If somebody tells you that I’ve got a SDOF system with mass m, stiffness k, and damping of 5%, you’d interpret that to mean the damping ratio is 5%, right?
Squink
January 29, 2009, 3:02am
2
I can’t answer, but I did wonder what you were asking:
SDOF = Single degree of freedom.
http://www.efunda.com/formulae/vibrations/sdof_free_damped.cfm
MikeS
January 29, 2009, 1:22pm
3
Snarky_Kong:
If somebody tells you that I’ve got a SDOF system with mass m, stiffness k, and damping of 5%, you’d interpret that to mean the damping ratio is 5%, right?
I would guess so. It can’t be the damping coefficient itself, since it would have to have units, and the only other dimensionless number associated with damped harmonic systems is the quality factor.
zut
January 29, 2009, 1:55pm
4
“Percent damping” is really “percent of critical damping,” which is how damping ratio is defined.
USGS Earthquake Hazards Program :
Viscoelestic damping article
The classic complimentary solution to the transient, free vibration response of [a SDOF system] yields the analytical representation of viscous damping as the damping ratio, [symbol]z[/symbol] [where [symbol]z[/symbol] = c/c[sub]o[/sub]]. The term c[sub]o[/sub] is the critical viscous damping coefficient. The critical damping for a system is defined as the smallest level of viscous damping in which the mass [in a SDOF system] will exhibit no oscillation when displaced from equilibrium. The damping ratio is often presented as a percentage of the fraction of critical damping or percent critical damping , %Cr.