PSI - Issue 71

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ScienceDirect

Procedia Structural Integrity 71 (2025) 58–65

5 th International Structural Integrity Conference & Exhibition (SICE 2024) CTOD Evaluation Using ASTM 1820 and BS 7448 Nagaraj Ekabote KLE Technological University, Vidya Nagar, Hubballi-580031, India .

Keywords: J -integral, CTOD, ASTM 1820, BS 7448, Constraint parameter ( m ) 1. Introduction Crack Tip Opening Displacement ( CTOD or δ ) is the oldest fracture toughness parameter used in many applications (Moore and Pisarski, 2013; Liao M, 2010). The estimation of CTOD can be done through direct measurement, Plastic Hinge Model (PHM), and J -integral ( J ). In direct measurement, the CTOD is measured through experimental testing of the fracture specimen. The popular methods are Digital Image Correlation (DIC), double clip gage method, and Silica Replica method (Khor W et al., 2016; Jandejsek, Ivan, and Daniel Vavřík, 2016; Silvestre et al., 2017) . These methods claimed to measure the CTOD accurately but relatively expensive and time consuming over other methods. In PHM, the CTOD is estimated using elastic and plastic part of CTOD . The data collected during fracture toughness testing (load vs. Crack Mouth Opening Displacement ( CMOD ) curves) will be utilized to determine the CTOD . PHM methods seems to be accurate in estimation of CTOD and used in British and Japanese CTOD standards. ∗ Corresponding author . Tel.: +91 9591017854, E-mail address: ekabotenagaraj@gmail.com Abstract Crack Tip Opening Displacement ( CTOD or δ ) is used as a fracture toughness parameter in ASTM 1820 and BS 7448. The critical CTOD is estimated in these standards through distinct concepts and also resulting in varied magnitudes. Here, the comparison between CTOD estimation standards ASTM 1820 and BS 7448 is carried out for AA2050-T84 alloy. Firstly, the CTOD as per ASTM 1820 is estimated for Compact Tension (CT), Disc-Shaped Compact Tension (DCT), and Single Edge Notch Bend (SENB) by varying yield stress to ultimate stress ( S yt /S ut ) and crack length to width of the specimen ( a/W ). The constraint parameter ( m ) equations used to relate J -integral ( J ) and CTOD were modified to first order polynomials. The error of less than 1% between third order (recommended in ASTM 1820) and first order polynomial equations ensured the accuracy of the newly proposed equations. Further, the CTOD were estimated by both ASTM 1820 and BS 7448 for various S yt /S ut using experimental results of AA2050-T84 alloy made CT specimen. The CTOD estimated from BS 7448 were almost four times higher compared to ASTM 1820. Finally, author recommends the necessity of reliable J - CTOD relationship among the standards, to popularize the CTOD as a fracture toughness parameter. © 2025 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 SICE 2024 organizers

2452-3216 © 2025 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 SICE 2024 organizers 10.1016/j.prostr.2025.08.009