Issue 48

R. Nikhil et alii, Frattura ed Integrità Strutturale, 48 (2019) 523-529; DOI: 10.3221/IGF-ESIS.48.50 523 Focused on “Showcasing Structural Integrity Research in India” Limit load based evaluation of plastic η factor for C(T) specimen with a mismatched weld R. Nikhil, S.A. Krishnan, G. Sasikala, A. Moitra Materials development and Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu, India rnikhil@igcar.gov.in, sakrish@igcar.gov.in , gsasi@igcar.gov.in, moitra@igcar.gov.in A BSTRACT . Plastic η factor is adopted to account for crack tip plasticity while evaluating the fracture toughness of the materials as per ASTM E1820. It is valid only for homogeneous materials. The plastic η factor for Compact Type (C(T)) geometry with type 316LN stainless steel weld has been evaluated based on elastic-plastic FE analysis. The incremental elastic-plastic material model with various values for strength mismatch ratio ( M ) i.e. ratio of yield strength of weld metal to that of base metal, from 1.2 to 2.2 have been considered. The weld width ( h ) parallel to the crack plane is varied from 4 mm to 16 mm. The η values thus obtained are analyzed and the inferences are discussed. K EYWORDS . Limit load; Plastic η; Elastic-plastic; Strength mismatch level. Citation: Nikhil, R., Krishnan, S.A., Sasikala, G., Moitra, A., Limit load based evaluation of plastic η factor for C(T) specimen with a mismatched weld, Frattura ed Integrità Strutturale, 48 (2019) 523-529. Received: 28.11.2018 Accepted: 28.02.2019 Published: 01.04.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION eld joints are more likely to contain flaws or defects. The fracture toughness of weldment under the influence of base material strength is an essential input for integrity assessment of welded structures. J -integral as a measure of fracture toughness is generally determined according to ASTM E1820. It is a fracture characterizing parameter based on non-linear elastic material model applied to elastic-plastic materials. The J -integral is divided into elastic (linear), J e and plastic (non-linear), J p components. The elastic component of J ( ' 2 E K J e  ) is same as Griffith energy release rate and the plastic part is given ( Bb A J p p   ), where η is a geometry normalizing parameter to account crack tip plasticity i.e. spread of plastic zone around the crack tip. It is influenced by geometry of the test specimen. For compact tension (CT) specimens, ASTM has adopted an expression (eqn. 1) as obtained by Landes and Clarke [1].        W b 522 .02  (1) W