PSI - Issue 14

Ramesh Kumar et al. / Procedia Structural Integrity 14 (2019) 577–583 R. Kumar/ Structural Integrity Procedia 00 (2018) 000–000

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3.2. DHC initiation condition near rolled joint region

The assessment was performed for pressure tube inlet and outlet rolled joint region. Bounding flaws for DHC initiation were assumed to have axial flaw length(c) equal to15mm. Additional rolled joint residual stress value equal to 75MPa was assumed with pressure stress.

r = 0.015 r = 0.05 r =0.13

40

35

r = 0.4 r = 0.5

30

25

20

Threshol Bulk Heq (ppm)

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 15

Fret Depth (mm)

Fig. 5. Threshold bulk Heq for DHC initiation for BPF under normal operation for pressure tube inlet (Rolled joint region)

Fig.5 shows that bounding flaw depth is higher for larger flaw root radius. The minimum bounding flaw depth of 0.25mm with bulk H eq equal to 26.5ppm is bounding for DHC initiation for root radius equal to 0.015mm near PT inlet.

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 30 35 40 45 50 55 60 65 70 75 80 85 Threshold Bulk Heq (ppm) Fret Depth (mm) r = 0.015 r = 0.05 r = 0.13 r = 0.4 r = 0.5

.

Fig. 6. Threshold bulk Heq for DHC initiation for BPF under normal operation for pressure tube outlet (Rolled Joint region)