PSI - Issue 5

Robert Hannemann et al. / Procedia Structural Integrity 5 (2017) 861–868 Hannemann et al./ Structural Integrity Procedia 00 (2017) 000 – 000

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opposite signs near the surface intersection points. This is due to the pure out-of-plane shear in the middle and the pure in-plane shear on the ending points of the crack front of the semi-elliptical crack under torsional loading. Accordingly the distribution of K III is vice versa, i.e. maximum in the middle and minimum near the surface points. In comparison of the diagrams, the distributions for K II and K III for the both phase shift angles change significantly. Due to the change in direction of the torsion, the corresponding graphic trends are reflected on the abscissa, which means that K III is positive while K II is arising now. The respective distributions for K I are nearly unchanged.

a)

b)

Fig. 8. Evaluation of the SIF for mode I, II and III over the normalized position s on the crack front at: a) ϕ = 0° and b) ϕ = 90°.

5. Conclusion

An assessment of appropriate inspection intervals for wheelset axles can be made by using a reliable computed remaining lifetime prediction . But, the calculation of the remaining lifetime of thick-walled shaft structures is still under research and does not consider different crucial influencing factors, which have been addressed within this paper. The results can be summarized as follows: a) Crack growth curves with different negative stress ratios have been determined and statistically analyzed. b) A rotating bending test rig for scaled specimen with design details of a railway axle, which can be tested under constant and variable amplitude loading, has been developed. c) With the rotating bending test rig the influence of transition radii with different stress concentration factors on the crack propagation was examined. These experimental results show a tilting of the crack front at higher stress concentration factors and decreasing a/c -ratios with increasing crack depth. Additionally, the influence of press-fit loads on the crack path was investigated. The superimposed press-fit load leads to a tilting crack front at low stress concentration factors. Furthermore, the influence of different transition radii on the residual lifetime was investigated. d) Moreover, a bending-torsion test rig has been developed, with which bending and torsion can be superimposed in-phase and out-of-phase. The numerical results show that the stress intensity factors for semi-elliptical cracks in the specimens depend on the phase angle as well as the position of the crack front.

Acknowledgements

The authors gratefully acknowledge the financial support of this research project S047/10029/2013 provided by the Karl-Vossloh foundation in Essen, Germany.