Multiaxial random fatigue of magnesium laserbeam-welded joints - experimental results and numerical fatigue life evaluation

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 Ls = 5•104 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 rref = 0.05 mm. The stress-based hypotheses were applied: EESH, SIH, Findley, modified Gough-Pollard. A non-proportionality factor is introduced in order to improve assessment under non-proportional loadings.