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Lundberg, Mattias
Publications (10 of 16) Show all publications
Lundberg, M. (2018). Residual stresses, fatigue and deformation in cast iron. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Residual stresses, fatigue and deformation in cast iron
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The complex geometry of cylinder heads in heavy-duty diesel engines makes grey iron or compact graphite iron a preferred material choice due to its price, castability, thermal conductivity and damping capacity. Today’s strict emission laws have increased the demands on engine performance and engine efficiency. This means that material properties such as fatigue resistance need to be improved. Shot peening is often used to improve the fatigue resistance of components and the benefits of shot peening are associated with the induced compressive surface stresses and surface hardening. How different shot peening parameters can affect fatigue strength of grey and compact graphite iron has been investigated within the project underlying this thesis. To do this, X-ray diffraction (XRD) was utilized for residual stress measurements, scanning electron microscopy (SEM) for microstructural characterizations and mechanical fatigue testing for mechanical quantifications. The ultimate aim of this work has been to increase the fatigue resistance of cast iron by residual stress optimization.

XRD measurements and SEM examinations revealed that the shot peening parameters shot size and peening intensity significantly influence residual stresses and surface deformation. Residual stress profiles, similar to the one general considered to improve the fatigue strength in steels, were obtained for both grey and compact graphite iron. Uniaxial push-pull fatigue testing on grey iron with these shot peening parameters reduced the fatigue strength with 15–20 %. The negative effect is likely related to surface damage associated with over peening and relatively high subsurface tensile residual stresses. With very gentle shot peening parameters, the uniaxial fatigue strength were unaltered from the base material but when subjected to bending fatigue an increase in fatigue strength were observed. An alternative way to increase the fatigue strength was to conduct a 30 min annealing heat treatment at 285 XC which increased the fatigue strength by almost 10 % in uniaxial loading. The improvement could be an effect of favourable precipitates forming during the annealing, which could hinder dislocation movement during fatigue.

Measuring residual stresses using XRD and the sin2 -method demands accurate X-ray elastic constants (XEC) for meticulous stress analysis. The XEC referred to as 1~2s2 should therefore always be calibrated for the specific material used. The experiments conducted revealed that the XEC value is independent of the testing method used in this work. A small correction from the theoretical value should be applied when the material contains small amounts of residual stresses. The amount of residual stresses has a great impact on the XEC and thus on the stress analysis. Concluding that proper analysis of residual stresses in cast iron is not straight forward.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 44
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1908
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-150783 (URN)10.3384/diss.diva-150783 (DOI)9789176853580 (ISBN)
Public defence
2018-09-28, ACAS, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2018-08-30 Created: 2018-08-30 Last updated: 2018-09-21Bibliographically approved
Lundberg, M. (2017). Cast Iron and Micro Cracks. In: : . Paper presented at EUROMAT17, Thessaloniki 17-21 September 2017,Greece (pp. 1-1).
Open this publication in new window or tab >>Cast Iron and Micro Cracks
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-143979 (URN)
Conference
EUROMAT17, Thessaloniki 17-21 September 2017,Greece
Available from: 2018-01-01 Created: 2018-01-01 Last updated: 2018-01-16Bibliographically approved
Lundberg, M., Saarimäki, J., Moverare, J. & Peng, R. L. (2017). Effective X-ray Elastic Constant of Cast Iron. Journal of Materials Science, 53(4), 2766-2773
Open this publication in new window or tab >>Effective X-ray Elastic Constant of Cast Iron
2017 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 4, p. 2766-2773Article in journal (Refereed) Published
Abstract [en]

X-ray diffraction is a non-destructive method used for strain measurements in crystalline materials. Conversion of strain to stress can be achieved using the X-ray elastic constants (XEC), s1 and ½s2. The sin2ψ method was used during in situ loading to determine XEC for flake, vermicular, and spherical graphite iron. A fully pearlitic steel was used as reference. Uniaxial testing was conducted on the cast iron to create a homogeneous strain field, as well as four-point bending in both tension and compression due to the tension/compression asymmetry. The commonly used XEC value ½s2 = 5.81 × 10−6 MPa−1 is theoretically derived from an α-Fe single crystal. When investigating materials that contain ferrite, such as polycrystalline cast iron, this value is not accurate. Determination of an effective XEC for polycrystalline cast iron yields a better correlation between the measured microstrains and the properties observed on a macroscopic scale. The need for an effective XEC is evident, especially when it comes to model validation of, for example, casting simulations. Effective XEC values have been determined for flake, vermicular, and spherical graphite iron. The determined value is lower than the theoretical value.

National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-141980 (URN)10.1007/s10853-017-1657-6 (DOI)000416544500040 ()2-s2.0-85031402118 (Scopus ID)
Note

Funding agencies: Agora Materiae, graduate school, the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Volvo Trucks; Vinnova FFI, Scania

Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2018-08-30Bibliographically approved
Lundberg, M., Saarimäki, J., Peng, R. & Moverare, J. (2017). Residual Stresses in Uniaxial Cyclic Loaded Pearlitic Lamellar Graphite Iron. In: Residual Stresses 2016:ICRS-10, Materials Research Proceedings 2 (2016: . Paper presented at International Conference in Residual Stresses ICRS-10, 4-8 July 2016, Sydney, Australia (pp. 67-72).
Open this publication in new window or tab >>Residual Stresses in Uniaxial Cyclic Loaded Pearlitic Lamellar Graphite Iron
2017 (English)In: Residual Stresses 2016:ICRS-10, Materials Research Proceedings 2 (2016, 2017, p. 67-72Conference paper, Published paper (Refereed)
Series
Materials Research Proceeding, ISSN 2474-395X
Keywords
Residual stress, XRD, lamellar graphite iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-130893 (URN)10.21741/9781945291173-12 (DOI)000401041500012 ()978-1-9452-9116-6 (ISBN)
Conference
International Conference in Residual Stresses ICRS-10, 4-8 July 2016, Sydney, Australia
Available from: 2016-08-30 Created: 2016-08-30 Last updated: 2018-08-30Bibliographically approved
Schmidt, P., Peng, R., Davydov, V., Lundberg, M., Ahmad, M., Vuoristo, T., . . . Johansson, S. (2014). Analysis of Residual Stress in Stres Harps of Grey Iron by Experiment and Simulation. In: : . Paper presented at 9th European Conference on Residual Stresses ECRS-9, Troyes, France, 7-10 July 2014.
Open this publication in new window or tab >>Analysis of Residual Stress in Stres Harps of Grey Iron by Experiment and Simulation
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2014 (English)Conference paper, Published paper (Refereed)
Keywords
residual stress, cast iron, FE simulation, neutron diffraction, hole drilling
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-108773 (URN)
Conference
9th European Conference on Residual Stresses ECRS-9, Troyes, France, 7-10 July 2014
Available from: 2014-07-04 Created: 2014-07-04 Last updated: 2018-08-30
Lundberg, M., Peng, R., Ahmad, M., Bäckström, D., Vuoristo, T. & Johansson, S. (2014). Fatigue strength of Machined and Shot Peened Grey Cast Iron. In: : . Paper presented at Fatigue 2014 11th International Fatigue Congress, Melbourne Cricket Ground, Melbourne, Australis, 2-7 March 3014. (pp. 30-35). Trans Tech Publications Inc., 891-892
Open this publication in new window or tab >>Fatigue strength of Machined and Shot Peened Grey Cast Iron
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2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A common opinion is that cast iron, especially grey cast iron, is not as notch sensitive as steel therefore is not typically treated by shot peening to suppress crack initiation. For a heterogeneous material that also is brittle, just like grey cast iron, the shot peening parameters needed to induce beneficial surface residual stresses can be problematic to identify. Fatigue testing under uniaxial loading with an R value of -1, on mechanically polished and shot peened specimens, has been performed to determine the fatigue strength at 10(7) cycles as well as complete Wohler-curves. Two different types of specimen geometries were tested, one smooth and one notched specimen having k(t) equal to 1.05 and 1.33 respectively. With large shots and high peening intensity (heavy SP) the fatigue strength clearly decreased whereas small shots and low peening intensity (gentle SP) might have lowered the fatigue strength. A short annealing at 285 degrees after gentle SP increased the fatigue strength. The results are discussed and explained based on x-ray diffraction (XRD) measurements, i.e. residual stress and full width at half maximum profiles, as well as microstructural investigations using scanning electron microscope (SEM).

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2014
Keywords
fatigue strength, grey cast iron, residual stresses, shot peening
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-104640 (URN)10.4028/www.scientific.net/AMR.891-892.30 (DOI)000337767700005 ()
Conference
Fatigue 2014 11th International Fatigue Congress, Melbourne Cricket Ground, Melbourne, Australis, 2-7 March 3014.
Available from: 2014-02-20 Created: 2014-02-20 Last updated: 2014-12-10
Peng, R., Vuoristo, T., Bäckström, D., Ahmad, M., Lundberg, M. & Johansson, S. (2014). Fatigue Strength of Shot Peened Compacted Graphite Iron. In: : . Paper presented at 12th International Conference on Shot Peening, 15-18 September 2014, Goslar, Germany.
Open this publication in new window or tab >>Fatigue Strength of Shot Peened Compacted Graphite Iron
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2014 (English)Conference paper, Published paper (Refereed)
Keywords
compacted graphite iron, shot peening, fatigue, residual stress
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-109606 (URN)
Conference
12th International Conference on Shot Peening, 15-18 September 2014, Goslar, Germany
Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2018-08-30
Lundberg, M., Peng, R., Ahmad, M., Bäckström, D., Vuoristo, T. & Johansson, S. (2014). Graphite Morphology's Influence on Shot Peening Results in Cast Irons. In: : . Paper presented at International Conference on Residual Stresses 9 (ICRS 9), Garmisch-Partenkirchen, Germany, 7 – 9 October 2012 (pp. 542-549). Trans Tech Publications Inc., 768-769
Open this publication in new window or tab >>Graphite Morphology's Influence on Shot Peening Results in Cast Irons
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2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The different shot peening responds of a grey cast iron (GI) with its flake graphite and a compacted cast iron (CGI) with its vermicular graphite was analyzed and compared in this paper. For peening using identical parameters, CGI showed a larger plastic deformation zone with higher subsurface compressive stresses than GI. Electron backscatter diffraction (EBSD) mapping and backscatter electron imaging revealed that plastic deformation of the matrix near graphite inclusions is affected by the size and geometry of the graphite. The different behaviors of graphite are explained by their capability to damp mechanical force but at the same time to cause stress concentration in the matrix. The better shot peening results for CGI may be attributed to a lower damping effect of its graphite inclusions and capability of the matrix for larger plastic deformation.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2014
Keywords
shot peening, cast iron, graphite morphology, EBSD, residual stress
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-89582 (URN)10.4028/www.scientific.net/MSF.768-769.542 (DOI)000336693000071 ()
Conference
International Conference on Residual Stresses 9 (ICRS 9), Garmisch-Partenkirchen, Germany, 7 – 9 October 2012
Available from: 2013-03-13 Created: 2013-02-27 Last updated: 2018-08-30Bibliographically approved
Lundberg, M., Peng, R., Ahmad, M., Vuoristo, T., Bäckström, D. & Johansson, S. (2014). Influence of Shot Peening Parameters on Residual Stresses in Flake and Vermicular Cast Irons. In: : . Paper presented at International Conference on Residual Stresses 9 (ICRS 9), Garmisch-Partenkirchen, Germany, 7 – 9 October 2012 (pp. 534-541). Trans Tech Publications Inc., 768-769
Open this publication in new window or tab >>Influence of Shot Peening Parameters on Residual Stresses in Flake and Vermicular Cast Irons
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2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Test samples of grey and compacted graphite cast irons with pearlitic matrix were shot-peened to different surface conditions using twelve different combinations of shot size, peening intensity and peening coverage percentage. Relatively high surface compressive residual stresses varying between 245 to 565 MPa were observed and the compressive residual stresses reached a depth between 280 µm and 770 µm. Within the range of peening parameters used, the compacted graphite cast iron with its vermicular graphite showed a somewhat better response to the same shot-peening treatment than the grey cast iron containing flake graphite, giving a larger peening affected zone with higher compressive residual stresses. For both the cast irons, an increase in peening coverage percentage, shot size or peening intensity led often to a lower surface compressive stress. However, peening using a higher intensity greatly increased the degree and extent of plastic deformation and therefore increased the magnitude and penetration depth of the subsurface compressive residual stresses, while the effect of increasing shot size also depends on the peening intensity. On the other hand, measurements on the grey cast iron samples showed that the peening coverage has little effect on the depth profile of residual stress.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2014
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-89578 (URN)10.4028/www.scientific.net/MSF.768-769.534 (DOI)000336693000070 ()
Conference
International Conference on Residual Stresses 9 (ICRS 9), Garmisch-Partenkirchen, Germany, 7 – 9 October 2012
Available from: 2013-03-13 Created: 2013-02-27 Last updated: 2018-08-30Bibliographically approved
Lundberg, M., Peng, R., Ahmad, M., Vuoristo, T., Bäckström, D. & Johansson, S. (2014). Residual Stresses in Shot Peened Grey and Compact Iron. Paper presented at International Conference on Residual Stresses ICRS9, October 7-9,2012 in Garmisch-Partenkirchen, Germany. HTM Journal of Heat Treatment and Materials, 69(1), 38-45
Open this publication in new window or tab >>Residual Stresses in Shot Peened Grey and Compact Iron
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2014 (English)In: HTM Journal of Heat Treatment and Materials, ISSN 1867-2493, Vol. 69, no 1, p. 38-45Article in journal (Refereed) Published
Abstract [en]

Grey cast iron and compacted graphite iron with a pearlitic matrix are investigated in this study after shot peening using twelve unique combinations of parameters, namely shot size, peening intensity and coverage, followed by residual stress measurements and evaluations. Cylindrical test samples were cut out from heavy truck cylinder heads and polished on the top flat surface to decrease effects from cutting. Residual stresses and the affected depth from the different peening conditions varied between −245 MPa to −565 MPa and from 280 μm to 770 μm in depth. Resultant surface compressive stresses decrease with increasing shot size, peening intensity or coverage whereas the affected depth increases with increasing intensity. The increased affected depth is a result from the increased extent and magnitude of plastic deformation. The compacted graphite iron was more affected by shot peening than the grey cast iron, meaning that the same shot peening parameters resulted in both higher compressive stresses and larger deformation depth.

Place, publisher, year, edition, pages
Carl Hanser Verlag GmbH, 2014
Keywords
Residual stress, FWHM, cast iron, shot peening, X-ray diffraction
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-105158 (URN)10.3139/105.110207 (DOI)2-s2.0-84896531682 (Scopus ID)
Conference
International Conference on Residual Stresses ICRS9, October 7-9,2012 in Garmisch-Partenkirchen, Germany
Note

Enhanced contribution based upon a presentation at the International Conference on Residual Stresses ICRS9, October 7–9, 2012, in Garmisch-Partenkirchen, Germany

Available from: 2014-03-10 Created: 2014-03-10 Last updated: 2018-08-30Bibliographically approved
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