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Publications (10 of 28) Show all publications
Razanica, S., Josefson, L., Larsson, R. & Sjögren, T. (2021). Validation of the ductile fracture modeling of CGI at quasi-static loading conditions. International journal of damage mechanics, 30(9), 1400-1422
Open this publication in new window or tab >>Validation of the ductile fracture modeling of CGI at quasi-static loading conditions
2021 (English)In: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, Vol. 30, no 9, p. 1400-1422Article in journal (Refereed) Published
Abstract [en]

Fracture modeling and experimental validation of Compacted Graphite Iron (CGI) specimens loaded under quasi-static conditions at room temperature are considered. Continuum damage mechanics coupled to plasticity is adopted to describe the evolution of damage. The damage production is based on a recently developed rate dependent damage evolution law, where the damage–plasticity coupling is modeled based on a damage driving energy that involves both stored energy and plasticity contributions. To describe ductile fracture accounting for stress triaxiality on the damage initiation, the inelastic contribution to the damage driving energy is controlled by the Johnson-Cook failure criterion. Three different damage models are defined based on elastic/inelastic damage driving energies. The damage models are validated against experiments on a set of notched specimens made of CGI with different notch geometries, where the global force-displacement curves and corresponding strain fields are obtained using digital image correlation technology. It is shown from the testing and the simulations that plastic strains generally need to be accounted for in order to properly describe the different failure processes of the CGI specimens. In addition, the ductile damage model is shown to more accurately predict the experimental force-displacement response as compared to the more simplistic stress drop, element deletion technique. 

Place, publisher, year, edition, pages
SAGE Publications Ltd, 2021
Keywords
brittle fracture, Damage driving energy, ductile fracture, stress triaxiality, Continuum damage mechanics, Strain, Compacted graphite iron, Digital image correlations, Ductile damage models, Experimental validations, Force-displacement response, Inelastic contributions, Quasi-static conditions, Quasi-static loading
National Category
Applied Mechanics
Identifiers
urn:nbn:se:ri:diva-52972 (URN)10.1177/1056789521997545 (DOI)2-s2.0-85104043949 (Scopus ID)
Note

Funding text 1: The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Family Ekman’s Research Donation and the Swedish National Research Program FFI (Strategic Vehicle Research and Innovation).

Available from: 2021-04-21 Created: 2021-04-21 Last updated: 2023-06-08Bibliographically approved
Sjögren, T., Hall, S., Elmquist, L., Dartfeldt, E., Larsson, E., Majkut, M., . . . Engqvist, J. (2020). In situ analysis of cast irons mechanical behaviour using synchrotron x-ray tomography and 3DXRD. In: : . Paper presented at MCWASP XV - Modelling of Casting, Welding and Advanced Solidification Processes (pp. 012039). , 861
Open this publication in new window or tab >>In situ analysis of cast irons mechanical behaviour using synchrotron x-ray tomography and 3DXRD
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2020 (English)Conference paper, Published paper (Refereed)
Abstract [en]

When subjecting cast irons to mechanical loading the deformation and damage mechanisms occur on a microstructural level and are dependent on the inherent microstructure. A deeper understanding of the relation between the different microstructural constituents and the macroscopic mechanical behaviour would be beneficial in material development efforts and for the ability to design and cast components with tailored properties. Traditionally, microscopy examinations on sectioned cast iron samples have been used when analysing the microstructure in cast irons. Since all microstructural heterogeneity is in three-dimensions (3D), methods that provide a three-dimensional characterisation are essential for a deeper understanding of, both the microstructural features as well as the deformation and damage of cast irons. Therefore, different cast iron grades have been studied using synchrotron X-ray tomography and 3D x-ray diffraction (3DXRD) at ESRF in Grenoble, France. The samples were stepwise loaded and unloaded in-situ at in the tomography/3DXRD set-up to study the deformation with regard to microstructural constituents and the microstructural evolution in 3D. Based on the 3D tomography image sequences, digital volume correlation (DVC) was used for full strain field analysis and for the analysis of damage and deformation mechanisms. In addition, 3DXRD data were analysed to provide details on the lattice parameters and lattice strain of individual ferrite grains. This work shows the possibilities of such synchrotron experiments for advanced study of the mechanical behaviour of cast iron.

Series
IOP Conference Series: Materials Science and Engineering
Keywords
Synchrotron X-ray microtomography, in situ, cast iron
National Category
Metallurgy and Metallic Materials Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:ri:diva-45140 (URN)10.1088/1757-899X/861/1/012039 (DOI)2-s2.0-85087020333 (Scopus ID)
Conference
MCWASP XV - Modelling of Casting, Welding and Advanced Solidification Processes
Available from: 2020-06-29 Created: 2020-06-29 Last updated: 2023-06-08Bibliographically approved
Elmquist, L., Hall, S., Sjögren, T., Dartfeldt, E., Skoglund, P., Elfsberg, J. & Majkut, M. (2018). Mechanical and structural characterization of cast iron using synchrotron light. In: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings: . Paper presented at 73rd World Foundry Congress: Creative Foundry, WFC 2018, 23 September 2018 through 27 September 2018 (pp. 129-130).
Open this publication in new window or tab >>Mechanical and structural characterization of cast iron using synchrotron light
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2018 (English)In: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings, 2018, p. 129-130Conference paper, Published paper (Refereed)
Abstract [en]

The paper describes work done using synchrotron light to investigate the microstructure and how it behaves in 3D when a load is applied. Two different cast iron materials with different matrix structures and graphite morphologies were investigated; SiMo51, which is basically a spheroidal iron (SGI) alloyed with Si and Mo, and a lamellar graphite iron (LGI). The tensile test specimens were loaded in steps, at which x-ray tomography as well as 3DXRD measurements were made to characterize the microstructure. The result shows how the crack propagates and which path it takes through the materials. DVC was applied to analyze the strain fields. This work also shows how useful synchrotron experiments can be in the study of the mechanical behavior of cast iron.

Keywords
Crack propagation, DVC, Graphite, SiMo ductile iron, Synchrotron light, Cracks, Foundries, Microstructure, Synchrotron radiation, Tensile testing, Cast iron materials, Graphite morphology, Matrix structure, Mechanical behavior, Structural characterization, Test specimens, X-ray tomography, Cast iron
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38240 (URN)2-s2.0-85062302876 (Scopus ID)9788390430638 (ISBN)
Conference
73rd World Foundry Congress: Creative Foundry, WFC 2018, 23 September 2018 through 27 September 2018
Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2023-06-08Bibliographically approved
Zhang, Y., Hammam, T., Belov, I., Sjögren, T., Bakowski, M. & Nee, H. P. (2017). Thermomechanical Analysis and Characterization of a Press-Pack Structure for SiC Power Module Packaging Applications. IEEE Transactions on Components, Packaging, and Manufacturing Technology, 7(7), 1089-1100
Open this publication in new window or tab >>Thermomechanical Analysis and Characterization of a Press-Pack Structure for SiC Power Module Packaging Applications
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2017 (English)In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 7, no 7, p. 1089-1100Article in journal (Refereed) Published
Abstract [en]

This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silver-metallized (1 μm) silicon carbide die (400 μm) in contact with rhodium-coated (0.4 μm) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been $± $0.1 μm, which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces' silicon carbide-molybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging.

Keywords
Bars, Finite-element (FE) analysis, Friction, measurement techniques, Multichip modules, optical imaging, power electronics, Silicon carbide, stress, Temperature measurement, thermal expansion., Thermomechanical processes, Bars (metal), Carbide dies, Electronics packaging, Finite element method, Molybdenum, Silicon, Silver, Stress analysis, Stresses, Structural design, Tensile stress, Thermal expansion, Tribology, Wide band gap semiconductors, Digital image correlation technique, Experimental methodology, Measurement and simulation, Thermo-mechanical analysis, Thermo-mechanical performance, Thermomechanical process, Presses (machine tools)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-30870 (URN)10.1109/TCPMT.2017.2711272 (DOI)2-s2.0-85023771342 (Scopus ID)
Available from: 2017-09-06 Created: 2017-09-06 Last updated: 2024-02-06Bibliographically approved
Jacobsson, L., Sandström, J., Flansbjer, M., Sjögren, T. & Brander, L. (2016). ONKALO POSE Experiment - Laboratory Determination of Density, Porosity and Mechanical Anisotropy of Gneiss and Granite.
Open this publication in new window or tab >>ONKALO POSE Experiment - Laboratory Determination of Density, Porosity and Mechanical Anisotropy of Gneiss and Granite
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2016 (English)Report (Other academic)
Publisher
p. 288
Series
Posiva working report ; 31
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-27911 (URN)
Available from: 2017-01-20 Created: 2017-01-20 Last updated: 2023-12-27Bibliographically approved
Sjögren, T., Lausmaa, J., Snis, A., Engqvist, H. & Karlsson, J. (2014). Digital image correlation analysis of local strain fields on Ti6A14V manufactured by electron beam melting (ed.). Materials Science & Engineering A, 618, 456-461
Open this publication in new window or tab >>Digital image correlation analysis of local strain fields on Ti6A14V manufactured by electron beam melting
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2014 (English)In: Materials Science & Engineering A, Vol. 618, p. 456-461Article in journal (Other academic) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6630 (URN)16676 (Local ID)16676 (Archive number)16676 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2023-06-08Bibliographically approved
Karlsson, J., Sjögren, T., Snis, A., Engqvist, H. & Lausmaa, J. (2014). Digital image correlation analysis of local strain fields on Ti6Al4V manufactured by electron beam melting (ed.). Materials Science & Engineering: A, 618, 456-461
Open this publication in new window or tab >>Digital image correlation analysis of local strain fields on Ti6Al4V manufactured by electron beam melting
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2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 618, p. 456-461Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM®) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level.

Keywords
Additive manufacturing, Characterization, Digital image correlation, Electron beam melting, Mechanical, Titanium alloys Digital image correlation analysis of local strain fields on Ti6Al4V manufactured by electron beam melting Understanding mechanisms and factors related to implant fixation, a model study of removal torque
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-27311 (URN)10.1016/j.msea.2014.09.022 (DOI)2-s2.0-84907755816 (Scopus ID)
Note

A3376

Available from: 2016-12-08 Created: 2016-12-08 Last updated: 2023-06-08Bibliographically approved
Sjögren, T. (2014). Materials performance assessment of precision cast aluminium components with novel strain analysis techniques (ed.). International Foundry Research (3), 10
Open this publication in new window or tab >>Materials performance assessment of precision cast aluminium components with novel strain analysis techniques
2014 (English)In: International Foundry Research, no 3, p. 10-Article in journal (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6624 (URN)16571 (Local ID)16571 (Archive number)16571 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2023-06-08Bibliographically approved
Sjögren, T., Skoglund, P. & Moverare, J. (2013). Fatigue and strength of new grey iron alloys for brake discs (ed.). In: Konferensbidrag till 7th International on Low Cycle Conference Fatigue (LCF7): . Paper presented at Konferensbidrag till 7th International on Low Cycle Conference Fatigue (LCF7) October 9-11 i Aachen, Germany..
Open this publication in new window or tab >>Fatigue and strength of new grey iron alloys for brake discs
2013 (English)In: Konferensbidrag till 7th International on Low Cycle Conference Fatigue (LCF7), 2013Conference paper, Published paper (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12256 (URN)14972 (Local ID)14972 (Archive number)14972 (OAI)
Conference
Konferensbidrag till 7th International on Low Cycle Conference Fatigue (LCF7) October 9-11 i Aachen, Germany.
Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2023-06-08Bibliographically approved
Diaconu, V. L., Sjögren, T., Skoglund, P. & Diószegi, A. (2013). Stress relaxation of compacted graphite iron alloyed with molybdenum. International Journal of Cast Metals Research, 26(1), 51-57
Open this publication in new window or tab >>Stress relaxation of compacted graphite iron alloyed with molybdenum
2013 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 26, no 1, p. 51-57Article in journal (Refereed) Published
Abstract [en]

In a previous study, the thermomechanical fatigue resistance of four compacted graphite irons (CGIs) and one grey cast iron was investigated. The molybdenum content of the four CGIs varied between 0 and 1.01 wt-%. It was observed that during thermal cycling, the maximum value of the compressive stress continuously decreased while the value of the maximum tensile stress continuously increased. The continuous decrease in compressive stresses showed that stress relaxation occurs at elevated temperatures during thermal cycling. The goal of the present investigation was to investigate the phenomenon of stress relaxation at elevated temperatures. The tests were performed at 350 and 600uC respectively. The results of the stress relaxation tests performed at 600uC showed the same trend observed at thermomechanical fatigue testing. The tests showed that additions of molybdenum improved the fatigue resistance of CGI by lowering the stress relaxation rate.

Keywords
Compacted graphite iron, Molybdenum alloying, Stress relaxation, Thermomechanical fatigue, Elevated temperature, Grey cast iron, Molybdenum content, Stress relaxation rate, Stress relaxation tests, Thermo mechanical fatigues (TMF), Compressive stress, Fatigue of materials, Fatigue testing, Graphite, Iron, Molybdenum, Thermal cycling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-49955 (URN)10.1179/1743133612Y.0000000036 (DOI)2-s2.0-84872693720 (Scopus ID)
Available from: 2020-10-29 Created: 2020-10-29 Last updated: 2023-06-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6657-1792

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