PSI - Issue 60

M.K. Sahu et al. / Procedia Structural Integrity 60 (2024) 390–401 M. K. Sahu et.al./ Structural Integrity Procedia 00 (2019) 000 – 000

398

9

Table 3. Load reduction factors, β .

=

, (kNm)

Failure-Cycles, (From Table 2)

Cyclic Tests

Related Monotonic Test

, (kNm)

|

Cyclic Tests

, (kNm)

S.N.

8-QCSP-60-TWC- CSB-LC1 8-QCSP-60-TWC CSB-LC3 8-QCSP-60-TWC CSB-LC4 12-QCSP-60-TWC SSW-LC5

182.4

1.011

184.4

145.8

0.79

14

1.

2.

182.4

1.045

190.6

141.3

0.74

18

3.

182.4

1.045

190.6

121.5

0.64

108

410.8

0.9857

404.9

287.5

0.71

127

4.

| =2 2 (2 cos 2 − sin )| (3) It is well known that the limit moment is linear proportional to the capacity moment of the pipe. Thus, capacity moment corresponding to geometries of the pipe tested under cyclic loading , can be estimated based on the capacity moment of the pipe tested under monotonic loading , , using Eqs. (1) and (2), , = , (4) where, geometric correction factor, can be written as, = 2 2 (2 cos 2 − sin )| 2 2 (2 cos 2 − sin )| (5) This corrected capacity load using Eq. (4) is used in Eq. (1) for calculation of the corrected load reduction factor β as shown in Table 3. 4. Results and discussions USNRC NUREG reports, NUREG-6440 by Rudland. et. al. (1996) and NUREG 6233-2 by Kramer et. al. (1997) has reported that under load controlled reversible cyclic loadings the cracked structure may go to unstable ductile tearing even when the maximum load applied in cyclic loading , , is significantly lower magnitude than the load bearing capacity of a pipe under monotonic loading , . Subsequently, Gupta et.al. (2000) have performed comprehensive studies and developed a cyclic tearing failure assessment diagram (CTFAD) which is a plot of load reduction factor β versus number of loading cycles to failure . A best fit curve equation to evaluate load reduction factor for an applied number of loading cycles was given as ,