Viewing Operational Deflection Shapes (ODS) from a Gas Turbine Generator

As its name suggests Operational Deflection Shape analysis shows the vibration pattern experienced during normal operational condition. This is different to other structural vibration tests such as impact hammer tests, bump tests or shaker tests which require a more controlled excitation force and are used to determine specific characteristics of the structure under test, such as natural or resonant frequencies.

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What Is Resonance?

We hear the word used a lot, but what is resonance? First, in order to explain we have to explain the terms we will use.

  • A period is the amount of time it takes to complete one cycle
  • The number of cycles in one second is the frequency of an oscillation.
  • Frequency is measured in Hertz, named after the 19th-century German physicist Heinrich Rudolf Hertz
  • One Hertz is equal to one cycle per second.

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