However, the introduction of any sharp corner into a model will lead to a stress singularity at that location. It is common to omit small details like fillet radii from a finite element model to simplify the analysis and to keep the model size reasonable. If the exact stress in this location is required, the fillet between the components must be modeled accurately and the stiffness of the parent structure must also be considered. In reality there probably will be a small fillet between the lug and the parent structure, and the parent structure will be deformable, not rigid. These idealizations lead to the stress singularity. The connection between the lug and the parent structure has been modeled as a sharp corner, and the parent structure has been modeled as rigid. This singularity occurs because of the idealizations used in the finite element model. Theoretically the stress is infinite at this location therefore, increasing the mesh density will not produce a converged stress value at this location. A stress singularity exists at the corner of the lug where it attaches to the parent structure.
Mesh refinement significantly changes the stress calculated at the attachment of the connecting lug it continues to increase with continued mesh refinement. The peak stress at the bottom inner surface of the hole converges much more slowly than the displacements because stress and strain are calculated from the displacement gradients thus, a much finer mesh is required to predict accurate displacement gradients than is needed to calculate accurate displacements. The normal mesh is, therefore, converged as far as the displacements are concerned. The coarse mesh predicts less accurate displacements at the bottom inner surface of hole, but the normal, fine, and very fine meshes all predict similar results. Max Von Mises stress at bottom inner surface of hole (N/mm2) Max displacement at bottom inner surface of hole (mm) The results for each of the four mesh densities are compared in the table below. The peak von Mises stress where the lug is attached to the parent structure.