Crack propagation in rails based on the concept of material forces
Övrigt konferensbidrag, 2011
To properly simulate the propagation of an existing crack, we need to model how fast
and in what direction it grows. A Generalized Crack Driving Force (GCDF), based on the
concept of material forces cf. , is used to formulate a framework for crack propagation
models. This framework can be used to formulate different crack propagation strategies:
Explicit Proportional Extension (EPE), Implicit Proportional Extension (IPE) and Maximum
Parallel Release Rate (MPRR), cf. . Here, it is shown that all three strategies produce
quantitatively good results compared with experiments, for the case of a three point bending
test with an eccentric edge crack and internal holes .
In railway applications, highly complex loading cases arise in the wheel–rail interface, due
to a moving contact load. For this particular loading case it is observed that the perpendicular
component of the GCDF is highly dependent on the chosen parameters of the numerical
algorithm. Hence, it is concluded that only the MPRR method remains applicable as it is only
dependent on the parallel component of the GCDF and therefore more robust. Furthermore,
the high loads in the wheel-rail interface result in large plastic deformation whereby the
fracture resistance of the material becomes anisotropic .
Based on the MPRR method, the propagation of a single head check crack in a piece of
rail, under realistic Rolling Contact Fatigue (RCF) loading conditions, is simulated by the
use of a 2D FE model incorporating elastoplastic material behaviour. Finally, results from
the simulations are presented and qualitatively compared to field observations.