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THERMAL ANALYSIS OF WELDING

In large steel fabrication industries such as shipbuilding, and high-speed train guide way, the problem of residual stresses and overall distortion continues to be a major issue. In the last few decades, various research efforts have been directed at the control of the welding process parameters aiming at reducing the distortions and residual stress effects. In fusion welding, a weldment is locally heated by the welding heat source. Due to the non-uniform temperature distribution during the thermal cycle, incompatible strains lead to thermal stresses.

These incompatible strains due to dimensional changes associated with solidification of the weld metal (WM), metallurgical transformations, and plastic deformation, are the sources of residual stresses and distortion. Hence, to avoid failures in the welded joints there is a necessity that these stresses are to be kept minimum. Various methods are available to reduce these stresses and the selected method for this present work is the effect of post weld heat treatment on weldment. Estimating the magnitude and distribution of welding residual stresses is important. It is, therefore, necessary to develop a model for the welding process.

 This study applies thermal elasto-plastic analysis, using finite element techniques, to analyze the thermo mechanical behavior and evaluate the residual stresses in cantilever-welded joints. Two dimensional finite element analysis of the single pass weld is considered for this analysis. The TIG(Tungstun Inert Gas) welding process is simulated using Finite Element Method (FEM) program ANSYS. The simulations were carried out using a two-step process; non-linear heat transfer that produces the dynamic temperature distribution throughout the weld seam and the plates, and the elasto-plastic analysis, which yields residual stresses.



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