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An evaluation of the statistics of steel material model parameters
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.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
2012 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 212, no 6, 1288-1297 p.Article in journal (Refereed) Published
Abstract [en]

In robustness studies, variations of material properties are often represented by simple assumptions, such as scaling of stress-strain relations, often due to lack of knowledge or deeper understanding of the material physics and the material model applied. By performing material characterisation tests on several batches of a DP600 steel and fitting a phenomenological material model to each batch, this paper studies the dispersion of material model parameters, as well as correlations between both experimental and model parameters. It is concluded that some of the charcterisation tests may be omitted in the future, due to correlations found between parameters. The results may also be applied in a robustness study by inversely using the retrieved statistics to generate reasonable new sets of material model parameters. The methodology presented may be adopted for any other type of material characterisation process.

Place, publisher, year, edition, pages
Elsevier, 2012. Vol. 212, no 6, 1288-1297 p.
Keyword [en]
Robustness studies, material model parameter variations, dual phase steel
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-70193DOI: 10.1016/j.jmatprotec.2012.01.016ISI: 000303176900008OAI: oai:DiVA.org:liu-70193DiVA: diva2:436682
Note
funding agencies|SFS ProViking project Super Light Steel Structures||Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Robust optimisation of structures: Evaluation and incorporation of variations in simulation based design
Open this publication in new window or tab >>Robust optimisation of structures: Evaluation and incorporation of variations in simulation based design
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the robustness of structures considering various uncertainties. The overall objective is to evaluate and develop simulation based design methods in order to find solutions that are optimal both in the sense of handling typical load cases and minimising the variability of the response, i.e. robust optimal designs. Conventionally optimised structures may show a tendency of being sensitive to small perturbations in the design or loading conditions. These variations are of course inevitable. To create robust designs, it is necessary to account for all conceivable variations (or at least the influencing ones) in the design process. The thesis is divided into two parts. The first part serves as a theoretical background for this work. It includes introductions to the concept of robust design, basic statistics, optimisation theory and metamodelling. The second part consists of five appended papers on the topic.

The first and third papers focuse on the evaluation of robustness, given some dispersions in the input data. Established existing methods are applied, and for paper three, comparisons with experimentally evaluated dispersions on a larger system are made.

The second and fourth paper introduce two new approaches to perform robust optimisation, i.e. optimisations where the mean performance and the robustness in the objectives are simultaneously optimised. These methods are demonstrated both on an analytical example and on a Finite Element model design example. The fifth paper studies the variations in mechanical properties between several different batches of the same steel grade. A material model is fitted to each batch of material, whereby dispersions seen in test specimens are transferred to material model parameter variations. The correlations between both test and material model parameters are studied.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 39 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1382
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70199 (URN)978-91-7393-129-8 (ISBN)
Public defence
2011-09-23, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2011-09-07Bibliographically approved
2. On Material Modelling of High Strength Steel Sheets
Open this publication in new window or tab >>On Material Modelling of High Strength Steel Sheets
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work done in this thesis aims at developing and improving material models for use in industrial applications.

The mechanical behaviour of three advanced high strength steel grades, Docol 600DP, Docol 1200M and HyTens 1000, has been experimentally investigated under various types of deformation, and material models of their behaviour have been developed. The origins of all these material models are experimental findings from physical tests on the materials.

Sheet metal forming is an important industrial process and is used to produce a wide range of products. The continuously increasing demand on the weight to performance ratio of many products promotes the use of advanced high strength steel. In order to take full advantage of such steel, most product development is done by means of computer aided engineering, CAE. In advanced product development, the use of simulation based design, SBD, is continuously increasing. With SBD, the functionality of a product, as well as its manufacturing process, can be analysed and optimised with a minimum of physical prototype testing. Accurate numerical tools are absolutely necessary with this methodology, and the model of the material behaviour is one important aspect of such tools.

This thesis consists of an introduction followed by five appended papers. In the first paper, the dual phase Docol 600DP steel and the martensitic Docol 1200M steel were subjected to deformations, both under linear and non-linear strain paths. Plastic anisotropy and hardening were evaluated and modelled using both virgin materials, i.e. as received, and materials which were pre-strained in various material directions.

In the second paper, the austenitic stainless steel HyTens 1000 was subjected to deformations under various proportional strain paths and strain rates. It was experimentally shown that this material is sensitive both to dynamic and static strain ageing. A constitutive model accounting for these effects was developed, calibrated, implemented in a Finite Element software and, finally, validated on physical test data.

The third paper concerns the material dispersions in batches of Docol 600DP. A material model was calibrated to a number of material batches of the same steel grade. The paper provides a statistical analysis of the resulting material parameters.

The fourth paper deals with a simple modelling of distortional hardening. This type of hardening is able to represent the variation of plastic anisotropy during deformation. This is not the case with a regular isotropic hardening, where the anisotropy is fixed during deformation.

The strain rate effect is an important phenomenon, which often needs to be considered in a material model. In the fifth paper, the strain rate effects in Docol 600DP are investigated and modelled. Furthermore, the strain rate effect on strain localisation is discussed.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 59 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1478
Keyword
material modelling
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-80115 (URN)978-91-7519-791-3 (ISBN)
Public defence
2012-10-26, C3, Hus C, Campus Valla, Linköpings Universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Projects
SFS ProViking Super Light Steel Structures
Available from: 2012-09-25 Created: 2012-08-21 Last updated: 2012-09-25Bibliographically approved

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Aspenberg, DavidLarsson, RikardNilsson, Larsgunnar

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