Stability Behaviour of a Railway Bogie

Some modern high-speed trains show the phenomenon of grumbling noise. Together with this phenomenon, polygonalisation of the wheels occurs, i.e. the wheels of these trains lose their roundness after short running time. A possible cause for this behaviour are periodic fluctuations of the wheel loads. These fluctuations can result from unbalance forces in the wheelset or from periodic track stiffnesses due to passing the sleepers. The wheel load fluctuations lead to fluctuations of the creep coefficients, which can cause parametric excited vibrations. This leads to a loss of stability at lower speeds than the critical speed, which is calculated with constant wheel loads. For models of wheelset, which are known from literature, it is assumed, that the wheel loads for both wheels are equal. Here, with respect to wheel load fluctuations, we allow different wheel loads at the left and right wheel contact. Thus, the mechanical system loses its symmetric structure. This results in a coupling of the antisymmetric and symmetric motions of the wheelset and the bogie. Therefore, new equations of motion have been developed, which describe a bogie with different wheel loads at the left and right wheels. The stability of this system is investigated to find parametric instabilities.