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Anisotropic fracture criteria for a dual-phase steel
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)Manuscript (preprint) (Other academic)
Abstract [en]

The main objective of this work is to examine the use of anisotropic fracture criteria in order to predict fracture in dual-phase steel. The introduction of a material directional function into the fracture criterion was used in order to account for anisotropy observed in experiments. Selected fracture criteria were fist calibrated by ordinary tensile and in-plane shear tests using specimens cut in three material directions. In order to validate the performance, two types of validation tests were conducted. First, plane strain (notched tensile) tests were carried out in three material directions. Second, Nakajima tests with a waist of 130 mm were conducted, also in three material directions. The fit to the calibration tests was improved with all material directional functions compared to the isotropic criterion. Overall best performance was achieved when a material direction function based on the structural tensors was introduced.

Place, publisher, year, edition, pages
2014.
Keyword [en]
Sheet metal failure, anisotropy, ductile tensile fracture, ductile shear fracture
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-105212OAI: oai:DiVA.org:liu-105212DiVA: diva2:704785
Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2014-03-13Bibliographically 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.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1579
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-105213 (URN)10.3384/diss.diva-105213 (DOI)978-91-7519-389-2 (ISBN)
Public defence
2014-04-11, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2014-05-27Bibliographically approved

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Björklund, OscarNilsson, Larsgunnar

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