FEM is the abbreviation for "Finite-Element-Method".
Within the calculation of components according to conventional methods, so-called calculations by hand, the problem arises that analytic solutions exist only for simple components such as slabs or beams. Due to more modern manufacturing options, e.g. injection moulding or die casting, components become even more complex and corresponding solutions can no longer be found. Looking at a simple component such as the housing of a handy, calculation by hand already cannot offer reasonable results.
The Finite-Element-Method aims at analysing complex components by an approximation procedure. Looking at any component, flow channel or an aerial field , there is an infinite quantity of spots offering the calculation of results. Moreover, there is an infinite quantity of time steps in time-dependent solutions which can be analyzed. As „indefinite“ means an indefinite number of data, data volume must be reduced by choosing a finite number of spots and time steps being representative for the component’s behaviour.
The effects of this rough discretization of space and time influence strongly the results. The chosen spots are called vertices. The distance between two vertices is called edge length. The vertices form the so-called elements which are simple geometrical bodies (hexahedron, pentahedron, tetrahedron...).
The selected times are referred to as time points. The distance between two time points is called time step. The edge length can vary over the model in the same way as the time step over total time. Explosions occuring in a range of milliseconds are almost as impossible to describe in a time interval of 1 second as notch stress effects with only one element in the notch.
Selection of the right discretization and the right time steps for the calculation objective characterize qualified FEM specialists. In an Excel spreadsheet, three co-workers get the same result. In a FEM computation, three co-workers get three results. However, experienced FEM specialists draw the same conclusions from the different results.