PSI - Issue 2_A

N. Ab Razak et al. / Procedia Structural Integrity 2 (2016) 855–862 N. Ab Razak et al./ Structural Integrity Procedia 00 (2016) 000–000

859

5

10.0

10.0

(b)

(a)

T (°C ) t f (h) K max (MPa√m)

T (°C ) t

f (h) K max (MPa√m)

CT-A CT-B CT-C1 CT-C2 CT-A 620 1125 25.02 CT-B 600 311 25.11 CT-C1 625 408 22.82 CT-C2 625 240 28.83

CT-M-1 CT-FX-1 CT-A 620 1125 25.02 CT-B 600 311 25.11 CT-C1 625 408 22.82 CT-C2 625 240 28.83 CT-A-1 CT-A-2

8.0

8.0

6.0

6.0

Δ a (mm )

P max P min

LLD (mm)

4.0

4.0

t

t h

2.0

2.0

0.0

0.0

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

t/t f

N/N f

Fig.3. (a) Crack extension versus normalized number of cycles; b) Load line displacement versus normalized time

1.E-01

T (°C)

f (Hz)

K max (MPa√m)

CT-M-1 CT-FX-1 CT-A-1 CT-A-2 CT-C CT-C

CT-A 620 0.0017 CT-B 600 0.0017

25.02 25.11 22.82 28.83

1.E-02

625 0.0017 625 0.0017

ASTM T=625, th=600s, 7.5kN ASTM T=625, th=600s, P=9kN Ref 10 625 .001 Ref 10 625 .0017 CFCG Ali,T=625,f=0.001 CFCG Ali,T=625,f=0.01 CFCG Ali, T=625,f=1.0 Ref 9 625 0.0 10 Ref 9 625 0.01 Ref 9 625 1.0 Ref 14 600 0.0 027 Ref 14 600 0.0 27 CFCGmagdalena, T=600, th=60min CFCGmagdalena,T=600,th=6min FCG magdalena,T=600, f=0.5Hz FCG,Gra T=600C, f=0.05 Hz - - Ref 14 600 0.5 - Ref 4 0 0. 5 - - - 10.2 10.3 9.7

1.E-03

CFCG

1.E-04 da/dN (mm/cycle)

1.E-05

FCG

1.E-06

1.E+01

1.E+02

Δ K (MPa√m)

Fig.4. Crack growth for P91 steel at various cyclic frequencies

5.2. Crack growth correlation with the C* parameter The CFCG test data has been correlated with the C* parameter and compared with available static creep crack growth (CCG) data for P91 steel in the temperature range 600°C to 625°C from literature Speicher.M et al. (2013), Maleki (2015), Mehmanparast et al. (2011), as shown in Figure 5. P91 CCG scatter data band at 580°C to 625°C and predictive NSWA model (Eqn 8) has been plotted in Fig.5. A power-law creep exponent of n = 8.24 (Narasimhachary and Saxena, 2013) and a uniaxial failure strain of 33% has been used in the NSWA model. In Fig. 5 the closed symbols refer to CFCG data whilst the open symbol indicate the static CCG data. It is apparent that the CFCG data fall into the same scatter band as the static CCG data (Maleki (2015), Speicher.M et al. (2013)), however the CFCG data generally falls towards the upper bound of the static CCG data and there is some indication that an increase in temperature results in a high crack grwoth rate. The CFCG data are mostly bounded by the NSWA prediction line, however the plane strain NSWA model overly predicts the crack growth rate.