PSI - Issue 13

Hiroaki Ito et al. / Procedia Structural Integrity 13 (2018) 1105–1110 Author name / Structural Integrity Procedia 00 (2018) 000–000

1109

5

R15

1.35

1.6

62

5

15

5

R12.5 (a)Geometrical configuration of test specimens

(b) overview of the fatigue test condition

Fig. 5 Condition of the fatigue experiment

4. Results Paris equation is employed to calculate the fatigue life, expressed as � � � � � � � �

(7)

�� � � ���

(8) where is the loading cycle, is CTOD, ��� is the average diameter and, , and are determined by experimental results. Parameters of Paris equations were fitted with the results of steel B and were employed to predict the S-N curves for different steels. � ���� � ��� , and � � ��� � �� �� . The predicted results of S-N curves for steels B, C, and D were compared with those of experimental results, as shown in Fig. 6. The predicted fatigue lives show good agreement with experimental ones for all steels. Fatigue limits are also predicted well for B and C. Although the predicted fatigue limit of D doesn’t show good agreement, the slope of S-N curve shows good agreement.

(a) Steel B 100 120 140 160 180 200 1,0E+04 1,0E+05 1,0E+06 1,0E+07 Experiments Fitted Number of cycles

Nonminal stress amplitude [MPa]

100 120 140 160 180 200 1,0E+04 1,0E+05 1,0E+06 1,0E+07 Experiments Predicted Number of cycles

100 120 140 160 180 200 1,0E+04 1,0E+05 1,0E+06 1,0E+07 Experiments Predicted Number of cycles

Nonminal stress amplitude [MPa]

Nonminal stress amplitude ⬚ [MPa]

(b) Steel C (c) Steel N Fig. 6 Comparison of experimental results and predicted results for S-N curves and fatigue limits