PSI - Issue 19

Masaru Bodai et al. / Procedia Structural Integrity 19 (2019) 64–72 Bodai,M et al. / Procedia Engineering 00 (2019) 000 – 000

68

5

= 5.09 × 10 4 −0.485 + 0.488

(1)

where, E of austenitic stainless steels = 1.95×10 5 (MPa)

10

Mean Stress

3mm crack

Through wall crack

No No No

TP-A TP-B TP-C TP-D TP-E TP-F

1

Yes Yes Yes

0,1 Strain Amplitude, ε a (%)

Small Specimen BFC by DFC

0,01

1,E+02 1,E+03 1,E+04 1,E+05 1,E+06 1,E+07

Number of Cycles, N

Fig. 3. Comparison of fatigue lives between piping tests and small specimen tests.

2.4 Observation of crack Each crack depth ( a ) and crack length (2 C ) of the beach mark was measured for all piping tests ( Bodai et al ., 2018). The fatigue crack growths of crack depth are shown in Fig. 4, the fatigue crack growths of crack length are shown in Fig. 5, and reciprocals of aspect ratio (2 C/a ) for the normalized number of cycles are shown in Fig. 6. Each number of cycles at which visible cracks were identified by replica printing is also plotted in Fig. 4, Fig. 5 as a reference, because the replica printing was periodically performed at typical cycles and the crack depth could not be measured for such small visible cracks.

100

100

TP-A TP-B TP-C TP-D TP-E TP-F (Note) Solid marks: Mean strain testing

(Note) Solid marks: Mean strain testing

2 C

2 C

TP-A TP-B TP-C TP-D TP-E TP-F

a

a

10

1 Crack Depth, a (mm)

10 Crack Length, 2 C (mm)

N of Visible Cracks (for ref.)

N of Visible Cracks (for ref.)

TP-A TP-B TP-C TP-D TP-E TP-F

TP-A TP-B TP-C TP-D TP-E TP-F

1

0,1

1,E+03

1,E+04

1,E+05

1,E+06

1,E+03

1,E+04

1,E+05

1,E+06

Number of Cycles, N (cycle)

Number of Cycles, N( cycle)

Fig. 4. Fatigue crack growth (crack depth a ).

Fig. 5. Fatigue crack growth (crack length 2 C ).