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VIBRATION ANALYSIS FOR CBM
BASIC CONCEPTS – UNIT 1
BY DIBYENDU DE
ALL MACHINES VIBRATE
Because of:
Inertia
Stiffness
Imposed forces
VIBRATION MONITORING
What causes Vibration ?
INDUCED FORCE
&
FREEDOM FOR MOVEMENT
VIBRATION MONITORING
Types of Forces ?
Inertia Forces
Acceleration & Deceleration
Looseness & Impacts
MACHINE VIBRATION IS COMPLEX
• Behaviour of each component creates their
own frequencies
• Frequency tells us about a poss...
ONE CYCLE OF VIBRATION
• Movement of weight from neutral
position to upper limit
• Upper limit back through neutral
positi...
FREE & FORCED VIBRATION
• With sudden impulse the system will
vibrate at its natural frequency
• Free vibrations die out w...
FORCE, MOBILITY & VIBRATION
• Response to forced
vibration is not uniform at
all frequencies.
• Response depends on the
mo...
MEASUREMENT OF AMPLITUDE & FREQUENCY
Peak  for velocity and
acceleration (used for algorithms)
Peak to Peak  Displacemen...
MEASUREMENT OF AMPLITUDE
Peak  for velocity and
acceleration
Peak to Peak  Displacement
RMS  Velocity & acceleration
(E...
DISPLACEMENT, VELOCITY & ACCELERATION
What?
• Displacement = d = x = A sin (wt)
• Velocity = v = dx / dt = Aw cos wt = Aw ...
VIBRATION - CAR ANALOGY
Low Frequency
Long period (T)
High displacement
Average Velocity
Low Acceleration
Medium Frequency...
THANK YOU FOR COMPLETING UNIT 1
CONTACT: FOR FACILITATED TRAINING
DIBYENDU DE, EMAIL ID: DDE337@GMAIL.COM
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Vibration analysis unit1

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This relates to a series of posts on Vibration Analysis. The purpose is education of engineers and managers to effectively improve availability, reliability and performance of their manufacturing plants and improve profitability of their business

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Vibration analysis unit1

  1. 1. VIBRATION ANALYSIS FOR CBM BASIC CONCEPTS – UNIT 1 BY DIBYENDU DE
  2. 2. ALL MACHINES VIBRATE Because of: Inertia Stiffness Imposed forces
  3. 3. VIBRATION MONITORING What causes Vibration ? INDUCED FORCE & FREEDOM FOR MOVEMENT
  4. 4. VIBRATION MONITORING Types of Forces ? Inertia Forces Acceleration & Deceleration Looseness & Impacts
  5. 5. MACHINE VIBRATION IS COMPLEX • Behaviour of each component creates their own frequencies • Frequency tells us about a possible problem. • Amplitude tells us about the severity of the problem. • Multiple frequencies combine to produce the overall vibration • Vibration from 1 Hz to 1000 Hz captures overall amplitude
  6. 6. ONE CYCLE OF VIBRATION • Movement of weight from neutral position to upper limit • Upper limit back through neutral position to lower limit • Lower limit to neutral position • The movement of the weight plotted against time is a sine wave •
  7. 7. FREE & FORCED VIBRATION • With sudden impulse the system will vibrate at its natural frequency • Free vibrations die out with time if the system is stable. (Bump test) • Forced vibration are periodically imposed on the system (like motor). The response is also periodic
  8. 8. FORCE, MOBILITY & VIBRATION • Response to forced vibration is not uniform at all frequencies. • Response depends on the mobility of the structure • Mobility varies with frequencies. High at resonance. Low where damping is present.
  9. 9. MEASUREMENT OF AMPLITUDE & FREQUENCY Peak  for velocity and acceleration (used for algorithms) Peak to Peak  Displacement RMS  Velocity & acceleration (Europe) Energy content (only for sine wave) Average  Not used in vibration analysis Frequency = 1/Period (Hz/CPM)
  10. 10. MEASUREMENT OF AMPLITUDE Peak  for velocity and acceleration Peak to Peak  Displacement RMS  Velocity & acceleration (Europe) Energy content (only for sine wave) Average  Not used in vibration analysis
  11. 11. DISPLACEMENT, VELOCITY & ACCELERATION What? • Displacement = d = x = A sin (wt) • Velocity = v = dx / dt = Aw cos wt = Aw sin (wt + 90o) • Acceleration = a = dv /dt = - Aw2 sin wt = Aw2 sin (wt + 180o) Why? • Strain Energy ∝ to d2 • Kinetic Energy ∝ to v2 • Acoustic Pressure ∝ to a2 • Force
  12. 12. VIBRATION - CAR ANALOGY Low Frequency Long period (T) High displacement Average Velocity Low Acceleration Medium Frequency Medium period (T) Average displacement Average Velocity Average Acceleration High Frequency Short period (T) Low displacement Average Velocity High Acceleration
  13. 13. THANK YOU FOR COMPLETING UNIT 1 CONTACT: FOR FACILITATED TRAINING DIBYENDU DE, EMAIL ID: DDE337@GMAIL.COM

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