八轴连通式油气悬架车辆行驶性能和通过性能研究

行驶性能和通过性能是评估车辆越野性能的基本指标.为得到八轴连通式油气悬架车辆的越野性能,分别对行驶性能和通过性能开展了研究.简化了整车的物理模型,根据拉格朗日方程推导了车辆的振动方程,建立了白噪声路面输入方程;通过仿真结果与实验结果的对比,验证了柔性模型的合理性.基于柔性模型,以路面不平度系数为输入变量,得到了车辆在较...     

Measurement and analysis of truck transport vibration levels and damage to packaged tangerines during transit

The purpose of this study was to measure the vibration levels in commercial truck shipments in Thailand and observe the effects on packaged fruit. The study measured the vibration levels in two of the most commonly used truck types to ship packaged goods as a function of road condition and vehicle speed. The suspension type on the trailers studied was leaf‐spring. The results of damage to packaged tangerine fruit as a function of location in the payload are also presented. The data presented in this study will assist product and package designers to reduce damage in transit. The results showed that vibration levels increased with speed and as a result of road condition. Analysis of variance indicated that three controlling factors, road surface, truck speed and truck type, significantly affected (p ≤ 0.05) peak PSD, PSD* (root mean square) over the frequency range 2–5 Hz, and fruit damage. As expected, based on previous work, an increase in truck speed resulted in an increase in vibration levels and damage to packaged fruit. The laterite road condition produced the highest vibration level for a given truck and travelling speed followed by concrete highway and asphalt road conditions. Fruit damage was found to be greatest in the uppermost container for every combination of road, truck type and travelling speed, which also corresponded to the highest vibration levels recorded. The results showed that a significant amount of damage can occur on unpaved roads (laterite), while the packages are transported from farms and harvesting areas to regional truck terminals. Damage on asphalt road conditions was minimal. This paper provides an updated history of measured and quantified levels of vibration for these specific trucks and road conditions. Copyright © 2005 John Wiley & Sons, Ltd.     

基于路面等级匹配的重卡包装物运输激励研究

目的利用传感器搭配数据采集卡收集路面不平频谱,将路面信息匹配标准路面等级以及车辆行驶速度。方法通过Matlab将标准PSD与随机激励匹配路面等级,同时建立1/2四轴重卡动力学模型,并用能量法建立动力学方程。将收集的路面不平频谱对应到相应的路面等级,再结合车辆速度的设定,最后求解得到车辆受激励后轮胎的动载位移频谱,分析得出被运输包装物的半挂车平板动载位移。结果重卡运输前轴轮胎在A级路面以60 km/h的车速经过该路面的动载位移量在0.8和9.8 s时达到峰值,且路面响应位移不超过6 cm。结论求得被运输包装物的所受激励频谱,为被包装物的运输振动安全性研究提供支撑,可结合具体被运输包装物的脆值理论,提供被运输物品发生运输损坏的数值仿真。     

特种平车线路试验加速度异常分析与仿真

在对特种平车(如双层集装箱凹底平车)进行120 km/h线路动力学试验中,多次出现重车下心盘处垂向加速度过大,甚至高于车辆空载时的异常现象,而同时试验的其他敞车或棚车等却没有此问题.在对试验取得的垂向加速度频谱分析后,发现车体振动的主要频率高于车体的低阶弹性自振频率,并且响应主频会随着车速的提高而线性增大,这与之前一些研究认为加速度过大是由线路不平顺激起车体的弹性振动结果不一致.为了解其机理,建立具有刚柔耦合车体的凹底平车整车非线性动力学模型进行仿真,并与C70敞车的仿真结果进行了对比,仿真结果与试验基本一致.结果表明,加速度超标的主要因是:在线路不平顺激扰下,重车时转向架减振斜楔产生较大冲击力作用于凹底平车心盘,而此处的等效被冲击质量偏小,从而在车体心盘处产生较大的垂向加速度.     

Measurement of Truck Transport Vibration Levels in China as a Function of Road Conditions,Truck Speed and Load Level

Transport vibration levels in trucks were measured as a function of truck speed, road conditions and load level. The trucks consisted of one normally loaded truck and one overloaded truck with leaf‐spring suspensions. Truck speeds were divided into three groups: 0–30 km/h, 31–60 km/h and 61–90 km/h. Traffic roads consisted of highways, arterial roads (ARs), secondary roads (SRs) and tertiary roads (TRs). The results revealed that transport vibration levels increased with truck speed; TRs contributed to the highest transport vibration levels, followed by SRs, ARs and highways. The power spectral density peaks were at 3 or 3.5 Hz. Overloading probably suppressed transport vibration levels especially at low speeds. Copyright © 2015 John Wiley & Sons, Ltd.     

Test protocol for simulating truck and rail vibration and rail impacts in shipments of automotive engine racks

A study of the truck and rail transport environments using racks containing Ford engines was conducted to quantify shock and vibration levels during shipment. Tri-axial acceleration data was collected at several locations on the floor of the vehicles and on the racks themselves to determine the severity of shock and vibration input from truck trailers and rail boxcars. Power Spectral Density plots were developed from the data collected and used to simulate truck and rail shipments on an electro-hydraulic vibration table. The results showed that the highest vibration levels in the steel racks occurred at 4 Hz in the vertical direction for truck shipments, and between 12–16 Hz for rail shipments. The vibration levels in the longitudinal and lateral directions were much lower than in the vertical direction for truck shipments. The most severe shock to a rack in rail shipments was 5.7 G peak in the longitudinal direction as a result of coupling.     

铁路环境振动对厂房内精密仪器的影响分析

以龙烟铁路沿线厂房内的精密仪器为研究对象,利用有限元法,建立轨道-桥梁及桥墩-基础-土体计算模型,计算货车在不同运行速度下引起的大地振动响应,得出振动加速度、速度及位移沿距离的衰减规律,分析铁路环境振动对铁路沿线厂房内精密仪器的影响。研究表明：列车速度对振动响应的影响较大,速度越高,地面上相同位置上的振动响应越大;振动加速度、速度和位移沿距离的衰减特性基本一致,呈现指数曲线的衰减规律;若不考虑精密仪器的自身隔振能力,两列货车以120km/h和100km/h的速度在精密仪器附近交会时,加速度、位移及y方向的速度预测值满足仪器振动限值要求,x和z方向的速度预测值超出了仪器振动限值要求;考虑精密仪器自身基础的隔振能力后,振动预测值均满足仪器振动限值要求。     

Bicyclist injury severities in bicycle-motor vehicle accidents

This research explores the factors contributing to the injury severity of bicyclists in bicycle-motor vehicle accidents using a multinomial logit model. The model predicts the probability of four injury severity outcomes: fatal, incapacitating, non-incapacitating, and possible or no injury. The analysis is based on police-reported accident data between 1997 and 2002 from North Carolina, USA. The results show several factors which more than double the probability of a bicyclist suffering a fatal injury in an accident, all other things being kept constant. Notably, inclement weather, darkness with no streetlights, a.m. peak (06:00 a.m. to 09:59 a.m.), head-on collision, speeding-involved, vehicle speeds above 48.3 km/h (30 mph), truck involved, intoxicated driver, bicyclist age 55 or over, and intoxicated bicyclist. The largest effect is caused when estimated vehicle speed prior to impact is greater than 80.5 km/h (50 mph), where the probability of fatal injury increases more than 16-fold. Speed also shows a threshold effect at 32.2 km/h (20 mph), which supports the commonly used 30km/h speed limit in residential neighborhoods. The results also imply that bicyclist fault is more closely correlated with greater bicyclist injury severity than driver fault.     

A New Approach for Road‐Vehicle Vibration Simulation

A new approach for road‐vehicle vibration simulation is proposed and demonstrated feasible by testing with three express‐road vehicle‐vibration records, that is, record A, two‐wheel electric bicycle, 80% loaded, traveling on urban road; record B, median van, 50% loaded, traveling on urban road; and record C, minivan, 80% loaded, traveling on urban road too. This method decomposes the original signal into a series of approximate Gaussian‐vibration segments and a shock segment with high kurtosis by moving crest factor and one‐tenth peak‐value method. Simulate Gaussian‐distribution vibration one by one from the power spectral density (PSD) of each decomposed segments. The overall signal is simulated by concatenating of each decomposed Gaussian segment. The simulated signal has not only the same overall root‐mean‐square (RMS), duration as the original signal, but also has a similar PSD to the original signal, without incurring excessive acceleration levels. This allows an improved and more representative simulated input signal to be generated that can be use in the current generation of vibration table.     

不同车载工况下桥梁振动响应试验

基于梁的横向振动理论,利用奇异函数建立移动车载作用下单跨简支梁的振动响应方程,利用Mathcad软件求解得到了不同车载工况下桥梁振动的位移及加速度响应。以校内双车道玉泉桥为测试对象,在四个截面布设双排传感器,设计单一车载、同向双车载、相向双车载三种工况,每种工况设置4级车速,利用无线遥测动态应变测试分析系统采集各次试验中桥梁的加速度响应,分析了车载工况、车载速度对桥梁各截面加速度峰值的影响。研究表明：（1）实测同重量双车载同向运行时的振动响应小于单一车载作用下响应的两倍;（2）相同车速下,三种工况中单一车载作用下振动加速度峰值最小;（3）对于桥东两个截面,车速较小时,双车同向比双车相向时梁的加速度峰值高;而在车速较大时,情况则相反;（4）对于桥西两个截面,双车同向均比双车相向时的加速度峰值高;（5）速度较低时,三种工况下各截面的加速度峰值相差不大,而在速度较高时,三种工况下桥东的A截面的加速度峰值最大,桥西的D截面的最小。     

Analysis of in‐flight vibration of a twin‐engine turbo propeller aircraft

A data recorder was utilized to record in‐flight vibration of a twin engine turbo propeller (feeder) aircraft. The data recorded produced power spectral density (PSD) profiles which are currently used in laboratory settings to drive vibration tables in order to simulate a particular vehicle type. Overall Grms values were averaged and compared to previous research studies. The data collected from this research study could be utilized for packaging research when developing products and packages that will pass through a distribution cycle which includes transportation via a feeder aircraft. One example of this type of distribution cycle is the small parcel shipping environment. The PSD profiles which were analyzed from this research could simulate in‐flight aircraft vibration of the aircraft chassis in a laboratory environment. This will enable further research in the air transport environment. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison study on simulation effect of improved simulation methods for packaging random vibration test

In general, existing testing methods for packaging design employ Gaussian distributions to represent vibration induced by road profiles. However, the actual road vehicle vibration is non‐Gaussian. The key limitation is that the simulated Gaussian vibration cannot reconstruct the shock events buried in the vibration, which will result in inaccurate reliability evaluation of cushion packaging. A new simulation technique called shock extraction has been proposed and validated in our earlier study. This article is a further study of our previous research. The shock extraction method has been compared with other three representative simulation methods including the single‐level PSD, three‐way split spectral, and wavelet decomposition in terms of simulation effect. Signal simulated by the shock extraction method possesses the same vibration intensity, duration, approximate statistical characteristics, and PSD plots with the original signal. The results show that the simulation effect of the shock extraction method is the best, and the worst is the single‐level PSD. The wavelet decomposition and three‐way split spectral are somewhere in the middle.     

CRTS III型板式无砟轨道桥梁段环境振动测试分析

为研究CRTS III型板式无砟轨道环境振动特点,对成灌铁路某桥梁段地面振动进行现场测试,分析不同测点地面振动加速度时程特点、频谱特征,并进行1/3倍频程分析和Z振级的衰减分析。结果表明,列车以180 km/h速度通过时,地面振动持续时间约6 s,距线路中心10 m处振动峰值加速度为60 mm/s2;在10 m处振动频谱分布范围在20～90 Hz,高频振动随距离衰减更快,大于20 m处振动主要以15～45 Hz为主;地面振动Z振级的衰减符合对数衰减规律。     

可调阻尼油气式减震器匹配整车平顺性的仿真分析

 可调阻尼油气式减震器对越野摩托车的行驶平顺性有至关重要的影响。用Matlab软件建立整车五自由度动态模型以及路面谱的数学模型,对越野摩托车行驶平顺性进行仿真研究。结果表明,匹配于道路行驶特性的减震器刚度与阻尼参数,能使振动能量峰值远离人体敏感频段并降低整车在敏感频段的振动加速度水平,提高整车平顺性。此仿真程序可为新车型选配各类减震器提供参考,加快整车开发。     

大孔径反射镜组件随机振动响应分析与试验

大孔径反射镜的柔性支撑在随机振动试验中应力响应较大,可能产生残余应变进而导致空间光学遥感器成像质量下降,因此,对大孔径反射镜组件进行随机振动响应分析尤为必要。阐述了随机振动分析的基本原理及其有限元实现。建立了反射镜组件的有限元模型,对其进行了随机振动响应分析,得出了反射镜的加速度均方根响应和柔性支撑的均值应力响应。分析结果表明：反射镜加速度响应均方根为16.3Grms;柔性支撑的均值应力响应为34.9MPa。随后进行了随机振动试验验证,结果表明：反射镜组件均方根加速度响应为16.0Grms;均值应力响应为30.3MPa。均方根加速度响应分析误差为1.8%,均值应力分析误差为13.2%,满足精度要求,验证了该方法的正确性。     

主动悬架与EPS集成控制系统操纵稳定性试验

在主动悬架与EPS集成控制系统动力学模型建立、控制策略设计及其仿真计算分析基础上,为进一步验证集成控制系统车辆的抗侧倾能力,进行了车速为50 km/h和60 km/h的蛇行试验,试验结果表明,相对于被动系统,车速为50 km/h时经过集成控制后的侧向加速度峰值和标准差分别下降了21.4 %和15.9 %,车身侧倾角峰值和标准差分别下降了13.4 %和15.1 %,有效提高了车辆转弯时的操纵稳定性能。     

Effects of transverse rumble strips on safety of pedestrian crosswalks on rural roads in China

The primary objective of this study is to evaluate the impacts of transverse rumble strips in reducing crashes and vehicle speeds at pedestrian crosswalks on rural roads in China. Using crash data reported at 366 sites, the research team conducted an observational before-after study using a comparison group and the Empirical Bayesian (EB) method to evaluate the effectiveness of transverse rumble strips in reducing crashes at pedestrian crosswalks. It was found that transverse rumble strips may reduce expected crash frequency at pedestrian crosswalks by 25%. The research team collected more than 15,000 speed observations at 12 sites. The speed data analysis results show that transverse rumble strips significantly reduce vehicle speeds in vicinity of pedestrian crosswalks on rural roads with posted speed limits of 60 km/h and 80 km/h. On average, the mean speed at pedestrian crosswalks declined 9.2 km/h on roads with a speed limit of 60 km/h; and 11.9 km/h on roads with a speed limit of 80 km/h. The 85th percentile speed declined 9.1 km/h on roads with a speed limit of 60 km/h; and 12.0 km/h on roads with a speed limit of 80 km/h. However, the speed reduction impacts were not found to be statistically significant for the pedestrian crosswalk on the road with a speed limit of 40 km/h. The study also looked extensively at the influence area of transverse rumble strips on rural roads. Speed profiles developed in this study show that the influence area of transverse rumble strips is generally less than 0.3 km.     

MapleSim在振动仿真中的应用

目的利用MapleSim软件,探究数值-符号仿真应用于包装振动领域的可行性。方法首先,根据单自由度振动模型构建并验证理论状态下的单层负载振动模型;在此基础上提出可应用于随机振动的仿真模型,进一步研究仿真关键参数的计算方法;最后进行随机振动试验,将试验与仿真结果进行对比与分析。结果 PSD分析表明,不论中间还是角落位置,仿真PSD与实验PSD的变化趋势一致,但仿真PSD在低频(10~40 Hz)下会产生一定的误差,该误差对于角落振动的情况更为显著;Grms值的对比表明仿真误差小于10%。结论基于MapleSim的数值-符号仿真模型能够反映真实振动,该方法应用于随机振动具有可行性及可信度,但文中方法尚存在仿真误差,需进一步优化仿真关键参数的计算方法。     

客车异常振动噪声的分析和控制

某款轻型客车样车在90 km/h左右速度行驶时,车厢地板出现剧烈振动并伴随共鸣噪声,严重影响汽车NVH性能。通过试验手段,在五档加速工况对振动频率进行时间跟踪,找到可能的激励源。从三维频谱图识别出车内主要振动和噪声频率与传动轴的1阶和2阶转动频率相同。对此进行加强传动轴支架,支架加橡胶垫和改换悬置为进口悬置的改进。由此可使整车振动噪声水平大幅度降低。     

国内包装件在汽车及推车配送环节的振动对比

目的明确推车配送环节的振动水平(PSD曲线),通过对比实验提供汽车与推车配送环节的振动差异数据,为更好地进行运输包装设计提供可靠依据。方法利用路谱记录仪DER-1000进行实验数据的记录。首先通过准备实验明确推车配送环节的加速度均方根(grms)水平;进而制作轻、重2种包装件原型,先后测量推车配送环节不同道路和不同固定状态下的数据以及日照—上海实测汽车配送数据;最后,通过对比相应的grms和PSD曲线,分别对推车配送环节与汽车公路运输环节进行对比分析。结论推车配送环节的振动水平显著高于汽车运输环节,约为公路运输的10倍,在进行实际包装件设计时必须考虑推车配送环节的振动情况。