PSI - Issue 66

Guido Dhondt et al. / Procedia Structural Integrity 66 (2024) 102–107 Author name / Structural Integrity Procedia 00 (2025) 000–000

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 The mean angle criterion, in which the mission deflection angle is a weighted average of the deflection angle in each loading step. As weight (da/dN)* may be taken.  The dominant step or max criterion, in which the mission deflection angle is the deflection angle of step smax (R=0 is assumed)  The dominant cycle or min-max criterion, in which the mission deflection angle is the deflection angle corresponding to the smin-smax cycle.  The min(0,min)-max criterion. This corresponds to the dominant cycle criterion for R ≤ 0 and to the dominant step criterion for R>0. 3. Experiments Two kinds of experiments were performed: tension-torsion tests at the University of Rostock, Köster et al. (2020) and cruciform specimen tests at the Technical University of Darmstadt, Conrad et al. (2022). The geometry of the tension torsion specimen is shown in Figure 3, the loading in Figure 4. The latter consisted of a combination of tension and torsion with an optional phase shift between them. The R-value for the torsion loading was -1, for the tension loading it was -1 and 0. The ratio of the magnitude of the torque to the axial force was also varied leading to a ratio of the shear stress to normal stress of 1.31, 1 and 0.76. For details the reader is referred to Rodella et al. (2021).

Figure 3: Geometry of the tension-torsion specimen

Figure 4: Loading on the tension-torsion specimen

Figure 5: Geometry of the cruciform specimen

The geometry of the cruciform specimen is shown in Figure 5. The loading along one pair of arms was static and along the other pair cyclic. The idea is that the cyclic loading simulates high cycle fatigue in a blade of a blisk due to vibrations and the static loading low cycle fatigue due to the centrifugal loading in the disk. For details the reader is referred to Conrad et al. (2022).