An investigation on the influence of rotary bending and press fitting on stress intensity factors and fatigue crack growth in railway axles

Abstract

The present paper summarizes the results of fatigue crack growth investigations on a hollow railway axle which were performed as a joint research project between the Politecnico di Milano, Italy, and the GKSS Research Centre Geesthacht, Germany, in the frame of an ESIS-TC24 activity. Since no analytical K factors (SIF) solutions for semi-elliptical surface cracks in the S-transitions of railway axles were available, the first step in the research was to generate them for both reverse and rotary bending. The results were then used to investigate the effects of rotary bending and of the press fits at the wheel and gear on the fatigue crack growth and residual lifetime so as to provide essential input information for setting up inspection intervals. It was found that the effect of rotary bending, although existent, was rather moderate whereas the press fits had a large and detrimental effect.

Parameters affecting the damage tolerance behaviour of railway axles

“…Madia et al [20], investigating the press fit effect on the T transition crack in another hollow axle geometry subjected to constant amplitude loading, even found a reduction in residual lifetime of a factor 4.2. The results clearly indicate that the T transition, compared to the wheel press fit crack, is the more critical position with respect to damage tolerance.…”

“…There are a few exceptions for solid and thick-walled hollow cylinders, however, without geometrical transitions [30,31]. In [20] Madia et al…”

“…No detailed discussion on this topic will be given here, see, however [7] and [20]. The parameter α necessary for determining the crack closure function ƒ such as recommended in [21] for steels was assumed to be 2.5.…”

“…Whereas the local loading beneath the press fit is characterised by compression it is local tension at the surface of the adjacent geometrical transitions, e.g., at the T transition. distribution (according to [20]). …”

“…The friction coefficient was chosen as μ = 0.6. For more details see [20]. The analyses were carried out for variable amplitude loading.…”