Análise numérica de uma junta soldada dissimilar utilizada em equipamentos off-shore

Abstract

The search for structural efficiency in the mechanical systems has been strongly used with the purpose of economic optimization and structural safety assurance, mainly. In this sense, the structural efficiency is supported in the prediction of potential failures, that with the advent of the computational tools, situations of structural criticality are previously detected through numerical simulations applied. Studies carried out in recent years have sought to understand the response of materials to the presence of cracks in dissimilar welded joints, but not yet sufficient to fully uncover fracture toughness responses due to the heterogeneity present in these joints. This union type of mechanical components is widely used in the industry worldwide, especially in the oil and gas sector. Thus, fracture toughness evaluations have become current applications in the design and structural integrity analysis of components and mechanical systems. Experimental work presented significant deviations from the test crack in relation to the fatigue pre - crack plane, towards the soft material present in dissimilar welded joints. This work analyzes the behavior of the crack tip zone, from the perspective of fracture mechanics, located in a dissimilar butyl welded joint used to join flanges to pipelines present in the offshore oil production lines investigated by Almeida (2014). The weld joint sample (SE (B)) shows a crack located 1mm from the AISI 8630M-INCONEL 625 interface, which causes high triaxiality in the material. The deviation of the crack in dissimilar welded joints may be related to the stress and strain fields generated in the crack tip vicinity. Numerical results show the behavior of the stress fields and strain fields generated from the imposed loads. Critical stresses zones were observed, evidenced by the numerical tool of finite element method. A preferential plastic flow was also observed in the dissimilar welded joint specimen, which the literature claims to be a harbinger of the crack growth path. Numerical analysis presented significant accuracy in relation to the plastic flow and the crack developed during the tests performed. The results obtained are in agreement with the literature and the experimental study of Almeida (2014).