PSI - Issue 57

Rando Tungga Dewa et al. / Procedia Structural Integrity 57 (2024) 762–771 Dewa et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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The displacement, load and strain signals were measured for each cycle. One cycle comprises 200 data points. The test was terminated until specimen separation or fracture. This is need to be done in order to investigate the complete fracture surface. However, the fatigue life criterion is defined according to the 25% reduction in stress range after macrocrack initiated. Finally, metallography examination was carried out with the help of electron microscope.

Fig. 1. The as-received microstructure of Alloy 617.

1000

800

600

400

200

Yield stress (MPa) Ultimate Tensile Strength (MPa) Elongation % 346,6 811,1 59,9

Engineering stress (MPa)

0

-0,1 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

Engineering strain (%)

Fig. 2. Monotonic stress-strain curve of Alloy 617.

3. Low-Cycle Fatigue Life and Analysis The influence of strain rate on the LCF life is shown in Fig. 3. It is noticed that the fatigue life is decreased with decreasing of strain rate. The linear relationship within fatigue life and strain rate can be drawn in the logarithmic function as shown in the figure. The equation used to describe above relationship is: