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Failure characteristics of a dual-phase steel sheet
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
2014 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, Vol. 214, 1190-1204 p.Article in journal (Refereed) Published
Abstract [en]

Failure in ductile sheet metal structures is usually caused by one, or a combination of, ductile tensile fractures, ductile shear fractures or localised instability. In this paper the failure characteristics of the high strength steel Docol 600DP are explored. The study includes both experimental and numerical sections. In the experimental sections, the fracture surface of the sheet subjected to Nakajima tests is studied under the microscope with the aim of finding which failure mechanism causes the fracture. In the numerical sections, finite element (FE) simulations have been conducted using solid elements. From these simulations, local stresses and strains have been extracted and analysed with the aim of identifying the fracture dependency of the stress triaxiality and Lode parameter.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 214, 1190-1204 p.
Keyword [en]
Sheet metal failure; Forming limit; Instability; Ductile tensile fracture; Ductile shear fracture
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-105209DOI: 10.1016/j.jmatprotec.2014.01.004ISI: 000334006600003OAI: diva2:704776
Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2014-05-14Bibliographically approved
In thesis
1. Ductile Failure in High Strength Steel Sheets
Open this publication in new window or tab >>Ductile Failure in High Strength Steel Sheets
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Developments in computer-aided engineering and the rapid growth of computational power have made simulation-driven process and product development efficient and useful since it enables detailed evaluation of product designs and their manufacturing processes. In the context of a sheet metal component, it is vital to predict possible failure both during its forming process and its subsequent usage. Accurate numerical models are needed in order to obtain trustworthy simulation results. Furthermore, the increasing demands imposed on improved weight-to-performance ratio for many products endorse the use of high-strength steels. These steels often show anisotropic behaviour and more complex hardening and fracturing compared to conventional steels. Consequently, demand for research on material and failure models suitable for these steels has increased.

In this work, the mechanical and fracture behaviour of two high-strength steels, Docol 600DP and Docol 1200M, have been studied under various deformation processes. Experimental results have been used both for material characterisation and for calibration of fracture criteria. One major requirement as concerns the fracture criteria studied is that they should be simple to apply in industrial applications, i.e. it should be possible to easily calibrate the fracture criteria in simple mechanical experiments and they should be efficient and accurate. Consequently, un-coupled phenomenological damage models have been the main focus throughout this work.

Detailed finite element models including accurate constitutive laws have be used to predict and capture material instabilities. Most of the fracture criteria studied are modifications of the plastic work to fracture. Ductile tensile and ductile shear types of fracture are of particular interest in sheet metal applications. For these fractures the modification of the plastic work relates to void coalescence and void collapse, respectively. Anisotropy in fracture behaviour can be captured by the introduction of a material directional function.

The dissertation consists of two parts. The first part contains theory and background. The second consists of five papers.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 60 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1579
National Category
Engineering and Technology
urn:nbn:se:liu:diva-105213 (URN)10.3384/diss.diva-105213 (DOI)978-91-7519-389-2 (print) (ISBN)
Public defence
2014-04-11, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2014-05-27Bibliographically approved

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