Residual Stress Analysis Of The Pipe Joint Based On Contour

Pressure pipelines are widely used in petroleum,nuclear power and chemical industries.Welding is the main connection method of pressure pipelines,which will inevitably produce residual stress.The existence of residual stress will reduce the mechanical and fatigue properties of the pipeline,and make the welded joint crack more easily.T-welded pipe joint is one of the main joints used in pressure pipeline,and its residual stress distribution is complex.Therefore,it is of great engineering value to study the magnitude and distribution of residual stress in Twelded pipe joints.In this paper,the contour method is used to measure the residual stress of the T-shaped welded pipe joint,analyze the residual stress distribution of the joint,and find out its stress distribution law.Based on the theory of contour method,a new contour value processing method is proposed,that is,the least square method is used to determine the base plane of the cutting surface contour point cloud with the covariance as the index.The method of radius filtering is used to denoise the contour of the cutting surface with the radius threshold as the index.Interpolation method is used to smooth the denoised contour.The precision of the contour method was verified by cutting method and X-ray diffraction method on the flat butt joint.The verification results show that the data processing method is correct and the precision of the contour method meets the requirements.The stress measurement results of flat welded joints show that the tensile stress is mainly distributed in the welded joint area,and the peak value is 315 MPa,located in the center of the weld seam.The compressive stress is mainly distributed in the edge area of the test plate far away from the weld,and the peak value is-150 MPa,located at 125 mm away from the weld.The residual stress of T-welded pipe joint with specific size is analyzed by contour method.The results show that the peak tensile stress of the pipe joint is located on the branch pipe which is 4mm away from the inner surface of the branch pipe,and its value is 390 MPa.The peak stress in the weld area is located in the toe area near the parent tube,and its value is 125 MPa.In the surface stress distribution of pipe joint,the weld surface at the bottom of the joint surface and near the toe on the side of the parent pipe is the tensile stress distribution area,and its value is95 MPa and 65 MPa,respectively.