Buckle Propagation Research Of Subsea Pipelines Under External Pressure

The great external pressure may lead to local buckling phenomenon of pipe during its installation and operational period.When the external pressure exceeds the buckle propagation pressure,local buckling will propagate along the pipeline,so that the overall structure of the pipe failure,resulting in heavy losses.Therefore,it is necessary to have a depth study on the submarine pipeline buckle propagation under external pressure and provide guidance for pipeline design and applications.The main works are summarized as follows:(1)Using two-dimensional ring-link model to get the single layer pipe theoretical result of buckle propagation pressure.Simplified single layer pipe to two-dimensional ring-link model,use nonlinear method of discrete spring model to simulate the contact between the pipe wall and incremental method to establish ring potential energy value equation.Finally obtain the single layer pipe buckle propagation pressure according to the energy conservation equation and verify the reasonableness and accuracy of the theoretical formula through extensive finite element parametric analysis.(2)Fitting the single layer pipe buckle propagation pressure prediction formula through extensive finite element model results.Build and calculate large quantities of single layer pipe finite element model by Python parametric modeling method.Analysis the influence of pipe diameter to thickness ratio,steel grades and material strain hardening behavior on the buckle propagation pressure.Based on finite element numerical results,fitting the single layer pipe buckle propagation pressure prediction formula.Proof the accuracy of fitting formula through the comparison with formulas from specifications and existing test results.(3)Analysis the influence factors of sandwich pipe on buckle propagation pressure.Establish sandwich pipe buckle propagation finite element model and consider the interlayer adhesion properties of sandwich pipe with fully bonded and unbonded case.Analysis the influence of pipe diameter to thickness ratio,steel grades and material strain hardening of inner and outer pipe,core layer thickness and elastic modulus on buckle propagation pressure.The results show that,under external pressure,the cross-sectional geometry and material properties of submarine pipeline have more significant impact on the buckle propagation characteristics.In addition,the interlayer adhesion properties of the sandwich pipe also have a greater impact on it.