This study presents the finite element analysis of the weld joints used in the off-highway vehicles. A coupled field thermal and static analysis is performed to find the residual stresses in weld and its effect on the fatigue life of the double plate full penetration weld joint. The Design of Experiments approach, via Response Surface Methodology (RSM), is used considering the influence of the parameters like Plate Thickness, Load and Prep angle on the fatigue life. The central composite design, a model in RSM is used to minimize the number of simulations. The Analysis of Variance (ANOVA) is carried out to find the influences of Plate Thickness, Load and Prep angle on the fatigue life. The Regression Equation, obtained through ANOVA, helps to understand the influences of parameters on fatigue life. Later the regression equation is validated with finite element results. The Optimization study is carried out to find optimized parameters for maximum fatigue life. Confirmation simulation using finite element analysis reveals the integrity of optimization study. © 2021, Politechnica University of Bucharest. All rights reserved.