Analysis of the Effect of Tungsten Inert Gas Welding Sequences on Residual Stress and Distortion of CFETR Vacuum Vessel Using Finite Element Simulations

Abstract

The as-welded sectors of China Fusion Engineering Testing Reactor (CFETR) vacuum vessel (VV) have very tight tolerances. However, it is difficult to investigate the welding stress and distortion without the production of a full-scale prototype. Therefore, it is important to predict and reduce the welding stress and distortion to guarantee the final assembly by using an accurately adjusted finite element model. In this paper, a full-scale finite element model of the 1/32 VV mock-up was built by ABAQUS which is a powerful finite element software for engineering simulation, and three different tungsten inert gas (TIG) welding sequences were simulated to study the effect of welding sequences on the welding stress and distortion. The results showed that the main welding stress happened on the weld zone, and the maximum distortion occurred on the shell near the welding joints between the inboard segment (PS1) and the lower segment (PS4). The inboard segment (PS1), upper segment (PS2), and lower segment (PS4) distorted to inside of the shell perpendicularly, while the equatorial segment (PS3) distorted to outside of the shell perpendicularly. According to the further analysis, the maximum welding stresses in sequence 1, sequence 2, and sequence 3 were 234.509 MPa, 234.731 MPa, and 234.508 MPa, respectively, and the average welding stresses were 117.268 MPa, 117.367 MPa, and 117.241 MPa, respectively, meanwhile, the maximum welding displacements in sequence 1, sequence 2, and sequence 3 were 1.158 mm, 1.157 mm, and 1.149 mm, respectively, and the average welding displacements were 1.048 mm, 1.053 mm, and 1.042 mm, respectively. Thus, an optimized welding sequence 3 was obtained and could be applied to the practical assembly process of the 1/32 VV mock-up.

Finite Element Prediction of Residual Stress and Deformation Induced by Double-Pass TIG Welding of Al 2219 Plate

“…The thermal analysis is based on the transient thermal field induced on the material via the TIG welding arc, which is applied as a volumetric heat source having the front and rear ellipsoidal shapes proposed by Goldak et al [29]. This heat source model is established with a steep temperature gradient in front of the weld and the slow cooling rate at the rear section of the welding torch due to heat convection in the weld pool [30,31]. Figure 4 illustrates the Goldak’s heat source.…”

Current research and industrial application of laser powder directed energy deposition

“…In the industry, Tungsten Inert Gas (TIG) welding was the first technique used for repairing damaged components [5,49]. Despite its relatively simple applicability, the TIG process induces a huge amount of heat in the repaired component, and this leads to high residual stresses and distortions [50]. On the other hand, Plasma Transferred Arc Welding (PTAW) and Electron Beam Welding (EBW) processes satisfy the requirement of a low heat input; however, their equipment is more complex and expensive [49,51,52].…”

Multi-Objective Welding-Parameter Optimization Using Overlaid Contour Plots and the Butterfly Optimization Algorithm

“…They observed the effect of welding current, voltage, and gas flow rate on the angular distortion of welded parts. Zhang et al [23] used FEM simulations to observe the overall distortion in a large vacuum vessel, cutting down the cost of constructing a prototype of the vessel. Lorza et al [24] built a thermomechanical model to simulate the TIG welding process.…”