Study On Weld Residual Stress And Strength Of Steel Pipeline Girth

The welding process is a permanent connection, caused by the binding and diffusion of their atoms or molecules,between one and the other materials which are same or not properties. Girth weld seam is the most common mothed of connection used in pipeline heads, therefore, the correct understanding of temperature field,stress and strain field when pipeline girth weld is processing or had been processed is the best way to secure those operation and repair them.This article investigates a large number of domestic and foreign theory research on girth welds temperature field and stress field, and summarizes a great deal of finite element simulation welding achievements, finally establish thermal analysis program and stress analysis program based on ANSYS Parameter Design Language.and those two programs achieve indirect coupling to welding simulation.Inherent strain,welding residual stress and mechanical model of the generating residual stress are the basis for better understanding of residual stress in welding process. The finite element theories of welding temperature field and stress field is the basis for ANSYS simulation, in this article above two aspects have been detailly explained.and the main research works as follow:(1) Explain detailly APDL modeling processes of thermal analysis and stress analysis procedures:1) Determine the elements of the two programs.2) Analyze material parameters required in the two programs.3) Note nonlinear moving heat source in the thermal analysis program.4) Describe briefly the process loading the thermal analysis results into stress analysis program and the ANSYS set in the two processes.(2) Run the two no wrong side APDL procedures under ANSYS software platforms.and analyze the results of temperature and stress-strain fields and get the change law.(3) Run the two wrong sides(0.0005m,0.001m) defect APDL procedures under ANSYS software platforms and analyze the results of simulation.and apply MATLAB software to fit the incremental residual stress of axial direction along the pipe and access more regularity of distribution relationships.(4) Analyze the non-match of girth weld material used on pipe and seam, and establish M=0.8. and1.2two non-matched coefficients of girth weld simulation procedures based on APDL, and get more regular and residual stress distribution of those effects, and girth weld strength under the three different intensity matched coefficient. Based on welding residual stress.establish finite element simulation model in three different class pressure (5MPa,1OMPa and15MPa) and analyze equivalent stress distribution along the axial distance appart from the pipeline girth welds center.All in all,the finite element method analysis results of pipelie girth welds will be helpful engineers to more clearly understand the distribution of girth residual stress, welding material non-matched the different impacting on residual stress and strength, selecting effective measures to eliminate residual stress and analysis the redistribution of residual stress subjected to different pipeline internal pressure, which contribute to ensure engineering quality.