PSI - Issue 60

Available online at www.sciencedirect.com StructuralIntegrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 60 (2024) 115–122

© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers The present study aims to bring out the individual effect of peak equivalent strain and strain gradient on the fatigue life in presence of notch/discontinuity. Tests have been conducted under remote pure axial and pure torsion conditions on tubes of C Mn steel with single circular hole. Tubes having different size holes have been taken to study the effect of strain gradient. The remote strain amplitude has been so adjusted that it results nearly same peak equivalent strain amplitude (using pre-test FE analyses) for different size holes. This test methodology brings out the individual effects of fatigue damage in terms of fatigue crack initiation life as a function of strain gradient (owing to different hole size) and peak equivalent strain amplitude at hole tip. Further, the localized strains ahead of hole have been measured using digital image correlation and strain gauge techniques. The fatigue life has been predicted using point based critical distance and critical plane models. The predicted fatigue life is compared with test fatigue life for different hole sizes and remote pure axial/ pure torsion conditions. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers 2452-3216© 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers Fatigue damage in a material is caused due to alternating stress/ strain field. The quantification of fatigue damage on continuum length scale is challenging and its complexity gets pronounced in presence of notches/discontinuity. The piping components (having such notches/ discontinuities) of Indian Nuclear Power Plants (NPPs) are subjected to various service induced cyclic remote loading, these remote loading results in amplification of stress/strain at discontinuity locations. Arora et al. (2016) studied the fatigue behavior of IPHWR by conducting tests on unnotched tube specimens under uniaxial and multiaxial loading condition considering different wave form, phase angle and shear to axial strain ratio. Although the state of stress remains elastic at remote location, however, localized cyclic plastification takes place at such discontinuity location as reported 2452-3216© 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers Fatigue damage in a material is caused due to alternating stress/ strain field. The quantification of fatigue damage on continuum length scale is challenging and its complexity gets pronounced in presence of notches/discontinuity. The piping components (having such notches/ discontinuities) of Indian Nuclear Power Plants (NPPs) are subjected to various service induced cyclic remote loading, these remote loading results in amplification of stress/strain at discontinuity locations. Arora et al. (2016) studied the fatigue behavior of IPHWR by conducting tests on unnotched tube specimens under uniaxial and multiaxial loading condition considering different wave form, phase angle and shear to axial strain ratio. Although the state of stress remains elastic at remote location, however, localized cyclic plastification takes place at such discontinuity location as reported The present study aims to bring out the individual effect of peak equivalent strain and strain gradient on the fatigue life in presence of notch/discontinuity. Tests have been conducted under remote pure axial and pure torsion conditions on tubes of C Mn steel with single circular hole. Tubes having different size holes have been taken to study the effect of strain gradient. The remote strain amplitude has been so adjusted that it results nearly same peak equivalent strain amplitude (using pre-test FE analyses) for different size holes. This test methodology brings out the individual effects of fatigue damage in terms of fatigue crack initiation life as a function of strain gradient (owing to different hole size) and peak equivalent strain amplitude at hole tip. Further, the localized strains ahead of hole have been measured using digital image correlation and strain gauge techniques. The fatigue life has been predicted using point based critical distance and critical plane models. The predicted fatigue life is compared with test fatigue life for different hole sizes and remote pure axial/ pure torsion conditions. Keywords: Digital Image Correlation; Crack initiation; Low cycle fatigue test; Notch/discontinuity. Keywords: Digital Image Correlation; Crack initiation; Low cycle fatigue test; Notch/discontinuity. 1. Introduction 1. Introduction Third International Conference on Structural Integrity 2023 (ICONS 2023) Axial/torsional fatigue tests on notched tubular specimens of carbon steel and Third International Conference on Structural Integrity 2023 (ICONS 2023) Axial/torsional fatigue tests on notched tubular specimens of carbon steel and life estimation using theory of critical distance method Shreebanta Kumar Jena 1,2* , Punit Arora 2 , Suneel K. Gupta 1,2 andJ.Chattopadhyay 1,2 1 Department of Engineering Sciences, Homi Bhabha National Institute, Mumbai, India 2 Reactor Safety Division, Bhabha Atomic research Centre (BARC), Mumbai, India life estimation using theory of critical distance method Shreebanta Kumar Jena 1,2* , Punit Arora 2 , Suneel K. Gupta 1,2 andJ.Chattopadhyay 1,2 1 Department of Engineering Sciences, Homi Bhabha National Institute, Mumbai, India 2 Reactor Safety Division, Bhabha Atomic research Centre (BARC), Mumbai, India Abstract Abstract

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers 10.1016/j.prostr.2024.05.034