PSI - Issue 17

Felix Kresinsky et al. / Procedia Structural Integrity 17 (2019) 162–169 Felix Kresinsky / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Discussion and conclusion

The investigations (in detail Kresinsky (2018)) show that the maximum transmissible torsional moment for keyed shaft-hub connections, based on the permissible surface pressure, is mostly underestimated. Starting from the limit key length l tr /d = 1.3, the transmission reserves increase with decreasing key length. A practically harmless keyway expansion was defined as the limit criterion. The key still has a tight fit in the keyway. This makes it clear that exceeding the specified limit values leads to a larger keyway expansion, but not to a total failure of the connection. It was not possible to generalize the investigations beyond low-strength shaft materials (C45+N). At high-strength shaft materials (e.g. 42CrMo4+QT and 16MnCr5E, case-hardened) the failure location moves from the keyway flank into the keyway, i.e. a shaft break occurs before an impermissible keyway expansion is reached. The design criterion for these materials is therefore the fatigue strength of the shaft or the connection. The notch effect factors which are necessary for the determination of the fatigue strength can only be determined for the connection by experimental way. It should be noted that some of the determined values deviate considerably from the values calculated according to DIN 743 to the unsafe side. Furthermore, a higher material strength cannot be transferred to a higher load capacity of the component. The statistically verified fatigue strength for 16MnCr5E resulting from step tests confirms these differences between DIN 743 and test values. This is due to the notch effect figures contained in DIN 743, which urgently require correction for pure torsion. The revision of the notch effect figures in DIN 743 is the subject of a current research project, which will also include the influence of various strength-relevant parameters (e.g. interference between shaft and hub).

Acknowledgement

The authors would like to thank the German Federation of Industrial Cooperative Research Associations (AiF) and the German Research Association for Power Transmission Engineering (FVA) for the financial support.

References

DIN 743, 2012: Tragfähigkeitsberechnung von Achsen und Wellen, Beuth Verlag, Berlin DIN 6885, 1968: Passfedern, Nuten – hohe Form, Beuth Verlag, Berlin

DIN 6892, 2012: Mitnehmerverbindungen ohne Anzug - Passfedern - Berechnung und Gestaltung, Beuth Verlag, Berlin FKM-Richtlinie, 2012: Rechnerischer Festigkeitsnachweis für Maschinenbauteile, VDMA Verlag GmbH, Frankfurt Bruzek, B., Leidich, E., 2012: Dauerfeste Dimensionierung von Passfederverbindungen, VDI-Berichte 2176, pp. 71-82 Bruzek, B., Leidich, E., 2014: Neue Grenzbelastungen für torsionsbeanspruchte Passfederverbindungen, VDI-Berichte, 2238, pp. 177-186 Bruzek, B., Hofmann, S., Leidich, E., 2013: Gestaltfestigkeit von Pressverbindungen II, FKM-Abschlussbericht, Heft 320, Frankfurt Eissa, M., Fessler, H., 1983: Reduction of Elastic Stress Concentrations in Endmilled Keyed Connections, Experimental Mechanics, pp. 401-408 Fessler, H., Eissa, M., 1983: Three-dimensional, Elastic Stress Distribution in Endmilled Keyed Connections, J. of Strain Analysis, pp. 143-149 Floer, M., 2000: Beanspruchungsanalyse an torsionsbelasteten Paßfederverbindungen, Shaker Verlag, Aachen, Dissertation TU Chemnitz Forbrig, F., 2006: Untersuchungen zur Gestaltfestigkeit von Passfederverbindungen, Shaker Verlag, Aachen, TU Chemnitz Dissertation Hück, M., 1983: Ein verbessertes Verfahren für die Auswertung von Treppenstufenversuchen, Werkstofftechnik, Nr. 14, pp. 406-417 Hofmann, S., Leidich, E., 2014: On the fatigue strength of case-hardened keyed shaft-hub connections, 31st Danubia-Adria Symposium on Advances in Experimental Mechanics, Proceedings, pp. 201-202 Hofmann, S., Leidich, E., Podlesak, H., 2015: Dauergestaltfestigkeitsuntersuchungen an einsatzgehärteten Passfederverbindungen, Forschungsvereinigung Antriebstechnik, Heft 1146, Frankfurt Kresinsky, F., Leidich, E., 2018: Ermittlung der Grenzbelastungen von torsionsbeanspruchten Passfederverbindungen, Forschungsvereinigung Antriebstechnik, Heft 1285, Frankfurt Lätzer, M., Leidich, E., 2016: Größeneinfluss bei Welle-Nabe-Verbindungen, Antriebstechnik 4, pp. 92-99 Militzer, O., 1975: Rechenmodell für die Auslegung von Wellen-Naben-Passfederverbindungen, TU Berlin Dissertation. Oldendorf, U., 1999: Lastübertragungsmechanismen und Dauerhaltbarkeit von Passfederverbindungen, TH Darmstadt Dissertation. Pedersen, N. L., 2010: Stress concentrations in keyways and optimization of keyway design. J Strain Anal Engineering Design, 45(8), 593-604. Vidner, J., Leidich, E., 2007: Enhanced Ruiz criterion for the evaluation of crack initiation in contact subjected to fretting fatigue, International Journal of Fatigue Volume 29, pp. 2040-2049 Weigand, M., Renneisen, A., Raab, W., 1990: Die Beanspruchung von Paßfederverbindungen - Literaturrecherche und -auswertung -, Forschungsgemeinschaft Antriebstechnik, Heft 317 , Frankfurt Wendler, J., Kresinsky, F., Schlecht, B., Leidich, E., 2016: Berechnung von Mehrfachkerben nach DIN 743 durch Einbindung von FEM Ergebnissen, Heft 1182, Forschungsvereinigung Antriebstechnik, Frankfurt