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The presence of residual stresses in a structure influences his behaviour. Fatigue strength of welded joints is significantly influenced by the presence of residual stresses, of flaws and notch sharpness at the weld toe. Plasma dressing at the weld toe is frequently used to remove flaws and to lessen the notch sharpness at the weld toe. With this re-melt, the stress field in the weld toe is also profoundly modified. The Finite Element Method (FEM) proves to be effective to simulate the stress fields generated by welding. The simplified two-dimensional models (2D) are efficient in this estimation. This paper presents a 2D finite element model to predict the residual stresses generated by Plasma dressing at the weld toe of a T-joint. The welded T-joints are made in St 52-3 steel, are obtained by covered electrode process and improved with plasma dressing. The analysis was developed with the MSC.Marc finite element code. The estimated stress field is validated with experimental stress results obtained using X-ray diffraction

Abstract. Fatigue strength of welded joints is significantly influenced by the presence of residual stresses due to welding, of flaws and notch sharpness at the weld toe. Compressive residual stresses enhance the fatigue behavior of the structure, while tensile ones impair it. TIG dressing at the weld toe is frequently used to remove flaws to lessen the notch sharpness at the weld toe and to introduce compressive residual stresses. This paper presents a 2D finite element model to predict the residual stresses generated in a TIG dressing at the weld toe of a T joint. The welded T joints are made in St 52-3 steel and are obtained by covered electrode process. The analysis was developed with the Marc finite element code. The modeled stress field is compared with some measurements of residual stresses obtained using X-ray diffraction and the strain gauges technique.

Resumo. As técnicas de refusão do pé do cordão de soldadura por TIG e plasma são frequentemente usadas para aumentar a resistência e a fiabilidade de peças solicitadas à fadiga. Neste trabalho apresentam-se resultados de um estudo de investigação sobre a utilização destas técnicas na recuperação da resistência à fadiga de juntas soldadas em T solicitadas por flexão em três pontos. As juntas são fabricadas em aço St 52 – 3 e obtidas por soldadura com eléctrodo revestido. São estudadas quatro situações: juntas não tratadas, juntas tratadas por refusão TIG, juntas pré-fissuradas e posteriormente tratadas por refusão TIG e juntas pré-fissuradas e posteriormente tratadas por refusão plasma. A eficiência dos tratamentos de refusão TIG e plasma na reabilitação da resistência à fadiga é analisada e discutida com base nos resultados de fadiga e em elementos complementares determinados durante a investigação, tais como: o perfil do pé dos cordões, a microestrutura e os perfis de dureza nas regiões soldada e afectada térmicamente e dos defeitos detectados no cordão. A eficiência obtida pelo processo de refusão por plasma é bastante satisfatória e muito superior à da refusão por TIG.