Mechanical vibrations

1. Mechanical vibrations

MECHANICAL
VIBRATIONS
Free vibration damped system
PRESNED TO :
Eng. Mohamed Shahata

2. PRESNTED BY

1- Hossam Hamdy

3. Contents

CONTENTS
1- Introduction
2- Definition of damping
3- Types of damping
4- Example
5- Application
6- Review
7- Measurement
8- Summary
9- References

4.

Every object, every particle and every system
oscillates in its own natural frequency or set of
frequencies.
what does natural Frequency mean…??

5. Damped Oscillations

DAMPED OSCILLATIONS
Amplitude goes on decreasing with time.

6. Types of Damping Oscillations

TYPES OF DAMPING
OSCILLATIONS
Over-damped
Critically damped
Under damped

7.

TYPES OF DAMPING OSCILLATIONS
Stringed instruments “Under-damped”
Gun “Critical”
Toilet flush button “Over-damped”

8. Types of damping

TYPES OF DAMPING
1- Material damping
(internal friction, mechanical hysteresis)
2- Friction at joints
3- Added layers of materials with high loss factors
(e.g. viscoelastic materials)
4- Hydraulic dampers (shock absorbers, hydromounts)
5- Air/oil pumping: squeeze-film damping

9. Types of damping

TYPES OF DAMPING
1- Material damping
(internal friction, mechanical hysteresis)
2- Friction at joints
3- Added layers of materials with high loss factors
(e.g. viscoelastic materials)
4- Hydraulic dampers (shock absorbers, hydromounts)
5- Air/oil pumping: squeeze-film damping

10. Hydraulic dampers

HYDRAULIC DAMPERS
Used for bridges, buildings and cars to absorb the impact from the
bumps and earthquakes.
In Bridges
In Buildings

11.

Hydro-mounts in car
Shock absorber in car

12. Review of Damping Mechanisms

REVIEW OF DAMPING
MECHANISMS
x
The equation of motion is
mx cx kx 0
inertia force
damping force
stiffness force

13. Free vibration effect of damping

FREE VIBRATION EFFECT OF
DAMPING
The under-damped displacement of the mass is given by

14.

Free vibration effect of damping

15.

16. References

REFERENCES
http://www.differencebetween.net/technology/difference-between-damped-andundamped-oscillations/#ixzz6809aeCmN
http://www.differencebetween.net/technology/difference-between-damped-andundamped-oscillations/#ixzz680BORYIN
http://www.differencebetween.net/technology/difference-between-damped-andundamped-oscillations/#ixzz680GFHgHg
https://www.youtube.com/watch?v=ZelrMxj7X0&list=PLdGICjKjvr_PxHrwtfTlleXz6WlybfzQt&index=7
https://www.quora.com
https://www.physicsforums.com

17.

Thanks
for your time