PSI - Issue 57

Felix-Christian Reissner et al. / Procedia Structural Integrity 57 (2024) 411–419 F.-C. Reissner et al. / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 2. S-N curves and results of the cyclic fatigue tests for (a) EN-GJS-700-2 and (b) 34CrNiMo6+QT.

Table 2. Results of the cyclic fatigue tests evaluated with Maximum Likelihood according to Störzel and Baumgartner (2021). Series Material Torque Torque amplitude Numbers Slope before Slope after Scatter ratio at the knee point of cycles the knee point the knee point ratio R T T in Nm N k k ∗ T UT 34CrNiMo6+QT -1 791 2 . 00 · 10 6 5.72 None 1.19 SR 34CrNiMo6+QT -1 802 7 . 94 · 10 5 3.56 None 1.02 SP1 34CrNiMo6+QT -1 880 6 . 31 · 10 5 4.49 None 1.10 SP2 34CrNiMo6+QT -1 816 2 . 34 · 10 6 5.85 None 1.26 SP3 34CrNiMo6+QT -1 865 8 . 91 · 10 5 5.21 None 1.04 UT EN-GJS-700-2 -1 502 1 . 26 · 10 6 5.01 None 1.05 SP1 EN-GJS-700-2 -1 632 2 . 82 · 10 6 11.2 None 1.09 SP2 EN-GJS-700-2 -1 592 3 . 55 · 10 6 9.49 None 1.06 specimens, the residual stresses disappear even under loads in the range of the torque amplitude at the knee point. Therefore, the results of the steel specimens do not show a strength-increasing effect caused by shot peening. The results of the stress-relieved specimens indicate a smaller fatigue strength compared to the other specimens, especially in the very high cycle fatigue domain. It can therefore be concluded, that the machining of the specimens already introduced residual stresses into the specimens. In addition, based on the comparison between shot-peened and stress-relieved steel speci mens, the results also show a strength-increasing effect of the shot peening treatment for steel specimens of approximately +10 % in the very high cycle fatigue domain. 3. Finite Element Analysis In order to simulate the change in residual stresses due to loading, it is necessary to simulate the shot peening process and the cyclic loading. As the shot peening process is a highly non-linear and computationally intensive process to simulate, the simulation is performed in two steps. In the first step, the shot peening is simulated and in the second step, the cyclic loading is applied. However the results of the first simulation, i.e., the residual stresses, are used as initial values for the second simulation.