PSI - Issue 60

Shreebanta Kumar Jena et al. / Procedia Structural Integrity 60 (2024) 115–122 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2.1. Structure Material and specimen details

Low C-Mn steel (SA333 Gr.6), the primary piping material of Indian Pressurized Heavy Water Reactor (IPHWR) has been used for present test study. The notched tube specimens with different sizes of one sided through thickness central notch in the gauge region (representing different strain gradient condition) have been fabricated in accordance with ASTM E2207 (2009). The details of the notched tube specimen with central notch have been presented in Fig. 1

Fig. 1. Notched tube specimen with one sided through-thickness hole

2.2. Test setup

The tests on notched tube specimens have been conducted using test facility comprising of Tension Torsion Machine (TTM), biaxial extensometer, DIC/ SG setups. The details of the test facility are shown in Fig. 2 . TTM machine is closed loop servo hydraulic system with axial and torsional servo controller having a specification of 100kN of axial and 1000Nm of torsional load carrying capacity.

Fig. 2. Typical test setup with tube specimen having single circular hole, biaxial extensometer to control remote strains, DIC/ SG to measure localized strains Further, biaxial extensometer has been used for performing axial strain and angle of twist-controlled tests (present study). This extensometer is capable of handling axial extension of ± 2 mm and angle of twist as ± 2.5 ° , respectively, with respect to 25 mm gauge length. In addition to the above, DIC system which is an optical and noncontact type displacement /strain measuring set up, has been used to capture the near hole displacements and strains field. This set up is useful for quantification of strain gradient ahead of the hole. However, single element strain gauge of 1mm gauge length has been used to measure localized small area averaged (based on foot-print of SG) strain ahead of hole. DIC technique has also been used to precisely capture the crack initiation event after the initiated crack has grown up to a size of 1mm. The typical minimum measurable crack size detected by