| dc.description.abstract | This study derives formulas about derailment quotients of train to investigate derailment criterions that can response the real conditions by different parameters. Then, it would be obtained on-line derailment quotients on in-situ testing by using these formulas. The computational theory was developed by considering the wheel unloading rates and theories of derailment quotients as well as vehicle system dynamics. To establish the Equations of Motion by vehicle system dynamics, releasing the degrees of freedom including horizontal movement, bounce, and roll on the rigid bodies is needed. In addition, there are four conditions about different positions of contact points at wheel-rail contact area at the derailment impending instant. Moreover, this theory separates two different types of derailment, which is climbing derailment and lifting derailment, to analyze the wheel-rail contact forces balance, including lateral and vertical contact forces, and obtain the relationship of derailment quotients and parameters of mechanical factors.
On the part of numerical simulation, a FEM model which is including one wheelset and two rail tracks is built by using LS-DYNA software to simulate the behavior of lifting derailment and obtain the limits of derailment quotients. Numerical examples demonstrate that, the larger the wheel unloading rates at the flange contact wheel are made, the smaller the limits of derailment quotients are. The variation of friction coefficients and flange angles cannot make the limits of derailment quotients obvious change.
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