Fatigue assessment in welded joints based on geometrical variations measured by laser scanning
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RESEARCH PAPER
Fatigue assessment in welded joints based on geometrical variations measured by laser scanning Gustav Hultgren 1
&
Zuheir Barsoum 1
Received: 25 November 2019 / Accepted: 15 July 2020 # The Author(s) 2020
Abstract In the current study a method to determine the location of fracture initiation for non-load carrying fillet welds based on continuous geometry measurements is proposed. Measurements and weld quality evaluation were carried out on welded specimens using the Winteria® software qWeld. One hundred nineteen specimens were produced, scanned, and fatigue tested until failure. The fracture surfaces have been investigated in order to find the location(s) for most probable point(s) of initiation. These data were then used to fit the proposed model parameters used to predict the point of initiation. Local weld geometry measurements were extracted from the predicted fracture initiation location(s) to analyse the correlation between local weld geometry and fatigue life. It was observed that fatigue life and leg length were positively correlated and that strong correlations exist between the individual geometrical parameters with regard to location of the fatigue crack initiation. Keywords Weld fatigue . Weld quality . Crack initiation . Quality assurance
1 Introduction Manufacturers of loader cranes, trucks, buses and other high strength machinery are increasing the use of high strength steel in load carrying products to save weight without reducing the performance. Welded joints in such structures are often the critical factor when it comes to fatigue failure as different material and geometrical imperfections are introduced in welded joints. Geometrical defects such as undercut, cold laps, small toe radii, and geometrical discontinuities can give rise to high stress concentrations at the weld toe, which in combination with cyclic loading leads to fatigue failure. Current research shows the importance of weld quality monitoring and assurance. High strength steel has an increased sensitivity to geometrical defects compared to mild steel, and consistency in the weld quality is therefore critical when it comes to high strength steel applications. The
Recommended for publication by Commission XIII - Fatigue of Welded Components and Structures * Gustav Hultgren [email protected] 1
Department of Engineering Mechanics, KTH Royal Institute of Technology, Teknikringen 8, 100 44 Stockholm, Sweden
correlation between the quality classifications and the fatigue properties have however shown to be weak [1–4]. Weld quality assurance in production is today mostly carried out using spot checking with analogue gauges in an audit process that is not integrated in the production line. This method has shown to be out-dated and the use of basic standard gauges needs to be investigated and improved to be representative in relation to the actual variation in production [5]. The implementation of analysis software that transforms laser line measurements of welded joints into qualitative measurements makes it possible t
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