【作者】 关庆华；

【导师】 曾京；

【作者基本信息】 西南交通大学 ， 载运工具运用工程， 2011， 博士

【摘要】 安全问题是铁路交通运输的永恒主题,高速和重载铁路的飞速发展对列车运行安全提出了新的挑战。一方面,高速和重载列车一旦脱轨将引起更大危害,尤其是高速列车脱轨有可能造成毁灭性的灾难。另一方面,高速列车的运行规律、性能以及运行环境等本质上有别于低速列车。然而,由于脱轨问题的复杂性,对于脱轨机理的认识目前仍停留在初级阶段,即使对于准静态脱轨仍未有统一的准确判别标准,源于1896年Nadal脱轨判别准则以及后来的修正准则是目前判别脱轨安全的基本准则,由于其建立基础为车轮准静态爬轨时的最保守力平衡条件,对于准静态滑轨、碰撞跳轨以及复杂因素引起的动态脱轨行为有相当的局限性。因此,基于深刻理解脱轨机理的基础上,提出具有广泛适用性的量化评价指标是列车运行安全研究的首要问题。本文针对列车脱轨机理以及运行安全评价,以轮轨相互作用为核心,对以下方面进行了系统的研究：(1)从轮轨接触约束特点和型面外形出发,对轮轨几何约束以及多点接触问题进行了深入研究,指出轮轨型面的轨向接触线曲率决定了两点或多点接触的可能性,而轮轨动态平衡条件决定了轮轨接触约束的存在条件,建立了考虑多点接触以及接触脱离的轮轨约束模型,分析了轮轨接触的不连续特性以及由此引起的接触冲击。轮轨型面曲率半径决定了轮缘接触时可能存在Hertz接触无效区域,给出了Hertz理论有效接触条件。建立了精确的轮轨单面约束动态模型,可考虑多点接触及接触脱离等引起的系统拓扑结构变化,并应用IAVSD基准模型进行了验证。(2)开展了单轮对准静态脱轨机理研究,分析了车轮脱轨临界状态时横向蠕滑力和法向力比值与冲角的变化规律,提出了考虑冲角影响的脱轨判别公式。改进的脱轨判别公式既保持了Nadal脱轨判别准则简单易用的优点,又能够考虑冲角、摩擦系数、轮缘角的影响,可统一判别准静态爬轨、滑轨脱轨,通过与JNR和TTCI试验结果的对比验证了改进准则的正确性。(3)建立了轮轨横向碰撞动力学模型,对轮轨横向碰撞的跳轨脱轨机理进行了探索性研究,同时对车轮跳轨脱轨的影响参数进行了详尽分析。研究发现,轮重、摩擦系数及横向碰撞速度对车轮跳轨影响显著。(4)以系统动态角度阐释了列车脱轨机理,提出了以轮轨相对横移函数为基础的动态脱轨评价方法,可用于准静态、动态以及跳轨脱轨的判别。动态脱轨准则包括脱轨危险系数及其一、二阶时间导数,其中脱轨危险系数可直接判别脱轨危险程度,而脱轨危险系数的一、二阶时间导数反映了车轮相对钢轨的运动速度及加速度。分别通过两种轮轨型面配合的接触几何学以及单轮对动态脱轨仿真对动态脱轨准则的有效性进行了验证。(5)研究了单轮对动态脱轨行为,包括外载荷作用下具有摇头刚度的轮对动态脱轨过程以及自由轮对的蛇行脱轨机理。对前者的研究表明,车轮以正冲角脱轨所需的横向力要远小于负冲角时。通过对单轮对蛇行脱轨机理的研究表明,轮轨系统存在脱轨临界速度,最大蛇行稳定极限环对应于脱轨临界速度,当运行速度超过脱轨临界速度时,任何微弱激扰将可能导致脱轨。同时,通过单轮对动态脱轨仿真,对比分析了动态脱轨评价方法和传统评价指标在评价脱轨时的效果。动态脱轨评价准则准确地判别了所有的工况,而脱轨系数及轮重减载率仅在一定程度上反映了脱轨危险,而进行准确判别时会出现误判。(6)从轮轨接触几何学、运动学和力平衡角度论述了车轮的脱轨条件。系统地分析了传统脱轨评价指标,研究了脱轨系数与轮重减载率的上下限及其与脱轨的关系,解释了脱轨系数以及轮重减载率超标而未必脱轨的现象。介绍了应用本文提出的考虑冲角影响准静态脱轨准则、轮轨碰撞跳轨准则以及动态脱轨准则的脱轨评价方法,对比分析了各脱轨准则的特点和适用条件,提出了脱轨安全性的综合评价方法。(7)建立了车辆系统动态分析模型,应用脱轨安全综合评价方法研究了曲线通过和蛇行失稳时车辆系统的运行安全性规律,分析了车辆蛇行脱轨的动态过程,对动态脱轨准则的正确性进行了进一步的验证。更多还原

【Abstract】 Safety is the eternal subject of railway transportation, the rapid development of high-speed and heavy-load railways brings new challenges for the running safety of trains. On the one hand, the derailment of high-speed or heavy-load train will cause more serious damage, especailly, if a high-speed train derailed, a catastrophe may be brought. And on the other hand, the running principles, performance, and dynamical enviroment of high speed train are essentially different with those of the ordinary train. However, due to the complexity of derailment problem, the knowledge on the derailment mechanism still stays at elementary stage; even there is no exact evaluation criterion for quasi-steady derailment. Nadal’s derailment criterion, founded in 1896, and its amendents laterward are the fundamental criteria for derailment evaluation nowadays. These criteria have considerable limitations for assessing dynamical derailment since they are based on the most conservative equilibrium condition for quasi-steady flange-climbing derailment. Therefore, to propose quantitative evaluation criteria with wide applicability based on thorough unstanding of derailment mechanism is the fundamental problem for the running safey research of trains.Aiming at derailment mechanism and running safety assessment, the following aspects are extensively studied based on the wheel/rail interactions:(1) The geometrical constraint and multi-point contact between wheel and rail are thoroughly studied based on the wheel/rail contact characteristic and profile shapes. It’s found that the probability of two-point or multi-point contact is determined by the curvatures of track-projected lines of wheel and rail profile, while the wheel/rail constraints are determined by the dynamical equilibrium of wheelset and rail. A wheel/rail constraint model which takes the multi-point contact and contact lose into account is set up, and the non-smooth effect and contact impact between wheel and rail are analyzed. The main curvatures of wheel and rail profiles determine the effective area of Hertz contact theory during flanging. An exact dynamical model with unilateral contact between wheel and rail which can take the multi-point-contact and contact lose into account is established, and the new model is verified by passing the IAVSD benchmark model.(2) The quasi-steady derailment mechanism of a single wheelset is investigated, the changing law between the ratio of lateral creep force to normal force and angle of attack is analysed. The improved derailment criteria are proposed, which maintain the simplicity of Nadal’s criterion, while take the effects of angle of attack, friction coefficient and flange angle into account. The new criteria are suitiable for evaluating quasi-steady flange-climbing and flange-sliding derailment, and the general applicality is verified by the comparision between experimental results of JNR and of TTCI and the results of the proposed criteria.(3) The wheel/rail lateral collision equation is set up, and the jumping derailment mechanism induced by the wheel/rail lateral impact is studied exploringly. The parametric study of wheel jumping derailment indicates that the wheel load, friction coefficient and lateral pre-collision velocity of wheelset have significant influence on the jumping derailment.(4) The derailment mechanism is explained in the viewpoint of the system dynamics. A novel dynamic derailment evaluation method based on the function of wheel/rail lateral displacment is suggested, and can applies to evaluating quasi-steady, dynamic and jumping derailment. The proposed dynamic derailment evaluation method includes derailment safety coefficient and its first and second time derivatives, of which the derailment safety coefficient can determine the degree of derailment risk directly, while the first and second time derivatives of derailment safety coefficient can reflect the relative lateral velocity and acceleration between wheel and rail in lateral direction. The geometrical contact of two wheel/rail profile pairs and the dynamic derailment simulation of a single wheelset are carried out to validate the dynamic derailment evaluation method.(5) The dynamic behaviours of a single wheelset during derailment are explored, including the dynamic derailment process of a single wheelset with yaw stiffness and external loads and the hunting derailment mechanism of free wheelset. The studies on the former case show that the lateral force to derail a wheel in positive angle of attack is much less than that to derail a wheel in negative angle of attack. And the simulation results of hunting derailment indicates that there is a derailment critical velocity which corresponds to the maximal stable limit cycle during hunting for wheel-rail system, any weak excitation will induce a derailment if the running velocity exceeds the derailment critical velocity. Furthermore, the comparsions between the dynamic derailment evaluation method and the traditional derailment criteria are performed through the hunting derailment simulation of single wheelset. It is found that the dynamic derailment evaluation criteria judges all of the cases correctly, while the derailment coefficient and wheel unloading ratio, although reflect the derailment risk to some extent, misjudges some of the cases.(6) From the point of view of the wheel/rail contact geometry, wheel/rail kinematics and force equilibrims, the derailment conditions of a wheel are discussed. The traditional derailment criteria are analyzed systematically, and their upper and lower limits and the relationship with derailment are studied. The phenomenon of no derailment occurring are explained even when derailment quotient and wheel unloading ratio exceed their critical values. The application of the proposed derailment criteria including the improved quasi-steady derailment criterion which takes the angle of attack into accout, the jumping derailment criterion for wheel/rail collision and the dynamic derailment criterion are introduced in detail, and the feathers and applicable conditions of these criteria are analyzed, the comprehensive derailment evaluation method are suggested.(7) The dynamic model of vehicle system is established, the running safety of curve passing and hunting are analyzed by virtue of the comprehensive derailment evaluation method, the dynamic process of vehicle hunting derailment is analyzed, and the correctness of the dynamic derailment criterion is further verified.更多还原