Estudo numérico da resistência ao colapso de tubos de revestimento na presença de imperfeições geométricas

Abstract

The variability inherent to manufacturing processes may lead to non-uniformity of Engineering products. In the case of OCTG (Oil Country Tubular Goods) sector, the effects of ovality and eccentricity are commonly observed. The first phenomenon is observed in tubes whose cross section does not preserve its circular aspect, due to thermal and mechanical treatments undergone in the lamination process, and the second one corresponds to a non-uniformity in the wall thickness. This work addresses the development of numerical models for analysis of the reduction of collapse strength in casing tubes, subject to these imperfections. The models are developed by using Abaqus software, a numerical analysis platform based on the Finite Element Method. The analysis is carried out in plane stress state, taking into account physical nonlinearity, by using finite quadrilateral elements. The collapse pressure equations provided in the API/TR 5C3 (2008) normative code are used as a reference for modeling and analysis of numerical results. Tubes with different slenderness ratios, subjected to various levels of eccentricity and ovality are analyzed, in order to evaluate their effects on the collapse strength. The results are compared to some values found in the literature and in the current standard, in order to contribute to the structural evaluation of well casing. It is proposed some equations to predict the loss of collapse strength due to the imperfections.