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A study of the unloading behaviour of dual phase steel
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
Saab AB, Linköping, Sweden.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 602, 119-126 p.Article in journal (Refereed) Published
Abstract [en]

It is important to understand the strain recovery of a steel sheet in order to predict its springback behaviour. During strain recovery, the stress–strain relation is non-linear and the resulting unloading modulus is decreased. Moreover, the unloading modulus will degrade with increasing plastic pre-straining. This study aims at adding new knowledge on these phenomena and the mechanisms causing them. The unloading behaviour of the dual-phase steel DP600 is characterised experimentally and finite element (FE) simulations of a representative volume element (RVE) of the microstructure are performed. The initial stress and strain state of the micromechanical FE model is found by a simplified simulation of the annealing processes. It is observed from the experimental characterisation that the decrease of the initial stiffness of the unloading is the main reason for the degrading unloading modulus. Furthermore, the developed micromechanical FE model exhibits non-linear strain recovery due to local plasticity caused by interaction between the two phases.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 602, 119-126 p.
Keyword [en]
Micromechanics; Representative volume element; Dual phase steel; Unloading modulus; Non-linear recovery
National Category
Metallurgy and Metallic Materials Applied Mechanics
Identifiers
URN: urn:nbn:se:liu:diva-106318DOI: 10.1016/j.msea.2014.02.069ISI: 000335098500015OAI: oai:DiVA.org:liu-106318DiVA: diva2:715429
Available from: 2014-05-05 Created: 2014-05-05 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Finite Element Analysis of Sheet Metal Assemblies: Prediction of Product Performance Considering the Manufacturing Process
Open this publication in new window or tab >>Finite Element Analysis of Sheet Metal Assemblies: Prediction of Product Performance Considering the Manufacturing Process
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the development of methodologies to be used to simulate complete manufacturing chains of sheet components and the study of how different mechanical properties propagate and influence succeeding component performance.

Since sheet metal assemblies are a major constituent of a wide range of products it is vital to develop methodologies that enable detailed evaluation of assembly designs and manufacturing processes. The manufacturing process influences several key aspects of a sheet metal assembly, aspects such as shape fulfilment, variation and risk of material failure.

Developments in computer-aided engineering and computational resources have made simulation-based process and product development efficient and useful since it allows for detailed, rapid evaluation of the capabilities and qualities of both process and product. Simulations of individual manufacturing processes are useful, but greater benefits can be gained by studying the complete sequence of a product's manufacturing processes. This enables evaluation of the entire manufacturing process chain, as well as the final product. Moreover, the accuracy of each individual manufacturing process simulation is improved by establishing appropriate initial conditions, including inherited material properties.

In this thesis, a methodology of sequentially simulating each step in the manufacturing process of a sheet metal assembly is presented. The methodology is thoroughly studied using different application examples with experimental validation. The importance of information transfer between all simulation steps is also studied. Furthermore, the methodology is used as the foundation of a new approach to investigate the variation of mechanical properties in a sheet metal assembly. The multi-stage manufacturing process of the assembly is segmented, and stochastic analyses of each stage is performed and coupled to the succeeding stage in order to predict the assembly's final variation in properties.

Two additional studies are presented where the methodology of chaining manufacturing processes is utilised. The influence of the dual phase microstructure on non-linear strain recovery is investigated using a micromechanical approach that considers the annealing process chain. It is vital to understand the non-linear strain recovery in order to improve springback prediction. In addition, the prediction of fracture in a dual phase steel subjected to non-linear straining is studied by simulating the manufacturing chain and subsequent stretch test of a sheet metal component.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 47 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1605
National Category
Metallurgy and Metallic Materials Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-106637 (URN)10.3384/diss.diva-106637 (DOI)978-91-7519-300-7 (ISBN)
Public defence
2014-06-05, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2014-05-16 Created: 2014-05-16 Last updated: 2014-05-23Bibliographically approved

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Govik, AlexanderNilsson, Larsgunnar

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