Forecast Of The Welding Residual Stress In Complicated Joints Of The High-strength Steel Of Offshore Platform

During the building of offshore platform, because the using high-strength steel andultrahigh-strength steel. Steel structure welding technique of high-strength, heavy-thickness,complicated joints becomes the critical technique of the building platform. The performanceof welded structures may be affected by the greater residual stresses and deformation due tothe concentration input of the welding heat in the welding process. Therefore, the weldingresidual stress control technology of offshore platform structure becomes of the greatestimportant. There is of a practical significance of forecasting the welding residual stresses.This thesis first use different welding procedure and welding method weld (butt andfillet) EH36and EQ56(steel used for offshore platform). After welding (weld seampolishing, weld edge re-melting, UIT, post-weld heat treatment), by measuring the residualstress on the butt plate through the blind hole method, and the result is compared andanalyzed. Finally, we study the influence of different process conditions on welding residualstress.Second, this thesis used the FEM software ANSYS to calculate the butt (EQ56).the inputconditions (material parameter, thermal input) is the same as first plate. Compared thesimulation results and measuring results (first plate), has some errors. Analyze the reasonsand prove simulate welding residual stress by using FEM software ANSYS is feasible.Provide an effective test method to select reasonable welding methods and welding processconditions and can further study the welding deformation and residual stress variation inwelding structures.Finally, this thesis simulate the complicated joints of offshore platform (upright postand cross brace, thruster’s pedestal), obtaining the results shows that the maximum weldingresidual stress locates on the weld toe and weld junctures, reaches400MPa.