PSI - Issue 47

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Procedia Structural Integrity 47 (2023) 873–881 Structural Integrity Procedia 00 (2023) 000–000 Structural Integrity Procedia 00 (2023) 000–000

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27th International Conference on Fracture and Structural Integrity (IGF27) Energetic approach to predict the elliptical crack growth Gianmarco Villani a, ∗ , Valerio G. Belardi a , Pietro Salvini a , Francesco Vivio a a Department of Enterprise Engineering - University of Rome Tor Vergata, Via del Politecnico, 1, 00133, Rome, Italy 27th International Conference on Fracture and Structural Integrity (IGF27) Energetic approach to predict the elliptical crack growth Gianmarco Villani a, ∗ , Valerio G. Belardi a , Pietro Salvini a , Francesco Vivio a a Department of Enterprise Engineering - University of Rome Tor Vergata, Via del Politecnico, 1, 00133, Rome, Italy

© 2023 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 IGF27 chairpersons © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the IGF27 chairpersons. Keywords: Elliptical crack; energetic approach; bi-axial stress Abstract The propagation of elliptical cracks that develop superficially under bending loads and bi-axial stresses is investigated using an energetic approach. At present, computational tools allow assessments to be made on fractured components through analyses based on fracture mechanics. Therefore, an approach is proposed to determine the geometric shape assumed by an evolving crack on the surface and in the bulk. Assuming a minimum energy criterion, the geometry of the crack during the propagation is addressed by this hypothesis. The objective of this work is to assess whether the prediction of elliptical advance (governed by varying axes ratio) is consistent with the experimental evidence. © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the IGF27 chairpersons. Keywords: Elliptical crack; energetic approach; bi-axial stress Abstract The propagation of elliptical cracks that develop superficially under bending loads and bi-axial stresses is investigated using an energetic approach. At present, computational tools allow assessments to be made on fractured components through analyses based on fracture mechanics. Therefore, an approach is proposed to determine the geometric shape assumed by an evolving crack on the surface and in the bulk. Assuming a minimum energy criterion, the geometry of the crack during the propagation is addressed by this hypothesis. The objective of this work is to assess whether the prediction of elliptical advance (governed by varying axes ratio) is consistent with the experimental evidence. In various structures, including pipelines, pressure vessels and aircraft components, cracks are frequently found and recognised as a cause of potential failure. Fatigue crack propagation from these defects has been a significant subject of study in recent decades. Therefore, the crack shape evolution is a critical aspect in fatigue loading analysis. A stress intensity factor approach is commonly used to calculate the crack evolution and the elliptical crack shape is frequently considered to model the crack. In many researches, authors assume that the crack is elliptical and maintains its elliptical shape during the crack propagation Newman Jr. and Raju (1981). The crack growth increments are often estimated on the front nodes allowing crack growth on two elliptical semi axes Liu et al. (2010), assuming the expanding crack to be elliptical in shape, but allows for variation in crack aspect ratio. Two linked Paris fatigue crack growth equations are often used to determine fatigue crack growth in both the depth and surface directions Paris and Erdogan (1963). This technique has been widely adopted in practical evaluations of surface fatigue crack propagation. Several studies have attempted to improve the accuracy of crack growth prediction by increasing the number of points considered along the crack front. For instance, Lin, Smith and Gilchrist Lin and Smith (1997, 1999a,b); In various structures, including pipelines, pressure vessels and aircraft components, cracks are frequently found and recognised as a cause of potential failure. Fatigue crack propagation from these defects has been a significant subject of study in recent decades. Therefore, the crack shape evolution is a critical aspect in fatigue loading analysis. A stress intensity factor approach is commonly used to calculate the crack evolution and the elliptical crack shape is frequently considered to model the crack. In many researches, authors assume that the crack is elliptical and maintains its elliptical shape during the crack propagation Newman Jr. and Raju (1981). The crack growth increments are often estimated on the front nodes allowing crack growth on two elliptical semi axes Liu et al. (2010), assuming the expanding crack to be elliptical in shape, but allows for variation in crack aspect ratio. Two linked Paris fatigue crack growth equations are often used to determine fatigue crack growth in both the depth and surface directions Paris and Erdogan (1963). This technique has been widely adopted in practical evaluations of surface fatigue crack propagation. Several studies have attempted to improve the accuracy of crack growth prediction by increasing the number of points considered along the crack front. For instance, Lin, Smith and Gilchrist Lin and Smith (1997, 1999a,b); 1. Introduction 1. Introduction

∗ Corresponding author. Tel.: + 39 06 72597143. E-mail address: gianmarco.villani@uniroma2.it ∗ Corresponding author. Tel.: + 39 06 72597143. E-mail address: gianmarco.villani@uniroma2.it

2452-3216 © 2023 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 IGF27 chairpersons 10.1016/j.prostr.2023.07.032 2210-7843 © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the IGF27 chairpersons. 2210-7843 © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the IGF27 chairpersons.