The Numerical Simulation Study Of Welding Residual Stresses In The Spherical Tank

Spherical tank is a kind of large-scale, complicated pressure vessel which uses welding as the main processing method and which is widely used in petroleum, chemical, metallurgical and other industries. Spherical tank produces dynamic stress and welding residual stress during welding, which will affect the safety performance of the spherical tank. Therefore, it is important to know the stress variation of Spherical tank welding joint in the welding process and finally the formation of residual stress by the numerical simulation of welding process.To begin with, the residual welding stress in the real plate welded joint was tested and measured by X-ray method. Then, a dynamic simulation of the welding process of plate welded joint was carried out and measured. Finally, we compared the testing results with the numerical simulation results. The results matched which means the simulation method is feasible. By improving the simulation method, we conducted three dimensional numerical simulation of welding process on spherical tank and obtained the temperature field and residual stress-strain field of welded girth joint were obtained. This paper includes the following studies:Take 2 plate welded joints as samples (1 with Q245R and another with Q345R) and the surface residual stress field of plate welded joint was measured by X-ray method. Then, the distribution of residual stress field after welding was obtained.Three-dimensional model of plate welded joint was built based on finite-element analyzing software ANSYS, and the numerical simulation of welding process and condition on plate welded joints was carried out with these 2 joints respectively. Then, the temperature field and strain-stress field distribution rule was gained by the post-treatment of ANSYS. Finally, the results of the welding residual stress by FEM were compared with the previous test results to verify the feasibility of the numerical simulation method.Use ANSYS, the FEA software, to build 3D finite element model of the spherical tank Girth weld (with 9 layers). The variation of thermal-physical properties and mechanical properties of material with temperature was considered. The parametric language APDL and element birth and death technology was applied to simulate the weld metal filling process. The welding thermal process was analyzed based on Gaussian heat source model. After analysis, the dynamic distribution rule of temperature field was obtained. Based on the temperature field calculated before, stress field changes during welding can be worked out.