Regardless of the welding method, a new joint and the surrounding area are inevitably subjected to thermo-physical perturbation. The paper presents analyses of many different issues involved in welding and potential solutions including adoption of simplifying assumptions, application of numerical algorithms and development of reliable representative models. The Finite Element Method is used to determine residual stress distribution, using results from thermo-physical tests and widely known mechanical properties of metals subjected to welding processes. Experimental and numerical methods for determining residual stress are compared for welds generated using both TIG (Tungsten Inert Gas, Gas Tungsten Arc Welding) and a laser beam. This data reveals that it is necessary to precisely define location of the analyzed welded fragment to correctly determine thermal boundary conditions.