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Évolution des contraintes résiduelles des assemblages soudés sous sollicitations mécaniques - Étude et modélisation

Abstract : Gas metal arc welding processes are widely applied in the automotive industry for the assembly of steel suspension parts. A welding operation generates significant thermal, metallurgical and mechanical property gradients. These gradients cause residual stresses that affect the mechanical response and service life of the welded structures. The objective of this thesis project is to study their evolution under mechanical fatigue loading. Residual stress analyses by X-ray diffraction were carried out on welded specimens and on suspension parts in the "as-welded" and "post-loading" states. These studies have shown that the monitoring of stress changes under mechanical stresses requires a characterisation of the initial mechanical and metallurgical states. Based on critical case studies for the design of welded suspension parts, three simple welded structure geometries were designed. The endurance limits of each structure were determined for a million cycles in pure tension (R=0.1). Interrupted fatigue tests, in the high cycle fatigue domain, were conducted on the three structures at the previously determined endurance limits. Mapping of the residual stress fields on the surface, before and after loading, was carried out. These analyses highlight the evolution of residual stresses in the polycyclic domain. At the foot of the bead, a decrease of around 40% was observed, while in certain areas of the structures, the stresses remained. In-situ tests were used to identify the kinetics of stress evolution at the scale of the structures. In the direction of loading, the stresses evolve under quasi-static loading with evolutions detected for loads of the order of 10% of the endurance limit. The stress analyses carried out on the three structures show that the changes in residual welding stresses are due to local and structural effects.
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Submitted on : Thursday, June 16, 2022 - 9:51:14 AM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM

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  • HAL Id : tel-03696583, version 1

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Hugo Tryla. Évolution des contraintes résiduelles des assemblages soudés sous sollicitations mécaniques - Étude et modélisation. Mécanique des matériaux [physics.class-ph]. HESAM Université, 2022. Français. ⟨NNT : 2022HESAE017⟩. ⟨tel-03696583⟩

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