PSI - Issue 19

Masaru Bodai et al. / Procedia Structural Integrity 19 (2019) 64–72 Bodai,M et al. / Structural Integrity Procedia 27 (2019) 000 – 000

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2.2 Fatigue tests procedure A 4 - point bending equipment for piping was developed and 4 - point bending under displacement control with a triangular waveform was applied to tested pipes using the MTS 10 MN testing machine as shown in Fig. 2. Strain gages were attached to the tested pipes to monitor the strain at testing.

Strain Gage

Load [Load Cell]

Strain Gage

Thermocouple

L

Displacement, δ a [Actuator]

Fig. 2. Pipe testing facility.

6 pipes were tested as shown in Table 3. Periodical beach marking was applied to all piping tests to identify crack shapes.

Table 3. Test cases for austenitic piping.

Target Strain Amplitude (%)

Target Mean Strain (%)

Notes

Test No.

─ ─ ─

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

±0.50 ±0.44 ±0.25 ±0.25 ±0.50 ±0.20

Including function tests

+2.25 +2.00 +2.30

Through-wall cracking could not be achieved.

2.3 Test results Each crack depth of the beach mark was measured after the bending fatigue test ( Bodai et al ., 2018). The number of cycles at 3 mm deep crack depth was interpolated from those of the beach marks. The number of cycles at 3 mm deep crack and through - wall crack and the fatigue lives by the small specimen tests for the tested pipe material are compared as shown in Fig. 3. Here, the following best - fit curve (BFC) developed by the DFC subcommittee ( Kanasaki et al., 2013) is also plotted with dividing by the Young’s modulus ( E ) and using σ u = 556 MPa obtained by the small spacemen testing.