In the course of this master´s thesis, the damage of switch rails made from two rail steel grades is assessed. A dynamic FE-analysis and a new material assessment software developed with Python at Materials Center Leoben (MCL) called ’Assessment Tool’ are combined. In particular, the degradation due to the impact of differently worn wheels with standard geometry S1002 on a toz+ 60E1-500 1:12 switch rail is investigated. At first, the local contact loads are extracted from the FE model after 100 loading cycles considering an elastic-plastic material behavior. Then the characteristic contact parameters maximum contact pressure pmax, longitudinal creepage cL and contact length 2a are evaluated and transferred to the Assessment Tool. In the Assessment Tool four different mechanisms are examined: The depth of wear according to Archard’s model [1], the energy-based T − model [2], the crack initiation on the surface according to the shakedown theory [3], as well as crack initiation below the surface according to the Dang-Van criterion [4] are evaluated. The Assessment Tool does not account directly for plastic deformation but it is assumed that after 100 load cycles stresses stabilize and a run-in state prevails. The Assessment Tool allows to compute the damage indicators for different loading constellations with respect to wheel distributions and tonnage with low computational effort. However, the Assessment Tool includes some approximations, which affect the accuracy of the results. Therefore, a benchmarking of the damage parameters computed in the FE post-processing using the full FE contact output and those of the Assessment Tool is performed for validation of the results. The maximum observed deviation amounts to less than 30 %. Consequently, the Assessment Tool is applicable to assess switch rails quickly with very low computational costs.
It was found that for the investigated switch rail geometry, loading condition and materials (R350HT and 400UHC) wear is the dominant damage mechanism. The material comparison states that 400UHC, with higher hardness than R350HT, exhibits a better damage resistance.
This thesis shows that the Assessment Tool is a powerful tool to quickly assess and compare different materials using local contact loads. Therefore, an application to other railway components such as crossing noses or stock rails is conceivable.