PSI - Issue 7

C. Garb et al. / Procedia Structural Integrity 7 (2017) 497–504

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C. Garb et Al. / Structural Integrity Procedia 00 (2017) 000–000

Fig. 1 High-cycle fatigue test results of ch AlSi8 Sr T5 Pos. 1

Fig. 2 High-cycle fatigue test results of cc AlSi8 Sr T6 Pos. 1

The first negative inverted slope k 1 stays approximately the same for 150 °C comparing to room temperature, but the fatigue strength at N = 10 7 significantly decreases by about 25 % at 150 °C. Assessing the S/N-curves for cc AlSi8 Sr T6 Pos. 1, shown in Fig. 2, N D also increases, but the negative inverted slope k 1 gets flatter for the resulting curve at 150 °C.

Fig. 3 High-cycle fatigue test results of cc AlSi8 Sr T6 Pos. 2

Fig. 4 Summary of the High-cycle fatigue test results, S/N-curves at 50 % survival probability

The decrease in the fatigue strength also appears, but it is not that pronounced with a value of 7 %, comparing to ch AlSi8 Sr T5 Pos. 1. The S/N-curves of cc AlSi8 Sr T6 Pos. 2 are shown in Fig. 3 and again exhibit a slightly difference in the negative inverted slope k 1 to a flatter curve at 150 °C. The major contrast to the other specifications is that it hardly reveals any decrease in fatigue limit at 150 °C. The reduction of 2 % for the fatigue limit is negligible, considering the scatter band of the S/N-curves. In addition, N D decreases at 150 °C, which is also contraire compared to the other specifications. A summary of the S/N-curves at room temperature and at 150 °C for a survival probability of 50 % is shown in Fig. 4, also listed with the fatigue strength reductions in percentage. 4. Fractography All tested specimens are fractographically analysed by scanning electron microscope (SEM) to identify the crack origin and additionally characterize the particular failure mechanism for each sample. Auxiliary, computed