Research On Lateral Buckling Of The Tensile Armor In Ocean Flexible Pipe

Unbonded flexible pipe is the transportation channel of oil in marine Oil and Gas Development,which will be subjected to axial compression during the installation and operation.However,there is no specific layer designed for the axial compression load,which may lead to lateral buckling failure of tensile steel wire armor.Moreover,guiding suggestions about the axial compression strength is presented in the design specification.Once the lateral buckling failure happens,the capacity of the pipe will be dramatically reduced,which causes the decrease of fatigue life and even pipeline damage,resulting in oil leakage.Therefore,it is of great engineering significance to study the lateral buckling mechanism of tensile armor wires in flexible pipe.Firstly,the application background,the structural characteristics and the research status of the lateral buckling of the armored steel wires are performed in this paper.Secondly,the definition and classification of buckling and instability criterion are given,especially the lateral buckling definition of tensile armor.Lateral buckling mechanism of the armored wires is presented briefly,and critical load is derived through the theory of thin-walled curved beam.Considering the deficiency of current research,the key parameters of this analysis are presented: friction coefficient and helical angle based on the structural characteristics of the pipe and the theoretical formula.Thirdly,the mechanism model of tensile armor is established considering the contact between layers and the effect of high strength tape,ignoring the structure inside tensile armor.Failure mechanism of lateral buckling is analyzed through numerical simulation and the sensitivity of critical load to friction coefficient and spiral angle is performed,which gives the design range of key parameters.Finally,considering the contact between different layers and between steel wires and ignoring the inside structure,a whole model of flexible pipe is established.The characteristics of lateral buckling behavior of armor wires are stated.The sensitivity analysis of critical load to friction coefficient is conducted.It is concluded that friction coefficient has a significant impact on the mode of lateral buckling.Research of this paper is sponsored by Hi-Tech Research and Development Program of China(863 Program).This work has the guiding significance for the analysis and design of the anti-lateral buckling in flexible pipe.