PSI - Issue 46

T.J. Gschwandl et al. / Procedia Structural Integrity 46 (2023) 17–23 T.J. Gschwandl et al. / Structural Integrity Procedia 00 (2021) 000–000

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Fig. 2 Change of residual stresses in a rail after operation – adapted from Lichtberger (2010).

2. Residual Stress Investigation This section briefly discusses the applied methods which have been used for the residual stress investigation. 2.1. Finite Element Analysis (FEA) One major task of this work has been the set-up of a cyclic simulation for a new rail to investigate the development of the residual stresses after several rollovers. For this part, an already established open-source plugin for the commercial Finite Element (FE) software Abaqus (2020, Dassault Systèmes, France) from Meyer et al. (2021) has been used. With this tool, a cyclic simulation for a typical wheel-rail contact situation can be easily set-up by first specifying the geometry of the rail and the wheel. Consequently, the input data of the simulation such as the static load, the friction parameters, the number of rollover cycles and other parameters need to be defined. In addition to the quick model build-up the tool provides a faster computation due to the usage of periodic boundary conditions, shadow elements and model reductions. The boundary conditions and shadow elements are employed to enable a continuous simulation without lifting off the wheel from the rail. Thereby, the wheel rolls over the rail for a full rolling length and then it is mapped back to the starting position. (Meyer et al. (2021)) Using the introduced methodology, the residual stresses in a pearlitic rail are investigated after 100 rollover cycles of a cylindrical wheel contacting in the middle of the rail head without varying the position. The rail was modeled using an elasto-plastic Chaboche-type cyclic material model. The FE calculations were carried out by using 8 CPUs on a cluster (2x AMD EPYC 7352 24-Core, 256 RAM) and the entire computation took approximately 8 hours. The longitudinal stress distribution in the rail head was analyzed to compare the stress with the other applied methods. 2.2. Contour Method (CM) A rather recent method to measure residual stresses in components is the so-called contour method, which was first introduced by Michael B. Prime around 2000 (M. B. Prime et al. (2004), Michael B. Prime and Adrian T. DeWald (2013), Prime (2001), Prime and Gonzales (2000)). The contour method relies on Bueckner’s superposition principle. For a measurement based on the contour method, first the component or specimen needs to be cut in half along a plane. For rails Electrical Discharge Machining (EDM) is a suitable cutting option as little influence of the cutting process is expected. Thereby, the surface normal to the cut plane deforms due to the relaxation of the residual stresses.