Operating Deflection Shape Analysis – The Dynamic Shape Of The Structure

Operating deflection shape analysis is used to determine the shape at which a structure vibrates. From these shapes it is possible to learn about the vibration characteristics of the structure, and then find strategies to reduce the vibration level.

The measurement procedure uses a reference accelerometer and roving response accelerometers. The relative amplitude and phase is calculated for each of the response accelerometer locations with respect to the reference accelerometer. This relative amplitude and phase is animated on a stick figure of the structure.

In general the frequency animated is between resonances and is a combination of modes shapes.  When the structure is excited by a random excitation source such as turbulence generated by wind or tire noise, the response spectra peaks will be at resonance and the  shape at these frequencies are a good representation of the mode shape.