轮式车辆“水滑”现象的初始条件

轮式车辆在积水路面行驶时会发生"水滑",从而给行驶安全造成危害,已为驾驶人员所共知。工程技术人员对此作了一些的实验性工作,并得出了实验公式。该公式虽体现了车轮胎压的影响,但对于另一个主要参数———水深的影响缺少合理的表述。本文结合实验公式并考虑到水深、胎压、车速等条件,应用动量转换原理和液流斜楔动压理论对此现象进行了分析,得出了理论公式,该公式对水滑现象作出了比较合理的解释。     

轮式车辆"水滑"现象的初始条件

轮式车辆在积水路面行驶时会发生"水滑",从而给行驶安全造成危害,已为驾驶人员所共知.工程技术人员对此作了一些的实验性工作,并得出了实验公式.该公式虽体现了车轮胎压的影响,但对于另一个主要参数--水深的影响缺少合理的表述.本文结合实验公式并考虑到水深、胎压、车速等条件,应用动量转换原理和液流斜楔动压理论对此现象进行了分析,得出了理论公式,该公式对水滑现象作出了比较合理的解释.     

电动轮汽车主动控制技术

电动轮驱动车辆的驱动主动控制技术是电动车领域一项富有特色的关键技术,文章在综合了大量文献的基础上,分析了电动轮驱动技术的特点,重点对电动轮驱动的主动控制技术中的电子差速技术、驱动防滑技术、动力学控制及参数估算的研究现状和存在的问题进行了分析,最后结合问题提出了未来的研究方向.     

Turning Resistance Coefficient Model for Skid-Steer Wheeled Vehicles

在分析轮式车辆速差转向过程中轮胎工作状态的基础上,考虑轮胎侧向非线性滑动和载荷非均匀分布,参考履带车辆转向理论,建立了速差转向轮式车辆的转向阻力系数模型.通过实时采集实车转向机构油压数据,间接测量速差转向车辆在不同转向半径下的转向阻力系数.试验结果表明,转向阻力系数模型具有一定精度,轮式车辆转向阻力系数小于履带车辆.     

轮式工程车辆两种转向方式的对比分析

轮式工程车辆的转向系统要求能够灵活地转向行驶,应避免轮子的滑移或侧滑。常见的工程车辆有两种转向方式,通过对两种转向运动形式进行详细的运动和动力学分析,提出它们的使用范围,并对这两种转向方式的轮式车辆提出应该重视的技术问题及措施。     

钢箱梁桥抗倾覆稳定性分析

钢箱梁桥受力性能好,但结构的横向抗倾覆稳定性较差。该文采用Midas对工程实例进行建模计算,发现设计中存在的问题,讨论与横向抗倾覆稳定性有关的因素。     

Lateral Stability of Towed Flexible Vehicles

The highway transport of mobile homes is a matter of concern for the increasingly safety-minded driving public. The low speeds of towed vehicles necessary to maintain stability, together with the requirements for excessive lane widths due to clearance for the lateral motion, result in increased likelihood of traffic accidents, impeded traffic flow, and reduced highway capacity. A safe increase in the stable cruising speed, coupled with a decreased amplitude in the pendular motion helps alleviate all three of the aforementioned problems. Energy input at hitch point and lateral forces between the road and tires permit lateral vehicular motions, which occur above a critical speed, to increase in amplitude until possibly a limit cycle or instability is reached. One would expect that structural dynamics could have a pronounced influence on the lateral response of towed vehicles with large and relatively flexible chassis, such as mobile homes. The objective of this research is to determine the influence of chassis structural parameters on the lateral stability of towed flexible bodies during transport. The mass of the towing vehicle is assumed infinitely large, thus eliminating any dynamic interconnection between the towing and towed vehicles. The assumed modes method is used to describe the lateral deflection of the flexible towed vehicle. Results of the study of this model indicate that increase in structural rigidity of towed vehicle increases the critical towing speed whereas increase in the tire cornering coefficient reduces the safe towing speed, which is true only for this simplified model where the dynamic interaction with the towing vehicle is not included.     

公路独柱窄幅桥梁倾覆稳定性能

基于公路、铁路相关规范关于桥梁抗倾覆性能条文的不同规定,采用剪力-柔性梁格分析方法,对一座多跨独柱曲线预应力混凝土桥梁进行横向整体抗倾覆稳定性分析。采用桥梁结构专用分析程序,针对两种典型支座布置下的算例桥梁进行计算简化并建立空间网格分析模型。认为,针对公路独柱曲线窄幅桥梁,采用公、铁2种计算方法的结果基本接近。建议采用公路桥梁计算表达式进行结构设计,以增大其安全储备;采用铁路桥梁计算表达式对其进行结构验算,可有效简化验算工作,并能真实反映结构的横向整体抗倾覆性能。     

基于改进水压分布的岩石边坡倾覆稳定性分析

基于改进地下水力分布假设,运用极限平衡方法,综合考虑锚固效应、冰雪冻胀作用和地震荷载的影响,推导出典型岩石边坡倾覆稳定系数计算式.算例分析表明:采用改进后的水力分布假设进行岩石边坡倾覆稳定性分析更加合理;出流缝堵塞、地下水位升高、锚杆(索)锚固力和设置高度降低、冰雪冻胀作用加强、水平背向坡体和竖直向上的等效地震荷载对岩石边坡倾覆稳定性不利;锚杆(索)设置角度对边坡倾覆稳定性影响不大.同时,绘制了饱水岩石边坡倾覆稳定系数与几何要素之间的关系图,据此可迅速判定复杂条件下一定几何要素饱水边坡的倾覆稳定状态,便于工程实际运用.     

Stability and Riding Quality of Railway Vehicles

The so-called critical speed of a linearized railway vehicle is shown to be no useful measure for the stability of the system in practice. The important interaction between vehicle and track can be taken into account by the riding quality for a certain vehicle on every particular piece of track. The riding quality is determined by the accelerations transmitted to the payload, weighted according to comfort standards, and the relative displacements between wheel and rail. From the riding quality demands both for vehicle design and for maintenance of the track can be derived.     

独柱墩连续曲线箱梁桥抗倾覆稳定性研究

分析独柱墩连续曲线箱梁倾覆失稳破坏过程,综合考虑其临界倾覆时的实际空间受力状况,运用计算机辅助图形设计和有限元计算分析技术,结合工程实例,提出一种计算思路清晰、方便快捷的连续曲线箱梁抗倾覆稳定性计算方法,为连续曲线箱梁的设计、检测计算分析提供借鉴参考.     

Steering and Dynamic Stability of Railway Vehicles

SUMMARY

For railway vehicles having coned wheels mounted on solid axles there is a conflict between dynamic stability and steering ability

It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed

For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a single wheelset and which is a motion in which pure rolling occurs

Similar results are obtained with vehicles with three or more axles if adjacent axles are connected by shear structures. However, it is shown that it is possible to satisfy both the requirements of perfect steering and a non-zero critical speed if the vehicle has zero bending stiffness and if, in addition to adjacent wheelsets being connected in shear, at least one pair of non-adjacent axles are connected by a shear structure.     

The Static Stability of Articulated Commercial Vehicles

SUMMARY

This review of the state of the art emphasizes recent results that have been obtained in extending conventionalanalysis techniques to the treatment of “Highway Trains”, that is, to heavy trucks that have multiple articulation points and employ suspensions with multiple axles. Equations of motion applicable to the equilibrium turning performances of articulated vehicles are examined with respect to using analysis techniques involving steering gains, understeer gradients, effective wheel-bases, handling diagrams, and critical speeds. These examinations provide the basis for in sights into simplified approaches for understanding the steady turning mechanics of articulated, multi-axle vehicles riding on pneumatic tires.     

The Static Stability of Articulated Commercial Vehicles

This review of the state of the art emphasizes recent results that have been obtained in extending conventionalanalysis techniques to the treatment of “Highway Trains”, that is, to heavy trucks that have multiple articulation points and employ suspensions with multiple axles. Equations of motion applicable to the equilibrium turning performances of articulated vehicles are examined with respect to using analysis techniques involving steering gains, understeer gradients, effective wheel-bases, handling diagrams, and critical speeds. These examinations provide the basis for in sights into simplified approaches for understanding the steady turning mechanics of articulated, multi-axle vehicles riding on pneumatic tires.     

Steering and Dynamic Stability of Railway Vehicles

For railway vehicles having coned wheels mounted on solid axles there is a conflict between dynamic stability and steering ability

It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed

For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a single wheelset and which is a motion in which pure rolling occurs

Similar results are obtained with vehicles with three or more axles if adjacent axles are connected by shear structures. However, it is shown that it is possible to satisfy both the requirements of perfect steering and a non-zero critical speed if the vehicle has zero bending stiffness and if, in addition to adjacent wheelsets being connected in shear, at least one pair of non-adjacent axles are connected by a shear structure.     

独柱支承梁式桥倾覆稳定性验算方法研究

为减少独柱支撑匝道桥倾覆事故的发生,对该类桥梁倾覆稳定性验算方法进行研究.根据结构及受力特点,对独柱支承梁式桥进行分类,以北京市此类桥梁为背景,研究该类桥梁倾覆稳定性.研究结果表明,中墩固结独柱支承梁式桥倾覆破坏为构件强度破坏;中墩铰结独柱支承梁式桥倾覆破坏首先表现为边支座脱空,然后出现中墩支座转角超限,最终发生结构倾覆的本质特征,据此制定出了适用于验算独柱支承梁式桥倾覆稳定性的方法,可供同类桥梁的设计及维修加固参考.