An Analytical Frame for Predicting Residual Contact Pressure for Mechanically Lined Pipe using von Mises Criterion and Finite Strain Theory

Resumo

Mechanically Lined Pipe (MLP) is a bi-metallic pipe consists of an external carbon steel pipe internally coated with a thin Corrosion Resistant Alloy (CRA) lining. This CRA layer acts as a barrier against corrosive substance present in the production fluid from offshore Oil & Gas fields, while the high-strength, low-carbon steel outer pipe bears the external loads. Hydroforming expansion stands as the primary method for bonding the liner onto the external carrier pipe. The pursuit of precise and reliable theoretical models is ongoing to improve fabrication efficiency and establish a standard for subsequent failure analysis. The Tresca criterion is traditionally utilized in stress-strain analysis of MLP fabrication due to its mathematical formulation. However, it tends to provide conservative estimations of metallic structure yielding. And comparing the results of theoretical models employing the Tresca yield criterion with the mainstream numerical simulation software relying the von Mises yield criterion poses another difficulty. Hence, its suitability for analyzing MLP fabrication is subject to debate. To enhance accuracy, nonlinear theoretical analysis of MLP incorporating the finite strain theory and the von Mises yield criterion has been performed. Analytical prediction of residual contact pressure is achieved through the circumferential strain compatibility. An axisymmetric Finite Element Model (FEM) is constructed to compare against the theoretical models. Furthermore, the investigation delves into the impact of introducing an appropriate level of carrier pipe plastification on residual contact pressure.