Research On Assessment Method Of Steel Pipeline With Volumetric Corrosion Defects Based On Finite Element Analysis

Energy is the basis of modern industry.Since the 1980 s,the country has advocated sustainable development of energy,and new energy fields such as solar,wind and hydro power have flourished,but this is not enough to support China’s huge industrial system,and traditional energy sources,mainly oil and natural gas,are still in a pivotal position.In the pipelines that have been put into use,with the increase in the number of years of use,the problem of aging pipelines is becoming increasingly prominent,such as corrosion,dents and cracks and other defects,will not only reduce the quality of oil and gas transportation,and in serious cases will lead to pipeline failure,causing leaks,explosions and other accidents.Therefore,a more accurate adaptation evaluation of the residual strength of pipelines containing corrosion defects is needed.In this thesis,the analysis model of steel pipes with volumetric corrosion defects was established by using ABAQUS finite element analysis software according to the water pressure blasting test data of pipes with volumetric corrosion defects,and the numerical simulation results were obtained.The calculated results were compared with the results of water pressure blasting test,ASME B31 G standard,DVN RP-F101 standard,PCORRC method and SY/T 6151-2009 standard to ensure the reliability of the finite element model analysis method.A nonlinear finite element analysis was carried out on steel pipelines with volumetric corrosion defects under internal pressure.Finite element simulation tests were carried out to study the change of stress distribution in the corrosion defect area caused by the change of geometric size of corrosion defects.The influences of the geometrical shape of corrosion defects,three geometrical dimension parameters(axial length,circumferential length and corrosion depth),location,pipeline material and other factors on the failure pressure of steel pipelines were analyzed.The residual strength prediction formula of steel pipeline with volume type corrosion defects was obtained through 1st Opt software fitting,and the fitting results were compared with the blasting test data.The calculation error of the fitting formula was smaller,which verified the reliability of the fitting formula in calculating the failure pressure of medium-strength steel pipeline with corrosion defects.Subsequently,based on the above research results,a finite element model of medium-strength steel pipe with composite defects containing corrosion depression was established,simulation experiments were conducted,and the failure mechanism of the pipe with composite defects was studied based on the calculation results,including its damage mode,damage process and stress-strain analysis;the influence of factors such as corrosion defect size,loading depth,diameter-thickness ratio and indenter radius on the failure pressure of the pipe with compound defects was considered.Using the simulation results,the formula for calculating the residual strength of the pipeline containing corrosion depression compound defects was obtained by fitting the 1st Opt software.The residual strength evaluation software for steel pipelines containing corrosion defects was developed,mainly including the existing evaluation standards or methods such as ASME B31 G,DVN RP-F101 standard,PCORRC method and SY/T6151-2009 standard and the new evaluation methods derived from this thesis’ s research,to evaluate the data in batch or single point,and to provide convenience for staff to perform residual strength evaluation for pipelines provide convenience.