A strategy for lightweight designing of a railway vehicle car body including composite material and dynamic structural optimization

Rolling stock manufacturers are finding structural solutions to reduce power required by the vehicles,and the lightweight design of the car body represents a possible solution.Optimization processes and innovative materials can be combined in order to achieve this goal.In this framework,we propose the redesign and optimization process of the car body roof for a light rail vehicle,introducing a sandwich structure.Bonded joint was used as a fastening system.The project was carried out on a single car of a modern tram platform.This preliminary numerical work was developed in two main steps:redesign of the car body structure and optimization of the innovated system.Objective of the process was the mass reduction of the whole metallic structure,while the constraint condition was imposed on the first frequency of vibration of the system.The effect of introducing a sandwich panel within the roof assembly was evaluated,focusing on the mechanical and dynamic performances of the whole car body.A mass saving of 63%on the optimized components was achieved,corresponding to a 7.6%if compared to the complete car body shell.In addition,a positive increasing of 17.7%on the first frequency of vibration was observed.Encouraging results have been achieved in terms of weight reduction and mechanical behaviour of the innovated car body.

Application of Hot Forming High Strength Steel Parts on Car Body in Side Impact

Lightweight structure is an important method to increase vehicle fuel efficiency. High strength steel is applied for replacing mild steel in automotive structures to decrease thickness of parts for lightweight. However, the lightweight structures must show the improved capability for structural rigidity and crash energy absorption. Advanced high strength steels are attractive materials to achieve higher strength for energy absorption and reduce weight of vehicles. Currently, many research works focus on component level axial crash testing and simulation of high strength steels. However, the effects of high strength steel parts to the impact of auto body are not considered. The goal of this research is to study the application of hot forming high strength steel（HFHSS） in order to evaluate the potential using in vehicle design for lightweight and passive safety. The performance of HFHSS is investigated by using both experimental and analytical techniques. In particular, the focus is on HFHSS which may have potential to enhance the passive safety for lightweight auto body. Automotive components made of HFHSS and general high strength steel（GHSS） are considered in this study. The material characterization of HFHSS is carried out through material experiments. The finite element method, in conjunction with the validated model is used to simulate the side impact of a car with GHSS and HFHSS parts according to China New Car Assessment Programme（C-NCAP） crash test. The deformation and acceleration characteristics of car body are analyzed and the injuries of an occupant are calculated. The results from the simulation analyses of HFHSS are compared with those of GHSS. The comparison indicates that the HFHSS parts on car body enhance the passive safety for the lightweight car body in side impact. Parts of HFHSS reduce weight of vehicle through thinner thickness offering higher strength of parts. Passive safety of lightweight car body is improved through reduction of crash deformation on car body by the application of HFHSS parts. The experiments and simulation are conducted to the HFHSS parts on auto body. The results demonstrate the feasibility of the application of HFHSS materials on automotive components for improved capability of passive safety and lightweight.

Design of lightweight magnesium car body structure under crash and vibration constraints

Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality.In this paper,material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight.Through finite element simulations,full frontal,offset frontal,and side crashes of a full car model are evaluated for peak acceleration,intrusion distance,and the internal energy absorbed by the structural parts.In addition,the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints.The wall thicknesses of twenty-two parts are considered as the design variables.Latin Hypercube Sampling is used to sample the design space,while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies.A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints.Using Sequential Quadratic Programming,the design optimization problem is solved with the results verified by finite element simulations.The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.

基于eM-Carbody平台的轿车白车身工艺规划系统

分析了轿车白车身工艺规划的需求特点,提出了基于eM-Carbody平台的白车身工艺规划系统.系统主要由三大部分构成:工艺数据模型、工艺数据模型信息提取模块以及eM-Carbody平台.依据工艺数据模型,建立零件库、资源库、操作库和工艺知识库等工艺数据库,利用工艺数据模型信息提取模块,实现工艺数据模型与eM-Carbody平台的信息互通.应用该系统成功规划了轿车左前门制造工艺,证明这一系统能很好地满足白车身工艺规划的需求.

Compact Car-Body Surface Design with T-spline Surface

Creating proper B-spline surface models is a very challenging task for designers in car-body surface design.Due to the tensor-product structure of B-spline surface,some undesirable issues of the redundant control points addition,incomplete surface definition and the difficulty of trimming boundary alteration frequently occur,when designing the car-body surface with B-spline surfaces in local-feature-lines construction,full-boundary-merging and visual surface trimming.A more efficient approach is proposed to design the car-body surface by replacing B-spline surface with classical T-spline surface.With the local refinability and multilateral definition offered by Tspline surface,those designing issues related with B-spline surface can be overcomed.Finally,modeling examples of the door,hood and rear-window are given to demonstrate the advantage of T-spline surface over B-spline surface in car-body surface design.

Fatigue test loading methodfor wagon body basedon measured load

Purpose–In this paper,the C80 special coal gondola car was taken as the subject,and the load test data of the car body at the center plate,side bearing and coupler measured on the dedicated line were broken down to generate the random load component spectrums of the car body under five working conditions,namely expansion,bouncing,rolling,torsion and pitching according to the typical motion attitude of the car body.Design/methodology/approach–On the basis of processing the measured load data,the random load component spectrums were equivalently converted into sinusoidal load component spectrums for bench test based on the principle of pseudo-damage equivalence of load.Relying on the fatigue and vibration test bench of the whole railway wagon,by taking each sinusoidal load component spectrum as the simulation target,the time waveform replication(TWR)iteration technology was adopted to create the drive signal of each loading actuator required for the fatigue test of car body on the bench,and the drive signal was corrected based on the equivalence principle of measured stress fatigue damage to obtain the fatigue test loads of car body under various typical working conditions.Findings–The fatigue test results on the test bench were substantially close to the measured test results on the line.According to the results,the relative error between the fatigue damage of the car body on the test bench and the measured damage on the line was within the range of
16.03%–27.14%.Originality/value–The bench test results basically reproduced the fatigue damage of the key parts of the car body on the line.

基于不同标准的煤炭漏斗车车体焊缝疲劳寿命研究

利用接触非线性分析技术,基于AAR标准的名义应力法和ASME标准的结构应力法研究煤炭漏斗车车体焊缝的疲劳问题。首先,建立漏斗车重载车体强度分析模型,利用修正D-P本构模型的实体单元模拟散粒煤、接触单元模拟散粒煤与车体结构的作用,并通过主要载荷作用下车体静强度试验结果验证车体仿真分析结果,应力最大误差小于15%。其次,运用名义应力法,在标准和实测载荷谱下分析车体焊缝疲劳寿命,结果表明:端墙与端漏斗板焊缝寿命最短,为2.72×10^(6)km;基于标准纵向载荷谱的焊缝寿命小于基于实测的计算结果,表明标准的纵向载荷谱相对恶劣。最后,在标准中100t漏斗车重车心盘载荷谱和实测纵向载荷谱下运用结构应力法对车体焊缝进行应力与寿命分析。结果表明:基于结构应力法的焊缝疲劳寿命不及基于名义应力法的疲劳寿命,主要原因是结构应力法的疲劳性能参数适用于各类接头形式,且分析承载复杂焊缝时考虑了面内剪切结构应力的影响。因此,对接头几何形状和应力状态复杂的车体从板座及底架区域的焊缝建议采用结构应力法对其进行疲劳寿命分析。

汽车车身造型设计与气动力分析

为研究车身造型对气动力的影响,根据人机工程相关参数,运用Rhino软件的非统一有理B样条(non-uniform rational B-splines, NURBS)建模技术,构建车身外形,并采用计算流体动力学方法对其外流场进行仿真,得到气动力特性。流场中气流始终附着在车身表面没有出现分离,表明车身造型合理,有利于减小气动阻力。针对尾部结构进行曲线再造,改进后的模型的气动阻力明显减小;附加尾翼和鸭尾造型气动升力减小,侧倾力矩减弱,有利于提高汽车对地面的附着力,提高稳定性,更适合于赛车。文中采用的方法可为设计符合汽车空气动力学特性的车身造型方案及风洞试验提供理论参考。

大头金蝇3龄幼虫细菌多样性分析及其分离菌株分解纤维素的应用研究

Illumina高通量测序平台Novaseq,对大头金蝇(Chrysomya megacephala)3龄幼虫体表与体内细菌进行测序分析。大头金蝇3龄幼虫体表与体内贮存细菌样本中共注释396 OTUs,共注释到13门19纲49目82科137属119种细菌。体内贮存细菌的优势菌属为克雷伯氏菌属(Klebsiella,57.87%),通过纤维素筛选培养基培养,纯化后得到单一菌落,经鉴定为密歇根克雷伯氏菌(Klebsiella michiganensis),制成菌液后进行室内、外模拟秸秆分解试验,室内秸秆平均分解效率为87.31%,室外模拟农田中的秸秆平均分解率为88.52%,进一步对其施用于农业废弃物搭建的人工模拟土壤中,模拟土壤肥力增加,在泥土:麦麸:锯末:豆饼的比例为10:2:2:1和10:2.5:2.5:1时种子发芽指数较高,种子平均发芽指数分别达到80.25%和78.45%。结果表明,大头金蝇3龄幼虫体表携带细菌与体内贮存菌的组成结构及多样性复杂,为其分解纤维素能力及土壤改良等提供理论依据。

基于ADAMS/CAR的麦弗逊悬架优化设计

汽车悬架系统为一多体系统,部件之间的运动关系十分复杂,传统的人工计算很难将悬架的各种特性表述清楚。以国产某轿车为例,应用多体运动学与动力学仿真软件ADAMS中的CAR专业模块建立该车的前后悬架多刚体模型,对其悬架的各种性能进行了仿真分析,研究了悬架几何参数对汽车操纵稳定性的影响,在理论验证的基础上揭示了该悬架的运动规律,在进行优化分析的同时还提出了改进的意见。

车体刚强度结构优化对连发武器射击精度的影响

为减小射击时车体振动对车载连发武器射击精度的影响,建立了某轮式车辆车体有限元模型,对火炮典型射击工况下车体的受力进行了分析,以提高车体结构刚强度为优化目标,在车体后方横向增加变截面梁来改进相应的薄弱结构。车体改进前后的模态测试与射击试验结果表明,经过车体结构优化可有效改善整车环境下对射击精度影响较大的身管一阶模态频率,5连发射击时的射击精度得到有效提高。

基于天棚-PID算法的履带车体振动控制研究

随着履带式高炮的快速发展,对行进间车体平稳性提出了更高的要求,因此研究在不同路面下如何减小履带车体振动具有重要意义。在对履带车体进行合理简化的基础,建立拉格朗日运动方程,并引入状态方程进行计算。其次,利用Simulink搭建了履带车体模型,分析了车体在B、D、F级路面下以25 km/h速度行驶时的车体振动情况。然后采用PID控制和天棚-PID控制对模型进行优化。仿真结果表明:从B级、D级到F级路面,传统、PID和天棚-PID控制方式下车体振动的平均增幅分别为5倍、4倍和2倍,天棚-PID控制算法的稳定性较好;在相同等级路面时,采用天棚-PID控制的减振效果明显,车体垂向位移和俯仰角的减缓程度比PID控制提升接近40%,车体横滚角的减缓程度比PID控制提升50%以上。因此,采用天棚-PID控制的履带车体在颠簸路面行驶更加平稳。

基于正交试验法的铝合金车体高压水清洗喷嘴结构优化

抑尘剂等复杂的化合物黏着在铝合金车体上,导致车体污染十分严重,高压水射流清洗方法能够有效去除铝合金车辆车体表面黏着的化合物。通过分析圆柱形、锥形、文丘里形和余弦形喷嘴的射流流场分布、射流出口速度、最大壁面静压、相同清洗宽度下压力值范围,得到余弦形喷嘴的清洗性能最佳,锥形喷嘴次之。基于正交试验法设计五因素、四水平正交试验表,得到常用清洗压力下余弦形喷嘴的最优结构参数:进口直径为40 mm、出口直径为20 mm、过渡段半径为40 mm、出射段长度为25 mm、过渡与余弦部分长度比为4。按照最优喷嘴结构参数进行建模,得到三组压力值下高压水出射速度比未优化前提高了2%,且优化效果随着入口压力值的提高而有所下降。在优化后的喷嘴结构参数下进一步计算得出入口压力为10 MPa时,靶距设置为250 mm能达到较好的清洗效果和节能作用。

基于三维线形的轻型高速公路纵断面指标研究

为了探究轻型高速公路路线纵断面设计关键参数,基于Carsim/Trucksim软件搭建了人-车-路耦合系统,根据普遍性和不利性原则,选取轿车、面包车和轻型货车作为轻型车辆的代表性车型,开展了代表性车型在直坡路段和弯坡组合路段的行驶仿真。根据轻型车辆在纵断面和弯坡组合路段运行特征,确定了轻型高速公路的控制车型以及路线纵断面的坡度、坡长参数。结果表明:轻型高速公路纵断面设计参数应以轻型货车和面包车作为控制车型;高速行驶下,车辆在弯坡组合路段的速度衰减比在单纵坡路段更为剧烈;根据速度衰减特性和允许速度降幅,轻型高速公路设计速度为100km/h时,若允许轻型货车通行,应以比功率为25W/kg的轻型货车作为控制车辆,路线纵断面最大纵坡为5%,最大坡长为750m,若不允许轻型货车通行,路线纵断面最大纵坡为6%,可不限制最大坡长;设计速度为120km/h和140km/h时,应以比功率为35W/kg的面包车作为控制车辆,路线纵断面最大纵坡分别为6%和5%,对应的最大坡长均为1200m。

发射载荷作用下特种车辆动态响应仿真分析与优化

基于HyperMesh-LS-DYNA有限元建模与仿真方法,探究了特种车辆在发射载荷作用下车体的稳定性问题。以某型特种车辆为研究对象,在车辆数值仿真模型中构建了悬架等相关柔性化组件,对车体在发射载荷作用下的稳定性进行分析,发现发射载荷未能均匀分散到各支撑结构,且在发射底座、 g-h轴对应轮胎与地面的接触压力较大,发射筒摆动幅度较大。基于上述结果,提出调整支腿结构的刚度阻尼系数和增加附加支撑结构两种优化方案,以达到减小车辆与地面的接触压力以及车体纵向摆动幅度的目的,并进行了仿真验证。结果表明,辅助支撑的数量与位置对车体稳定性的影响较大,靠近底座以及数量越多,对车体稳定的保持效果较好,其中在g-h轴之间增加一对附加支腿,底座接触力减少16%;在b-c、 g-h轴之间同时各增加一对附加支腿,底座接触压力减少20%,发射筒摆动幅度范围缩减12.1%。

基于ADAMS/car的汽车操作稳定性建模与仿真

利用多体动力学仿真软件ADAMS建立了车辆的模型,并对汽车进行了稳态回转试验和双移线试验的设计和仿真分析.依据仿真结果,对汽车的操纵稳定性做出了评价.结果表明,利用ADAMS软件可以对汽车的操纵稳定性进行精确的仿真试验,进而达到优化产品设计方案的目的.

基于COOT算法的城轨车辆车体称重调簧算法优化

现有城轨车辆车体称重调簧模型忽略了车体的非均匀弹性变形、弹簧刚度的非线性等问题。针对该问题,文章首先建立了基于最小二乘法拟合二系支撑位刚度的改进称重调簧模型,该模型相较于传统称重调簧模型更贴合车体的实际负载情况;利用改进白骨顶鸡(COOT)算法对称重调簧算法进行多目标改造和搜索机制优化,相较于模拟退火(SA)算法、粒子群优化(PSO)算法、遗传算法(GA),改进COOT算法使稳定收敛载荷偏差分别降低了3.2 N、2.1 N和7.4 N,收敛速度分别提高了3.5%、6.8%和18.0%,具有更好的精度、效率和鲁棒性;基于C#和MATLAB搭建了整套称重调簧试验系统,并进行模拟试验及实车验证,证明了改进COOT算法及称重调簧系统的准确性和稳定性。

基于Moldflow的车身后护板微孔发泡注塑工艺多目标优化

使用Moldflow软件模拟车身后护板注塑工艺,采用正交试验及灰色关联分析结合熵权法优化注塑工艺参数,并进行了实际试模验证。结果表明:使用微孔发泡注塑成型可实现车身后护板减重及降低翘曲变形量;优化的工艺参数为熔体温度235℃,模具温度35℃,充填时间3.5 s,充填体积百分比92%,初始气体含量1.2%(w),所制零件总质量为1362.2 g,z方向翘曲变形量为1.006 mm,较采用微孔发泡默认工艺组合分别减少了18.4 g,0.478 mm;采用灰色关联分析结合熵权法对工艺优化能满足产品减重和降低翘曲变形量的要求。

赛车前悬架和转向系统ADAMS/CAR建模及仿真

借助ADAMS/CAR,对某FSAE赛车双横臂独立前悬架和转向系统建立多体动力学模型,并对其进行前轮同向跳动仿真,对下控制臂球头铰上移和下移后再次仿真.仿真结果表明,下控制臂球头铰位置的变化对前轮定位参数影响显著.

地铁列车车体关键区域与车钩载荷相关性研究

为研究车钩载荷对车体关键区域的影响,文章以北京地铁某线路列车为例,阐述了列车半永久车钩静力标定试验及获得的半永久车钩应变和车钩力拟合曲线;分析了列车正线载客试验时车体关键区域测点动应力与车钩载荷的相关性,以及车钩载荷变化对各测点疲劳损伤值的贡献程度。研究表明,牵引梁端部、牵引梁车钩座旁、枕梁中心销垫板外侧焊缝、枕梁下盖板与边梁端部焊缝受车钩载荷变化的影响较大。