01-Beginning Vibration Analysis.pdf

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Beginning Vibration
Analysis
with
Basic Fundamentals
By: Jack Peters
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Beginning Vibration
Introduction
Understanding the basics and fundamentals of vibration analysis are
very important in forming a solid background to analyze problems on
rotating machinery.
Switching between time and frequency is a common tool used for
analysis. Because the frequency spectrum is derived from the data in
the time domain, the relationship between time and frequency is very
important. Units of acceleration, velocity, and displacement are
typical. Additional terms such as peak-peak, peak, and rms. are often
used. Switching units correctly, and keeping terms straight is a must.
As much as possible, this training will follow the criteria as established
by the Vibration Institute.
Jack D. Peters
2
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Mass & Stiffness
Mass & Stiffness
All machines can be broken down
into two specific categories.
Mass & Stiffness
Mass is represented by an object
that wants to move or rotate.
Stiffness is represented by springs
or constraints of that movement.
Jack D. Peters
3
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Mass & Stiffness
Mass & Stiffness
f n
= 1 / 2 П k/m
Where:
f n = natural frequency (Hz)
k = stiffness (lb/in)
m = mass
mass = weight/gravity
weight (lb)
gravity (386.1 in/sec 2 )
Jack D. Peters
4
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Mass & Stiffness
Concept !
f n
= 1 / 2 П k/m
If k increases
Then f increases
If k decreases
Then f decreases
Jack D. Peters
5
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