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# Composite Modal Damping solidworks simulation

Composite modal damping allows the definition of the damping as a material property. Material damping ratio MDAMP is defined in the Properties tab of the Material dialog box. The program uses this property to calculate equivalent modal damping ratio for each mode.

The composite modal damping is defined in terms of equivalent modal damping ratios as:

If you specify material damping ratio MDAMP to be m for all materials in the model, the equivalent modal damping ratio will be m for all modes.

## Viscous Damping Ratios for Different Systems and Materials

System Viscous Damping Ratio ζ (as percentages of critical damping)
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
The data above are taken from: Vince Adams and Abraham Askenazi, Building Better Products with Finite Element Analysis, OnWord Press, Santa Fe, NM.
Material Viscous Damping Ratio ζ (under approximately 20 ºC)
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
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.