PSI - Issue 60

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

395

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

Table 2. Geometries of pipe specimens and experimental load cycles corresponding to cyclic tearing tests.

(mm)

Peak Moment (kNm) ,

Peak Load(kN) , = ,

Inner Span, L (mm)

Size ( 2 ) *

Load cycles ( )

Outer Span, Z (mm)

Length (mm)

Sl. No.

Experiment Name

t (mm)

0.80 8 =360 145.8 14 0.775 8 =349 141.3 18 0.67 8 =300 121.5 108 0.67 12 =500 287.5 127

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

1

219.0

18.6

880

2500

2945

63.31 o

2

220.0

19.0

880

2500

2977

62.50 o

3

220.0

19.0

880

2500

2982

62.50 o

4

324.0

27.1

1300

3600

4010

61.89 o

Note: QCSP: Quasi Cyclic Straight Pipe; TWC: Through Wall circumferential Crack; CSB: Carbon Steel Base; SSW: Stainless Steel Weld. * After fatigue pre-cracking

All tests have been conducted under fully reversing cyclic bending load (minimum to maximum load ratio = = ⁄ =−1 ). In all the cases the orientation of the crack notch is circumferential and through wall. All tests have been performed on pipes having through-wall cracks. Before starting any of the tests, the component was subjected to pre-fatigue cycles for sharpening the machined notch. All these tests have been conducted in four-point bend test set-up under load-controlled condition under operating temperature i.e. 300 o C. Fig. 2(a) shows the schematic of the test setup and cross-sectional views of through-wall cracks. The loading scheme is shown schematically in Fig. 2(b). For all the tests, loading ratio R = -1 is adopted i.e., the load is completely reversed. Actual photograph of one 8-inch pipe under test set up for cyclic test is shown in Fig. 2(c). 3.4. Cyclic tearing test results This maximum experimental load , = 450.25kN for monotonic fracture test of pipe 8-QMSP-60-TWC CSB-M1 is used as relevant base line data for the other identical 8 -inch pipes, which are to be tested under cyclic loadings. The through-wall cracked pipes 8-QCSP-60-TWC- CSB-LC1, 8-QCSP-60-TWC-CSB-LC3, 8-QCSP-60 TWC-CSB-LC4, were tested for different load values , as per Table 2 for cyclic loadings. All the 8-inch through wall cracked pipes are identical in geometry, material and loading configurations. For the explanatory purpose, the plots of salient test results of a cyclic tearing test 8-QCSP-60-TWC-CSB-LC3 are shown in Fig. 3. 3.5. Evaluation of load reduction factor, The magnitude of maximum value of cyclic load, , have been decided such that it is premediated fraction of the capacity moment of the identical pipe, , , which is estimated by the monotonic fracture testing on