# Finite Element Mesh Coarsening

Modern structures typically have complex geometries which can require hundreds of thousands of degrees of freedom (DOF). Even relatively simple structures may have bolted or welded connections between members which can be difficult to model without resorting to a fine FE mesh. The computational burden involved in analyzing a model of such large order can be significant. Most FE models make simplifying assumptions about the geometry and connections of a structure in order to keep the order of the model computationally manageable or because the type of simulation only requires a coarse model. For example, the fine density in acoustic analysis is determined from the frequency range of interest.

In many cases the level of detail can be significantly reduced if equivalent properties are used for the remaining elements. These are values assigned to physical properties (for example element thickness or spring stiffness) so that they provide the mass and stiffness of the corresponding detailed structured.

FE model updating can be used as a method to modify the properties of elements in a coarse mesh to become equivalent properties. In this case, the detailed model or test data serve as reference data.