Abstract
An accurate method for estimating high-cycle fatigue for shaft–hub connections is desired for safe machine design. Especially in drive-train applications, different multiaxial loads act on the joined parts. The resulting multiaxial stress state near the contact edge as well as the corresponding tribological state influence the fatigue strength in high-cycle fatigue regime. Investigating different load parameters, staircase fatigue experiments were performed under conditions of combined rotating bending and dynamic torsion of shrink-fitted shaft–hub connections with pairings of like materials. The comparison of normalized C45+N steel with quenched and tempered 42CrMo4+QT steel in particular revealed a difference in sensitivity to tribological stress. Where material strength is greater, greater loads lead to greater relative motion between shaft and hub, as well as more variation in contact pressure due to bending. This greater tribological stress leads to more extensive surface degradation and crack initiation occurs at lower loads compared to the higher material strength. To consider these effects in the fatigue calculation, integral fatigue criteria are used to determine the critical distance where the equivalent stress should be evaluated (Fig. 1). Due to crack-closing compressive loads caused by the contact pressure, greater critical distances (point method) were determined than are known for free surface cracks in the literature using the finite element method. The empirically determined material sensitivity could not be reproduced by adaptating the critical distance for the quenched and tempered steel.
Published Version
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