Out-of-round tram wheels - Multibody simulation study based on measured wheel rim geometry

The article discusses the influence of out-of-roundness (OOR) type of wheel shape deviations on its interaction with the rail. The analysis was carried out using multibody simulation technique (MBS). Measurements of tram wheel rims and sample models of flat spots were used as input data. It has been observed that the presence of wheel OOR deviations caused a significant increase in vertical impact loads at the interface between the wheel and the rail, which favours rolling contact fatigue formation. Deviations created at the stage of manufacturing the wheel rim (usually while the profile of the rim itself is turned on a lathe) were amplified by increasing amplitudes and were also visible during the measurement of worn rims, thus creating inequalities with dominant amplitudes. Flat spots present on the rolling surfaces of the wheels cause cyclic jumps of vertical force at the contact point of the wheel and the rail, with maximum values depending on the depth and radius of the rounded edges of the flat spot, and thus subject to change in subsequent stages of the flat spot development. Taking into account the observations made, preventive measures have been proposed against the development of OOR deviations in tram wheels, the origin of which is primarily in the machining process.