Effect of hot-melt welding process parameters on welding residual stress of polyethylene gas pipeline
Polyethylene(PE-HD)pipeline has the advantages of high toughness and corrosion resistance,and is widely used in the fields of water and gas transmission,nuclear industry and hydrogen energy.Due to the limitation of machining technology and welding technology,there are production residual stress and welding residual stress in PE-HD pipeline system.The existence of residual stress accelerate the initiation and expansion of cracks inside the pipeline,and significantly reduce the service life of the pipeline.Therefore,the study of residual stress is of great significance to accurately evaluate the reliability of PE-HD pipeline.The hoop residual stress of PE-HD pipe substrate and hot-melt joint was measured by open-ring method and blind hole method respec-tively.Based on the elastic-plastic constitutive model,the finite element model of hot-melt welding with temperature-displacement coupling was established.The distribution of residual stress in hot-melt welded joints and the influence of welding process parame-ters on temperature field and residual stress were investigated.The results measured by the blind hole method and the open ring method are approximately equal.Compared with the traditional viscoelastic model,the calculation results of the elastic-plastic hot-melt welding finite element model established are closer to the experimental measurements.The thickness of molten layer increases with the increase of welding temperature and heating time,and the length of hot-melt joint increases with the increase of heating time.The residual stress in the weld and fusion zone is tensile stress,and the tensile stress in the inner wall is greater than that in the outer wall.The increase of welding temperature and heating time will increase the residual stress value.
high density polyethylene pipehot-melt weldingresidual stresselastic-plastic constitutivenumerical simulation
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