Finite element method (FEM) has been used to find out the fundamental reason of shape function due to the nonconvergence of stress in calculating the trapezoidal tooth dovetail attachments of aeroengine. We have used two different methods, representing actual models, for the calculation of contact stress. Comparative analysis of these methods, and the already reported ones, led us to conclude that the displacement extraction method is better and efficient for the engineering applications. This method was successively applied to contact model of indenter with shaped edge, a model with an inclined contact surface and dovetail attachment model, while these stress results are compared with that of photoelastic. Moreover, we found that the photoelastic and displacement error in extraction method is small and the method can be widely used for the calculation of structural stress with sharp edge.