Dynamic aspects during full scale rotating bending axle tests using new generation of facilities with increased load frequency

According to EN 13261, EN 13103, EN 13104, rotating bending fatigue tests of full scale axles are one of the requested tests, when a new axle type, new material supplier or new manufacturer is intending to provide components for railway rolling stock. One of the test methods, how to generate the rotating bending moment, is to attach the half wheelset using the wheel to the horizontal ground base and to rotate an eccentric mass on the axle top. Such principle is used in the majority of test rigs available on the market. In the past, typical load frequency was 15 - 17 Hz. Under such conditions, only dynamic forces of the eccentric mass could be considered. However, recent design changes of the Sincotec facilities have resulted in increase of test frequencies to more than 25 - 30 Hz, which makes the tests significantly shorter. On the other hand, unlike the previous case, dynamic aspects of loading calibration have to be considered. A detailed example is shown and discussed. At static loading, the experimentally evaluated stresses on the axle surface corresponded to theoretical values exactly with the exception of near hub edge area, where an expected stress redistribution occurred. When the axle was loaded dynamically by rotating bending, the stress distribution on the axle surface was changed due to additional centrifugal forces of the axle itself, whereas at test frequencies around 30 Hz, such additional forces could no more be neglected. Note that the new character of load distribution cannot be always considered as optimum.