Types of Damping

Viscous Damping

It is encountered by bodies moving at moderate speed through liquid. This type of damping leads to a resisting force proportional to the velocity. 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

Colomb 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

Where µ =co-eff of friction

N = normal force

Solid or structural Damping

This is due to internal friction within the material itself.Experiment indicates that the solid damping differs from viscous damping in that it is independent of frequency and proportional to maximum stress of vibration cycle.

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. This type is essentially of a linear type.