TY - BOOK

T1 - Damage in Railway Crossings - Numerical Models

AU - Pletz, Martin

N1 - no embargo

PY - 2012

Y1 - 2012

N2 - Damage in rails and turnouts is an important issue as it is one of the main causes for maintenance such as reprofiling (grinding) and replacing of rails. In the contact areas between rail and wheel, very high loads are produced that cause this damage in the form of wear and development of surface cracks. In the crossing panel of turnouts, the wheel has to change from one rail to another, causing a vertical impact. As the wheel has to roll on different rolling radii during this change, slip is produced. The impact thus leads to high contact pressures and high slip. Important parameters of the impact are the train speed, the wheel profile, the axle load and the crossing’s support. In this thesis, dynamic and quasi-static finite element models for the passing over the crossing have been developed. Three models are used for describing the damage arising in crossings: A global dynamic model that calculates the run of a wheel through a three- metre crossing, a dynamic model that calculates the repeated impact of the wheel on the crossing nose and a quasi-static two-dimensional crack model. Loads have been transferred between those models, which shows that there are three important mechanisms for damage in crossings: a) The dynamics of the impact, determined mainly by crossing and wheel geometry, train speed and crossing support, b) the plastic adaption of the crossing to the wheel profile and c) the build-up of residual stresses near the crossing’s surface. The plastic adaption and the residual stresses both reduce the loading of a crack and strongly depend on the plastic behaviour of the crossing material. Understanding these mechanisms that cause the loading of crossings allow for the optimization of crossings in terms of their material, support and geometry.

AB - Damage in rails and turnouts is an important issue as it is one of the main causes for maintenance such as reprofiling (grinding) and replacing of rails. In the contact areas between rail and wheel, very high loads are produced that cause this damage in the form of wear and development of surface cracks. In the crossing panel of turnouts, the wheel has to change from one rail to another, causing a vertical impact. As the wheel has to roll on different rolling radii during this change, slip is produced. The impact thus leads to high contact pressures and high slip. Important parameters of the impact are the train speed, the wheel profile, the axle load and the crossing’s support. In this thesis, dynamic and quasi-static finite element models for the passing over the crossing have been developed. Three models are used for describing the damage arising in crossings: A global dynamic model that calculates the run of a wheel through a three- metre crossing, a dynamic model that calculates the repeated impact of the wheel on the crossing nose and a quasi-static two-dimensional crack model. Loads have been transferred between those models, which shows that there are three important mechanisms for damage in crossings: a) The dynamics of the impact, determined mainly by crossing and wheel geometry, train speed and crossing support, b) the plastic adaption of the crossing to the wheel profile and c) the build-up of residual stresses near the crossing’s surface. The plastic adaption and the residual stresses both reduce the loading of a crack and strongly depend on the plastic behaviour of the crossing material. Understanding these mechanisms that cause the loading of crossings allow for the optimization of crossings in terms of their material, support and geometry.

KW - rolling contact

KW - crossings

KW - impact

KW - damage

KW - wear

KW - Rollkontakt

KW - Herzstücke

KW - Stoß

KW - Schädigung

KW - Verschleiß

M3 - Doctoral Thesis

ER -