What is the Damping ?

• Damping is a dissipation of energy from a vibrating structure. The term dissipate is used to mean the transformation of mechanical energy into other form of energy and, therefore, a removal of mechanical energy from the vibrating system. or
• Damping is restraining of vibratory motion, such as mechanical oscillations or noise by dissipation of energy. In vibrating systems, the effect of friction is referred to as damping.

There are many types of Mechanical damping.

##Types of Damping :

1. Viscous damping.

2. Coulomb or Dry Friction Damping.

3. Solid or Structural Damping or Material or Hysteretic Damping.

4. Slip or Intrefacial damping

5. Magnetic Damping.

1.Viscous Damping

The damping provided by fluid resistance is known as viscous damping. It is encountered by bodies moving at moderate speed through fluid medium like: air, gas, water or oil. This is the most commonly used damping mechanism to reduce the amplitude of vibrations. This type of damping leads to a resisting force proportional to the Relative velocity of vibrating body. The damping force- Fd ∝ dx/dt Fd = cx 'c' is the constant of proportionality and is called viscous damping Co-eff. With the dimension of N-S/m

Fluid Dashpot Damping

•A dashpot is a mechanical device, a damper which resists motion via viscous friction.

• The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing encrgy. It is commonly uscd in conjunction with a spring (which acts to resist displacement).

Applications

• Door closer.

• Dampers and shock absorbers.

• Automobile shock absorber.

• Large forces and high speeds can be controlled by dashpots. For example, aircraft carrier decks.

2.Colomb Damping or Dry Friction Damping

This type of damping arises from sliding of dry surfaces. The friction force is nearly constant and depends upon the nature of sliding surface and normal pressure between them as expressed by the equation of kinetic friction

F= µN

Friction Where,

u =co-eff of friction

N= normal force (a)

3.Solid or structural Damping or Hysteretic Damping

This is due to internal friction within the material itself. The damping caused by the friction between the internal planes that slip or slide as the material deforms is called hysteresis (or solid or structural) damping. The stress strain diagram for vibrating body is not straight line but forms hysteresis loop, the area of which represents energy dissipated to molecular friction per cycle per unit volume.

4.Slip or Intrefacial damping

Energy of vibration is dissipated by microscopic slip on the interfaces of machine parts in contact under fluctuating loads. Microscopic slip also occurs on the interface of the machine elements having various types of joints. The amount of damping depends upon the surface roughness of a mating parts, the contact pressure and amplitude of vibration.

5.Magnetic Damping

A phenomenon that has been observed for many years by which vibrating, oscillating or rotating conductors are slowly be brought to rest in the presence of a magnetic field. Damping due to eddy currents selup by the movement of a system in a magnetic field.