing of aluminium tubes against published numerical results and theoretical prediction. A numerical design of experiments is conducted for arriving at a front-end design that will yield desirable safety performance during impact against a rigid barrier at 30 mph (FMVSS 208 condition). For comparable new car assessment program performance at a higher speed of 35 mph, a lumped parameter idealization is used to identify the principal design changes that may be necessary. The current approach of component level testing combined with finite element and lumped parameter-based simulations can be regarded as an effective and time-saving procedure in the crash safety design of new vehicles.     

某车辆动力总成异常振动分析与改进

针对某SUV车柴油机动力总成产生异常振动导致操纵手柄剧烈振动这一实际问题,将振动试验测试与有限元仿真分析结合起来研究动力总成的振动动态特性。通过整车道路试验及转鼓试验,发现柴油机工作转速的二阶激励激起了动力总成系统共振,通过采用有限元方法建立了一种柴油机动力总成振动分析模型,计算分析了此动力总成的振动固有频率和固有振型,找到了导致动力总成弯曲刚度变差的原因—飞轮壳结构刚度不足。在验证了有限元仿真模型计算合理性基础上,通过改进设计飞轮壳结构,提高了动力总成的固有频率,使其避开了共振频率区间,最终消除了操纵手柄的异常振动。该试验与仿真分析方法对解决同类工程问题具有参考指导和应用价值。     

大客车侧翻碰撞护栏事故仿真分析及改进

建立大客车与护栏有限元模型,仿真大客车侧翻碰撞护栏型交通事故,并与我国GB/T 17578-1998及欧盟ECE R66规定对比。仿真结果表明此类侧翻事故的损害程度远超规定;进而改进大客车侧面立柱材料及厚度,仿真验证表明,此方法可减小事故损失。可供设计人员参考。     

声障板对圆柱换能器轴向波束抑制技术研究

文章研究了声障板对圆柱换能器轴向波束抑制特性。利用有限元仿真方法建立了带轴向反声障板的圆柱形换能器的水中模型,通过改变障板距离圆柱形换能器的相对距离、直径等参数,探索了障板对圆柱形换能器轴向波束的抑制效果,并实际制作了带轴向障板的圆柱形换能器。结果表明:有限元仿真计算结果与试验测试结果吻合较好,利用障板技术可以有效地抑制圆柱换能器轴向声压。