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Fatigue life assessment of improved joints welded with alternative welding techniques
University West, Department of Engineering Science, Research Enviroment Production Technology West. (PTW)ORCID iD: 0000-0002-5290-6619
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.

Place, publisher, year, edition, pages
2014. Vol. 42, no July, 10-21 p.
Keyword [en]
Weld improvement, Fracture mechanics, Crack growth analysis, Fatigue testing
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-9335DOI: 10.1016/j.engfailanal.2014.03.012OAI: oai:DiVA.org:hv-9335DiVA: diva2:925610
Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2016-05-02Bibliographically approved
In thesis
1. A Framework for optimised welding of fatigue loaded structures: Applied to gas metal arc welding of fillet welds
Open this publication in new window or tab >>A Framework for optimised welding of fatigue loaded structures: Applied to gas metal arc welding of fillet welds
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
GMAW, Fatigue, Welding procedures, Fillet welds, Weld quality
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9339 (URN)978-91-87531-26-2 (ISBN)978-91-87531-27-9 (ISBN)
Public defence
2016-05-31, C118, Trollhättan, 13:15 (English)
Opponent
Supervisors
Available from: 2016-05-04 Created: 2016-05-02 Last updated: 2016-10-31Bibliographically approved

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