| 1. |
- Ekh, Magnus, 1969, et al.
(författare)
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A comparison of approaches to model anisotropy evolution in pearlitic steel
- 2014
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Ingår i: Proceedings of 11th World Congress on Computational Mechanics (WCCM XI).
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Konferensbidrag (refereegranskat)abstract
- In this contribution a model, tailored for a pearlitic steel, based on the framework of computational homogenization is used to study the impact of altering the type of homogenization scheme on the resulting stress response. The starting point in the employed multiscale model is two different types of micromodels which are calibrated to experimental data from micro-pillar testing.
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| 2. |
- Ekh, Magnus, 1969, et al.
(författare)
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A comparison of homogenization approaches for modelling the mechanical behaviour of pearlitic steel
- 2014
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper different homogenization approaches are adopted for two micromechanical based models of elasto-plasticity in pearlitic steel. Both models are based on the assumption that the yielding is primarily caused by shear of the ferrite between the cementite lamellae. The orientation distribution of the cementite lamellae determines the macroscopic anisotropy characteristics of pearlitic steel. Properties of the cementite and the ferrite are determined from microcompression tests where the orientation of the cementite lamellae is varied. This is done for both of the micromechanical based models. The first of these models is a micromodel where cementite and ferrite are modeled individually. The second model is a mesomodel where a homogenization approach of a cementite lamella together with the surrounding ferrite is proposed. The anisotropy evolution is assumed to be governed by the re-orientation of the cementite lamellae during the deformation. The most fundamental model that is studied is a 3D grain structure where the fluctuating displacement field within the grain structure is solved by using Finite Element Method (FEM). The re-orientation of the cementite lamellae is governed by the deformation of the grain structure. In the analytically homogenized models the re-orientation is assumed to follow the areal affine assumption where the normals of the cementite lamellae are convected with the macroscopic deformation gradient. Numerical results for the different models, when subjected to simple shear loading, are given and comparisons of stress-strain response are shown.
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| 3. |
- Ekh, Magnus, 1969, et al.
(författare)
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Computational modeling of the influence of the interlamellar spacing in pearlitic steel
- 2010
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Ingår i: IV European Congress on Computational Mechanics (ECCM IV): Solids, Structures and Coupled Problems in Engineering.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- On the microscopic scale pearlite is a two-phase material with hard and brittle cementite lamellas that are embedded in a softer ferrite matrix. In each pearlite colony the cementite has a preferred direction whereas the crystallographic directions for the ferrite are the same within a nodule. An important microstructural property of a pearlitic steel is the distance between the cementite lamellas, i.e. the interlamellar spacing. It is well-known from experiments that a decreased interlamellar spacing results in an increased strength of the material. In this contribution, different modeling assumptions will be discussed how to predict such a dependence of the interlamellar spacing (or in other words the size dependence of the ferritic matrix between the cementite lamellas). The key modeling assumption that is adopted for the ferrite is a crystal plasticity model with gradient hardening.
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| 4. |
- LARIJANI, NASIM, 1983, et al.
(författare)
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On the modeling of deformation induced anisotropy of pearlitic steel
- 2009
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Ingår i: Proceedings of the twenty second nordic seminar on computational mechanics. - 1901-7278. ; , s. 55-57
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this contribution, different types of homogenization methods of a micromechanically based plasticity model for pearlitic steal are investigated. The model takes into account large strains as well as deformation induced anisotropy. The initially randomly oriented cementite lamellas in the pearlitic steel will tend to align with the deformation which causes a development of anisotropy.
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| 5. |
- LARIJANI, NASIM, 1983, et al.
(författare)
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On the modeling of deformation induced anisotropy of pearlitic steel
- 2010
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Ingår i: Proceedings of the 23rd nordic seminar on computational mechanics, pp. 153-156. - 0348-467X.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A micromechanically based plasticity model for modeling of anisotropy in pearlitic steel is investigated. The model was proposed in Johansson and Ekh~[1] and takes into account large strains as well as deformation induced anisotropy. The initially randomly oriented cementite lamellae in the pearlitic steel will tend to align with the deformation which causes a development of anisotropy.
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| 6. |
- Lindfeldt, Erik, 1982, et al.
(författare)
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Computational modeling of the interlamellar spacing in pearlitic steel
- 2010
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Ingår i: Proceedings of NSCM-23: the 23rd Nordic Seminar on Computational Mechanics. Editors: Anders Eriksson, Gunnar Tibert. - 0348-467X. ; , s. 150-152
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this contribution, modeling and numerical aspects of gradient crystal plasticity applied to pearlitic steel will be discussed. The goal is to capture the influence of the cementite lamella spacing on the mechanical response.
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| 7. |
- Lindfeldt, Erik, 1982
(författare)
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Computational Multiscale Modeling of Pearlitic Steel
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this thesis is to investigate the possibilities to describe the mechanical behaviorof a pearlitic steel by using computational homogenization, or multiscale modeling. The proposed model contains three scales: the engineering macroscale, the mesoscale representing the colonies of the pearlite and the microscale containing the individual cementite lamellae and the ferrite matrix. On the mesoscale of a pearlitic steel, two constituents can be identified in the form of cementite lamellae embedded in a ferrite matrix. These lamellae appear in domains, referred to as colonies, within which the corresponding orientation is ideally constant. The different domains, with their cementite (morphological) orientations but also with their crystallographic orientations of the ferrite, are homogenized in the modeling to obtain a macroscopic behavior of the pearlite. In the appended papers, different orientation distributions have been assumed and their influence on the macroscopic response has been studied. In addition, the number of orientations that should beincluded in the mesomodel to obtain a representative response has been investigated.To capture the mechanical behavior of the constituents and their orientations, the mesomodel islinked to a micromodel using different prolongation conditions (both Taylor, Dirichlet and periodic). In the micromodel the ferrite is modeled by using crystal plasticity while the cementite is assumed to behave elastically. The micromodel is rotated depending on what cementite lamella orientation/colony it should represent. In addition, the crystallographic orientations of theferrite are chosen depending on what colony that is modeled. The influence on the macroscopic response of the size of the micromodel and the prolongation condition from the mesomodel to the micromodel has been examined.A number of numerical examples are presented within the appended papers illustrating the overallpossibility of using the proposed multiscale model to predict the behavior of a pearlitic steel. In particular, both 2D and 3D models are used to show different sources of anisotropy. Finally, it is shown how the proposed multiscale model can be used to predict macroscopic yield surfaces.
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| 8. |
- Lindfeldt, Erik, 1982, et al.
(författare)
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Estimation of microscale strain fields in a pearlitic steel using DIC and in-situ SEM
- 2014
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Ingår i: Proceedings of 14th European Mechanics of Materials Conference - EMMC14.
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Konferensbidrag (refereegranskat)abstract
- In this contribution the Digital Image Correlation (DIC) technique is used to identify strain fields within a pearlitic microstructure from in-situ obtained SEM images. Typically this is done using a synthetic speckle but in this study the intensity field variations, related to themicrostructure of pearlite, are used as a natural speckle.As a means to avoid subsets with inadequate information content (in terms of intensity field variations) a tracebility criterion is introduced. This criterion is based on the eigenvalues of the Hessian of the autocorrelation function. A pertaining algorithm, which can be used to identify high quality subsets (in terms of tracebility) within a certain Region Of Interest (ROI),is also presented. By using the obtained irregular subsets grids together with synthetically deformed images thedisplacement and deformation gradient errors (both local and average) are studied as a function of the applied loading for various subset sizes.
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| 9. |
- Lindfeldt, Erik, 1982, et al.
(författare)
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Identification of microscale strain fields from in-situ SEM images of a pearlitic steel using DIC
- 2014
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- By using a standard type of DIC framework two series of \textit{in-situ} SEM images (1200x and 2000x) of a pearlitic steel are analyzed. The variations of the intensity field corresponding to the morphological variations (cementite lamellae embedded in a ferrite matrix) of the material are used as a natural speckle. Two traceability indicators are proposed which can be combined to a quality measure of the subsets. These indicators are the foundation of a proposed method that can be used to identify high-quality subsets within a domain of interest. The accuracy of the employed framework is evaluated using synthetically deformed images. Finally, the possibility to correlate the obtained results to variations of the microstructure are investigated.
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| 10. |
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