单轮对纵向颤振数值仿真及机理分析

在进行机车车辆动力学分析时,除了进行启动和制动研究外,通常将机车的前进速度考虑为恒速,且不考虑轮对纵向振动指标.最新的研究表明,轮对纵向振动作用因素不可忽视,强烈的轮对纵向振动会导致踏面剥离和车体垂向异常振动现象的发生.为了研究轮对纵向振动问题,在将轮对纵向运动考虑为非恒速的基础上建立了单轮对纵向振动简化模型,并推导出包含7个自由度的轮对运动方程,其中轮轨接触考虑为准弹性接触模型.通过根轨迹分析确定了轮对纵向振动的固有频率,发现轮对纵向振动是一种自激振动,在参数不变的条件下具有固定的频率.通过分析提出一种轮对纵向颤振速度的预测方法,研究了轮对纵向颤振的产生机理,指出线路不平顺、轮对横移、摇头的作用是诱发轮对纵向颤振的原因,并通过数值仿真再现了轮对纵向振动现象.

Numerical Simulation and Mechanism Nalysis of Longitudinal Flutter of Single Wheel-set

In the dynamic research of railway vehicles, the forward speed of the railway vehicle is always deemed as constant, and the index of wheel-set longitudinal vibration is not taken into consideration, except the research on traction and brake. The latest research shows that the wheel-set longitudinal vibration can not ignored, as it may cause the occurrence of wheel tread spalling and abnormal carbody vertical vibrations. To investigate the longitudinal vibration of the wheel-set, the simplified longitudinal vibration model of single wheel-set is built based on the precondition that the forward speed of the wheel-set is not a constant value. An equation of the wheel-set which includes 7 degrees of freedom is deduced, and the wheel/rail contact model is considered a quasi-elastic contact model. Through the root locus analysis the fixed frequency of wheel-set longitudinal vibration is defined. It is pointed out that the wheel-set longitudinal vibration is a self-excited vibration, which features fixed frequency when the parameter are not changed. A forecast method of the speed of wheel-set longitudinal flutter is put forward. The mechanism of wheel-set longitudinal flutter is studied. It is pointed out that unsmooth line, lateral movement of wheelset and yaw movement are the reasons leading to wheel-set longitudinal vibration. Wheel-set longitudinal vibration is generated through numerical simulations.