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Järvstråt, Niklas
Publications (9 of 9) Show all publications
Nordström, M. & Järvstråt, N. (2009). An appearance-based measure of surface defects. International Journal of Material Forming, 2(2), 83-91
Open this publication in new window or tab >>An appearance-based measure of surface defects
2009 (English)In: International Journal of Material Forming, Vol. 2, no 2, p. 83-91Article in journal (Refereed) Published
Keywords
Appearance, Ray-trace, Sheet metal forming, Surface defects
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1687 (URN)10.1007/s12289-009-0393-0 (DOI)
Available from: 2009-09-28 Created: 2009-09-25 Last updated: 2020-04-01Bibliographically approved
Lorentzon, J., Järvstråt, N. & Josefson, B. L. (2009). Modelling chip formation of alloy 718. Journal of Materials Processing Technology, 209(10), 4645-4653
Open this publication in new window or tab >>Modelling chip formation of alloy 718
2009 (English)In: Journal of Materials Processing Technology, Vol. 209, no 10, p. 4645-4653Article in journal (Refereed) Published
Keywords
Alloy 718, Chip formation, Damage models, FEM, Segmented chips
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1684 (URN)10.1016/j.jmatprotec.2008.11.029 (DOI)
Available from: 2009-09-28 Created: 2009-09-25 Last updated: 2020-04-01Bibliographically approved
Lorentzon, J. & Järvstråt, N. (2008). Modelling tool wear in cemented-carbide machining alloy 718. International journal of machine tools & manufacture, 48(10), 1072-1080
Open this publication in new window or tab >>Modelling tool wear in cemented-carbide machining alloy 718
2008 (English)In: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 48, no 10, p. 1072-1080Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2008
Keywords
FEM, Friction, Inconel 718, Modelling, Tool wear
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1527 (URN)10.1016/j.ijmachtools.2008.03.001 (DOI)
Available from: 2009-05-13 Created: 2009-05-13 Last updated: 2020-04-01Bibliographically approved
Charles, C. & Järvstråt, N. (2007). Development of a Microstructure Model for Metal Deposition of Titanium Alloy Ti-6Al-4V. In: Ti-2007 : science and technology : proceedings of the 11th World Conference on Titanium (JIMIC 5): held at Kyoto International Conference Center, Kyoto, Japan, 3 - 7 June 2007. Paper presented at 11th World Conference on Titanium (JIMIC 5), Kyoto, Japan, 3 - 7 June 2007 (pp. 1201-1205).
Open this publication in new window or tab >>Development of a Microstructure Model for Metal Deposition of Titanium Alloy Ti-6Al-4V
2007 (English)In: Ti-2007 : science and technology : proceedings of the 11th World Conference on Titanium (JIMIC 5): held at Kyoto International Conference Center, Kyoto, Japan, 3 - 7 June 2007, 2007, p. 1201-1205Conference paper, Published paper (Refereed)
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-193 (URN)978-4-88903-406-6 (ISBN)
Conference
11th World Conference on Titanium (JIMIC 5), Kyoto, Japan, 3 - 7 June 2007
Available from: 2009-04-22 Created: 2009-04-22 Last updated: 2020-04-01Bibliographically approved
Farajian-Sohi, M. & Järvstråt, N. (2006). A fractographical investigation of weld toe imperfections in tandem gas metal arc welding. Steel Research International, 77(12), 889-895
Open this publication in new window or tab >>A fractographical investigation of weld toe imperfections in tandem gas metal arc welding
2006 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 77, no 12, p. 889-895Article in journal (Refereed) Published
Abstract [en]

Prediction and control of flaws in welds play important roles in design of complex structures against fatigue and fracture failure. Cold laps - outer lack of fusion - are small geometrical imperfections at weld toes, which act as fatigue crack initiation sites and reduce the life of welded structures drastically. The aim of this work is to characterize and categorize different types of such imperfections in the tandem gas metal arc welding process and find the mechanisms of their formation. Tandem welding process with different welding parameters was used to produce bead-on-plate coupons. These coupons were then sliced to smaller specimens for further investigations. For studying the weld toes, all the specimens were hit in an impact test machine and then the fracture surfaces of welds and base materials were analysed by scanning electron microscopy (SEM). Two types of cold laps were observed at weld toes, namely overlap and spatter. Observation and measurement showed that these imperfections are in the form of micro cracks with depth between 0.1 to 1.5mm and length between 0.1 to 4 mm.

Keywords
Cold laps, Overlap, Spatter, Tandem GMA welding, Weld defects, Weld quality, Failure (mechanical), Fracture, Gas metal arc welding, Scanning electron microscopy, Structural design, Welds, Fractography
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1806 (URN)
Available from: 2009-10-12 Created: 2009-10-08 Last updated: 2020-12-10Bibliographically approved
Majid, F. & Järvstråt, N. (2006). A imperfect fractographical investigation of weld toe ions in Tandem GMA welding. Steel Research International, 77(12), 889-895
Open this publication in new window or tab >>A imperfect fractographical investigation of weld toe ions in Tandem GMA welding
2006 (English)In: Steel Research International, ISSN 1611-3683, Vol. 77, no 12, p. 889-895Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Verlag Stahleisen, 2006
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1875 (URN)
Available from: 2009-11-03 Created: 2009-11-03 Last updated: 2020-04-01Bibliographically approved
Charles, C. & Järvstråt, N. (2006). Finite Element Modelling of Microstructure on GTAW Metal Deposition of Ti-6Al-4V alloy. In: Computer Technology in Welding and Manufacturing : 16th International Conference & Mathematical Modelling and Information Technologies in Welding and Related Processes: Kiev, Ukraine, June 6-8. Paper presented at 16th International Conference & Mathematical Modelling and Information Technologies in Welding and Related Processes.
Open this publication in new window or tab >>Finite Element Modelling of Microstructure on GTAW Metal Deposition of Ti-6Al-4V alloy
2006 (English)In: Computer Technology in Welding and Manufacturing : 16th International Conference & Mathematical Modelling and Information Technologies in Welding and Related Processes: Kiev, Ukraine, June 6-8, 2006Conference paper, Published paper (Other academic)
National Category
Other Materials Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1879 (URN)9668872053 (ISBN)9789668872051 (ISBN)
Conference
16th International Conference & Mathematical Modelling and Information Technologies in Welding and Related Processes
Available from: 2009-11-04 Created: 2009-11-04 Last updated: 2020-04-01Bibliographically approved
Majid, F. & Järvstråt, N. (2006). Surface geometry measurements and the experimental and numerical investigation of stress concentration in fillet welds. In: 59th Annual Assembly and the International Conference of the International Institute of Welding: Sep, Quebec, Canada. Paper presented at 59th Annual Assembly and the International Conference of the International Institute of Welding, Sep, Quebec, Canada.
Open this publication in new window or tab >>Surface geometry measurements and the experimental and numerical investigation of stress concentration in fillet welds
2006 (English)In: 59th Annual Assembly and the International Conference of the International Institute of Welding: Sep, Quebec, Canada, 2006Conference paper, Published paper (Other academic)
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1920 (URN)
Conference
59th Annual Assembly and the International Conference of the International Institute of Welding, Sep, Quebec, Canada
Available from: 2009-11-06 Created: 2009-11-06 Last updated: 2020-04-01Bibliographically approved
Lorentzon, J. & Järvstråt, N. (2006). Tool Wear Geometry Updating in Inconel 718 Turning Simulations.. In: 9th CIRP International Workshop on Modelling of Machining Operation: Bled, Slovenia. Paper presented at 9th CIRP International Workshop on Modelling of Machining Operation, Bled, Slovenia (pp. 491-498).
Open this publication in new window or tab >>Tool Wear Geometry Updating in Inconel 718 Turning Simulations.
2006 (English)In: 9th CIRP International Workshop on Modelling of Machining Operation: Bled, Slovenia, 2006, p. 491-498Conference paper, Published paper (Other academic)
Abstract [en]

In machining of nickel based superalloys, such as Inconel 718, tool wear is a major problem due to the high stresses and the high temperatures at the tool chip interface. Enhanced knowledge of the tool wear mechanism and capability to predict tool wear are therefore of great importance in machining of nickel based superalloys. The objective with this paper is to investigate if the finite element method (FEM) can be used to predict the flank and crater wear of uncoated cemented carbide tool in turning ofInconel 718. An empirical model has been implemented in a commercial FE-code and the tool geometry is continuously updated to capture the evolution of wear. Experiments have been conducted to obtain parameters for the empirical wear model and for validation of the simulations. The worn geometry at the flank and rake face as well as the cutting edge radius was measured with white light interferometry. Wear model parameters were calibrated by fitting a simulation against measured worn geometries at the flank and rake face. Then separate simulations at other cutting speeds were compared with corresponding experiments to validate the model performance.

National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-1909 (URN)
Conference
9th CIRP International Workshop on Modelling of Machining Operation, Bled, Slovenia
Available from: 2009-11-05 Created: 2009-11-05 Last updated: 2020-04-01Bibliographically approved
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