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Experimental results and fatigue life evaluation of magnesium laserbeam-welded joints under proportional and non-proportional multiaxial fatigue loading with variable amplitudes

: Bolchoun, A.; Sonsino, C.M.; Kaufmann, H.; Melz, T.


Materialwissenschaft und Werkstofftechnik 48 (2017), Nr.2, S.88-100
ISSN: 0933-5137
Deutsche Forschungsgemeinschaft DFG
SO 184/12
Fraunhofer LBF ()

Fatigue life of magnesium laserbeam-welds (AZ31 and AZ61 alloys) was assessed experimentally under variable amplitude loadings. The specimens were subjected to load-controlled cyclic loadings. The tests were carried out using a Gauss-distributed amplitude sequence of length L-S = 5.10(4) cycles and loading ratio R = -1 under pure axial, pure torsion as well as in-phase and out-of-phase combined loadings. The notch stresses were obtained from a linear-elastic FE-model using the reference radius approach with r(ref) = 0.05 mm. The stress-based hypotheses were applied: Effective equivalent stress hypothesis (EESH), shear stress intensity hypothesis (SIH), Findley, and modified Gough-Pollard. A non-proportionality factor is introduced and steps required for computing are presented in order to improve fatigue life assessment under non-proportional loadings.