University of Oulu

P Plosila et al 2023 IOP Conf. Ser.: Mater. Sci. Eng. 1284 012022,

Strain evolution during hole expansion testing of 800 MPa tensile strength hot-rolled steels

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Author: Plosila, P.1; Kesti, V.2; Kaijalainen, A.1;
Organizations: 1Materials and Mechanical Engineering, University of Oulu, P.O. Box 4200, FI-90014 University of Oulu, Finland
2SSAB Europe, Rautaruukintie 155, P.O. Box 93, FI-92101 Raahe, Finland
3Arctic Steel and Mining, Lapland University of Applied Sciences, Tietokatu 1, FI- 94600 Kemi, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2 MB)
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Language: English
Published: IOP Publishing, 2023
Publish Date: 2023-06-27


One limitation of the standardized ISO 16630 hole expansion test is that it provides only one result: limiting hole expansion ratio (HER). In practice, steels with similar HER values can have different cut edge forming behavior due to possible differences in strain localization tendencies. Digital image correlation (DIC) strain measurement during formability testing allows more in-detail analysis of strain-state near the cut edge. In this paper, strain evolution during hole expansion testing was investigated for three 800 MPa tensile strength grade hot-rolled strip steels. The steels were selected to have differences in microstructures and anisotropies of mechanical properties. Two different hole expansion test methods with DIC strain measurement were utilized to investigate different edge loading scenarios: in-plane stretching with a flat-top punch and more out-of-plane stretching with a hemispherical punch. Test holes were prepared according to ISO 16630 standard. In order to examine strain evolution and localization during testing, strains were measured with circle-shape sections around the hole in various distances from the cut edge. Strain localization behavior was investigated in different sheet directions and the effect on the hole expansion ratio was evaluated. Results show considerable differences in the cut edge forming behavior between the investigated materials.

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Series: IOP conference series. Materials science and engineering
ISSN: 1757-8981
ISSN-E: 1757-899X
ISSN-L: 1757-8981
Volume: 1284
Issue: 1
Article number: 012022
DOI: 10.1088/1757-899x/1284/1/012022
Host publication: 42nd International Deep Drawing Research Group (IDDRG) Conference Luleå, Sweden, 19-22 June 2023
Host publication editor: Asnafi, Nader
Lindgren, Lars-Erik
Conference: International Deep Drawing Research Group Conference
Type of Publication: A4 Article in conference proceedings
Field of Science: 216 Materials engineering
Funding: Financial support for the research work by Business Finland project FOSSA – Fossil-Free Steel Applications is highly appreciated.
Copyright information: © The Author(s) 2023. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd.