PSI - Issue 66

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

105

4

4. Evaluating the tension-torsion tests The simulation of the tension-torsion tests leads to a varying K-mixture along the mission, especially for the phase shifted tests. At first the mean angle criterion and the dominant step criterion were compared. Figure 6 shows the experimental result (triangulation) together with the numerical simulation using the mean angle criterion (blue surface) and the dominant step criterion (red surface) for R axial =0 and a tension-torsion phase shift of 0° (left) and 40° (right). From the figures it is clear that the dominant step criterion leads to a better match between the experiment and the numerical prediction. All details can be found in Rodella et al. (2021).

Figure 6: Mean angle criterion (blue) and dominant step criterion (red) for R axial = 0 and 0° phase shift (left) and 40° phase shift (right)

Figure 7: Comparison of the angle measured at the free surface in the experiments with the numerical prediction Next, the dominant step criterion ( max ) was compared with the dominant cycle criterion ( min-max ). To this end the deflection angle at the free surfaces was measured and compared with the numerical prediction. Details on how the angle was determined can be found in Amato et al. (2023). Figure 7, upper diagram, shows an absolute comparison of the experimental with the numerical angle obtained with the min-max criterion, the max criterion and the commercial software FRANC3D (2022). The lower part of the figure shows a relative comparison with the experiment. The tests were coded as a_1_b_c, were a=0,1 corresponds to R axial =0 and -1, respectively, b is the phase shift in ° and c=1, 2 and 3 corresponds to τ N / σ N =1.31, 1 and 0.76, respectively. From the figure it is clear that the min-