运输包装系统随机振动频域分析

为了研究包装件在实际流通环境振动特性下的振动规律,以车辆、包装件构成的六自由度运输包装系统为基础,构建了在以白噪声为输入的路面不平激励下的振动模型,建立了路面不平激励的数学模型、运输车辆以及包装件的动力学模型。借助Matlab/Simulink仿真技术,对运输包装系统随机振动进行了频域分析,得到了内装产品及易损零件随机振动加速度响应的幅值频谱和功率谱密度。仿真结果表明了随机振动强弱程度与频率的关系,全面反映了随机振动规律,为缓冲包装设计提供了理论依据。     

双轮辙激励下多轴重型车辆动载特性仿真分析

为研究双轮辙激励下多轴重型车辆动载特性,采用有理函数功率谱密度的谐波叠加法模拟双轮辙激励的空间域随机路面,建立刚柔耦合的车辆整车虚拟样机,集成创建一个双轮辙激励的空间域路面车辆行驶动力学模型,仿真计算了车辆各轴两侧轮胎的法向作用力和车轮法向动载系数。结果表明,与单轮辙激励相比,双轮辙激励下得到的车辆各轴两侧车轮法向作用力的大小和变化规律均不相同,而且轮胎法向作用力最大值出现的位置也不同;不同车速下,车辆各轴两侧车轮的法向动载系数大小和变化规律完全不同,车辆前中轴的法向动载系数最小,中后、后轴的法向动载系数最大。研究结果可为精确计算多轴车辆轮胎动载荷,预测路面动态响应提供参考依据。     

非平稳行驶条件下重型汽车轮胎动载特性分析

为分析非平稳行驶条件下重型汽车轮胎附加动载特性、探讨与匀速平稳行驶工况下的差异,基于车辆行驶动力学理论,建立三轴重型汽车系统动力学模型和路面非平稳随机激励时域模型,采用MATLAB/Simulink软件仿真分析了车辆非平稳行驶条件下轮胎动载的响应规律,并与匀速平稳行驶条件下的分析结果进行比较。结果表明:车辆加速时轮胎动载荷幅值变大、减速时动载荷幅值减小;车辆等时通过同一段道路时,匀速平稳行驶时的动载荷较小;随着加速度、初速度和路面不平度的增加,动载荷幅值变大。研究结果可为精确模拟车辆轮胎动载荷、道路友好性分析和路面损伤破坏预测提供参考。     

路面多种激励下汽车运输包装产品动态响应的数值仿真

为果蔬等产品在汽车运输中的疲劳损伤度计算提供依据,以4自由度汽车振动系统为基础,建立了路面脉冲激励和路面位移随机激励共同作用下的车辆-包装件动力学模型,并且推导了其相应的动力学方程.讨论了路面位移随机激励的时域模型并对其B级公路路面不平度进行仿真.结合一个工程实例,在B级公路路面位移随机激励和路面脉冲激励共同作用下,利用Newmark和Runge-Kutta数值积分方法分别对车身的响应和对包装产品的动态响应进行数值仿真.     

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,得到了车辆在较好路面、一般路面、较差路面、恶劣路面的行驶性能;通过建立脉冲冲击、台阶冲击、震荡冲击的数学模型,得到了车辆的通过性能。结果表明:随着路面等级变差,八轴车辆的极限车速下降,B级路面极限速度为144 km/h,C级路面极限速度为64.8 km/h,D级路面极限速度为32.4 km/h,E级路面极限速度为7.2 km/h;路面冲击类型主要影响车头的加速度和车轮相对动载的极值,脉冲冲击时车轮发生腾空,且车头垂向加速度超过2.5倍重力加速度,而台阶冲击和震荡冲击均未出现轮胎腾空和车头2.5倍重力加速度的过载。     

基于改进多目标粒子群算法的商用车悬架系统优化EI北大核心CSCD

为改善商用车辆的平顺性、安全性并减小轮胎动载对路面的破坏,以某6×4牵引列车为研究对象,建立12自由度振动力学模型。以车辆平顺性和轮胎动载为优化目标,选择前后悬架弹簧刚度、减振器阻尼系数为优化参数,设计了一种基于改进多目标粒子群优化算法MDPL-MOPSO的悬架系统多目标优化策略。悬架系统优化前后的结果对比表明,提出的改进多目标粒子群优化策略在改善车辆平顺性的同时,兼顾了轮胎动载对路面的损坏,具有较好的优化效果,对重型商用车在开发阶段平顺性和安全性优化评估具有一定的指导意义。     

基于改进多目标粒子群算法的商用车悬架系统优化

为改善商用车辆的平顺性、安全性并减小轮胎动载对路面的破坏,以某6×4牵引列车为研究对象,建立12自由度振动力学模型。以车辆平顺性和轮胎动载为优化目标,选择前后悬架弹簧刚度、减振器阻尼系数为优化参数,设计了一种基于改进多目标粒子群优化算法MDPL-MOPSO的悬架系统多目标优化策略。悬架系统优化前后的结果对比表明,提出的改进多目标粒子群优化策略在改善车辆平顺性的同时,兼顾了轮胎动载对路面的损坏,具有较好的优化效果,对重型商用车在开发阶段平顺性和安全性优化评估具有一定的指导意义。     

路面脉冲激励下汽车运输包装产品响应的数值仿真

首先建立了脉冲激励下车辆-包装物的动力学方程,然后运用Newmark和Rungekutta数值积分法获得该动力学方程的数值解,最后讨论了冲击脉冲大小对运输包装产品加速度幅值的影响.     

速度与载重对车-路系统影响的试验研究

针对车辆荷载与速度在路面结构破坏中的重要性,通过试验研究了不同载荷(空载、满载、超载)和行驶速度(60 km/h、80 km/h、100 km/h)对车-路系统的影响.试验结果表明, 车辆行驶过程中,各车轮的垂直振动加速度随着行车速度的增大而呈上升趋势;在速度一定的情况下,车辆空载与超载产生的动载效应明显要大于满载;车速为60 km/h和100 km/h时,车辆后轮空载的法向荷载大于满载的法向荷载;超载行车下,车轮的法向荷载相较静载均增加;车辆空载条件下,路面动位移随着车辆速度的提高先增大后又略下降,但在满载和超载的条件下,路面动位移却随着车速的提高而增大;在车辆低速行驶时,空载时的路面动位移大于满载和超载,而在车辆高速行驶时,路面动位移是随着载重的增加而增加的.     

道路不平顺激励下车辆运输非线性包装系统动力学响应

目的研究运输车辆-非线性包装系统耦合系统在路面脉冲激励下的隔振特性。方法整体考虑路面-运载工具-缓冲包装材料-物品之间耦合的非线性振动传递模型,建立基于二分之一系统的五自由度路面脉冲激励下车辆-非线性包装系统运动分析理论模型,推导得到系统动力学方程并求解。依据结果比较考虑车辆-非线性包装系统耦合及不考虑两者耦合对运输包装件的影响,从而得知考虑车辆-非线性包装件系统耦合系统下包装件最大竖向位移是不考虑两者耦合情况下的1.25倍左右,并分别对隔振材料非线性因素及路面不平顺因素对包装件的影响进行分析。结果在车辆运输过程中,隔振材料的非线性因素及路面不平顺因素对包装件系统的响应会产生一定的影响。结论对于精确进行被动隔振设计和隔振效果评价具有积极意义。     

Variations in dynamic vehicle load on road pavement

This study proposes a spectral approach to the evaluation of variations in dynamic vehicle load on road pavement associated with a vehicle moving at constant speed along a road with a rough surface. The influence of vehicle speed and road roughness on variations in dynamic vehicle load was investigated. The results show that the standard deviation of dynamic vehicle load increases twofold, with a fourfold increase in the road roughness coefficient, and increases approximately linearly with the increase in vehicle speed.     

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.     

车、路的相互作用下沥青路面动力学特性分析

文中采用二自由度四分之一汽车悬架模型模拟汽车系统,依据弹性层状体系理论,建立路面结构的三维有限元分析模型,考虑车路相互作用,采用ANSYS有限元分析软件对移动车辆荷载作用下路面各结构层中的位移、应力、应变进行了模拟。计算分析了行车速度、悬架刚度、悬架阻尼、轮胎刚度和轮胎阻尼五个参数对路面动力响应的影响。结果表明：沥青面层处于三向受压状态,层内切应力是引起其破坏的主要原因;最大水平拉应力和最大横向拉应力均发生在路面结构的基层和底基层结合处;车速对路面动态响应的影响规律很复杂,应考虑车辆模型和路面不平整度,并划分速度区间加以探讨;路面动态响应随轮胎刚度、悬架刚度和悬架阻尼的增大而减小。上述结论对于深入分析路面结构动力响应与疲劳损坏以及研究车辆与路面相互作用的机理有重要价值。     

Field evaluation and analysis of road subgrade dynamic responses under heavy duty vehicle

The study of dynamic responses of a layered road system under heavy duty vehicle is one of the most important areas in the field of transportation. This paper introduced a field testing programme of traffic-induced road vibration in Guangxi, China and investigated the subgrade vibration induced by a heavy duty truck with various axle weights and speeds through a series of field tests. The vertical stress and acceleration of the road subgrade at different depths from the tests were presented and analysed. According to the test road, a semi-analytical model of the layered road was established via the stiffness matrix method and the heavy duty vehicle was simulated by ten moving rectangular load pressures. Numerical results in the space domain were derived by performing Fast Fourier Transform and were used to compare its results with the field measurements. The agreement between the numerical and the field results was good, which indicates that the proposed method is useful in predicting the dynamic stress and acceleration of a multi-layered road structure.     

Analysis of measured strain response of asphalt pavements and relevant prediction models

In order to investigate the actual strain response of asphalt pavement under real condition, three types of asphalt pavement sections with typical surface structures are built. The effects of axle configuration, axle load, speed and testing temperature on strain response of asphalt pavement were analysed through in situ dynamic loading. Experimental results indicate that the strain response at the bottom of the asphalt surface layer increases with increasing axle load and temperature, but decreases with the rise of speed. On the other hand, the temperature exerts different influence levels on pavement sections with different structures. It is also concluded that the tandem axle load could lead to a greater strain response than that of single axle load. Applying the analysis of variance, the effects of pavement surface temperature, axle load, speed and their double interactions are studied as well. Finally, the paper proposes prediction models of the strain response at the bottom of asphalt layer by means of multivariate regression analysis.     

汽车悬架及司机座椅动态参数优化

汽车悬架及司机座椅动态参数对汽车行驶的平顺性有着重要影响。本文以八自由度三维空间质弹系统作为汽车振动系统的力学模型，用前后四轮路面随机激励作为系统输入，对车厢及司机座椅的输入功率谱进行分析，在此基础上对该模型的悬架及司机座椅动态参数进行优化，并给出悬架参数及司机座椅参数的优化结果。     

考虑车轮-路面接触长度的桥头跳车动力荷载分析

对车辆经过桥头错台时的动力荷载进行分析,提出考虑轮胎-路面接触长度的车轮模型,并计及车轮的滚动轨迹。结合有限元动力学分析方法,对车辆上、下桥头错台时的动力荷载进行定量分析。数值仿真表明：考虑接触长度的模型更符合车轮与路面接触的实际情况,动力荷载计算值较平缓;下桥跳车时车轮脱空的临界速度计算值大大提高,10 mm错台跳车临界速度约60 km/h;跳车动力荷载与车轮悬挂方式、车速、跳车高度等有关,可由此控制轮载冲击系数;考虑车轮-路面接触长度后,桥头错台跳车的冲击系数仍较大。车辆以30 km/h以上速度通过10 mm错台时,冲击系数超过我国桥梁规范设计值,需引起重视。     

Assessment of the relationship between the international roughness index and dynamic loading of heavy vehicles

Due to imperfect surface profiles, heavy vehicles moving at high speed on flexible pavement structures oscillate in the vertical axis. This phenomenon induces dynamic loads, which oscillate at lower and higher values than the average load associated with static load considered with most pavement analysis and design applications. Higher loads applied to flexible pavements are likely to significantly reduce pavement service life. A new multibody dynamic truck model was used to study heavy vehicle wheel load for various pavement profiles of varying international roughness index (IRI). The modelled heavy vehicle wheel load response were used to calculate the dynamic load coefficient, and a relationship with IRI was proposed. On the basis of this relationship, the evolving pavement surface profile, and thus evolving IRI, was used to determine the evolution of dynamic loading with pavement life. A comparison of pavement service life for the classical static loading and for dynamic loading was made for three highway flexible pavement structures. When dynamic loads are considered, it was found that the pavement service life reduction may be reduced of about 29 and 20% for bottom-up fatigue cracking and structural rutting failure criteria.     

三向轮胎力作用下路面动力响应分析

摘 要：采用两自由度非线性汽车模型和地基上双层薄板建立三向轮胎力作用下的车-路系统。将非线性Gim模型与垂向点接触轮胎模型相结合对三向轮胎力进行描述。利用伽辽金方法推导三向轮胎力作用下路面响应的解析解,研究制动移线工况下各轮胎分力对路面响应的贡献,比较只考虑垂向轮胎力作用和考虑三向轮胎力作用时路面响应的差别,并分析系统参数对此差别的影响。研究成果有利于揭示车辆对道路的三向作用机理,为道路响应计算和道路寿命预测提供新的研究思路。