01 Beginning Vibration Analysis
Beginning Vibration
Analysis
with
Basic Fundamentals
By: Jack Peters
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
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
Mass & Stiffness
Mass & Stiffness fn = 1/2П k/m
Where:
fn = natural frequency (Hz) k = stiffness (lb/in) m = mass mass = weight/gravity weight (lb) gravity (386.1 in/sec2)
Jack D. Peters
4
Mass & Stiffness
Concept ! fn = 1/2П k/m
If k increases
Then f increases
If k decreases
Then f decreases
Jack D. Peters
5
Mass & Stiffness
Concept ! fn = 1/2П k/m
If m increases
Then f decreases
If m decreases
Then f increases
Jack D. Peters
6
Spectrum
What’s This ?
1
0.0002 inch Peak
Magnitude
0
0 Hz
Jack D. Peters
100 Hz
7
Spectrum
FFT, Frequency Spectrum, Power Spectrum
1
0.0002 inch Peak
Magnitude
0
0 Hz
Jack D. Peters
100 Hz
8
Spectrum
Scaling X & Y
1
0.0002 inch Peak
Y
Magnitude
0
0 Hz
100 Hz
X
Jack D. Peters
9
Spectrum
Scaling X & Y
A
M
1
0.0002
inch
Peak
P
L
I
Magnitude
T
U
D
E
Jack D. Peters
0
0 Hz
100 Hz
FREQUENCY
10
Spectrum
Scaling X & Y
1
H o w
B
a d 0.0002 inch Peak
Magnitude
Analysis
with
Basic Fundamentals
By: Jack Peters
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
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
Mass & Stiffness
Mass & Stiffness fn = 1/2П k/m
Where:
fn = natural frequency (Hz) k = stiffness (lb/in) m = mass mass = weight/gravity weight (lb) gravity (386.1 in/sec2)
Jack D. Peters
4
Mass & Stiffness
Concept ! fn = 1/2П k/m
If k increases
Then f increases
If k decreases
Then f decreases
Jack D. Peters
5
Mass & Stiffness
Concept ! fn = 1/2П k/m
If m increases
Then f decreases
If m decreases
Then f increases
Jack D. Peters
6
Spectrum
What’s This ?
1
0.0002 inch Peak
Magnitude
0
0 Hz
Jack D. Peters
100 Hz
7
Spectrum
FFT, Frequency Spectrum, Power Spectrum
1
0.0002 inch Peak
Magnitude
0
0 Hz
Jack D. Peters
100 Hz
8
Spectrum
Scaling X & Y
1
0.0002 inch Peak
Y
Magnitude
0
0 Hz
100 Hz
X
Jack D. Peters
9
Spectrum
Scaling X & Y
A
M
1
0.0002
inch
Peak
P
L
I
Magnitude
T
U
D
E
Jack D. Peters
0
0 Hz
100 Hz
FREQUENCY
10
Spectrum
Scaling X & Y
1
H o w
B
a d 0.0002 inch Peak
Magnitude