On modelling of the structural integrity of rails and crossings

Cheputeh, Ni-Asri (2023). On modelling of the structural integrity of rails and crossings. University of Birmingham. Ph.D.

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Abstract

Railway crossing is a vital asset for the railway system. Its complex geometry subjects it to high impact and dynamic loads from passing wheels, which can result in premature component failure. This study aims to enhance our understanding of dynamic interaction and increase the reliability of crossings. A finite element method (FEM) model of the wheel-crossing dynamic contact interaction has been successfully developed and utilised to investigate the impact of crossing material behaviour, wheel speed, and crossing angle on the vertical impact force exerted on the crossing nose by the passing wheels on the through route. It was observed that crossing with strain hardening behaviour exhibit less deformation and higher vertical impact force compared with perfect plastic crossing. Furthermore, a larger crossing angle leads to higher vertical impact forces, particularly at high wheel speed (> 100 km/h).
The extended finite element method (XFEM) was employed, and the XFEM model demonstrated good results in predicting crack growth in rail steel (R260) specimens under a three-point bending static test. However, when simulating crack growth in rail, which has a more complex geometry and mechanism, the current model relies on the traction-separation law, which yields excessively high predicted vertical static forces. This model should be improved by considering factors such as longitudinal traction, lateral traction, and shear stress.
The acoustic emission (AE) technique, combined with direct current potential drop (DCPD) measurements, was employed to monitor crack growth in cast manganese steel samples under a three-point bending fatigue test in the laboratory. The results show that the AE technique is successful in monitoring crack growth in this controlled environment.
Finally, the concept of level 1 fitness-for-service analysis has been adapted for a maintenance action plan on defective rails. This plan relies on the RCF crack depth and surface crack length criteria. In the future, an advanced level of fitness-for-service analysis, employing more sophisticated calculation techniques, will be developed to enhance the predictive maintenance strategy of railway infrastructure managers.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):