Analysis Of The Plate And Pipe Welding Residual Stress For High Strength Steel

In recent years, the high strength steel is used in ship and ocean engineering structuremore and more widely, the residual stress of high strength steel is caused by welding and hasa remarkable influence to safety of the structure.At present, the welding residual stress arecalculated by empirical formula, but different welding structure, different welding process anddifferent method will result in different welding residual stress, so it is necessary to studydeeply for the welding residual stress of high strength steel.This paper is based on the thermal elastic-plastic theory, combined with the actualwelding structure of the marine platform from Waigaoqiao shipyard, also researched for theplate butt welding, fillet weld and pipe butt welding which are composed of grade550MPahigh strength steel, the simulation of welding process and the method of the residual stressprediction are analyzed, and the following works have been completed:1) The heat conduction theory and the thermal elastic-plastic theory are all analyszed,according to the heat conduction equation, three kinds of heat conduction boundaryconditions are solved, with establishing the thermo-mechanical coupled equations, and thenonlinear elastic-plastic constitutive model as well as thermal strain constitutive model, thethermal coupling field is calculated.2) The double ellipsoid heat source model and calculate the heat load are established,with using APDL program language to finish the mobile loading procedure. Combining withthe element birth and death technique, The three kinds of boundary conditions are calculated.The influence of latent heat of phase transformation should be considered, so that the transientwelding temperature field can be solved, as well as distribution of temperature field andcondition of temperature change can be researched.3) The indirect thermo-mechanical coupled method of stress field can be used to finishanalysis, and the APDL program language should be used to realise temperature load in thestructure. With solving the welding stress field, the longitudinal and transverse distribution ofresidual stress and the condition of residual stress change can be obtained by any time.4) The staggered welding method is studied, and comparing with the traditional weldingsequence, the rationality of the staggered welding in engineering is presented, and a series ofmethods to eliminate the residual stress and deformation can be summarized. There are alsosome reasonable suggestions presented.