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Graduation Project Damage tolerance of rails

Modeling the fatigue crack growth rate and critical crack size in rails

Railway asset owners like ProRail are facing fatigue-related defects in their rails, see Figure 1. Replacement of all rails in which defects are observed is very expensive. This makes it necessary to apply a damage tolerant philosophy. Damage tolerant maintenance applied to rails allows cost-effective inspection and maintenance strategies. It is based on the estimation of the fatigue crack growth rate and the critical crack size. 
The fatigue crack growth rate is fundamental for determining the inspection intervals. If inspection intervals can be enlarged, this determines a lower cost of ownership, and increase the durability and the availability of the asset, reducing potential unnecessary traffic disruption. A more accurate determination of the fatigue crack growth rate is necessary for achieving these goals. 
This graduation project aims to identify the most relevant aspects affecting both fatigue crack propagation and critical crack size in rails. To reach the goal, the project involves challenging numerical modeling for applying fracture mechanics to rails using the finite element method.

Figure 1. Rail failure due to the propagation of a squat defect, from [1]

Outline:
Literature review:
o    Crack path
o    Location of initiation
o    Geometry of rail and crack
o    Type of loading
o    Finite element modeling of (rail) cracks
o    Fracture mechanics aspects like the stress intensity factor (SIF) and crack growth rate in different modes
    Development of the finite element model
o    Modeling of rail defects and their peculiarities
o    Effect of load application
o    Influence of boundary conditions
o    Determination of crack path
o    Sensitivity analysis of input parameters
o    Calculation of SIF-s
o    (Sensitivity to) crack growth and critical crack size

References:
[1]Jun, H. K., & You, W. H. (2010). Estimation of Crack Growth Life in Rail with a Squat Defect. In Key Engineering Materials (Vol. 417, pp. 313-316). Trans Tech Publications Ltd.
 

Interested?

The contact for this job posting is Davide Leonetti.