PSI - Issue 60

5

K. Mariappan et al. / Procedia Structural Integrity 60 (2024) 444–455 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

448

Type 316 L(N) SS 3x 10 -3 s -1

600 800 1000

400

200

(a) 300 K

600 800

400

200

True stress (MPa) (b) 823 K

600 800

400

200

0 N f 0.05 N f 0.3 N f

100

0.1 N f 0.5 N f

(c) 873 K

10 -3

10 -2

10 -1

True plastic strain (%)

Fig. 6 Variations in true stress vs. true plastic strain for the 0 N f , 0.05 N f , 0.1 N f , 0.3 N f , 0.5 N f specimen at (a) 300 K, (b) 823 K and(c) 873 K.

3. Results and discussion 3.1 True stress-true plastic strain behaviour

Figure 4 shows the typical hysteresis loops at room temperature for the 1, 90, 180, 550, 900 and 1837 cycles representing the fatigue damage fraction corresponding to the 0 N f , 0.05 N f , 0.1 N f , 0.3 N f , 0.5 N f and N f conditions. In order to correlate the state of prior work hardening in the specimen exposed to the varying percentage of cyclic life the cyclic stress response curves are plotted against the normalized fatigue life at 300, 823 and 873 K, and are shown in Fig. 5a. Figure 5b presents the plot of tensile peak stress values corresponding to the fatigue life fractions of 0 N f , 0.05 N f , 0.1 N f , 0.3 N f and 0.5 N f at 300, 823 and 873 K. It may be observed from Fig. 5a and 5b that at 300 K, all the prior cyclic damage conditions, except the 0 N f sample fall on the saturation stress regime of the cyclic stress response