PSI - Issue 42

B.Aydin Baykal et al. / Procedia Structural Integrity 42 (2022) 1350–1360 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The constitutive law is given below: Table 1: Constitutive law for Eurofer97 at 173K (E=214 GPa, ν =0.33)  ;DWĂͿ ε Ɖů ϲϲϲ Ϭ ϲϳϬ͘Ϯϱ Ϭ͘ϬϬϬϰ

ϲϴϯ͘ϴϮ Ϭ͘ϬϬϭϵϯϯ ϲϵϱ͘ϴϰ Ϭ͘ϬϬϯϵϵϲ ϳϭϭ͘ϮϮ Ϭ͘ϬϬϳϮϭϵ ϳϮϱ͘ϲϮ Ϭ͘ϬϭϬϲϵϵ ϳϲϭ͘ϰϱ Ϭ͘ϬϮϭϬϲ ϳϴϳ͘Ϯϴ Ϭ͘ϬϯϬϳϴϮ ϴϬϳ͘Ϯϱ Ϭ͘ϬϯϵϱϮϱ ϴϮϲ͘Ϭϲ Ϭ͘Ϭϰϵϵϯ ϴϰϮ͘Ϭϯ Ϭ͘ϬϲϬϵϳϴ ϴϱϰ͘ϰϲ Ϭ͘ϬϳϬϲϴϵ ϴϲϲ͘Ϭϲ Ϭ͘ϬϴϬϴϵϰ ϴϳϳ͘ϱϲ Ϭ͘Ϭϵϯϰϱϵ ϵϬϯ͘Ϯϴ Ϭ͘ϭϰ ϵϮϰ͘ϵϴ Ϭ͘ϮϮϴ ϵϯϭ͘ϵ Ϭ͘ϯϬϰ ϵϯϰ͘ϯ Ϭ͘ϯϳϱ ϵϯϰ͘ϰϱ Ϭ͘ϰϮ ϵϯϱ Ϭ͘ϱ

2.3 Modeling FEM models were generated for two different specimen sizes (1T-CT and 0.18T-CT) and two temperatures (-100 °C and -120 °C) using the same geometry, as shown in the preceding figures. Due to the unique scaling geometry of the CT specimen, it was possible to scale 1T specimens directly to calculate stress, strain and critical volume/area directly, cutting the required resources in half. The model represents a quarter of a CT specimen with two planes of symmetry, where the mesh was biased toward the free surface. The mesh was also refined near the crack tip to capture major deformation areas accurately for post-processing (in particular calculation of critical volume), and this area utilized quadratic elements whereas the rest of the specimen (farther than 400 microns away from the crack tip) featured linear elements. The area surrounding the pin was modeled with two rows of elastic elements in order to avoid potential plastic deformation in this area due to contact forces. The pin itself was modeled as a rigid shell fitting snugly into the slot on the CT specimen and used as the application point of the displacement. Initial simulations were run as long as possible before the 0.18T specimen was restricted to a displacement of 2 mm (crack mouth) to avoid unnaturally twisted or flipped elements. The crack tip profile was modeled as a semicircle (or a quarter circle in the simulation due to the crack plane also being a plane of symmetry) with a radius of 5 microns. Due to the relatively large displacement applied to the specimen, the initial root radius has no effect on the later stages of the simulation with higher loading. Post-processing was performed on the .odb and .fil files generated after the analysis by Abaqus/CAE 2021. J integrals were calculated using 30 contours in each position on the z-axis. Critical volumes were calculated using a self- made subroutine based on the nodal maximum principal stresses. Each element’s integration points were assigned an integration point volume and the volume was added to critical volume as long as the largest principal stress at the