Soudage MIG-MAG | EPFL Graph Search

vignette|225x225px|Soudage à l'arc avec fil - électrode fusible sous flux gazeux. vignette|Un poste à souder MIG/MAG. Le soudage MIG-MAG (respectivement 131 ou 132/133, et 135 ou 136/138 suivant la norme NF EN ISO 4063-2011), ou encore GMAW (Gas Metal Arc Welding) selon le code américain ASME (American Society of Mechanical Engineers) section IX, est un procédé de soudage semi-automatique. La fusion des métaux est obtenue par l’énergie calorifique dégagée par un arc électrique qui éclate dans une atmosphère de protection entre un fil électrode fusible et les pièces à assembler. Les acronymes MIG et MAG signifient respectivement Metal inert gas et Metal active gas. La différence entre les deux procédés tient à la composition du gaz. Le procédé MIG utilise un gaz neutre qui ne réagit pas avec le métal fondu (argon ou argon + hélium), contrairement au procédé MAG (mélange d'argon et de dioxyde de carbone ou dioxygène en proportions variables selon les métaux à souder). Le gaz est injecté

Experimental investigation of the cyclic properties of welds in mild structural steels

Selimcan Ozden

Structural steels have long been used in construction applications. Their mechanical properties and behavior under seismic loading or under fatigue design are of considerable interest for researchers and engineers. Although extensive studies have been conducted on the cyclic behavior of structural steels, they mostly focus on base material responses. However, base material response can be affected by changes in microstructural properties of steels. In steel construction this situation often arises in welding different components where due to thermal loading certain regions change their crystallographic phases and consequently their mechanical properties. This master's thesis is dedicated to the investigation of the lesser known large amplitude cyclic material behavior of these regions termed Heat Affected Zones (HAZ). The behavior of welded connections is of paramount importance for structural integrity. Their behavior under extreme loading conditions can be the determining factors for the failure of joints and subsequent structural collapse. Field observations following significant earthquake events (e.g. 1994 Northrigde incident) has shown that the assumed ductility of the steel construction can be put into question when poorly executed welded structural joints suffer premature fracture. The head-boomed experience from these suggests that failures often arise from combination of ill-conceived detailing and insufficient weld quality (e.g. large defects on low thoughness). As the understanding of this problem progressed, better detailing properties and quality controls have been proposed to avoid brittle nature of joint failure. In this master’s thesis the author investigates the behavior of S355J2+N structural steel as HAZ of welded material and base material subjected to uniaxial cyclic loading and large inelastic strain demands under seismic loading in the experimental and numerical level. HAZ at welded specimens is obtained through thermal loading in the laboratory environment. Uniaxial cyclic loading tests are performed in the laboratory as well. In addition, comparisons between the base and welded metals for the steel class of S355J2+N are provided as well including material parameters for Voce-Chaboche and Updated Voce-Chaboche models. Results of this study reveal that under cyclic loading welded material hardens more than base material. In addition, plateau region exercised in base material disappears in welded material and welded specimens experience rounding around the yield stress which is not the case for base material. Accuracy of simulation of welded material and correctness of model parameters greatly depend on whether Voce-Chaboche or Updated Voce-Chaboche model is applied to the right material being investigated.

2021

Multiscale, Multiphysics Numerical Modeling of Fusion Welding with Experimental Characterization and Validation

Jonathan Dantzig, Jun Liu, Yu Xie

Various physical interfacial phenomena occur during the process of welding and influence the final properties of welded structures. As the features of such interfaces depend on physics that resolve at different spatial scales, a multiscale and multiphysics numerical modeling approach is necessary. In a collaborative research project Modeling of Interface Evolution in Advanced Welding, a novel strategy of model linking is employed in a multiscale, multiphysics computational framework for fusion welding. We only directly link numerical models that are on neighboring spatial scales instead of trying to link all submodels directly together through all available spatial scales. This strategy ensures that the numerical models assist one another via smooth data transfer, avoiding the huge difficulty raised by forcing models to attempt communication over many spatial scales. Experimental activities contribute to the modeling work by providing valuable input parameters and validation data. Representative examples of the results of modeling, linking and characterization are presented.

Springer Verlag2013

Experimental investigation of the cyclic properties of welds in mild structural steels

Selimcan Ozden

2021