Wheel reprofiling of a high-speed electric-multiple-unit train based on a multi-objective optimization strategy

An approach to optimize the wheel reprofiling of a high-speed electric multiple unit (EMU) train is presented; it has three functions as objectives: the critical speed of the train, the contact stress that affects the contact fatigue of wheel/rail wear and the diameter of the nominal rolling circle of the wheel. The vertical coordinates of the control points on the curve of the wheel profile are used as design variables and the upper and lower values of each control point are utilized as additional limiting conditions of the curve, with the height, thickness and contact angle of the wheel flange as well as the derivative of the curve acting as constraints on the geometry parameters. A multi-objective optimization model is established for the wheel reprofiling of a high-speed EMU train; three models are created: standard, worn and optimized wheel profiles. Comparisons of wheel/rail contact, running stability and curving performance of the vehicle are performed. It is shown that the wheel profile obtained from the reprofiling optimization model satisfies the constraints and its corresponding dynamic performance has a good agreement with that of a standard wheel profile with a 30 mm thick wheel flange. A performance close to that of a standard wheel profile can be obtained even though the worn wheel is not reprofiled to have the standard profile. Also, the amount of diameter reduction in the direction of the nominal rolling circle is reduced and service life-time is extended by employing the proposed wheel reprofiling approach based on the multi-objective optimization strategy.