Equivalence Between Loss Factor, Rayleigh, and Viscous Damping
In frequency domain, it is possible to use Rayleigh damping in order to specify an equivalent viscous damping. Set the stiffness damping parameter βdK, to the loss factor, η, divided by the excitation frequency:
The mass damping factor, αdM, should be set to zero.
If, on the other hand, you would want to use a viscous damping, corresponding to a certain Rayleigh stiffness damping, the conversion to bulk and shear viscosity can be made using the expressions
where K and G are the bulk and shear moduli, respectively. Equivalently, you can transform between loss factor damping and viscous damping,