Numerical Simulation Studies in Tungsten Inert Gas Welding of Inconel 718 Alloy Sheet

In this present work, the TIG welding simulation of 1.65-mm Inconel 718 alloy sheet was performed using finite element analysis (FEA) to predict the thermal field, distortion, and residual stresses. A sequentially coupled thermo-elastic-plastic model was developed for this analysis and implemented in the FEA software, Sysweld (R). The double elliptical heat source (DEHS) was utilized for the non-linear transient analysis. The simulated thermal results were in good agreement with the experiments. The weld-induced out-of-plane and angular distortion of the welded sheet were experimentally measured by a coordinate measuring machine (CMM), and the residual stress distribution of the weldment was measured using the x-ray diffraction (XRD) method. The behavior of weld-induced deformation and residual stresses during TIG welding of the thin section was numerically analyzed by applying linear and non-linear geometric effect analysis. The residual stresses of non-linear model revealed that the magnitude of stresses in the fusion zone was tensile in nature and farther away from the fusion zone; the stresses were compressive in nature. Non-linear FEA displays a better correlation with experimental results compared to linear FEA as it accounts for the plastic strain evolution during welding. The accuracy of out-of-plane distortion and angular distortion predicted by the non-linear geometry effect correlates to about 87.9% and 93.9% of the experimental data, respectively. Also, surface residual stress patterns predicted using non-linear FEA show close agreement with experimental results. The study emphasizes the significance of non-linear FEA in the prediction of weldment stress state in the design stage to ensure the weldments response to service loading conditions.