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Hellström, KristinaORCID iD iconorcid.org/0000-0002-5311-7494
Publications (5 of 5) Show all publications
Andriollo, T., Hellström, K., Sonne, M. R., Thorborg, J., Tiedje, N. & Hattel, J. (2018). Uncovering the local inelastic interactions during manufacture of ductile cast iron: How the substructure of the graphite particles can induce residual stress concentrations in the matrix. Journal of the mechanics and physics of solids, 111, 333-357
Open this publication in new window or tab >>Uncovering the local inelastic interactions during manufacture of ductile cast iron: How the substructure of the graphite particles can induce residual stress concentrations in the matrix
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2018 (English)In: Journal of the mechanics and physics of solids, ISSN 0022-5096, E-ISSN 1873-4782, Vol. 111, p. 333-357Article in journal (Refereed) Published
Abstract [en]

Recent X-ray diffraction (XRD) measurements have revealed that plastic deformation and a residual elastic strain field can be present around the graphite particles in ductile cast iron after manufacturing, probably due to some local mismatch in thermal contraction. However, as only one component of the elastic strain tensor could be obtained from the XRD data, the shape and magnitude of the associated residual stress field have remained unknown. To compensate for this and to provide theoretical insight into this unexplored topic, a combined experimental-numerical approach is presented in this paper. First, a material equivalent to the ductile cast iron matrix is manufactured and subjected to dilatometric and high-temperature tensile tests. Subsequently, a two-scale hierarchical top-down model is devised, calibrated on the basis of the collected data and used to simulate the interaction between the graphite particles and the matrix during manufacturing of the industrial part considered in the XRD study. The model indicates that, besides the viscoplastic deformation of the matrix, the effect of the inelastic deformation of the graphite has to be considered to explain the magnitude of the XRD strain. Moreover, the model shows that the large elastic strain perturbations recorded with XRD close to the graphite–matrix interface are not artifacts due to e.g. sharp gradients in chemical composition, but correspond to residual stress concentrations induced by the conical sectors forming the internal structure of the graphite particles. In contrast to common belief, these results thus suggest that ductile cast iron parts cannot be considered, in general, as stress-free at the microstructural scale. 

Place, publisher, year, edition, pages
Elsevier, 2018
Keyword
Cast iron, Elastic–viscoplastic material B, Graphite, Inhomogeneous material B, Residual stress B, Thermomechanical processes A, Iron, Manufacture, Matrix algebra, Residual stresses, Stress concentration, Tensile testing, X ray diffraction, Chemical compositions, High temperature tensile tests, Inhomogeneous materials, Residual elastic strains, Residual stress fields, Thermomechanical process, Viscoplastic deformation, Viscoplastic materials
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-38304 (URN)10.1016/j.jmps.2017.11.005 (DOI)000424178500016 ()2-s2.0-85034637133 (Scopus ID)JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Available from: 2017-12-29 Created: 2017-12-29 Last updated: 2018-02-22Bibliographically approved
Hellström, K., Diószegi, A. & Diaconu, L. (2017). A broad literature review of density measurements of liquid cast iron. Metals, 7(5), Article ID 165.
Open this publication in new window or tab >>A broad literature review of density measurements of liquid cast iron
2017 (English)In: Metals, ISSN 2075-4701, Vol. 7, no 5, article id 165Article, review/survey (Refereed) Published
Abstract [en]

The literature on density measurements, with a particular interest in methods suitable for liquid cast iron, is reviewed. Different measurement methods based on a number of physical properties are highlighted and compared. Methods for the calculation of density are also reviewed, and the influence of alloying elements on density is, to some extent, discussed. The topic is of essence for the understanding of the material behaviour at solidification, which is pivotal in software applications for casting simulation. Since a deeper understanding of the relationship between the density of liquid cast iron and volume expansion is necessary, the conclusion that further research within the field is needed lies close at hand.

Place, publisher, year, edition, pages
MDPI, 2017
Keyword
Calculation, Density, Experimental methods
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-36608 (URN)10.3390/met7050165 (DOI)000404052600014 ()2-s2.0-85019918559 (Scopus ID)
Funder
VINNOVAKnowledge Foundation
Available from: 2017-07-04 Created: 2017-07-04 Last updated: 2017-11-13Bibliographically approved
Hellström, K., Svidró, P. & Diaconu, L. (2017). Density variations during solidification of grey cast iron. In: : . Paper presented at Presented at the International Symposium on the Science and Processing of Cast Iron (SPCI-XI), 4-7 September 2017, Jönköping, Sweden.
Open this publication in new window or tab >>Density variations during solidification of grey cast iron
2017 (English)Conference paper, Oral presentation only (Refereed)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-37868 (URN)
Conference
Presented at the International Symposium on the Science and Processing of Cast Iron (SPCI-XI), 4-7 September 2017, Jönköping, Sweden
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-13Bibliographically approved
Hellström, K. (2017). Density variations during solidification of lamellar graphite iron. (Licentiate dissertation). Jönköping: Jönköping University, School of Engineering
Open this publication in new window or tab >>Density variations during solidification of lamellar graphite iron
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2017. p. 58
Series
JTH Dissertation Series ; 32
Keyword
density, grey cast iron, measurements, modelling, densitet, gjutjärn, mätning, simulering
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-37869 (URN)978-91-87289-33-0 (ISBN)
Presentation
2017-12-04, E1405 (Gjuterisalen), Jönköping University, School of Engineering, Jönköping, 10:00 (English)
Opponent
Supervisors
Funder
VINNOVA
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-13Bibliographically approved
Hellström, K., Diaconu, L. & Diószegi, A. Density and thermal expansion coefficients of liquid grey cast iron and austenite. Metallurgical and Materials Transactions. A
Open this publication in new window or tab >>Density and thermal expansion coefficients of liquid grey cast iron and austenite
(English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940Article in journal (Other academic) Submitted
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-37867 (URN)
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-13
Organisations
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ORCID iD: ORCID iD iconorcid.org/0000-0002-5311-7494

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