Introduction of a wheel-rail and wheel-roller contact model for independent wheels in a multibody code

This paper reports the introduction of a contact model on multibody codes to simulate both wheel/rail and wheel/roller contact for independent wheel railway vehicle. The contact model has been developed both through external subroutines (used to develop the friction model and the determination of the creepages) and using standard element of the MBS code (used to define the kinematic constraints of the wheel). This model can be introduced in a general railway vehicle model with no limitations: each "contact element" so defined can be applied between two bodies of the MBS the one representing the wheel, the other the rail or the roller. It is possible to choose among several algorithms to solve the friction problem: the Fastsim code, the Polach's method, the linearized Kalker method or a simplified analytical method with saturation. It is also possible to perform simulations using constant value for the friction coefficient and for the normal load (fast simulations) or to use a nonlinear law for the friction coefficient and the actual value for the normal load on the wheel. Due to the structure of the code it is possible to change the shape of the wheels profiles during the simulations even if at the moment this features has not been introduced in the code. Finally, in the paper the behavior of a bogie on rail and on a roller is compared.