Visualizing Structural Vibrations Using Stroboscopic Light in a Novel Setup

Abstract

The visualization of structural vibrations has always been a key technology when teaching vibration analysis. If the structural motion can be perceived directly without numerical simulation or extensive measurements, basic modal analysis concepts like mode shapes, natural frequencies or resonances and anti-resonances are intuitively understood. The application of stroboscopes has a long tradition in vibration analysis and is particularly well established in rotor dynamics. Nevertheless a cheap and simple to use device for the visualization of larger structures like e.g. car wings was missing. The application of several arrays of white light high power light emitting diodes together with a power electronic circuit resulted in an innovative and highly flexible distributed light source perfectly suited to visualize resonant vibrations of flexible structures in the mid frequency range. Furthermore, the effect of aliasing is demonstrated convincingly and the results can be compared qualitatively to experimental modal analysis. In combination with an electrodynamic shaker the setup has been applied successfully to visualize vibrations of parts of car bodies, tennis rackets, skis, piano or cello strings as well as plate and shell structures.