Finite Element Analysis Of Welding Deformation And Residual Stress For Large Scale Structure Based On Local-Global Mapping

The thermo-elastic-plastic(TEP)finite element method(FEM)is a classical approach for welding simulation and has been widely used to research the welding thermodynamics of simple structures,owing to its unparalleled advantages in calculation accuracy and process adaptability compared with other numerical simulation methods.However,the TEP method has the disadvantages of large-scale computation and long-time consuming,and it is difficult to simulate the welding process of large and complex structures.Centered on the problem of lower efficiency of thermo-elastic-plastic finite element method,this paper proposed and validated a finite element simulation method of local thermo-elastic-plastic and global elastic(local-global)mapping aimed at laser-arc hybrid welding process,and realized the prediction of welding deformation and residual stress of large-scale diversion tube.The main research work included:Firstly,the hybrid Shell/solid finite element model of T-type welded joint was established.The nodal degrees on the interface between the shell and solid elements were connected by the coupling equations.The secondary development of surface-volume combined heat source model was completed based on ABAQUS user subroutines for the calculation of transient temperature.The numerical simulation of the welding deformation and residual stress of the T-type joint was achieved by the indirect coupling method.The simulation error of the maximum angular deformation was only 11.11%,and the computational efficiency was improved remarkably,which laid the foundation of the welding deformation and residual stress simulation for large scale structures.Secondly,an efficient numerical simulation method was introduced based on the local thermo-elastic-plastic and global elastic mapping.Through the preparation of pre-processing and post-processing secondary development program,the local residual plastic strain was extracted as inherent strain.Then,the initial stress load method was used to map the inherent strain to the whole T-joint weld zone.Compared with the experimental and traditional methods,it was found that the new method could improve the computational efficiency by about 53.7% under the premise of ensuring the accuracy of the calculation.Finally,the simulation analysis of welding deformation and residual stress of large diversion tube was realized.Based on the simulation method of "local-global" mapping proposed in this paper,the welding sequence of large-scale structural parts was optimized with the aim of smaller welding deformation and lower residual stress.On the foundation of the scheme of optimal welding sequence,the inherent strain of the local part was extracted and mapped to the whole structure,and the welding deformation prediction for the welding assembly of the inner shell and the annular partition of the large diversion tube was realized.On this basis,the deformation and residual stress distribution induced by the girth welding of diversion tube were studied to determine the maximum distortion and the high residual stress region of the whole structure.