effects of non-linear suspension on hunting and critical velocity of railway wheelset

in this paper the effects of non-linearity of suspension on dynamic behavior of a railway wheelset has been studied. this wheelset has four degrees of freedom that with two constraints it has reduced to two degrees of freedom. vermeulen-johnson theory has been used to calculate contact forces between wheel and rail. in this study the creep coefficients have considered constant. any linearization has not been used for obtaining motion equations. lateral suspension for these wheelset is dry friction which has been modeled by using kolesch theory. runge-kutta method has been used for solving these equations and results have presented to obtain limit cycles due to hunting behavior of wheelset.