Step (4): Assembling the element equations to obtain the overall equilibrium equations. Since the structure is composed of several finite elements, the stiffness matrices of the individual elements and the load vectors must be assembled and the overall balance equations must be formulated as step (5): The solution for the unknown nodal displacements On changing the boundary condition of the problem all equilibrium conditions must be maintained. After implementing the boundary conditions, the equilibrium equations can be expressed as step (6): Post-processing the results. The gradient of the solution or other desired quantities are calculated from the primary variables which are calculated in step (5). The results are represented in table or graph form. 4.4. The FEM formulation Figure 4.1 Infinitesimal element showing the stress state [28]. The FEM formulation is explained briefly in the following in the context of solid mechanics problems. Suppose that an isotropic elastic material is subjected to a force F as shown in Fig...4.1.