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 simulation of the primary cracks in the experiments in Figure 8 with the min/max criterion yielded a perfect match. Details will be available in Nöhring et al. (to be published). The in-house software used to calculate the crack propagation is not able to simulate crack initiation, so the secondary cracks in these experiments were not modeled. A comparison of experiment mAARTdf6 with the high static loading with several numerical procedures is shown in Figure 10. Both the min-max criterion and FRANC3D predict a nearly 90° deflection angle at the start of the simulation. This does not match well with the experiment (yellow line). An analysis of the da/dN* during this mini mission revealed at the values are such that R>0 in the complete mission, i.e. all R-values are strictly positive. Applying the max criterion, however, yielded a perfect match. So it looks like that for missions entirely in the positive R-range the max criterion has to be used. The max criterion for R>0 and the smin-smax criterion else can be summarized as a min(0,min)-max criterion.

Figure 10: Comparison of the numerical results with the experiment for test mAARTdf6

6. Conclusions Several tests were performed to determine which criterion should be used to predict the deflection angle of a mission with varying mode mixity. The tension-torsion tests indicated that the dominant cycle criterion might be most appropriate. However, additional cruciform specimen tests seem to indicate that for missions completely in the strictly positive R-range the dominant step criterion is better. Both criteria can be summarized as a min(0,min)-max criterion. References BEASY. V10r14 Documentation; C.M.BEASY Ltd.: Southampton, MA, USA, 2011. Rodella, J., Dhondt, G., Köster, P., Sander, M., Piorun, S., 2021. Determination of the Crack Propagation Direction in Mixed-Mode Missions due to Cyclic Loading. Appl. Sci 11, 1673. FRANC3D V7.4 Reference.pdf. Available from: www.fracanalysis.com [accessed on 3th of February 2022]. Köster, P., Benz, C., Heyer, H., Sander, M, 2020. In-phase and out-of-phase mixed mode loading: Investigation of fatigue crack growth in SEN specimen due to tension-compression and torsional loading. Theor. Appl. Fract. Mech. 108, 102586. Conrad, F., Blug, A., Regina, D., Kerl, J. Bertz, A., Kontermann, C., Carl, D., Oechsner, M., 2022. Direction- and path-independent DIC strain field evaluation for uniaxial and biaxial fatigue crack-growth investigations. Ninth International Conference on Low Cycle Fatigue, 21.-23. June 2022, Berlin. https://doi.org/10.48447/LCF9-2022-048. Amato, D., Mayrhofer, L., Robl, C., Dhondt, G., Citarella, R., 2023. Prediction of the crack growth propagation direction in non-proportional mixed-mode missions. Int. J. Fatigue 166, 107233. Nöhring, W., Conrad, F., Giannella, V., Dhondt, G., Konterman, C., Citarella, R., Oechsner, M. Prediction of the crack propagation direction in combined static-cyclic multi-axially loaded cruciform specimens. Submitted for publication to Eng. Frac. Mech.