Could someone explain undulation per revolution?

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SUMMARY

Undulation per revolution refers to the deviations in a rotating component's surface caused by factors such as mass imbalance, concentricity, or roundness. A mass imbalance results in variations in momentum, leading to vibrations during rotation. Concentricity issues occur when the center of a round part does not align with the rotating axis, typically producing one undulation per revolution. In contrast, if a part's surface is out-of-round, it can exhibit multiple deviations, resulting in more than one undulation per full revolution.

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  • Knowledge of mass imbalance effects
  • Familiarity with concentricity and roundness concepts
  • Basic mathematical functions related to vibration analysis
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  • Explore the effects of mass imbalance on vibration in rotating machinery
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Mechanical engineers, vibration analysts, and anyone involved in the design or maintenance of rotating machinery will benefit from this discussion.

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Could someone explain undulation per revolution? I would prefer to have a mathematical function defining it also if possible. Can any explain ONE also?

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Are you referring to a 1 per rev imbalance in a rotating component?
 
Perhaps one needs to distiguish between an undulation caused by - mass imbalance, or deviation in concentricity or roundness - any of which can result in the deviation (undulation) of a component's surface.

Mass imbalance implies a variation in momentum that would cause a part to vibrate during rotation. Similarly concentricity, in which the center (central axis) of a round part is not coincident with the rotating axis, e.g. the axis of a shaft. Now normally, this would like produced one undulation/rotation.

If a part's surface is out-of-round, it could have more than one deviation (from roundness) on the circumference and thus one would measure more than one undulation per full revolution.
 
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