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Influence des conditions de soudage sur le comportement en fatigue d'un acier THR Dual Phase soudé par point

Abstract : Models used for the fatigue assessment of spot-welded assembly only take into account geometrical parameters. Even so, residual stresses, microstructure of the Heat Affected Zone and notch root shape might be additional factors. This work consists in identifying the relevant parameters on the fatigue strength of spot welds made of High Strength Steel, to suggest welding conditions for an enhanced behaviour. To deeply analyze the tests results, methodologies and observation tools are developed: system to track the crack, SEM fractography and metallographic analysis. In the field of resistance spot welding, the primary structures observation enables to understand nugget growth formation. In some cases, solidification begins and occurs while current crosses the assembly. Many fatigue tests are carried out on tensile shear spot welded assembly made of Dual Phase steel. By the associated use of different observation tools, the welding conditions effect and the predominant influence factors are highlighted. There is few welding conditions influence on the propagation stage ; a reliability based model is proposed for this step. The initiation stage is a crucial step. An adapted weld cycle enables to obtain an enhanced fatigue behaviour thanks to an advantageous modification of the residual stresses field at notch root, by keeping admissible total weld time on component. These results open important outlooks for an industrial application.
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Contributor : Frédérique Rossillon <>
Submitted on : Wednesday, May 14, 2008 - 3:44:59 PM
Last modification on : Friday, October 23, 2020 - 4:41:42 PM
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  • HAL Id : tel-00279069, version 1

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Frédérique Rossillon. Influence des conditions de soudage sur le comportement en fatigue d'un acier THR Dual Phase soudé par point. Mécanique [physics.med-ph]. Université Blaise Pascal - Clermont-Ferrand II, 2007. Français. ⟨tel-00279069⟩

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