X80管线钢管端环焊缝电弧增材梯度强化结构设计与性能优化研究OA

To address the risk of failure caused by strength-toughness mismatch in X80 pipeline steel pipe end girth welds,a gradient reinforcement method based on arc additive manufacturing is proposed.This method achieves coordinated control of stress concentration and residual stress by optimizing the geo-metric parameters and deposition path of the additive layers added externally to the girth weld.Firstly,an optimization design for the dimensions of the additively manufactured thickening zone at the pipe end is conducted,and the orthogonal experiments are used to determine the regulatory effects of key geometric parameters on the stress-strain distribution.Secondly,based on the coupled thermal-mechanical-phase multi-field theory,a two-dimensional dynamic finite element model incorporating a life-death element activation algorithm is established.A double-ellipsoid heat source model is employed to characterize the thermo-mechanical coupling effect during the process of arc additive manufacturing,revealing the forming mechanism of the pipe end and its regulatory effect on the mechanical properties of the girth welds.Experi-mental results show that after optimizing the dimensions of the additively manufactured thickening zone with a layer length L=150 mm,wall thickness increment t=30%,and transition angle θ=150°,the strength in the girth weld zone is stabilized at 550 MPa,while the impact energy in the mixed zone increa-ses significantly.The strength in the Heat-affected Zone(HAZ)increases to 590 MPa,but the transverse yield-to-tensile ratio of the base metal is relatively high,indicating potential risks of plasticity degrada-tion and embrittlement.