PSI - Issue 71

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ScienceDirect

Procedia Structural Integrity 71 (2025) 142–149

5 th International Structural Integrity Conference & Exhibition (SICE 2024) Effect of Two-Scale Void Interaction on Crack Path Behaviour Under Mixed-Mode Loading

A.K. Dwivedi 1,2 1 Reactor Safety Division, Bhabha Atomic research Centre (BARC), Mumbai, India 2 Department of Engineering Sciences, Homi Bhabha National Institute (HBNI), Mumbai, India

The ductile fracture in structural alloys occurs via 3 stages of the process -void nucleation, void growth, and coalescence of voids (Baechem, 1963; Cox et al., 1974; Garrison et al., 1987). In ductile failure, voids — whether pre-exist in the material or nucleates during the deformation and grows until they connect or coalesce, creating a micro-crack. The growth of this micro-crack is influenced by the interaction and coalescence of voids at different scales. Larger voids, which nucleate early in the deformation stage, named as primary voids, while smaller voids, nucleating later and ranging from 0.1 to 0.01 times of the primary voids size, are termed secondary voids. Once the micro-crack forms, it interacts with the voids, either through individual void-void interactions or via multiple voids engaging simultaneously (Tvergaard et al. 1992; Tvergaard et al. 2002;). Theoretical and numerical models addressing the two primary mechanisms of ductile fracture have been extensively studied. For instance, (Tvergaard et al. 2007;) examined the differences in crack initiation toughness between idealized 2D cylindrical voids and more realistic spherical voids, noting an increase in toughness for the latter. Subsequent research has investigated various factors, such as the effect of the initial shape and distribution of primary and secondary voids on the voids coalescence (Kim et al., 2003; Hutter et al., 2012; Buljac et al., 2015; Dwivedi et al., 2022; Dwivedi et al., 2023; Dwivedi et al., 2024). Keywords: Crack path, primary and secondary voids, discrete modelling, fracture toughness, mixed-mode loading . 1. Introduction ∗ Corresponding author. Mob.: +917053546929 E-mail address: alok92.dwivedi@yahoo.com, akdwivedi@barc.gov.in Abstract The void interaction mechanism in front of the crack tip has been studied thoroughly. Various numerical analyses have been conducted to account for the distribution of primary voids, the initial shape of primary voids, and mix-mode loading on crack extension. In most of the work, only primary voids modeled in initial crack plane. A few studies also consider the secondary voids as being homogeneously distributed throughout the matrix. The interaction between the two distinct scales of voids has not been analyzed yet. In this work, the interaction effect of primary and secondary voids on the ductile crack propagation is analyzed. A plane strain, semi-infinite cracked small scale yielding boundary layer model is considered and the mix mode I and mode II of K field. loading is applied. “β” defines the ratio of mode II and mode I loading. Both larger and smaller voids are modeled explicitly in the process zone. Initially, only the primary voids configuration analyzed for the different loading scenario. Then, secondary voids are introduced in the intervoid ligament of primary voids to account for their effect on the material’s toughness. For certai n configurations and initial shapes of the secondary voids, the material resistance curve is plotted and compared with the case that consists only of primary voids. The present study reveals that the initial shape and distribution of secondary voids as well as the different value of “β” may alter the voids interaction mechanism and the crack may differ the path which affects the toughness of the material. © 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.2025.08.020