PSI - Issue 42

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Morgado et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1546 © 2020 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/) Teresa Morgado et al. / Procedia Structural Integrity 42 (2022) 1545–1551

Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; Life prediction models; 6060 aluminium alloy; manufacturing defects;extruded

1. Introduction Aluminium has been of great importance in the industry ’s evolution and is currently the most abundant metal on planet Earth (Han et al., 2017). It is widely used throughout the industry, not just in the automobile production area but also in civil construction and aeronautics, being the constituent of thousands of pieces. All manufacturing processes involve defects intrinsic to them that will affect the service durability of the components (Morgado, 2016). In this way, it is necessary to study the influence of these defects on structural durability and develop life prediction models for these components. Moreover, knowing that fatigue failure continues to be a significant concern in engineering design because the economic costs of fracture and its prevention are substantial, and an estimated 80% of these costs involve situations where fatigue is at least a contributing factor (Mori et al.,2018), the primary purpose of this work, is developed new models to predict the fatigue limit of 6060 extruded aluminium. Parts with different geometries and heat treatments are contemplated in this study. Experimental results of fatigue tests, manufacturing defects and microhardness are presented. A comparative analysis of the models of Murakami, Ueno and Schӧnbauer (Murakami et al., 1991), (Ueno et al., 2012), (Ueno et al., 2014), (Schӧnbauer et al., 2016), with the experimental results is performed. Nomenclature area of the defect estimated by extreme value statistics area of an internal inclusion and is obtained considering the extreme value area of a defect projected onto the plane perpendicular to the maximum tensile stress obtained considering the extreme value b empirical factor dependent on the defect position (surface, subsurface, and internal) BIL billet CO hollow circular cross-section piece Vickers hardness R stress ratio RM approximately rectangular cross-section, solid with rounded corners piece RO the hollow rectangular cross-section extruded piece empirical factor dependent on the variable hardness ∆ ℎ stress intensity factor range fatigue limit 2. State of the art Murakami et al. (1989) studied the correlation between fatigue fracture stress and the size and location of non metallic inclusions on steel. The study’s principal objective was to extend the equations (1) and (2) for surface defects to internal non-metallic inclusions. It was estimated the equation (3) for internal inclusions. Then they compare the predictions given by equation (3) with the experimental results and discussed the applicability of the equation to internal defects and cracks. This study concluded that the fatigue limit at the point of inclusion could be estimated using one of two equations. For a surface inclusion, the fatigue limit is given by equation (2), and for an internal inclusion is given by expression (3).