PSI - Issue 38

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2021) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2021) 000 – 000 Available online at www.sciencedirect.com Procedia Structural Integrity 38 (2022) 611–620

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FATIGUE DESIGN 2021, 9th Edition of the International Conference on Fatigue Design Scatter and size effect in High Cycle Fatigue of cast aluminum-silicon alloys: A comprehensive experimental investigation Driss EL KHOUKHI 1, 2, 3,*, Franck MOREL 1 , Nicolas SAINTIER 2 , Daniel BELLETT 1 , Pierre FATIGUE DESIGN 2021, 9th Edition of the International Conference on Fatigue Design Scatter and size effect in High Cycle Fatigue of cast aluminum-silicon alloys: A comprehensive experimental investigation Driss EL KHOUKHI 1, 2, 3,*, Franck MOREL 1 , Nicolas SAINTIER 2 , Daniel BELLETT 1 , Pierre

OSMOND 3 , Viet-Duc Le 1 , Jérôme ADRIEN 4 1 LAMPA, Arts et Métiers Paris Tech, 49 035 Angers, Cedex, France 2 I2M, Arts et Métiers Paris Tech, 33170 Talence, Cedex, France 3 STELLANTIS, 78955 Carrières-sous-Poissy, Cedex, France 4 MATEIS, INSA de Lyon, 69621 Villeurbanne, Cedex, France OSMOND 3 , Viet-Duc Le 1 , Jérôme ADRIEN 4 1 LA PA, Arts et Métiers Paris Tech, 49 35 A g rs, C dex, France 2 I2M, Arts et Métiers Paris Tech, 33170 Talence, C dex, France 3 STELLANTI , 78955 Carrières-sous-Poissy, , 4 MATEIS, INSA de Lyon, 69621 Villeurbanne, Cedex, France

© 2021 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 scientific committee of the Fatigue Design 2021 Organizers . LSEVIER B.V. i l NC N li ttps://creativeco mons.org/lic nses/by-nc-nd/4.0 ) O a s Keywords: HCF ; size effect ; stress gradient effect ; Highly Stressed Volume ; microstructural heterogeneities ; cast aluminum alloys ; scatter. Abstract Cast Al-Si alloys have be n widely u ed in automotive applications with regard to their low density and excellent thermal conductivity. Many compon nts made of these alloys are subjected to cyclic loads which an l ad to fatigue failure. For these materials, the well-known size effect i fatigue, wher by the fatigue strength is reduc d when the size is in reased, can be si nificant and needs to be properly evaluate . This paper analyses the role of casting defects on the fatigue scatter and siz effect. A uniaxial fatigue testing campaign (R=0.1) has b en conducted using two cast aluminum alloys, fabricat d by different casting processes (gravity die casting and lost foam c sting), associated with the T7 heat treat nt, and with different degr es of por sity. The fatigue response of different specimens (sm ot and notched) with different stressed olumes has been investi ated. The first part of this article is about the experimental characterization of the siz effect and scatt r in both alloys via the concept of the Highly Stressed Volume. The second part investigates the effect of the Highly Stressed Volume on the critical defect ize and th establishment of Kitagawa-Takahashi diagram. It is shown that the alloy B, with a population of defects of large size, shows a slight size effect and low scatter. In comparison, alloy A that exhibits a population of defects of relatively small size manifests significant size effect and high scatter. © 2021 The Authors. Published by ELSEVIER B.V. This is an ope acces article under CC BY-NC-ND lic nse ( https://creativecommons.o g/licenses/by-nc-nd/4.0 ) Peer-review under responsibility of the scientific committee of the Fatigue Design 2021 Organizers Keywords: HCF ; size effect ; stress gradient effect ; Highly Stressed Volume ; microstructural heterogeneities ; cast aluminum alloys ; scatter. Context, introduction and objectives The fatigue data transferability from laboratory specimens to real components or structures is very often difficult to handle because of the high number of parameters potentially affecting the fatigue strength. Besides the loading mode, the microstructural heterogeneities, the stress gradient, and the size of the loaded volume can show significant effects on the fatigue strength. In particular, it is generally accepted that the fatigue strength of certain materials decreases with an increase in the volume (Kelly and Morrison 1970) . This is referred to as either the “volume effect”, the “size effect” or the “scale effect” and is often simply explained by an increase in the probability of encountering a large material defect in the fatigue active volume. Abstract Cast Al-Si alloys have been widely used in automotive applications with regard to their low density and excellent thermal conductivity. Many components made of these alloys are subjected to cyclic loads which can lead to fatigue failure. For these materials, the well-known size effect in fatigue, whereby the fatigue strength is reduced when the size is increased, can be significant and needs to be properly evaluated. This paper analyses the role of casting defects on the fatigue scatter and size effect. A uniaxial fatigue testing campaign (R=0.1) has been conducted using two cast aluminum alloys, fabricated by different casting processes (gravity die casting and lost foam casting), associated with the T7 heat treatment, and with different degrees of porosity. The fatigue response of different specimens (smooth and notched) with different stressed volumes has been investigated. The first part of this article is about the experimental characterization of the size effect and scatter in both alloys via the concept of the Highly Stressed Volume. The second part investigates the effect of the Highly Stressed Volume on the critical defect size and the establishment of Kitagawa-Takahashi diagram. It is shown that the alloy B, with a population of defects of large size, shows a slight size effect and low scatter. In comparison, alloy A that exhibits a population of defects of relatively small size manifests significant size effect and high scatter. d b i a 1. Introduction 1.1 1. Introduction 1.1 Context, introduction and objectives The fatigue data transferability from laboratory specimens to real components or structures is very often difficult to handle because of the high number of parameters potentially affecting the fatigue strength. Besides the loading mode, the microstructural heterogeneities, the stress gradient, and the size of the loaded volume can show significant effects on the fatigue strength. In particular, it is generally accepted that the fatigue strength of certain materials decreases with an increase in the volume (Kelly and Morrison 1970) . This is referred to as either the “volume effect”, the “size effect” or the “scale effect” and is often simply explained by an increase in the probability of encountering a large material defect in the fatigue active volume.

* Corresponding author. Tel.: +33 (0) 6 48 50 81 78 E-mail address: driss.el-khoukhi@ensam.eu * Corresponding author. Tel.: +33 (0) 6 48 50 81 78 E-mail address: driss.el-khoukhi@ensam.eu

2452-3216 © 2021 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 scientific committee of the Fatigue Design 2021 Organizers 10.1016/j.prostr.2022.03.063 2452-3216 © 2021 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 scientific committee of the Fatigue Design 2021 Organizers 2452-3216 © 2021 The Authors. Published by ELSEVIER B.V. This is an ope acces article under CC BY-NC-ND lic nse (https://cr ativecommons.org/l c nses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Fatigue Design 2021 Organizers