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- Crack growth in simulated residual stress fields on tungsten inert gas dressed welded joints: a 2d approachPublication . Ramalho, Armando; Antunes, F.V.; Ferreira, J.A.M.In this paper is presented a 2D finite element model to predict the residual stresses generated by Tungsten Inert Gas (TIG) dressing at the weld toe of a T-joint. The welded T-joints, made of S355AR steel, are obtained by covered electrode process and improved with TIG 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. Over the estimated residual stress field is simulated the growth of fatigue cracks. The simulation is performed with the virtual crack closure technique, implemented in the MSC.Marc software. The obtained results are compared with the integration solutions of the Paris-Erdogan law, without influence of residual stresses, where the stress intensity factor is obtained using the Mk factor proposed by Bowness and Lee, included in BS 7910 standard. The numerical predictions are also compared with experimental results.
- Residual stresses analysis in plasma dressed welded jointsPublication . Ramalho, Armando; Ferreira, J.A.M.; Branco, C.M.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
- Simulation of crack growth in T-welded joints: residual stress field effectPublication . Ramalho, Armando; Antunes, F.V.; Ferreira, J.A.M.In this article, a three-dimensional finite element model is used to predict the growth of cracks at the weld toe of a T-joint. The model is developed using the MSC Marc software. Fatigue life is estimated by integrating the Paris-Erdogan law and the stress intensity factors are obtained by the virtual crack closure technique. The influence of residual stresses generated by plastic deformation at the weld toe on the crack propagation speed is analyzed. The existence of residual compression stress fields causes a delay in crack growth. The obtained results are compared with the integration solutions of the Paris-Erdogan law using the stress intensity factor computed through the Mk factor proposed by Bowness and Lee, included in BS 7910 standard.
- Residual stress analysis in TIG welded jointsPublication . Ramalho, Armando; Ferreira, J.A.M.; Branco, C.M.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.
- Previsão da resistência à fadiga em juntas soldadas reabilitadas por técnicas de refusãoPublication . Ramalho, ArmandoNeste trabalho realizou-se um estudo de fadiga no qual se analisou o efeito das técnicas de refusão TIG e plasma na reabilitação de juntas soldadas em T, fissuradas no pé do cordão. Os resultados obtidos para as juntas como soldadas, melhoradas por refusão TIG, melhoradas por refusão plasma, reabilitadas por refusão TIG e reabilitadas por refusão plasma são apresentados em curvas S-N com intervalo de confiança de 95%. Os benefícios na vida de fadiga das juntas reabilitadas pelas duas técnicas de refusão, foram avaliados através dos resultados experimentais e através de um modelo de estimação baseado na Mecânica da Fractura Linear Elástica. Foram avaliados, pela técnica do furo e por difracção de raios X, os valores das tensões residuais gerados nas diversas juntas, como soldada, melhoradas por refusão TIG ou Plasma e reabilitadas por refusão TIG ou plasma. Foi desenvolvido e validado um modelo de estimação das tensões residuais nas juntas melhoradas por refusão TIG ou plasma, utilizando o programa de elementos finitos MARC.