Finite element analysis (FEA)

Finite element analysis (FEA) is a numerical calculation based on the finite element method (FEM) that approximately solves physical problems on bodies of complex shape. In mechanical engineering it is used mainly to calculate stresses, deformations, temperature fields and natural frequencies of parts and assemblies where a hand calculation would be impossible or oversimplified.

How it works: the geometry from the CAD model is divided into a mesh of a finite number of simple elements connected at nodes. Within each element, the displacement field is approximated by a simple function, and all elements are assembled into one system of equations. Once the material, supports and loads are defined, the solver computes the nodal displacements and derives stresses and strains from them. A finer mesh usually gives a more accurate result but takes longer to solve.

The element type follows the shape of the part: beam elements for beams and frames, shell elements for sheet metal and thin-walled parts, and solid elements (tetrahedra and hexahedra) for bulky parts. Linear static analysis is the most common type. Others include natural frequencies (modal analysis), buckling of columns and plates, nonlinear problems with plasticity, large deformations or contact, heat transfer and dynamic response.

Most CAD systems now include a simulation module (SolidWorks Simulation, for example), while demanding problems go to dedicated software such as ANSYS, Abaqus or Nastran. The result is always just a model of reality: its accuracy depends on the boundary conditions, mesh quality and material data, not on how convincing the color plot looks.

FEA makes sense for parts with complex geometry, parts critical to safety or function, and anywhere you want to save weight and material: frames, brackets, weldments, castings, ribbed plastic housings, mounts, jigs and fixtures. It reveals stress concentrations, lets you compare design variants before a prototype is built and reduces the number of physical iterations.

For simple elements (a pin, a bolt, a simply supported beam), a hand calculation based on standards or engineering handbooks is often faster and more reliable. FEA then serves mainly to check details that the formulas do not cover.

The most common mistake is unrealistic boundary conditions. A perfectly rigid fixed support, a force applied at a single point or a sharp internal corner creates a singularity, where the stress keeps rising as the mesh is refined and its value has no physical meaning. Evaluate results away from these spots, refine the mesh until the values you monitor stop changing (convergence), and in thin walls use shell elements or at least two to three quadratic elements through the thickness.

A linear analysis assumes a linear elastic material. Stresses above the yield strength in a linear analysis do not reflect reality and call for a nonlinear analysis or a design change. For plastics and 3D-printed parts, datasheet values often do not apply because of anisotropy, temperature effects and creep. Check the results against a hand estimate or a test, and ask whoever runs the analysis for a report that documents the loads, supports, mesh and assumptions.