An approximate model to predict near-surface plastic shear strain deformation has been developed, in an effort to link the results from MBS simulations of railway vehicles to local rail damage due to ratcheting failure. The distinguishing feature of the model is, that it explicitly takes into account longitudinal, lateral and spin creep in calculating the plastic shear strain profiles. The model is computationally efficient, which allows plasticity calculations and the assessment of failure due to ratcheting based on the results of MBS simulations on cycle-by-cycle basis. Plastic shear strains calculated with the proposed ratcheting model are in good agreement with FE calculations for the load cases pure longitudinal creep, lateral creep and spin creep. The parametric study shows interaction between the plastic shear strain at the surface and wear, but the plastic shear strain used as a measure of material damage in the context of ratcheting failure is not sufficient to fully explain the interaction between material damage and wear, because the depth scales of wear and plastic shear deformation are different in the investigated cases. Wear depths per load pass are in the order of 0.01 µm, whereas plastic shear deformation takes place in depths in the order of 100 µm. Application of the approximate ratcheting model to the metro in Vienna as part of MBS simulations, show good agreement regarding the crack pattern found on the surface of the rails in-situ. The position and the expected orientation of the fatigue cracks, oriented normal to the direction of plastic deformation, have been well predicted by the simulation.
An approximate model to predict near-surface ratcheting of rails under high traction coefficients
2012
8 Seiten, 7 Bilder, 14 Quellen
Aufsatz (Konferenz)
Englisch
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