PSI - Issue 68

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ScienceDirect

Procedia Structural Integrity 68 (2025) 325–331 Structural Integrity Procedia 00 (2024) 000–000 Structural Integrity Procedia 00 (2024) 000–000

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European Conference on Fracture 2024 Failure assessment through various uncoupled damage models in flow forming processes European Conference on Fracture 2024 Failure assessment through various uncoupled damage models in flow forming processes

Tuncay Yalc¸inkaya a, ∗ , Hande Vural a , Tevfik Ozan Fenerciog˘lu b a Department of Aerospace Engineering, Middle East Technical University, 06800 Ankara , Tu¨rkiye b Repkon Machine and Tool Industry and Trade Inc., 34980 S¸ile, Istanbul, Tu¨rkiye Tuncay Yalc¸inkaya a, ∗ , Hande Vural a , Tevfik Ozan Fenerciog˘lu b a Department of Aerospace Engineering, Middle East Technical University, 06800 Ankara , Tu¨rkiye b Repkon Machine and Tool Industry and Trade Inc., 34980 S¸ile, Istanbul, Tu¨rkiye

Abstract Flow forming is a unique metal forming process that utilizes specially designed rollers and a mandrel to shape metal parts with high dimensional accuracy and structural integrity, especially for thin-walled, seamless tubes. Due to the incremental nature of the process, material is subjected to complex stress states and significant plastic deformation that can lead to many types of defects and cracks, and therefore it is crucial to make accurate forming limit predictions to optimize the manufacturing process. This study investigates the capabilities of uncoupled damage models in predicting fracture initiation and formability limits during the flow forming of IN718 alloy. In this regards ten di ff erent damage criteria are employed in Finite Element (FE) simulations including Ayada, Ayada-m, Brozzo, KH, Le-Roy (LR), McClintock (MC), Oh (OH), Rice-Tracey (RT), which are calibrated with tensile tests. Subsequently, these models are applied to flow forming simulations at varying thickness reduction ratios (37.5%, 50% and 70%). The results are compared with experimental trials to assess the prediction accuracy of each model regarding formability limits and fracture initiation. The initial investigations demonstrate that the Ayada criteria are better in predicting damage at all reduction ratios compared to other criteria, making them particularly suitable for this process. In addition, the KH model gives comparable predictions, although it is not successful at all reduction ratios. Abstract Flow forming is a unique metal forming process that utilizes specially designed rollers and a mandrel to shape metal parts with high dimensional accuracy and structural integrity, especially for thin-walled, seamless tubes. Due to the incremental nature of the process, material is subjected to complex stress states and significant plastic deformation that can lead to many types of defects and cracks, and therefore it is crucial to make accurate forming limit predictions to optimize the manufacturing process. This study investigates the capabilities of uncoupled damage models in predicting fracture initiation and formability limits during the flow forming of IN718 alloy. In this regards ten di ff erent damage criteria are employed in Finite Element (FE) simulations including Ayada, Ayada-m, Brozzo, KH, Le-Roy (LR), McClintock (MC), Oh (OH), Rice-Tracey (RT), which are calibrated with tensile tests. Subsequently, these models are applied to flow forming simulations at varying thickness reduction ratios (37.5%, 50% and 70%). The results are compared with experimental trials to assess the prediction accuracy of each model regarding formability limits and fracture initiation. The initial investigations demonstrate that the Ayada criteria are better in predicting damage at all reduction ratios compared to other criteria, making them particularly suitable for this process. In addition, the KH model gives comparable predictions, although it is not successful at all reduction ratios. © 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 ECF24 organizers © 2025 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 / ) © 2025 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 ECF24 organizers. Keywords: Flow forming process; Inconel 718; formability limits Peer-review under responsibility of ECF24 organizers. Keywords: Flow forming process; Inconel 718; formability limits

1. Introduction 1. Introduction

Flow forming is an advanced metal forming technique in the production of single-piece symmetrical sheets or large components in various industries such as automotive, defense and aerospace. This process provides high dimensional accuracy and structural integrity in constructing thin-walled, seamless tubes by utilizing axial and radial alignment of moving rollers and a mandrel. Unlike conventional spinning methods, flow forming ensures uniformity of the internal diameter cross-section while it reduces the wall thickness and elongates the part. This allows manufacturers to produce components, such as wheels, shafts, rocket bodies and launch tubes, with excellent geometric accuracy and surface Flow forming is an advanced metal forming technique in the production of single-piece symmetrical sheets or large components in various industries such as automotive, defense and aerospace. This process provides high dimensional accuracy and structural integrity in constructing thin-walled, seamless tubes by utilizing axial and radial alignment of moving rollers and a mandrel. Unlike conventional spinning methods, flow forming ensures uniformity of the internal diameter cross-section while it reduces the wall thickness and elongates the part. This allows manufacturers to produce components, such as wheels, shafts, rocket bodies and launch tubes, with excellent geometric accuracy and surface

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 ECF24 organizers 10.1016/j.prostr.2025.06.061 ∗ Yalc¸inkaya T. Tel.: + 90-312-210-4258 ; fax: + 90-312-210-4250. E-mail address: yalcinka@metu.edu.tr 2210-7843 © 2025 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 ECF24 organizers. ∗ Yalc¸inkaya T. Tel.: + 90-312-210-4258 ; fax: + 90-312-210-4250. E-mail address: yalcinka@metu.edu.tr 2210-7843 © 2025 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 ECF24 organizers.