Vibration Analysis - Investigating The Dynamic Behavior Of A Structure

The amplitude of machine vibration is a reliable indicator of the damage sustained. With higher levels of vibration, the resulting forces increase the fatigue-related damage to the structure and result in premature failure of bearings and other components.

Excessive and transient vibrations can have a multitude of sources. The most common sources are unbalance, misalignment, eccentricity, faulty bearings, gear damage and bent shafts.

Resonance will amplify the effect of any of these sources. In some instances, there can be self-excited vibration present, which can build up quickly or slowly, sometimes taking many years.

Techniques to determine the source of the problem include:

• measuring vibration simultaneously with rotation (synchronous time averaging)
• phase and amplitude measurements on machine trains
• spectral mapping to relate vibration amplitude and phase to machine speed - a powerful method to determine the critical frequencies of the system
• measuring vibrations and comparing them to recognized standards
• frequency or order display of the mapping results
• operating deflection shape analysis
• modal analysis
• transient vibration (speed sweep) analysis
• measuring acoustic intensity and noise path transmission
• hand-arm vibration severity indexing
• strain gauge analysis to measure durability and fatigue of  materials /structure
  
• durability and fatigue on rotating shafts using telemetry
  

These measurement techniques are invaluable to determine the source of an excessive or transient vibration problem.