A comparison of methodologies for fatigue analysis of shafts: DIN 743 vs. approaches based on Soderberg criterion

The design of rotating steel shafts is a classical mechanical engineering problem. Since the recognition of fatigue as a major source of failures in shafts, many different criteria for fatigue design of rotating steel shafts have been put forward. Two commonly used approaches are based on the Soderberg criterion and on the DIN 743 approach. However, in the vast and ever growing literature on fatigue design, comparisons of these two procedures, based on concrete examples, are not commonly available. Therefore, a clear need exists for a comparison of the two approaches. This article analyses these two approaches considering a simple and common case. This case is a transition in diameter of a steel shaft, assumed as the critical cross section where bending and torsion moments are applied. Contrary to expectation, substantial differences were found between the two approaches, including in the fatigue correction factors.