PSI - Issue 60

Md Rakim et al. / Procedia Structural Integrity 60 (2024) 136–148

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Md Rakim et al. / Structural Integrity Procedia 00 (2023) 000 – 000

given as inputs to the machine directly computing crack growth with an increasing potential drop across the CT specimen notch. The data acquisition software has been used to acquire data that specifies load ( P ), LLD and crack length ( a ) through test application. ⁄ = −34.714 + 85.149 ∗ ( ) − 68.616 ∗ ( ) 2 +18.567∗( ) 3 (4) where, V = Measured voltage drop from DCPD = Reference voltage drop corresponding to ⁄ = 0.4 a = Crack size W = Specimen width 3. Experimental Results and Discussion The FCG curves for base and welded materials have been established in terms of ⁄ vs. in log-log scale at 27 °C, 650 °C, 710 °C and 750 °C with different ageing times up to 20000 hours. A graphically represented ⁄ vs. curve has been shown in Figs. 2 to 5 for specific temperatures and ageing conditions on base and welded materials. The graph indicates that when decreases, correspondingly, the crack growth rate ( ⁄ ) also decreases. For calculating , according to ASTM E 647-15, a minimum of five points must be selected from the FCG curve where the crack growth rate lies between the ranges of 10 −9 to 10 −10 m/cycle along with the best fit linear curve obtained from those extracted points. And the value of has been obtained when ⁄ is 10 −10 m/cycle derived from the linear curve. Table 2 (Base metal) and Table 3 (weld metal) shows the obtained value for different testing conditions. The table shows that the value is higher for weld metal than the base metal for a given ageing time and temperature.

1E-8

1E-8

1E-9

1E-9

da/dN (m/cycle)

da/dN (m/cycle)

Material: Alloy 617M Base 710 °C and As-received condition

Material: Alloy 617M Base 27 °C and As-received condition

1E-10

1E-10

7

8

9

10 11 12 13 14 15

7

8

9

10 11 12 13 14 15 16

D K ( MPa.m 0.5 )

D K (MPa.m 0.5 )

Fig.2: ⁄ vs. curves in log-log scale at 27 °C and as-received condition for base material.

Fig.3: ⁄ vs. curves in log-log scale at 710 °C and as received condition for base material.