Operational vibration analysis
The operational vibration analysis is used to determine the operational vibration form of components, i.e. H. their vibration behavior in a certain operating state. In contrast to the modal analysis , in which the possible natural frequencies of structures are examined independently of the actual operational excitation, the type of excitation plays an essential role in the operational vibration analysis .
To determine the operational vibration form, the vibration of the structure is measured at a large number of points during operation (displacement, speed or acceleration sensors). As with the modal analysis, it must be ensured that the phase relationships between the measurement signals are recorded. This can be achieved in that all measuring points are recorded at the same time. If this is not possible, the excitation signal must be reproduced exactly and a reference signal must always be measured. The amplitudes occurring at the various measuring points are now displayed. This can be done either for the unfiltered signals or for individual frequency bands or frequencies.
One example is the representation of the vibration accelerations on the surface of a vehicle when excited by uneven road surfaces. Such a static representation with acceleration levels can no longer recognize the phase position of the signals with one another, but allows a quick overview of the amplitude distribution on the structure.
In the last few years, the technique of laser scanning vibrometry for determining the operational waveform has become more and more popular. A laser beam is guided through special optics over the structure to be measured, which measures the vibration velocity in the direction of the laser beam by means of laser Doppler vibrometry (LDV) . With a single laser it is therefore only possible to detect the vibration in one direction. This technique is therefore used particularly often for the operational vibration analysis of sheet metal structures, in which mostly only the vibration amplitude perpendicular to the sheet metal surface is of interest. However, systems for 3D laser scanning vibrometry are also in use that use three lasers to display the spatial movement of a structure.
literature
- F. Moser, M. Fischer, W. Rumold: Three-dimensional measurement of operational deflection shapes of squeaking disc brakes . VDI reports no. 2002, 1736, pp. 71-83.
- C. Ropers, E.-U. Saemann, F. Gauterin: Hybrid method for determining the operating vibrations of tires. In: DAGA 03 conference proceedings (progress in acoustics). German Society for Acoustics, Oldenburg 2003, ISBN 3-9808659-0-8 , pp. 302–303