PSI - Issue 38

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Matthias Hecht et al. / Structural Integrity Procedia 00 (2021) 00 –000

Matthias Hecht et al. / Procedia Structural Integrity 38 (2022) 251–259

for multiaxial loading: , , = 2

Pure torsion

Pure torsion

Pure tension

Multiaxial, = 90°

Pure tension

Multiaxial, = 0°

for multiaxial loading: � , � , = 2

Multiaxial, = 0°

Fig. 3 Experimental result of the fatigue test under tension, torsion and multiaxial load with and without phase shift under constant amplitudes (Woehler lines, = 0.1; left) and variable amplitudes (Gassner lines, � = 0.01; right) For loading under variable amplitudes the slope of the Gassner line was assumed with the same value as the Woehler lines in the corresponding load case. The test results under variable in comparison to constant amplitudes tend to show the same behavior. Here, too, the fatigue life is strongly dependent on the loading situation and the multiaxial loading ( = 0°) results again in a lower fatigue life. The stresses that can be endured are also almost equal under pure normal and torsional loading. A multiaxial, proportional loading ( = 0°) leads also to a slight decrease in fatigue life, as it is with constant amplitudes. The scatter is also low ( ≥ 1:1.1 3) and comparable to the Woehler lines. Table 1. Statistically determined parameters of the Woehler and Gassner lines Loading Amplitude Slope Scatter 1: Mean stress sensitivity Pure tension constant 13.5 1:1.08 - Pure torsion constant 14.7 1:1.15 - Multiaxial, = 0° constant 15.1 1:1.07 - Multiaxial, = 90° constant 14.8 1:1.07 - Pure tension variable 13.5 1:1.05 0.60 Pure torsion variable 14.7 1:1.13 0.26 Multiaxial, = 0° variable 15.1 1:1.08 0.43