Measuring Methods of Radius of Curvature and Tread Circle-Fitting Studies for Railway Wheel Profiles

Abstract

A railway wheel profile consists of short arcs with complex radii of curvature, and wheel wear leads to changes in the profile’s radius of curvature that ultimately affects the dynamic performance of the train. To track the evolution of in-service wheel profile curves, the radii of curvature of new foundry wheel profiles need to be measured. This study proposes a series of algorithms and calculation methods for measuring the radius of curvature of wheel profiles. Firstly, the curvature was estimated with the U-chord method, and the segment points were located. Secondly, the discrete derivative method and Two-Arcs Tangency Constrain (TATC) method were used to calculate the radius of curvature and the fitting circle radius, respectively. The experimental results of the three types of profiles showed that the wheel profile curves were precisely divided according to the estimated curvature method and that the maximum errors of the calculated results compared with standard values by the discrete derivative method and TATC method were 2.50% and 0.42%, respectively. Furthermore, the two measurement methods’ performances and repeated experiments were used to analyze the uncertainty.

Keywords

• radius of curvature
• wheel profile
• discrete derivative
• circle fitting
• uncertainty