This paper presents analytical and numerical models to predict the behavior of unbonded flexible risers under torsion.The analytical model takes local bending and torsion of tensile armor wires into consideration,and ...This paper presents analytical and numerical models to predict the behavior of unbonded flexible risers under torsion.The analytical model takes local bending and torsion of tensile armor wires into consideration,and equilibrium equations of forces and displacements of layers are deduced.The numerical model includes lay angle,cross-sectional profiles of carcass,pressure armor layer and contact between layers.Abaqus/Explicit quasi-static simulation and mass scaling are adopted to avoid convergence problem and excessive computation time caused by geometric and contact nonlinearities.Results show that local bending and torsion of helical strips may have great influence on torsional stiffness,but stress related to bending and torsion is negligible;the presentation of anti-friction tapes may have great influence both on torsional stiffness and stress;hysteresis of torsion-twist relationship under cyclic loading is obtained by numerical model,which cannot be predicted by analytical model because of the ignorance of friction between layers.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51579146 and 51490674)Shanghai Municipal Natural Science Foundation(Grant No.15ZR1423500)Shanghai Rising-Star Program(Grant No.16QA1402300)
文摘This paper presents analytical and numerical models to predict the behavior of unbonded flexible risers under torsion.The analytical model takes local bending and torsion of tensile armor wires into consideration,and equilibrium equations of forces and displacements of layers are deduced.The numerical model includes lay angle,cross-sectional profiles of carcass,pressure armor layer and contact between layers.Abaqus/Explicit quasi-static simulation and mass scaling are adopted to avoid convergence problem and excessive computation time caused by geometric and contact nonlinearities.Results show that local bending and torsion of helical strips may have great influence on torsional stiffness,but stress related to bending and torsion is negligible;the presentation of anti-friction tapes may have great influence both on torsional stiffness and stress;hysteresis of torsion-twist relationship under cyclic loading is obtained by numerical model,which cannot be predicted by analytical model because of the ignorance of friction between layers.
