Analysis of bus rollover protection under legislated standards using LS-DYNA software simulation techniques

A bus rollover is one of the worst vehicle accidents that can occur. Because of the large numbers of passengers, the casualties in a bus rollover are often high and severe. The compliance with rollover safety standards for buses and coaches is mandated by law. This paper presents a comparative analysis of the physical meanings of regulation number 66 of the Economic Commission for Europe (ECE R66) and standard number 220 of the American Federal Motor Vehicle Safety Standards (FMVSS 220). This comparison was carried out using a LS-DYNA finite-element analysis. After performing a comparative analysis following ECE R66 and FMVSS 220 assessments, the investigation further demonstrated the distortion configuration of the vehicle superstructure through the absorbed energy and its distribution over the vehicle and in sections of vehicle superstructure as well as the violation of the passenger compartment under the rollover testing conditions of both ECE R66 and FMVSS 220. Great differences were found between ECE R66 and FMVSS 220 in distortion configuration, reflecting differences in capability and rollover testing conditions. These findings provide a means of evaluating bus superstructure strength and provide guidelines useful in the assessment of regulations applied to the evaluation of bus rollover strength.     

基于ECER66法规的某大客车上部结构强度

以某全承载大客车作为研究对象,应用有限元分析理论,建构了客车有限元模型和客车上部结构强度的数值模拟研究环境.根据ECE R66的等效认证方法,进行了整车质心位置计算以及车体截段实车侧翻试验,评价了其上部结构的变形及其侵入乘员生存空间的状况.将车体截段试验结果与数值仿真结果对比,研究发现两者具有较好一致性.在此基础上,研...     

基于相对灵敏度分析的中型客车车架轻量化设计

建立了某客车车架的有限元模型,分析了车架的弯曲和扭转刚度。对车架各构件进行了灵敏度分析,取质量灵敏度与刚度灵敏度之比较大的构件厚度作为设计变量,以质量最小作为目标函数,以位移为约束条件,对车架进行了轻量化设计。优化结果表明,基于灵敏度分析的优化设计方法可行,轻量化效果明显。     

Methodology for bus structure torsion stiffness and natural vibration frequency prediction based on a dimensional analysis approach

Engineering bus design requires testing of bus structures prototypes in order to guarantee a certain level of strength and an appropriate static and dynamic behavior of the bus superstructure when exposed to road loads. However, experimental testing of real bus structures is very expensive as it requires expensive resources and space. If testing is done on a scale bus model the previous required expenses are considerably reduced. Therefore, a novel methodology based on dimensional analysis applied to bus structure prediction to evaluate the bus structure static and dynamic performance is proposed. The static performance is evaluated attending to torsion stiffness and the dynamic in terms of the natural vibration frequencies and rollover threshold. A scale bus has been manufactured and dimensionless parameters have been defined in order to project the results obtained in the scale bus model to a larger model. Validation of the proposed methodology has been carried out under experimental and finite element analysis.     

有限元分析在客车轻量化设计中的应用

采用HYPERMESH软件建立某大型公路客车的有限元模型,对整车结构使用OPTISTRUCT软件进行有限元分析。依据分析结果,在保证整车结构运行刚度和强度的情况下,对整车结构进行轻量化设计。最后对轻量化结构进行侧翻分析和优化设计,以保证整车上部结构强度的侧翻安全性。     

Load Transfer Analysis of a Bus Bay Section Under Standard Rollover Test Using <Emphasis Type="Italic">U</Emphasis>*<Subscript>M</Subscript> Index

Bus rollover accidents are receiving increasing attention due to the associated high fatality rate. In order to improve the bus structural performance during the rollover collision, it is necessary to investigate how the impact force is transferred within the bus superstructure. This paper introduced a method for studying the load transfer behavior of the bus superstructure during the standard rollover test by using the U * _M index. A bus bay section was used as the sample structure to demonstrate the proposed method. The result of the paper reveals that the load transfer analysis based on the U * _M index can provide engineers with the insight of the structural issues and the direction to improve the structural performance, which cannot be accomplished through the conventional finite element analysis.     

基于相对灵敏度分析的客车车架轻量化

以某客车车架为研究对象,进行模态分析并与试验模态比较,验证了有限元模型的准确性;进行刚度分析,验证了该车架弯曲刚度和扭转刚度符合设计要求。在此基础上,考虑车架结构件板厚对其低阶模态参数及质量的影响,对主要部件的板厚进行频率灵敏度和质量灵敏度分析。引入相对灵敏度,提取相对灵敏度较大的部件以板厚为设计变量进行优化分析。优化结果表明：车架固有频率降低,同时车架的质量也减少,达到了轻量化的目的。     

Variable Cross-Section Rectangular Beam and Sensitivity Analysis for Lightweight Design of Bus Frame

Timoshenko beam element of variable cross-section rectangular tube is developed and applied in the lightweight design of bus frame in this paper. Firstly, the finite element formulations of variable cross-section beam (VCB) are derived under the loadsteps of axial deformation, torsional deformation and bending deformation. Secondly, bending deformation experiment and its detailed shell finite element model (FEM) simulation of variable cross-section rectangular tube were conducted; and the proposed VCB, detailed shell FEM and experimental results can be highly consistent. Thirdly, VCBs are used to substitute for parts of the uniform ones in a bus frame. An innovatively lightweight bus frame is obtained and all the performance responses are improved simultaneously. Finally, rollover analysis further shows the advantage of variable cross-section bus frame in crashworthiness design.     

大客车结构有限元分析及轻量化设计

建立了某型大客车结构有限元模型,验证了该模型的正确性。完成了整车振动模态、扭转刚度的分析。在此基础上,以壳单元厚度为设计变量,以1阶扭转频率和扭转刚度为联合约束函数,以整车质量最轻为目标函数进行结构优化设计。通过对整车刚度、模态和强度的分析与校核,表明该大客车轻量化方案满足性能要求,具有可行性。     

有限元分析在改进客车骨架设计中的应用

利用有限元分析法对一改进设计的客车进行强度、刚度的分析,计算结果显示车身骨架不能满足转弯工况下的强度要求。根据初步分析的结果,结合实际设计经验对车身骨架进行二次改进设计,重新进行分析,车身骨架能满足四个典型工况的强度和刚度要求。     

基于PSO算法的反力架设计与优化

为提升盾构隧道专用反力架轻量化水平和降低制造及运输成本，对其结构进行优化。首先，依据设计的反力架结构建立其有限元模型，并结合工程数据类比确定载荷条件，验算反力架强度及刚度； 然后，以所有板材厚度为自变量、反力架总质量为因变量，利用方差分析的方法获得主效应图，确定5种对结构总质量贡献量大的板厚为优化变量； 最后，以5种板厚为设计变量，强度、刚度指标作为约束条件，反力架质量最小为优化目标，采用PSO算法进行求解。结果表明： 优化后结构的最大应力为252.2 MPa,最大变形为10.6 mm，反力架总质量从305.78 t降至274.85 t，减重比例为10.1%(30.90 t)，验证了结构优化的有效性。     

Rollover mitigation for a heavy commercial vehicle

A heavy commercial vehicle has a high probability of rollover because it is usually loaded heavily and thus has a high center of gravity. An anti-roll bar is efficient for rollover mitigation, but it can cause poor ride comfort when the roll stiffness is excessively high. Therefore, active roll control (ARC) systems have been developed to optimally control the roll state of a vehicle while maintaining ride comfort. Previously developed ARC systems have some disadvantages, such as cost, complexity, power consumption, and weight. In this study, an ARC-based rear air suspension for a heavy commercial vehicle, which does not require additional power for control, was designed and manufactured. The rollover index-based vehicle rollover mitigation control scheme was used for the ARC system. Multi-body dynamic models of the suspension subsystem and the full vehicle were used to design the rear air suspension and the ARC system. The reference rollover index was tuned through lab tests. Field tests, such as steady state cornering tests and step steer tests, demonstrated that the roll response characteristics in the steady state and transient state were improved.     

大客车CAE分析及轻量化设计

通过有限元分析方法,对12m大客车进行了多工况下的刚度及强度分析;并通过灵敏度分析,对车身骨架进行了优化设计;同时,也呈现了一套通过数值模拟方法对大客车轻量化进行设计的方案,此方案对于客车优化设计具有一定的参考价值。     

燃料电池客车骨架结构的有限元分析与优化设计

建立燃料电池客车骨架的有限元模型,计算弯曲、一轮悬空等典型工况下的静态强度、刚度及振动模态,对骨架结构进行优化设计,保证骨架结构的安全性及可靠性。     

大型宿营客车的设计开发

针对目前宿营车存在车型较小、睡眠空间不足、舒适性差等缺陷,提出了使用大客车改装成可以容纳33人宿营的自行式宿营车的技术方案,并应用虚拟装配技术进行了整车结构设计。运用ANSYS软件对展开工况下的顶围和活动侧围进行了仿真分析,结果表明宿营客车展开时的刚度和强度均能够符合设计要求。在实车测试中,宿营客车能满足33人同时舒适宿营的要求。     

全承载式大客车车身结构多目标优化

建立了全承载式大客车车身骨架的有限元模型,对车身骨架结构进行了振动模态和静力学分析.然后对车身骨架结构进行设计参数灵敏度分析,得出车身骨架扭转刚度和一阶扭转频率对各部件设计参数的灵敏度.在此基础上,以车身骨架杆件厚度为设计变量,通过两阶段结构优化设计,在整车骨架质量增加很少的条件下,提高了整车结构的扭转刚度和一阶扭转频率值;同时,一轮悬空工况下的整车结构应力峰值明显下降,应力分布更加均匀,整车骨架结构设计更为合理.     

客车蒙皮对侧翻碰撞仿真结果的影响

参照ECE/R66法规和我国GB/T17578-1998法规中的相关试验要求,建立了某6120型高床大客车车身骨架有限元模型和带蒙皮的整车车身有限元模型,通过车身立柱变形量和能量吸收情况两项指标,对比分析客车蒙皮对侧翻碰撞仿真分析结果的影响程度.仿真分析结果表明:客车蒙皮在侧翻碰撞仿真分析中对车身前后端立柱的变形量影响...     

Structural Optimization for Roof Crush Test Using an Enforced Displacement Method

A roof crush test has been utilized to reduce passengers’ injuries from a vehicle rollover. The Federal Motor Vehicle Safety Standards (FMVSS) 216 and the Insurance Institute for Highway Safety (IIHS) perform actual vehicle tests and evaluate the vehicle’s ratings. Nonlinear dynamic response structural optimization can be employed not only for achievement of a high rating but also minimization of the weight. However, the technique needs a huge computation time and cost because many nonlinear dynamic response analyses are required in the time domain. A novel method is proposed for nonlinear dynamic response structural optimization regarding the roof crush test. The process of the proposed method repeats the analysis domain and the design domain until the convergence criteria are satisfied. In the analysis domain, the roof crush test is simulated using a high fidelity model of nonlinear dynamic finite element analysis. In the design domain, a low fidelity model of linear static response structural optimization is utilized with enforced displacements that come from the analysis domain. Correction factors are employed to compensate the differences between a nonlinear dynamic analysis response and a linear static analysis response with enforced displacement. A full-scale vehicle problem is optimized with a constraint on the rigid wall force from the analysis in the design domain.     

基于参数优化的大客车车身骨架结构轻量化研究

采用有限元法、数学规划法对大客车车身骨架进行了轻量化研究，建立了车身骨架的优化设计数学模型，介绍了其在ANSYS中的实现过程，结合某典型大客车车身骨架进行了参数优化设计，在保证原骨架承载能力的前提下使其质量减轻约14．5％．取得了较好的轻量化效果。     

Transient Dynamic Analysis of a Linear Model of a Bus

Transient analysis of a linear model of a bus was performed. In the experiment the right front wheel of the bus rolled over a bump and one acceleration, two axil forces in the wheel suspension and two bending moments in the frame of the bus were measured. The different parts of the bus were modelled by uniform Rayleigh-Timoshenko beams and rigid bodies. This beam element has a uniformly distributed stiffness, inertia and viscous and/or hysteretic damping along its axis. The loading of the bus due to the bump was in the theoretical analysis modelled by a prescribed transient displacement of the model of the wheel. The fast Fourier transform technique was utilized. Fairly good agreement between calculated and measured values was obtained.