Study On Mechanical Properties Of Steel-strip Wound Reinforced Composite Pipeline

Submarine pipeline is an important component for marine oil and gas transportation.Traditionally,steel pipe used as submarine pipeline,corrosion,spanning pipeline static breakdown and fatigue breakdown are the main causes of its failure.Recently,in the United States and other countries,steel submarine pipeline was replaced by composite pipeline gradually.Generally,composite pipeline consists of inner lining layer,middle layer,protective layer and poly-laminate reinforced layer.Lining layer and protective layer can be made of rubber or resin while reinforcement layer can be wound by steel-wire or steel-strip.Compared with traditional steel pipelines,composite pipeline has many advantages,such as the ability to withstand greater deformation,easy installation and laying,convenience for transportation and longer service life.China's oil exploitation is turning attention to the deep sea gradually,which indicates that the steel-strip(steel-wire)wound reinforced composite pipeline will have a good application prospect.Thus,the study of the mechanical properties of steel-strip wound reinforced composite pipeline is of great significance.Many scholars used to study steel-wire wound reinforced composite pipeline.In contrast,the study on the mechanical properties of steel-strip wound reinforced composite pipeline is insufficient.Funded by the key technology projects on the prevention of major accidents in production 2013,on the basis of the practical construction of steel-strip wound reinforced composite pipeline,a three-dimensional finite element model was established hierarchically by ABAQUS in this paper,the mechanical properties and the functional failure mechanism of steel-strip wound reinforced flexible submarine pipeline were studied as following.(1)Researches on the mechanical property of composite pipeline under internal pressure.Internal media pressure is one of the main factors leading to the destruction of composite pipeline.Numerical model of steel-strip wound reinforced composite pipeline was established by ABAQUS,and the numerical simulation study of its static response under 16MPa working pressure was carried out.Meanwhile,the simulation results were compared with the relative experimental data so that the validity of the numerical model could be verified.The simulation results show that the internal pressure is borne mainly by 89° steel-strip layers,and its circumferential stress and radial stress are significant,which is one of the main factors leading to the functional failure of composite pipeline.(2)Researches on the mechanical property of composite pipeline under combined action of internal pressure and transverse load.Based on the wave data of the one-year recurrence in ChengDao Oilfield,the static response of composite pipeline under combined action of internal pressure and transverse hydrodynamic load was simulated by ABAQUS.The results show that the transverse hydrodynamic load exerting on suspend composite pipeline is mainly borne by 15° steel-strip layers,and its axial stress is significant,which implies that transverse hydrodynamic load is one of the main factors leading to the function failure of the suspended section of composite pipeline.(3)Researches on the factors influencing on the mechanical properties of composite pipeline.The mechanical properties of composite pipeline are affected by many factors.In this paper,the study on the factors such as internal media pressure,transverse hydrodynamic load,the thickness and the winding angle of steel-strip wound reinforcement layer affecting on the mechanical properties of composite pipeline was investigated by ABAQUS.The results show that the greater of internal media pressure and transverse hydrodynamic load,the more unsafe of composite pipelines would be.Moreover,the optimum winding angle of steel-strip wound reinforcement armor layer is between 15°-40°.Furthermore,in the process of the structure design of composite pipeline,the thicker steel-strip wound reinforcement layer should be chosen as far as possible,besides,the winding machining process of steel-strip should be taken into consideration.