3C Level Fracture Assessment Of Seaside Pipeline Based On BS7910

As a kind of engineering structure ,the submarineline has the abroad and important applications, which always is used to deliver the oil and the gas. In the same time , as a kind of welded structure ,the welded joint of the pipeline always has the inevitable welding defects.With the development of the engineering practice , people gradually use the principle of the"fitness for use"to assess the influence of the welding defects on the structures, and don't required that the structure should not contain any welding defects.This paper uses the principle of the"fitness for use"and the regulation of the BS7910:1999 to make an 3C assessment for the submarineline which is developed by the COOEC and is located between Lvshun and Dalian..To finish the assessment, at first ,we understand the regulations and the theories of the BS7910:1999. Then ,we obtain the tensile property of the X56 pipe by the analysis of the tensile and yield strength value which is obtained from the mill certificates, obtain the tensile property of the weld by performing the tensile testing of the weld metal and obtain the fracture toughness of the HAZ and the weld metal by determining the J-R cure of them.In the fracture assessment of 3C,J-integer is a very important parameter,which is also an important contents in the elastic-plastic fracture mechanics.In this paper,the available domestic ana foreign J-integeral estimation methods were collected and digested on extensively reading science and technology bibilographic references.We brought forward LBB.ENG2 J-integral estimation methods for pipesWith circuferential through-wall crack ,and we brought forward SC.ENG1 and SC.ENG2 J-integral estimation methods for pipes with circuferential surface crack.We developed the equivalent reduced section analogies and derived the function equations,which avoid especially complex elastic-plastic fracture analyses and finite element numerical computations.These estimation methods can be applied in the complete range between elastic and fully plastic condition.We assessed x56 seaside pipeline in 3C level based on the above work,obtaining 3C level invalidation assessment chart and a series of assessment points, catching through safety performance analysis。...