大型矿用车承载车架的模态试验与结构修改模拟分析

为确定一种大型矿用电动轮自卸车的承载车架的动特性和使其适应承载条件的要求,进行了模态分析试验和结构修改的模拟分析。文中着重阐明了这类重型复杂结构在模态分析试验中应予重视的若干特殊问题的解决方法,如空气弹簧支撑的应用、测量频带的选取和空间模态的获得等。文中结合实例阐明了结构修改模拟的“结构重分析法”,并给出了模态修改的结果。     

关于三跨简支悬索桥振动频率方程的讨论

笔者对文 [3]中的三跨简支悬索桥振动频率方程进行了详细推演 ,并对其中的几处笔误予以更正 ,可供读者参考     

Improvement of the volume-delay function by incorporating the impact of trucks on traffic flow

In current transportation modelling, travel time is the most important factor in decisions regarding transport modes, destinations and routes. The calculation of travel time is deployed by volume-delay functions (VDFs), a sub-model of route assignment procedure, using the correlation between increasing numbers of vehicles on a road and the road's restrictive capacity. By investigating existing VDFs, a clear gap is seen, demonstrating that current functions are not suited to reflect the empirically known large impact of trucks on passenger car travel times. This issue becomes crucial when transport models are used to reflect future scenarios where goods transportation is expected to increase greatly, and when transport models combine passenger and commercial traffic. This paper presents a new VDF which successfully includes trucks’ impact on traffic flow in the case of Germany and, with slight deviations, for North America. The function is developed using ideal-type data for German motorways. The differences between German and US data and their implications for VDFs are also discussed.     

大跨度悬索桥的多阶模态竖向涡振与控制

大跨度悬索桥具有多个竖向模态密集分布的特性。在常遇风速范围内,从低到高的各阶竖向模态随风速升高而逐个发生涡振,这就是大跨度悬索桥的多阶模态涡振问题。针对这一问题开展深入研究,讨论中国公路桥梁抗风设计规范中竖向涡振容许振幅的合理性;阐述了利用节段模型风洞试验和理论分析综合预测实桥多阶模态竖向涡振响应的基本方法,得到了各模态阻尼比相等时悬索桥各阶模态竖向涡振振幅基本相等的结论,并通过特殊设计的悬索桥竖向等效气弹模型和塔科马桥涡振实测资料,验证了这一结论;指出在既有桥梁上追加气动措施或安装调谐质量减振器抑制悬索桥多阶模态涡振都有很大的难度,进而提出了在加劲梁与桥塔之间安装直接耗能阻尼器的设想,并进行了气弹模型试验验证;讨论了采用电涡流阻尼器进行半主动涡振控制的可行性。研究结果表明：在相同阻尼比条件下大跨度悬索桥各阶竖弯模态的最大涡振振幅基本相等;依据最大加速度幅值按频率比的平方增加的原理,满足人体振动舒适性的高阶竖弯模态的容许振幅必然小于低阶模态,因此要更加重视起振风速在容许行车风速（25 m·s^-1）以内的高阶竖弯模态涡振;对于漂浮体系悬索桥,在加劲梁与对应桥塔之间设置阻尼器可有效抑制多阶模态涡振。     

基于轮胎-颗粒流动力学模型的避险车道参数匹配方案研究

为了优化山区公路避险车道参数设计方案,基于离散元基本理论与方法,建立轮胎与避险车道集料颗粒流模型。利用自主研发的轮胎性能测试系统对货车轮胎垂直特性进行了室内台架试验研究,通过检测不同输入条件下的响应,标定了轮胎颗粒流模型细观参数。采用漏斗法测量了避险车道集料休止角,结合离散元颗粒流仿真方法,对集料颗粒流模型表面摩擦因数进行了标定。基于所建立的轮胎与避险车道的集料颗粒流模型,仿真分析了轮胎在避险车道中的行驶过程,模拟了车辆在运行过程中的行驶距离、行驶速度与轮胎转速的变化趋势。在甘肃S308省道K209+400处避险车道进行了实车道路试验,试验结果验证了该仿真方法的正确性。通过所建立的轮胎-颗粒流模型对比分析了不同铺设厚度,不同集料大小下的仿真结果。综合考虑减速效果和施工成本,确立了避险车道铺设厚度、铺设长度、颗粒材料等设计技术参数。研究结果表明：离散元法能够很好地模拟车辆在避险车道中的行驶过程;考虑到颗粒固结等因素,建议避险车道铺设厚度不小于0.8 m;针对行驶速度大于90 km·h^-1的载货汽车,避险车道设计长度建议大于130 m;避险车道集料方面,建议选用粒径为1~3 cm且圆度较高的砾石作为路床材料。     

解放CA1110PK2L2型柴油车预热电路

介绍解放CA1110PK2L2型柴油车预热电路的组成和工作原理,阐述该电路常见故障的诊断及排除方法。     

The effect of railway local irregularities on ground vibration

The environmental effects of ground-borne vibrations generated due to localised railway defects is a growing concern in urban areas. Frequency domain modelling approaches are well suited for predicting vibration levels on standard railway lines due to track periodicity. However, when considering individual, non-periodic, localised defects (e.g. a rail joint), frequency domain modelling becomes challenging. Therefore in this study, a previously validated, time domain, three-dimensional ground vibration prediction model is modified to analyse such defects. A range of different local (discontinuous) rail and wheel irregularity are mathematically modelled, including: rail joints, switches, crossings and wheel flats. Each is investigated using a sensitivity analysis, where defect size and vehicle speed is varied. To quantify the effect on railroad ground-borne vibration levels, a variety of exposure–response relationships are analysed, including: peak particle velocity, maximum weighted time-averaged velocity and weighted decibel velocity. It is shown that local irregularities cause a significant increase in vibration in comparison to a smooth track, and that the vibrations can propagate to greater distances from the line. Furthermore, the results show that step-down joints generate the highest levels of vibration, whereas wheel flats generate much lower levels. It is also found that defect size influences vibration levels, and larger defects cause greater vibration. Lastly, it is shown that for different defect types, train speed effects are complex, and may cause either an increase or decrease in vibration levels.     

冷板冷藏车振动分析及隔振措施

建立了冷板冷藏车的动力学模型,运用模态分析方法建立相应的数学模型,分析了冷板冷藏车的振动特性,提出了在刚性冲击前提下的隔振方法。计算分析表明,在刚性冲击前提下所采用的隔振方法可以达到隔振的目的。     

Guidance for new policy developments on railway noise and vibration

Noise and vibration are two of the main problems associated with railways in residential areas. To ensure quality of life and well-being of inhabitants living in the vicinity of railway paths, it is important to evaluate, understand, control and regulate railway noise and vibration. Much attention has been focused on the impact of noise from railway traffic but the consideration of railway-induced vibration has often been neglected. This paper aims to provide policy guidance based on results obtained from the analyses of relationships estimated from ordinal logit models between human response, railway noise exposure and railway vibration exposure. This was achieved using data from case studies comprised of face-to-face interviews (N = 931), internal vibration measurements (N = 755), and noise calculations (N = 688) collected within the study “Human Response to Vibration in Residential Environments” by the University of Salford, UK. Firstly, the implications of neglecting vibration in railway noise policies are investigated. The findings suggest that it is important to account for railway induced vibrations in future noise and transport policies, as neglecting vibrations results in an underestimation of people highly annoyed by noise. Secondly, implications of neglecting different types of railway sources are presented. It was found that the impact of noise and vibration form maintenance operations should be better understood and should be taken into account when assessing the environmental impact of railways in residential environments. Finally, factors that were found to influence railway vibration annoyance are presented and expressed as weightings. The data shows that factors specific to a particular residential area should also be taken into account in future vibration policies as the literature shows that attitudinal, socio-demographic and situational factors have a large influence on vibration annoyance responses. This work will be of interest to researchers and environmental health practitioners involved in the assessment of vibration complaints, as well as to policy makers, planners and consultants involved in the design of buildings and railways.     

动车组天线梁随机振动疲劳寿命评估

为对动车组天线梁的随机振动疲劳寿命进行评估,首先,建立天线梁及构架结构有限元模型,并对其分析得到天线梁的固有频率;然后,利用软件编程得到德国低干扰轨道不平顺自功率谱,再根据自功率谱得到各轮对间互功率谱;最后,在有限元分析软件中对各轮对进行激励加载,采用模态叠加法对天线梁进行随机振动疲劳寿命分析,得到结构疲劳寿命薄弱位置。