An inverse shape design method for railway wheel profiles

Optimisation of a railway vehicle–track system is a complex process. The paper presents a procedure for optimal design of a wheel profile based on geometrical wheel/rail contact characteristics such as the rolling radii difference (RRD). The procedure uses optimality criteria based on an RRD function. The criteria account for stability of wheelset, cost efficiency, minimum wear of wheels and rails as well as safety requirements. The shape of the wheel profile approximated by a piecewise cubic Hermite interpolating polynomial is varied during the optimisation process to satisfy the optimality criteria. A numerical technique called multipoint approximations based on response surface fitting (MARS) has been chosen as an optimisation method. The proposed optimum design procedure has been applied to improve the performance of metro trains in Rotterdam (RET), The Netherlands. The trains were suffering from severe wheel tread wear and as a result of that from lateral vibrations (hunting). Using the proposed procedure, a new wheel profile has been obtained and applied to the RET metro trains. The results of the optimisation have shown that the performance of a railway vehicle can be improved by improving the contact properties of the wheel and rail. After the application of the optimised wheel profile, the instability of the metro trains has been eliminated and the lifetime of the wheels has been increased from 15,000 to 120,000 km.