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Title: Fatigue performance of welded connectors/components using high strength strip steels
Author: Hambling, S. J.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2004
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The drive to down-gauge steel components by substituting mild strip steel with thinner high strength steel means that design engineers are now working closer to the design limits with respect to fatigue performance of spot welded structures. Consequently, this study was initiated, aimed at evaluating the factors which influence the fatigue performance of spot welded H-beams, to provide the necessary information to develop appropriate design rules. This study was carried out on mild steel, high strength interstitial free and carbon manganese steels of sheet thickness ranging from 0.8mm to 1.2mm, which are representative of the steel thicknesses and grades used in typical body-in-white automotive structure. The results obtained indicated that steel strength has little effect on fatigue performance of welded H-beams for the range of steels studied. In contrast, the loading mode, weld size, and die sheet thickness had a significant influence. The results on fatigue performance under shear loading were up to ten times greater compared to peel loading conditions. Under shear loading conditions full plug failures were widely observed, whereas with peel loaded variants partial plug failures predominated. With respect to enhancing the fatigue properties the use of larger weld sizes was shown to be beneficial. Finite element analysis highlighted the ability of the Rupp technique to incorporate raw data into fatigue analysis software. The resultant generic fatigue curves were shown to have two distinct zones representing sheet failure and nugget failure modes. For the range of steels and components studied all data was accurately characterised within either the sheet or nugget failure zones when using the Rupp technique.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Eng.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available