机车车辆轮对踏面剥离问题

机车车辆轮对踏面剥离问题是一个世界性难题，本文通过研究轮轨纵向动态加速度异常增大现象及其发生机理，从改善机车车辆轮对纵向动力学特性的角度，提出了解决踏面剥离问题的新观点，主要研究内容与结论如下：1．分别建立包含传统轮对、独立旋转车轮和弹性阻尼耦合轮对3种情况的7自由度轮轨系统方程，研究弹性定位轮对纵向振动的普遍特性。其中轮轨空间几何接触关系的计算采用迹线法，并考虑了轮对的跳轨现象和弹性压缩变形量；蠕滑力计算采用Kalker简化理论，并分别采用约束方程求解法、赫兹非线性弹性理论和单边弹簧阻尼力元法求解轮轨法向力，比较不同方法对轮对纵向振动特性的影响；分析中还考虑了轮轴的扭转刚度及线路不平顺等影响因素。结论：轮对纵向摩擦自激振动是普遍现象，在一定条件下，它有可能发展为强烈颤振。研究得到了滚动颤振产生的条件，并给出了诱发轮对纵向颤振的危险速度简化预测公式。2．用简化模型详细分析了轨道不平顺、粘着系数、轮对质量、轮对纵向定位刚度等对轮对纵向振动的影响。由于轮对纵向振动的普遍性，其结论对具体机车车辆异常颤振现象和车轮疲劳损伤现象具有参考和指导意义。结论：轮对纵向强烈颤振与轨道不平顺、粘着系数、轮对质量和纵向定位刚度等密切相关。3．通过动力学软件SIMPACK建立了DF8B型机车的整车动力学模型，从整车的角度进一步研究弹性定位轮对纵向振动特性及车辆主要构造参数对它的影响。结论：除了上述影响因素外，改变轴重和一系悬挂纵向刚度或增加阻尼，可缓解轮对纵向强烈颤振，改善因强烈颤振引起的车轮踏面剥离问题。4．在新疆库尔勒对车轮严重多边形化的DF8B机车进行了试验：对昆明米轨DF21型机车踏面严重剥离现象提出的整改措施进行了2年试验验证。结论：试验证明，机车上轮对纵向振动加速度在某些条件下确实超出正常范畴，机务段调研数据证明，由于轮箍与轮芯之间摩擦面的阻尼效应，机车采用整体车轮后踏面剥离现象比采用分体车轮要严重得多；根据新的观点提出的整改措施完全解决了昆明米轨机车出现的严重踏面剥离现象。
逆变焊机
The wheel tread spalling phenomena of railway vehicle is a difficult problem in the world. The phenomena and mechanism of the wheel/rail longitudinal dynamic acceleration increase abnormal is researched in this paper. Put forward the new opinion of the solution method of wheel tread spalling problem through the point of view of improve the wheel set longitudinal dynamic performance of the railway vehicles. The main research contents and results are shown as follows.1. The longitudinal vibration models which consists of 7 degrees of freedom of traditional wheel set, independently rotating wheel, elasto-damper coupled wheel set were set up respectively to research the common character of the elasticity orientated wheel set longitudinal vibration.In which the trace method were adopted in calculation of the wheel/rail space geometry contact relation, and the wheel jump phenomena and the elasticity compress distortion were considered also. The Kalker simple method were adopted in the creep force calculation, and the constraint equation method, nonlinear Hertz elasticity theory and the single side spring damp force element method were adopted respectively to calculate the wheel/rail normal force, compared the influence of different methods to the wheel set longitudinal vibration character. The influence of torsion stiffness of the wheel axle and the track irregularity to wheel set longitudinal vibration were considered also.Results: the wheel set longitudinal friction excited vibration is general phenomena which may induce to violent resonance vibrations at some conditions. The happen condition of wheel set longitudinal vibration resonance is acquired in the research, and put forward the simple forecast formula of the wheel set forward danger speed at which may induce the wheel set longitudinal vibration resonance.2. analyses the influences of track irregularity, adhesion coefficient, wheel set mass and longitudinal stiffness in primary suspension to wheel set longitudinal vibration resonance based on the simplify model in detail. As the universality of the wheel set longitudinal vibration, the results of simplify model has reference and guide meaning to railway vehicles abnormal chatter phenomena and the wheel fatigue damage phenomena.Results: wheel set longitudinal violent vibration resonance has big relation with the track irregularity, adhesion coefficient, wheel set mass and longitudinal stiffness in primary suspension.3. the whole locomotive dynamic simulation model of DF8B were setup based on the soft ware SIMPACK, the longitudinal vibration character of elasticity oriented wheel set were carried from the point of view of whole locomotive and analyses the influence of parameter of the locomotive to the wheel set longitudinal vibration.Results: except above influence factors, change the wheel load and the longitudinal stiffness of primary suspension or increase the longitudinal damp of primary suspension can depress the wheel set longitudinal violent vibration. Improve the wheel tread spalling phenomena caused by violent longitudinal vibration.4. the line tests were carried with the DF8B locomotive which has a big problem of serious polygon of wheel in kuerle of Xinjiang province; The DF21 locomotive on the Kunming meter track has done 2 years line tests after done the improve method to solve the serious wheel tread spalling phenomena.Results: the line tests shown that the wheel set longitudinal vibration acceleration of the locomotive is really quite exceed the normal scope in some conditions, the investigate data shown that as the damp function of the outer part of the wheel and the inner part of the wheel, the wheel tread spalling phenomena of the locomotive with the integer wheel is much serious than the locomotive which adopted the separate wheel; the improve method which was based the new viewpoint has solved the wheel tread spalling phenomena of the locomotive on Kunming meter track.