Accurate Rail Vehicle Dynamic Simulations by DynaRail

A general purpose rail vehicle dynamic simulation tool has been developed at CAM (Center for Automated Mechanics). This tool allows the user to start any rail vehicle dynamic simulation with measured wheel and rail profile data without a need for generating pre-cooked wheel/rail contact geometry tables. Using the constrained multibody methods, the tool robustly solves the three dimensional wheel/rail interaction problem and computes the longitudinal, lateral and vertical locations of 1^st and 2^nd contacts, the sizes of all Hertzian contact areas, rolling radii, contact angles, normal reactions, the creepages and their associated forces and moments online and makes all the details available as outputs to the user for subsequent analysis and validation of the solution. The purpose of this study is to demonstrate the ability of the tool for predicting the detailed responses of the rail vehicle systems. For all simulations, in addition to the detailed contact reactions, the precise positions of all contacts in three-dimensional space are readily solved for and available for further considerations. This is an application paper and intends to introduce the railroad engineers and consultants to a tool that is capable of fulfilling their simulation and modeling needs for complex rail/vehicle systems. Such needs are not commonly provided by the specialized codes and very hard for the railroad engineers to fulfill them using other general purpose codes. DynaRail is particularly useful to the wheel/rail profile designers who may be concerned with the continuous movement of the contact point at an unprecedented accuracy. The online prediction and imposition of the contacts makes it possible to systematically include and consider the effect of the contact movements on its associated contact geometry variables such as the size of contact ellipses, rolling radii, contact angles and, ultimately the effect of all these on the stability and/or the resulting motion of wheel on rail.