Comparison of the stress distribution in the metallic layers of flexible pipes using two alternative Bflex formulations

Abstract

Axisymmetric load is the most common load acting on flexible pipe. Modelling axisymmetric load correctly is very important to estimate the strength of a flexible pipe. The purpose of the thesis is to compare the stress distribution in metallic layers under three load case, i.e. tension, internal pressure and external pressure. Literature study and discussion to mechanical properties of flexible pipe and finite element modelling method are included in the thesis. The modelling program is BFLEX program. Models for three flexible pipes are built in BFLEX for 6inch pipe, 8inch pipe and 16inch pipe. Different element models are applied to model metallic layers. Element PIPE52 are used to model all metallic layers for ITCODE31 model. For ITCODE0 model, element PIPE52 are used to model carcass and pressure armour; element HSHEAR352 is used to model helical tensile layer. For full FE model, carcass and pressure armour are modelled by element HSHEAR363 and tensile layer is modelled by element HSHEAR353. For ITCODE31 and ITCODE0 models, the computing stress is taken from local model after BPOST. For full FE model, the stress is from global model directly. Moreover, analytical solution is found to estimate the modelling performance.