PSI - Issue 35

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Procedia Structural Integrity 35 (2022) 228–236 Structural Integrity Procedia 00 (2021) 000–000 Structural Integrity Procedia 00 ( 021) 000–000

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2nd International Workshop on Plasticity, Damage and Fracture of Engineering Materials The influence of thickness / grain size ratio in microforming through crystal plasticity 2nd International Workshop on Plasticity, Damage and Fracture of Engineering Materials The influence of thickness / grain size ratio in microforming through crystal plasticity

Orhun Bulut a , Sadik Sefa Acar a,b , Tuncay Yalc¸inkaya a, ∗ a Department of Aerospace Engineering, Middle East Technical Universty, Ankara 06800, Turkey b Repkon Machine and Tool Industry and Trade Inc., Istanbul 34980, Turkey Orhun Bulut a , Sadik Sefa Acar a,b , Tuncay Yalc¸inkaya a, ∗ a Department of Aerospace Engineering, Middle East Technical Universty, Ankara 06800, Turkey b Repkon Machine and Tool Industry and Trade Inc., Istanbul 34980, Turkey

© 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 IWPDF 2021 Chair, Tuncay Yalçinkaya © 2021 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 / ) r-review under responsibility of IWPDF 2021 Chair, Tuncay Yalc¸inkaya. Keywords: Crystal Plasticity; Size e ff ect; Microforming Abstract Microscale forming operations have become popular due to miniaturisation which focuses on micro scale design and manufacturing of devices, components and parts, e.g. in RF-MEMS. In such processes when the component dimension becomes comparable with the grain size, considerable size e ff ect is observed. Recent experimental studies on micron sized sheet specimens have shown that the ratio between thickness (t) and grain size (d) has a significant influence on the mechanical behavior of materials which cannot be explained merely with the intrinsic (grain) size e ff ect. Even though the grain sizes are similar, remarkable di ff erences in mechanical response is obtained for cases with di ff erent thicknesses. In this context the aim of the current study is to address this extrinsic type size e ff ect through crystal plasticity simulations. A series of local crystal plasticity finite element simulations are conducted for di ff erent values of t / d ratio in tensile specimens. Di ff erent granular morphologies of polycrystalline samples are generated using Voronoi tessellation and tested under axial loading conditions. The macroscopic influence of varying t / d ratio is studied in detail and compared with the experimental findings in the literature. © 2021 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 IWPDF 2021 Chair, Tuncay Yalc¸inkaya. Keywords: Crystal Plasticity; Size e ff ect; Microforming Abstract Microscale forming operations have become popular due to miniaturisation which focuses on micro scale design and manufacturing of devices, components and parts, e.g. in RF-MEMS. In such processes when the component dimension becomes comparable with the grain size, considerable size e ff ect is observed. Recent experimental studies on micron sized sheet specimens have shown that the ratio between thickness (t) and grain size (d) has a significant influence on the mechanical behavior of materials which cannot be explained merely with the intrinsic (grain) size e ff ect. Even though the grain sizes are similar, remarkable di ff erences in mechanical response is obtained for cases with di ff erent thicknesses. In this context the aim of the current study is to address this extrinsic type size e ff ect through crystal plasticity simulations. A series of local crystal plasticity finite element simulations are conducted for di ff erent values of t / d ratio in tensile specimens. Di ff erent granular morphologies of polycrystalline samples are generated using Voronoi tessellation and tested under axial loading conditions. The macroscopic influence of varying t / d ratio is studied in detail and compared with the experimental findings in the literature.

1. Introduction 1. Introduction

The ongoing technological advancements lead to usage of micron-sized devices necessary in various industries. Because of the popularization of such tiny devices, there is a need for further investigation of the influence of mi crostructural characteristics on the mechanical response. At this length scale, di ff erent size e ff ect phenomena plays crucial role in the plastic behavior of the materials (see e.g. Yalc¸inkaya et al. (2018)). As the material become thinner, fewer grains are present along the thickness direction. Hall-Petch relation dictates that material strength strongly de pends on the grain size with an inverse relation, which assumes a certain dependency for every grain size independent of the specimen geometry. However, this traditional perspective of the grain size e ff ect is not enough to explain the The ongoing technological advancements lead to usage of micron-sized devices necessary in various industries. Because of the popularization of such tiny devices, there is a need for further investigation of the influence of mi crostructural characteristics on the mechanical response. At this length scale, di ff erent size e ff ect phenomena plays crucial role in the plastic behavior of the materials (see e.g. Yalc¸inkaya et al. (2018)). As the material become thinner, fewer grains are present along the thickness direction. Hall-Petch relation dictates that material strength strongly de pends on the grain size with an inverse relation, which assumes a certain dependency for every grain size independent of the specimen geometry. However, this traditional perspective of the grain size e ff ect is not enough to explain the

∗ Corresponding author. Tel.: + 903122104258 ; fax: + 903122104250. E-mail address: yalcinka@metu.edu.tr ∗ Corresponding author. Tel.: + 903122104258 ; fax: + 903122104250. E-mail address: yalcinka@metu.edu.tr

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 IWPDF 2021 Chair, Tuncay Yal ç inkaya 10.1016/j.prostr.2021.12.069 2210-7843 © 2021 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 IWPDF 2021 Chair, Tuncay Yalc¸inkaya. 210-7843 © u . li l i r . . is i i Y-NC D h : // creativecom ons.org / licenses / by-nc-nd / 4.0 / ) e r-review under esponsibility of IWPDF 2021 Chair, Tuncay Yalc¸inkaya.