PSI - Issue 60

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Gopal Sanyal et al. / Procedia Structural Integrity 60 (2024) 311–323 Author name / StructuralIntegrity Procedia 00 (2019) 000–000

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In order to carry out the mechanical tests suitable adapters and clevis grips were fabricated for mounting the specimen with an Instron make screw-driven load frame.Fig.3 shows a close-up view ofthe Teflon bath with 2-liter capacity fabricated for containing the electrolyte, with composition of 1N H 2 SO 4 aqueous solution, with As 2 O 3 (recombination poison), for in-situ electrochemical charging. A constant voltage, direct current source was used for in-situ experiments, where the sample was kept as cathode and a cleaned lead plate was used as anode.

Figure 3. A close-up view of the container and electrolytic bath with immersed sample and load train used for carrying out In-situ experiments. Tensile and fracture toughness tests were carried out at room temperaturewith a nominal pull rate of 0.01 mm/min. The in-situ tensile tests were carried out using the current density of 20, 40 and 400 mA/cm 2 . At the pull rate employed, the tensile tests were carried out at a strain rate of 8.33x10 -6 s -1 .The value of current to be applied for the achieving the required current density during the tests was estimated by calculating the immersed surface area of the specimens. The gauge region of the specimen was the immersed surface area during the tensile tests. During testing, timed load displacement data has been recorded for both the tensile and fracture tests. For the tensile tests the load was converted to stress by dividing with the original cross-sectional area, and the displacements were converted to strain by dividing with the original gauge length. The reduction in area is calculated from the diameters measured from the fractured sample from the original cross-sectional area. The formulas are given below : ���� � � ⁄ ���� ���� � � ⁄ ������� � �� � ��� � (1) where P = load ; A o = original area;  = strain;  L = displacement; L o = original gauge length; A f = fracture area ; A i = 0.7854*d i 2 ; i = o (original diameter), or f (fracture diameter). RA = reduction in area; %RA = RA x 100. As the specimens were immersed in corrosive bath, no COD gage was used for crack length monitoring during the fracture toughness test. The load line displacements during the fracture toughness test of the sample were obtained by subtracting the cross-head displacements obtained from a separate test with un-cracked side grooved sample. The initiation toughness as per standard ASTM E1820-01 (2001)was computed from the corrected load line displacements

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