Untersuchung zur Steigerung der Dauerfestigkeit von Wellen durch Festwalzen

In drive technology, resource efficiency, cost reduction and increased performance are the main requirements. At component level, this means strengthening the fatigue strength in the critical areas. Mechanical surface hardening influences the boundary layer properties, but there are currently gaps in knowledge regarding the effect of machining on the resulting load capacity. There is currently no known method of how the influence of the manufacturing process parameters can be taken into account in the fatigue strength assessment. This is where an ongoing research project comes in. In the experimental part, staircase tests according to Hück are being carried out on unhardened and deep-rolled components. The test programm includes small specimens, shafts and press fits. Different notch shapes, deep rolling parameters and materials form a comprehensive test programm. In order to be able to fully evaluate the increase in fatigue strength by deep rolling, the following influencing factors are analysed in addition to the cyclic fatigue tests

Surface roughness, which is generally reduced by deep rolling

The experimental fatigue strength increases achieved were up to 63%. In combination with the findings from the additional tests, it is clear that the use of a generalised hardening factor is not satisfactory. A comparison of the strengthening factors according to DIN 743 and the FKM guideline shows the uncertainties in the design. As residual stresses are not taken into account in the nominal stress concepts of DIN 743 and FKM guideline, the result of the linear elastic equivalent stress amplitude of 1392 MPa in the notch cannot be determined. The potential of deep rolling becomes clear here.