Keywords: crossing nose, turnout, dynamics, support, finite elements, wear, slip, rail.

A dynamic finite element model for the transition process of a railway wheel passing over a crossing nose is presented. The length of the modelled crossing amounts three metres. This allows for the investigation of the impact of the wheel on the crossing nose. The second wheel is regarded in terms of its influence on the angular velocity of the axle. The whole crossing is supported rigidly in the vertical direction by a spring-damper element.

The dynamic results of the model presented are the contact forces, the velocities and the displacements of the wheel and the crossing parts. The stress- and strain fields are calculated as well. In the contacting areas the frictional work and frictional power introduced into the surface are calculated and their maximums evaluated. During the process, their values are dependent on a combination of the contact pressure, the sliding velocity and the coefficient of friction. The frictional work and the frictional power are assumed to indicate surface damage.

The results show that the impact of the wheel on the crossing nose with a contact force reaching a value 1.6 times higher than the static load for a spring-damper support and 3.7 times higher for a rigid support. Due to the geometrical conditions in the transition zone, small contact patches lead to contact stresses and strains significantly higher than in other crossing parts with smooth contact. While the wheel is running towards the crossing nose, the rolling radius causes the angular velocity of the wheel to increase. During the transition process, the angular velocity has to decrease. The necessary adaption of the rolling velocity of the wheel set during this process is regarded and the slip velocities between the wheel and the crossing parts are calculated.

The values of the accumulated plastic strain, the frictional work and the frictional power have their highest values in the area of the transition of the wheel from the wing rail to the crossing nose. These maximums are significantly higher than the values before and after the impact. This suggests that the main damage will be located at this transition area. Furthermore, this shows that an optimization of the crossing has to regard not only the development of the vertical contact force.

The results of the model presented indicate wear and surface damage at locations of the crossing, which correspond well to the damage locations observed in the track.

The presented model provides output variables that scale damage in the crossing parts for given crossing geometries, train velocities, running directions, axle loads and wheel profiles. Thus it can help to understand and optimize the crossover process.

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