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Fatigue assessment of cut edges in high strength steel - Influence of surface quality
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. (KTH Weld Mechanics Group)ORCID iD: 0000-0003-4465-9299
HIAB AB.ORCID iD: 0000-0002-2847-1555
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. (KTH Weld Mechanics Group)ORCID iD: 0000-0003-4180-4710
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The influence of surface roughness on the fatigue strength in high strength steels which was cut using different cutting processes were studied. Fatigue testing was conducted on S700 and S960 material of different plate thicknesses cut in dog bone specimens using oxygen, plasma, laser and waterjet cutting. The surface roughness was measured on all specimens and residual stress measurements were conducted. Estimations of the fatigue strength were made using the measured surface roughness and the ISO 9013:2002 standard for thermal cutting quality tolerances. The testing proved a 15-70% increased fatigue strength compared to the estimation, proving a weak connection between the surface quality levels in ISO 9013:2002 and the fatigue test results. Different codes and design recommendations (IIW, EC3 and EN 13001) for fatigue strength of cut surfaces were compared with the fatigue test results which clearly showed an increased fatigue strength with enhanced quality and steel grades and where the codes and design recommendations do not allow for any fatigue strength improvement with improved quality and increased strength. 

Keyword [en]
High Strength Steels, Fatigue assessment, Thermal Cutting, Oxygen cutting, Plasma cutting, Laser cutting, Waterjet cutting, Quality, Surface roughness, Welded structures, Cut edges
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering; Solid Mechanics; Production Engineering; Machine Design
URN: urn:nbn:se:kth:diva-188541OAI: diva2:936239

QC 201606013

Available from: 2016-06-13 Created: 2016-06-13 Last updated: 2016-06-13Bibliographically approved
In thesis
1. Fatigue properties of cut and welded high strength steels: Quality aspects in design and production
Open this publication in new window or tab >>Fatigue properties of cut and welded high strength steels: Quality aspects in design and production
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This doctoral thesis concerns fatigue of welded structures. Welding is one of the world’s most common joining methods and it is frequently used in several structural applications in many fields. Some examples are construction vehicles, loader cranes, trucks, busses, forestry and agricultural machines, bridges and ships. Since these structures are subjected to repeated loading, fatigue is the most common cause of failure.

A novel numerical algorithm has been developed which assesses the welded surface and calculates and quantifies weld quality parameters and the presence of defects which are critical in fatigue applications. The algorithm is designed for implementation in serial production. It will provide robust and reliable feedback on the quality being produced, which is essential if high strength steels are utilized.

Two welding procedures which can increase the weld quality in as welded conditions have been assessed. These procedures utilize welding in different positions and pendling techniques, which can be accomplished using the existing welding equipment. It was found that by using these methods, the fatigue strength can be increased compared to normal weld quality.

Furthermore, two fatigue assessment methods ability to account for increased weld quality in low cycle and high cycle fatigue applications has been studied. One of these methods showed sufficient accuracy in predicting the fatigue strength with small scatter and also account for increased weld quality.

When implementing thinner high strength steels, the overall stress level in the structure increase. Therefore, other locations such as the steel cut edges may become critical for fatigue failure unless they are not designed and manufactured with the same quality as the welded joint. The influence of surface quality on cut edges was studied and the fatigue strength was estimated using international standards and a fatigue strength model for cut edges.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 56 p.
TRITA-AVE, ISSN 1651-7660 ; 2016:21
Welding, Fatigue assessment, Cutting, Weld quality, Fatigue design, Fracture Mechanics
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
urn:nbn:se:kth:diva-188225 (URN)978-91-7729-027-8 (ISBN)
Public defence
2016-08-26, F3, Lindstedtsvägen 26, Stockholm, 09:00 (English)

QC 20160613

Available from: 2016-06-13 Created: 2016-06-09 Last updated: 2016-06-13Bibliographically approved

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Stenberg, ThomasLindgren, EricBarsoum, Zuheir
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