Viscous Damping Ratios
|
System (a)
|
Viscous Damping Ratio z (b)
|
|
Metals (in elastic range)
|
less than 0.01
|
|
Continuous metal structures
|
0.02 - 0.04
|
|
Metal structures with joints
|
0.03 - 0.07
|
|
Aluminum / steel transmission lines
|
~ 0.04
|
|
Small diameter piping systems
|
0.01 - 0.02
|
|
Large diameter piping systems
|
0.02 -0.03
|
|
Auto shock absorbers
|
~ 0.30
|
|
Rubber
|
0.05
|
|
Large buildings during earthquake
|
0.01 - 0.05
|
|
Prestressed concrete structures
|
0.02 -0.05
|
|
Reinforced concrete structures
|
0.04 -0.07
|
(a) The data are taken from: Vince Adams and Abraham Askenazi, Building Better Products with Finite Element Analysis, OnWord Press, Santa Fe, NM.
(b) The viscous damping ratios are given as percentages of critical damping.
|
Material
|
Viscous Damping Ratio z (under approximately 20o C) (c)
|
|
Aluminum
|
~ 0.5 10-4
|
|
Lead (pure)
|
~ 10-2
|
|
Iron
|
1 to 3 10-4
|
|
Copper (polycrystalline)
|
10-3
|
|
Magnesium
|
~ 0.5 10-4
|
|
Brass
|
< 0.5 10-3
|
|
Nickel
|
< 0.5 10-3
|
|
Silver
|
< 1.5 10-3
|
|
Bismuth
|
~ 4 10-4
|
|
Zinc
|
~ 1.5 10-4
|
|
Tin
|
~ 10 10-4
|
(c) The viscous damping ratios are obtained by dividing by 2 the flexural loss factors of the materials given in: L.Cremer and M. Heckl, Stucture-Borne Sound, Springer-Verlag, New York, 1988.