Dependence of fracture strain on flaw size in rail switches-Experiments and theoretical modelling

In the present contribution static tests on three-point bending specimens with surface cracks of varying lengths are performed for four materials with different microstructures from medium to high strength rail grades. For the prediction of static failure the failure assessment diagram (FAD) is widely used where the normalized crack tip loading is plotted against the degree of plastification. To provide a diagram more readily applicable to design purposes, the nominal strain of the outer fiber at failure-obtained by finite element (FE) simulations of each individual experiment-is plotted against the crack size. This diagram for the dependence of the static failure strain on the flaw size can be seen as the static equivalent to the Kitagawa-Takahashi diagram for fatigue.