Experimentelle Modalanalyse  

The goal of an Experimental Modal Analysis is determination of a structure's dynamic characteristics. These characteristics are described by it's natural modes.

A natural mode is determined by its frequency, mode shape and damping coefficient. These dynamic parameters are determined through mass, stiffness and damping capacity of the structure. Mass and stiffness parameters being known, the structural natural frequencies and mode shapes can be also determined analytically. It is not possible to analytically determine a structure's damping capacity.

This means: Damping can be determined experimentally only. And: Mass is relatively easy to be determined. However: This does not apply to stiffness. No big problems arise as long as we are talking of a beam's bending or torsional stiffness. The core problem are the boundary conditions. Small mistakes with the boundary conditions result in large mistakes in the system stiffness properties and hence in the dynamic parameters. Just one example: Is "clamped-in" really clamped-in??

Therefore, experimental validation is looked for in all cases where the mass, stiffness and, above all, the damping properties of  a structure are important to reliably be known. 

 Next site