Numerical Simulation And Control Research On Thick Wall Welding Stress And Deformation Of Large Stainless Steel Vacuum Cavity

As a high-efficiency and low-cost additive manufacturing method,welding technology plays an irreplaceable role in the fields of national defense military,nuclear power,hydropower,traffic rails,pressure vessels,pipeline transportation,etc.During the welding process,due to the large amount of energy input at the local position of the weldment,a huge temperature gradient will be generated around the weld seam,resulting in uneven expansion of the material,which lead to the occurrence of plastic strain.After the material cools,these plastic strains will cause welding residual stress inside the weldment.On the one hand,this residual stress will adversely affect the rigidity,strength,and stress corrosion of the welded joint,on the other hand,the welding stress will also cause deformation of the component,affecting the assembly performance and manufacturing accuracy of the weldment.Therefore,it is necessary to quantitatively analyze the stress and deformation generated in the welding process.This paper takes submerged arc welding of stainless steel thick plates as the research object,and analyzes the welding temperature field,stress field,welding deformation and other issues.The content of this article is as follows:(1)Experiments were designed to measure the temperature,stress and deformation of the submerged arc multi-layer multi-pass plate,this part is used to provide verification for the FEM simulation model.The metallographic structure,hardness and tensile strength of the metal in different welding pass are observed.the effects of temperature field and residual stress on the structure and mechanical properties of the weld seam are analyzed according to the observation results,and it also provides a reference for the mechanical parameter settings of the FEM model.(2)Using general finite element software ABAQUS as the analysis platform,with python scripts and the "model change" function,a sequentially coupled three-dimensional thermal-mechanical analysis model was established to predict transient temperature and stress fields.The simulation result are compared with the experimental results to ensured accuracy.The thermo-elastoplastic model was used to analyze the stress and temperature field of SUS304 stainless steel multi-layer multi-pass welding.The distribution of horizontal residual stress,longitudinal residual stress and the distribution of temperature field were explained.An accurate and high-efficient FEM model paved the way for welding parameter optimization and selection..(3)Based on the analysis of the above FEM model,a simplified calculation model was established,and a three-factor three-level orthogonal experiment was designed to study the three thermal welding parameters,namely welding speed,interpass temperature and cooling rate.SPSS was used to analyze the variance of the simulation calculation results,and the influence trend and influence level of the three factors on the residual stress and deformation of the weldment were obtained.The SVM regression algorithm and Particle swarm optimization algorithm were used to calculate the optimal parameters within the specified level.This work provides a reference for the selection of welding parameters.(4)Based on the inherent strain theory,an elastic finite element model was established in ABAQUS to complete the welding deformation simulation of the large stainless steel vacuum chamber wall.The model simulates the change of the welding confinement state during the welding process by activating the welding plate and the welding seam life and death unit step by step.Calculate and compare the welding deformation under the three welding sequences,and choose the best plan.