PSI - Issue 57

6

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

767

1600

1200

5.10-4/s-1 10-3/s-1 6.10-3/s-1 10-2/s-1

1500

1100

1400

1000

1300

900

Macrocrack Initiation

1200

800

1100

700

Stress range

5.10-4/s-1 10-3/s-1 6.10-3/s-1 10-2/s-1

1000

600 Stress range (MPa)

900

500

800

400

0,0

0,2

0,4

0,6

0,8

1,0

10 0

10 1

10 2

10 3

10 4

Fraction of fatigue life (N/N f )

Cycles to failure

(a)

(b)

Fig. 5. (a) Cyclic stress response behaviour at different strain rates of Alloy 617, and (b) Normalised cycle of the cyclic stress response curves .

18

DOS=(S max -S c )/S c * 100%

16

14

12

10

8

6

4

Degree of Softening (%)

2

0.000 0.002 0.004 0.006 0.008 0.010 0

Strain rate (s -1 )

Fig. 6. Degree of softening ratio at different strain rates.

5. Fractography Examination Fig. 7 shows typical fractography SEM micrographs (with zoomed images on each zone) for LCF specimen tested at high strain rate. The figure shows typical fatigue fracture consists of initiation zone (pointed by the black