You can use damping to model the energy loss in a nonconservative
system.
There are two basic types of damping: material damping and modal
damping. This Damping feature should be used to configure modal
damping, but material damping must be chosen in the step configuration—see About Harmonic Response Steps and About Modal Dynamic Steps.
Damping is a step-dependent action; it is available only for harmonic response
steps and modal (linear) dynamic steps.