In the present study, the residual stresses distribution in the Linear Friction Welded (LFW) pieces were studied using Finite Element (FE) simulation and high energy synchrotron X-ray diffraction. Fully-coupled implicit thermo-mechanical analysis simulation procedure was employed, with semi-automatic re-meshing using Python scripting to accommodate large deformation and output contour tracking methods for extracting deformed configurations. Model validated by the multi-detector polychromatic synchrotron X-ray experimental data were used to study the distribution of residual stresses distribution in the Linear Friction Welded (LFW) pieces to provide a general function to describe the residual stresses distribution. A characteristic length scale was found in the plot.