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Assessment of fatigue for laser-scanned weld surfaces: Correlation between weld geometry and fatigue initiation
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The work conducted in this project proposes a method to determine the location of fracture initiation for non-load carrying fillet welds based on continuous geometry measurements. Measurements were carried out on welded specimens using a laser line triangluator together with the weld quality evaluation software qWeld from Winteria®. The 119 specimens produced were after scanning fatigue tested until failure. The fracture surfaces have been investigated in order to find the most probable location(s) of fracture initiation. This data was then used to fit the proposed model parameters used to analytically predict the point(s) of fracture initiation. Local weld geometry measurements were extracted from the predicted fracture initiation location(s) in an effort to analyse the correlation between local weld geometry and fatigue life. This showed that fatigue life and leg length were positively correlated and that strong correlations exists between the individual geometrical parameters. New specimens were produced to test the fitted data of the proposed model, this data was however inconclusive as the new specimens had a high ratio of weld defects.

Abstract [sv]

Arbetet i detta projekt föreslår en metod för att bestämma punkten/punkterna för sprickinitiering för icke-lastbärande kälsvetsar baserat på kontinuerliga mätmetoder. Mätningar utfördes på svetsade prover med hjälp av en laserlinjetriangluator tillsammans med utvärderingsprogrammet qWeld från Winteria®. De 119 provstavar som producerades testades efter mätningarna med en cyklisk belastning till de gick till brott. Brottytorna undersöktes sedan för att hitta platsen/platserna för de mest sannolika startpunkterna. Dessa punkter användes sedan för att passa de föreslagna modellparametrarna som användes för att förutsäga startpunkten. Lokal svetsgeometri extraherades från de förutsagda sprickinitieringsplatserna i ett försök att analysera korrelationen mellan lokal svetsgeometri och antalet cykler till brott. Detta visade att antalet cykler och katetlängden var positivt korrelerade och att det finns starka korrelationer mellan de enskilda geometriska parametrarna. Nya provbitar framställdes för att testa de anpassade parametrarna i den framtagna metoden, dessa gav dock inga tydliga resultat då en hög andel svetsdefekter upptäcktes efter att de provats.

Place, publisher, year, edition, pages
2019. , p. 30
Series
TRITA-SCI-GRU ; 2019:334
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-259518OAI: oai:DiVA.org:kth-259518DiVA, id: diva2:1351779
External cooperation
HIAB
Subject / course
Solid Mechanics
Supervisors
Examiners
Available from: 2019-09-16 Created: 2019-09-16 Last updated: 2019-09-26Bibliographically approved

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  • apa
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