Modal analysis

The modal analysis includes experimental and numerical characterization of the dynamic behavior of oscillatory systems using their natural oscillation parameters ( modal parameters ) natural frequency, mode shape, modal mass and modal damping. The vibration behavior in a given operational condition is, however, detected by the vibration analysis operation.

Mechanics / Acoustics

Much like a tuning fork with a certain frequency vibrates when it is struck, and other objects, such as in the art may be placed in their natural oscillations. The case, for example, excited in bridges, oil rigs, motor housings or aircraft wings natural vibration sizes provide global system properties out its knowledge allows a simple description and calculation of dynamic system behavior.

To determine the modal parameters to be investigated structure with a suitable excitation source ( pulse hammer, electrodynamic or hydraulic shaker ) is excited, the excitation force is usually measured with a piezoelectric force transducer. At the same time structural responses with accelerometers or laser vibrometers be detected. The frequency responses between excitation and response ( see also response spectrum ) then be fast- Fourier transforms calculated.

With common software packages, the eigenmodes of the system studied can be graphically animated pose. Mission-critical or unfavorable acoustic mode shapes of the structure can be discovered. Targeted changes in system properties, such as the material damping or additional Aussteifungssmaßnahmen, these can be changed so that critical frequency ranges can be avoided or passed through with reduced amplitude.

In the modal analysis is an experimental, analytical method of engineering science that is often used for the validation of numerical methods (FEM, also in connection with BEM).

As most spectacular example of a component failure due to extreme natural oscillations applies the Tacoma Narrows Bridge Disaster.

Electrodynamics

Another application of modal analysis is to determine which electromagnetic waves propagate in a medium, which is bounded by conductive structures of arbitrary geometry (eg waveguide, TEM - cell). Often, the propagation of a plane wave is desired, but the geometry allows the formation of other waves having electric or magnetic component in the propagation direction as well as by waves whose frequency is an integer multiple.