Users may wish to include a 1D spring/damper with frequency-dependent stiffness or damping values.  One could use COMBI214 with frequency-dependent values.  Although the frequency-dependent values refer to the spin velocity (tables with OMEGS independent variable), one could use a trick where only the COMBI214 elements are in an element component which has rotational velocity (CMOMEGA) applied.  In this way, the spring’s frequency-dependent stiffness and damping get activated.

Below is a simple Mechanical APDL input with a single DOF system.  Usually, a single DOF model would only show 1 frequency.  However, with the frequency-dependent stiffness and damping, 3 peaks are shown.

FREQ1 = 10
FREQ2 = 20
FREQ3 = 30

MASS1 = 10

OMEG1 = 2*acos(-1)*FREQ1
OMEG2 = 2*acos(-1)*FREQ2
OMEG3 = 2*acos(-1)*FREQ3

STIF1 = MASS1*OMEG1**2
STIF2 = MASS1*OMEG2**2
STIF3 = MASS1*OMEG3**2

DAMP1 = 10
DAMP2 = 1
DAMP3 = 1

*dim,TBL_STIF,table,3,,,OMEGS
TBL_STIF(1,0)=OMEG1,OMEG2,OMEG3
TBL_STIF(1,1)=STIF1,STIF2,STIF3

*dim,TBL_DAMP,table,3,,,OMEGS
TBL_DAMP(1,0)=OMEG1,OMEG2,OMEG3
TBL_DAMP(1,1)=DAMP1,DAMP2,DAMP3

/prep7
et,1,21,,,4
et,2,214,,0,0
r,1,MASS1
r,2,%TBL_STIF%,%TBL_STIF%
rmodif,2,5,%TBL_DAMP%,%TBL_DAMP%

n,1
n,2

! *** mass21
type,1
real,1
mat,1
e,2

! *** combi214
type,2
real,2
mat ,2
e,1,2

esel,s,elem,,2
cm,SPRING,elem

d,1,ux
d,all,uy
f,2,fx,1

allsel,all
finish

/solu
antype,harmic
hropt,full

*do,AR99,2,40,2
 harfrq,0,AR99
 nsubst,1
 kbc,1

 coriolis,on,,,on
 ! *** need omega to match 2*pi*freq
 cmomega,SPRING,2*acos(-1)*AR99

 solve
*enddo

finish

/post26
numvar,200
nsol,2,2,u,x
plvar,2