Subject:buckling Behavior Of Large Strain Pipeline Steel Pipe And Effect Of Strain Aging

As an important part of offshore oil and gas fields,the leakage of offshore pipelines will cause huge economic losses and serious environmental disasters.However,during the laying and service of submarine pipeline,due to the harsh and complex external environment,the steel pipe may have large bending deformation,buckling and even fracture.Therefore,it is of great theoretical value and application significance to systematically master the deformation behavior of large deformation steel pipe for offshore pipeline.In this paper,the L485 deep-water submarine pipeline with large strain,thick wall and large diameter is taken as the research object.Through the combination of reverse simulation technology and numerical calculation,the deformation strengthening ability of material,strain aging condition,geometric shape of steel pipe,such as outer diameter,wall thickness fluctuation and diameter thickness ratio,and the influence of internal pressure and external pressure on the buckling deformation behavior of steel pipe are mainly studied.The results show that the buckling behavior of L485 large strain offshore pipe is mainly affected by the mechanical properties of base metal,geometric parameters of steel pipe and service conditions.These three factors together determine the deformability of the steel pipe from elastic deformation to plastic deformation to structural failure.That is,the compression strain capacity of steel pipe.The combination of reverse simulation engineering and numerical calculation can accurately predict the buckling mode,buckling time and critical buckling strain of steel tube.The time corresponding to the maximum load point of the load-displacement curve is the buckling time of the steel pipe.The critical buckling strain of steel pipe has the best linear correlation with Rt5.0/Rt2.0;strain aging will increase the yield strength and yield ratio of the pipe,reduce the uniform elongation and n value,and the appearance of the yield platform will reduce the critical Buckling strain.The buckling position of the steel pipe is affected by the compression side diameter-thickness ratio.An increase in the steel pipe diameter-thickness ratio will reduce the critical buckling strain.If the internal pressure is far greater than the external pressure,it will bulge and bulge outward.If the internal pressure is slightly greater than the external pressure,the external convex bulge and the internal depression will coexist.If the internal pressure is less than the external pressure,the internal depression will collapse.The critical buckling strain of steel pipe increases with the increase of internal pressure,and decreases with the increase of external pressure.