Learning Forum

[Emiliano Maldonado]

Hi everyone,

I am trying to carry out a harmonic analysis of a structure using frequency dependent springs. For doing so, my plan is to write a script in workbench to use the COMBIN14, and the *DIM command.

Could anybody let me know how to include the *DIM script within COMBIN14?

I can write the scripts for both of the commands separately, but I cannot make them work together.

Thanks in advance for your help.

[Erik Kostson]

So first define a frequency dependent table for the stiffness called say k_freq using *dim that holds the stiffness values as function of freq.

Define the combin14 using ET command

Assign real constants for stiffness using the table k_freq as:

R,100,1,%k_freq%

or if in mechanical in the command snippet below a spring object (under connections/spring)

RMODIF,_sid,1,%k_freq%
Please see the *DIM. R, RMODIF, and ET commands for more info.
ALso have in mind that this can only be used with a full harmonic response.

All the best
Erik

[Emiliano Maldonado]

Thank you very much indeed for your help.
One more question: Could I include in the table not only the stiffness but the damping values as well? I suppose the only I need to do is another column within the table, isn't it?

[Erik Kostson]

I would make another table (called say c_freq) with the frequencies and the corresponding damping values , then assign both the k_freq table and c_freq table as follows:

R,100,1,%k_freq%,%c_freq%

or if in mechanical in the command snippet below a spring object (under connections/spring)

RMODIF,_sid,1,%k_freq%,%c_freq%

All the best

Erik

[Emiliano Maldonado]

I am trying to assign the COMBIN14 command to a volume's surface, but I cannot find the way to do that. What I am doing is listed as follows:
1) I assign a named selection for the surface (the name is, for instance, "FORMATION_LEVEL")
2) After that, I try to find an ID for the named selection in the *.dat input file. The only I can find is the following:
3) Finally, I try to write the snippet for defining the spring (I do not know how to identify the named selection):
/PREP7
!X STIFFNESS
ET,???,COMBIN14
KEYOPT,???,1,0
KEYOPT,???,2,1
R,1,%TABLE_KX%
TYPE,???
REAL,1
FINISH
/SOLU
Please let me know how could I write the ID for the named selection. Thank you very much in advance!
Emiliano.