Large-deformation theoretical analysis of open-end thick-walled tubes under internal pressure

Subsea pipelines and deepwater risers are critical components in offshore oil and gas production, often subjected to extreme internal pressure during operation and hydrotesting. This study proposes a rigorous theoretical model for stress-strain analysis on open-end thick-walled cylinders subjected to uniform internal pressure within a large deformation framework. By combining specific constitutive relations, compatibility and equilibrium equations, a numerical solution is developed and systematically validated against classical small-deformation analytical methods as well as linear and nonlinear finite element models. The proposed large-strain formulation shows excellent agreement with small-strain analytical results under small deformation conditions, confirming mutual validity in the small-strain regime. However, as the tube experiences post-yield expansion, the small-deformation solution exhibits significant deviations due to the unaccounted geometric nonlinearities, whereas the large-strain approach maintains high accuracy. This work extends large-deformation analysis to open-end boundary conditions, providing a validated analysis method for the design and integrity assessment of pipelines and other pressure-containing structures in scenarios involving substantial post-yield expansion of hollow cylinders.