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Multiaxial fatigue of welded shaft-flange connections of stirrers under random non-proportional torsion and bending

: Sonsino, C.M.; Pfohl, R.


International journal of fatigue 12 (1990), No.5, pp.425-431 : Abb.,Lit.
ISSN: 0142-1123
International Conference on Biaxial/Multiaxial Fatigue <3, 1989, Stuttgart>
Conference Paper
Fraunhofer LBF ()
Biegung; Einstufenbeanspruchung; Lebensdauerabschätzung; mehrachsige Beanspruchung; Mehrstufenbeanspruchung; Rundprobe; Schweißverbindung; torsion

Multiaxial fatigue failures of welded coupling flanges of stirrers in a fertilizer plant required an investigation of the reasons for the failures and the development of an improved design. Strain measurements carried out at the shaft showed that the stirrers experienced fluctuating torsional loads due to upward and downward driving from the gearbox and bending loads due to the viscous fluid stirred by impellers at the bottom of the shafts. The analysis of this variable-amplitude loading resulted in two particular cumulative frequency distributions for torsion and bending which then had to be combined to a single equivalent loading spectrum and extrapolated to the estimated period of usage. When using this spectrum for the combined multiaxial loading of the shafts and an appropriate damage accumulation hypothesis, the failures of the welds could be explained and redesign and optimization of the shaft-flange connections achieved.