o. d. s. page
operational deflection shape analysis
you might be familiar with "modal analysis". this is the study of the"mode shapes" of a structure. a mode shape is the what the structure looks like while it's "ringing" at one of its resonant frequencies. in modal analysis, we first construct a wire frame model, instrument significant points with vibration sensors, and hit the structure so that it rings.
an operational deflection shape is developed the same way that a mode shape is, except that the source of the vibration is not the structure's natural resonance, but the forces that act on the structure under some operational condition. thus, an operational deflection shape is a collection of vibration amplitudes and phases at various points and directions on the structure.
using computer software, the wire frame model can be animated using the experimental data to show a "movie" of the actual movement at a particular frequency. this can be a very powerful diagnostic tool in machinery vibration analysis.
the links below will show you some examples.note that while the models are to scale geometrically, the motions, while at a common scale, are exaggerated so as to be visible.
a press section of a paper machine
laying head in a wire mill
combustion turbine load gear
back to vanguard's home page
updated: january 2, 1998