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A Framework for optimised welding of fatigue loaded structures: Applied to gas metal arc welding of fillet welds
University West, Department of Engineering Science, Research Enviroment Production Technology West. (PTW)ORCID iD: 0000-0002-5290-6619
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Welding is a key process for heavy steel structures, but it is also a weak link in the structure since fatigue fractures in welds are a common cause of failure. This thesis proposes several changes in order to improve the fatigue properties in acost effective way, enabling reduced weight and reduced cost of welded structures. The main idea is to adapt the weld requirements and welding procedures to the load conditions of the weld. This approach ensures that the main focus in the welding process is the critical characteristics of the welds fatigue life properties. The fatigue life critical properties are most often related to the geometrical factors of the weld such as the radius at the weld toe or the penetration in the root. The thesis describes a holistic view of the subject and covers fatigue, weld quality, weld requirements and welding procedures. It becomes evident that the traditional way of working without a direct connection to fatigue is not the best. With an adaptation to the load conditions and fatigue, it is possible to enhance the fatigue life and reduce the welding cost. The main challenge is to connect the welding process, weld requirements and fatigue life properties. It is needed for an optimised welding process of heavy structures subjected to fatigue and toget a predictable fatigue life. Welds optimised for enhanced fatigue life properties are not necessary accepted according to the requirements in a current standard. Several welding procedures are proposed for improving the fatigue life properties of the weld, which indicate a high potential for enhanced fatigue lifeof fillet welds. The idea is to replace the "standard" fillet weld with three different weld types: (i) Welds with deep penetration, (ii) Welds with large weld toe radius and (iii) Welds produced with low cost. Together with customised requirements and reduced over-welding there is a vast potential for reduced weight, reduced cost and increased productivity.The main contribution of this thesis work is the cross-functional studies including design, analysis, production and quality control. This gives a framework for improvements supporting reduced cost and reduced weight of VIII welded structures without reducing the fatigue strength. Many shortcomings have been highlighted to change the welding from a state where welds are done in a way as they "always" have, by tradition, to a more contemporary situation where weld requirements and welding procedures are actively chosen to match the load conditions of the weld. This result in requirements and welding procedures which actually are connected to the fatigue properties as defined by the loading conditions, and where auditors with high probability can say that an accepted weld actually is better than a rejected weld.

Place, publisher, year, edition, pages
Trollhättan: University West , 2016. , 94 p.
Series
PhD Thesis: University West, 7
Keyword [en]
GMAW, Fatigue, Welding procedures, Fillet welds, Weld quality
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-9339ISBN: 978-91-87531-26-2 (print)ISBN: 978-91-87531-27-9 (electronic)OAI: oai:DiVA.org:hv-9339DiVA: diva2:925617
Public defence
2016-05-31, C118, Trollhättan, 13:15 (English)
Opponent
Supervisors
Available from: 2016-05-04 Created: 2016-05-02 Last updated: 2017-12-11Bibliographically approved
List of papers
1. The Ad Hoc Nature of Weld Quality and Welding Procedures for Fatigue
Open this publication in new window or tab >>The Ad Hoc Nature of Weld Quality and Welding Procedures for Fatigue
2013 (English)In: Design, Fabrication and Economy of Metal Structures: International Conference Proceedings 2013, Miskolc, Hungary, April 24-26, 2013 / [ed] Jármai, Károly, Farkas, József (Eds.), Berlin, 2013, 243-248 p.Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Berlin: , 2013
Keyword
Weld quality, weld procedures, fillet welds, fatigue, suppliers
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9334 (URN)10.1007/978-3-642-36691-8 (DOI)978-3-642-36691-8 (ISBN)978-3-642-43220-0 (ISBN)
Conference
International Conference on Design, Fabrication and Economy of Metal Structures, 24-26 April 2013 in Miskolc, Hungary
Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2016-05-02Bibliographically approved
2. A new innovative toolbox for lean welding of fatigue loaded structures
Open this publication in new window or tab >>A new innovative toolbox for lean welding of fatigue loaded structures
2015 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 81, no 1-4, 635-643 p.Article in journal (Refereed) Published
Abstract [en]

Welding is a key manufacturing technology in the production of heavy steel structures, but it is likewise a weak link in the production chain since fatigue fractures in welds is a common cause of failures. This paper proposes several changes in the process to make the manufacturing more efficient and to improve the fatigue properties. The idea is to adopt the weld quality demands for the purpose of the weld and to connect them to the welding procedures. This approach ensures that the primary focus during welding is at the critical characteristics which add value to the welded structure through an enhanced fatigue life. These fatigue life-critical properties have been found to be related to the local weld geometry in the weld toe and at the weld root. Traditional demands related to the good workmanship of welding can often be neglected, due to its limited effect to the fatigue life. The research presented in this paper has contributed to the development of welding procedures for improved fatigue life properties at the critical points of the weld. Results indicate a considerable potential for enhanced fatigue life of fillet welds. The idea is to replace the standard fillet welds with a new toolbox containing three different welds: (i) welds with optimized penetration, (ii) welds with optimized weld toe, and (iii) welds with a low cost. Right usage of these weld types contributes to an efficient production that offer a long fatigue life. This paper describes a holistic view of the subject and highlights issues with the traditional way of working. The challenge and the novelty in the paper are the connection between the welding process, weld demands, and fatigue life properties. This connection is necessary for the development of welding procedures that can contribute to the fabrication of weight optimized welded structures with a predictable life. © 2015 Springer-Verlag London

Keyword
Fatigue of materials, Joints (structural components), Manufacture, Structural properties, Welding, Critical properties, Enhanced fatigue lives, Fatigue properties, Fatigue strength, Fillet welds, Manufacturing technologies, Welded structures, Welding procedures, Welds
National Category
Other Mechanical Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7617 (URN)10.1007/s00170-015-7183-2 (DOI)000361629900053 ()2-s2.0-84942364679 (Scopus ID)
Note

Date: 12 May 2015           

Available from: 2015-06-02 Created: 2015-05-30 Last updated: 2017-12-04Bibliographically approved
3. Welding procedures for fatigue life improvement of the weld toe
Open this publication in new window or tab >>Welding procedures for fatigue life improvement of the weld toe
2016 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 60, no 3, 573-580 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents the results of an experimental study of gas metal arc welded, GMAW, cruciform joints made of common construction steel S355. The hypothesis is that smooth undercuts in as welded conditions can give enhanced fatigue properties similarly as post treated welds. Undercuts are generally seen as a defect or imperfection. Welders try to avoid these and repair them when they occur, which result in increased production lead time. Post weld improvement methods i.e. grinding or high-frequency-impact treatment (HFMI) as fatigue-enhancing post-treatment methods enforce amongst other effects a certain smooth undercut-shaped groove in the treated weld toe region. The obtained shallower weld toe transition reduces the geometrical notch effect and increases fatigue strength. This paper presents a study whereas welded specimens with a weld toe geometry similar to what is obtained by weld toe grinding or HFMI-treatment, has been produced, fatigue tested and analyzed. The improvement of the fatigue strength is comparable to post-weld treated specimens. It has proven to be an efficient way to achieve high-quality welds without introducing any additional operations in production, thus enabling weight reduction using cost-effective methods.

Keyword
Weld toes, Weld shape, Fatigue improvement, Fillet welds, GMA welding
National Category
Manufacturing, Surface and Joining Technology Applied Mechanics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-9298 (URN)10.1007/s40194-016-0309-9 (DOI)000379434400016 ()2-s2.0-84966378339 (Scopus ID)
Note

First online: 22 February 2016

Available from: 2016-04-07 Created: 2016-04-07 Last updated: 2017-11-30Bibliographically approved
4. Fatigue life assessment of improved joints welded with alternative welding techniques
Open this publication in new window or tab >>Fatigue life assessment of improved joints welded with alternative welding techniques
2014 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 42, no July, 10-21 p.Article in journal (Refereed) Published
Abstract [en]

In this study, the fatigue life improvement by adopting the toe weaving technique on nonload carrying cruciform welded joints has been investigated. Fatigue testing was conducted on two batches of specimens welded using double-pass manual welding. One batch had a straight second pass and the other was weaved. The influence of different weaving shape parameters was analyzed by performing crack growth analyses. The fatigue testing shows a slightly improved fatigue life for the two different batches compared to as-welded joints; the improvement is similar for both batches. The crack growth analysis concludes that the batch with the straight second pass should provide slightly higher fatigue life compared to the toe weaved batch. Measurements show a presence of undercuts in the vicinity of the crack initiation site. Nonetheless, an increased fatigue life is obtained, due to the low flank angle created during welding of the second pass, which reduces the stress concentration in the weld toe, prolonging the fatigue life.

Keyword
Weld improvement, Fracture mechanics, Crack growth analysis, Fatigue testing
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9335 (URN)10.1016/j.engfailanal.2014.03.012 (DOI)
Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2017-11-30Bibliographically approved
5. Improved fatigue properties of welded box beams by tailored welding procedures for high penetration fillet welds
Open this publication in new window or tab >>Improved fatigue properties of welded box beams by tailored welding procedures for high penetration fillet welds
(English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024Article in journal (Other academic) Submitted
Keyword
Fatigue, welded box
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9336 (URN)
Note

Ingår i avhandling

Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2017-11-30Bibliographically approved
6. Improved productivity by reduced variation in gas metal arc welding (GMAW)
Open this publication in new window or tab >>Improved productivity by reduced variation in gas metal arc welding (GMAW)
2017 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 92, no 1-4, 1027-1038 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the research conducted is to describe the consequences of variation in the welding industry and the effect it has on manufacturing productivity. The potential has shown to be hidden in unnecessarily stringent requirements and over-processing. This has been studied in steps: customer requirements, design and analysis, preparation, welding, and assessment. The effect of variation in each step has been analyzed including estimations of its productivity improvement potential. Theoretically, in a perfect situation, with customized requirements and eliminated variation, more than half of all welding could be removed. Such a reduction is certainly neither practical nor possible. However, a sensible, controlled reduction could still have a very high impact. The financial implications are therefore substantial. The improved productivity of the manufacturing resources could be used for business development and increased production. To be able to realize the potential, interdisciplinary efforts are necessary. Management across different functions need to agree on the intended product life and make decisions thereafter.

Keyword
Variation, weld, productivity, fatigue, interdisciplinary, requirements
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9337 (URN)10.1007/s00170-017-0214-4 (DOI)000407815500082 ()2-s2.0-85014517637 (Scopus ID)
Note

ingår i avhandling

Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2017-12-11Bibliographically approved

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