Freq domain analysis how to apply a displacement (real and imag)

1

Hello I am tying to apply an input displacement in freq domain in a model.
I am able to apply a real part of a displacement but i am not able to apply the imaginary part.
below how I set the analysis

*AMPLITUDE,NAME=A1
10.,1.,10000.,1.
*Step
*Frequency, Solver=Pardiso, Storage=Yes
10
*Boundary, op=New
*Boundary
Internal_Selection, 1, 6, 0
*Node print, Nset=test
U
*End step
** Step-2 ++++++++++++++++++++++++++++++++++++++++++++++++++
**
*STEP
*STEADY STATE DYNAMICS
10.,10000.,100
*Boundary,AMPLITUDE=A1
Internal_Selection, 1, 1, 1
*Node print, Nset=Test
U
*End step

the previous script work fine if i try to add the IMAG part of the the displacement using for example does not work
*Boundary,AMPLITUDE=A1
Internal_Selection, 1, 1, 1
*Boundary,AMPLITUDE=A1,LOAD CASE=2
Internal_Selection, 1, 1, 1
any idea? or work around?

thanks

2

Is there an error message or just no results ? Can you share the whole file ?

It may not work properly. In Abaqus, you can’t use prescribed displacement BCs in mode-based SSD analyses at all, you have to use *BASE MOTION instead.

3

Thanks for the replay,
attached by mail the model that I used for make a test.

if you try to add LOAD CASE=2 to boundary i did not get results for step 2.
Instead in calculix it is possible use the *BASE MOTION for providing in freq domain a real and imag excitation?
if yes can you provide to me an example?

(Attachment Barra_10_10_100_bound.inp is missing)

4

Unfortunately, the attachment is missing.

CalculiX has *BASE MOTION but with no “imaginary” option (unlike Abaqus).

5

sorry how can share to you the model? seems that i can not attached it by text file but just as image.

ok so BASE MOTION is not an option.

6

Upload it to some hosting website like WeTransfer, Google Drive or Dropbox and paste the link here.

7

thanks, here there is the model

if in the model you try to add for example you did not get consistent results:
*BOUNDARY,AMPLITUDE=A1,LOAD CASE=1
Internal_Selection-1_Incasro, 1, 1, 1
*BOUNDARY,AMPLITUDE=A1,LOAD CASE=2
Internal_Selection-1_Incasro, 1, 1, 1

Thanks

9

You have to set access to “Anyone with the link” first and then copy the link. Otherwise, we can’t access it.

10

Thanks,
Try now should be work

11

I submitted this in Abaqus (using direct integration type of SSD analysis because only this one allows non-zero BCs). Here are the results you requested:

real
real1159×609 9.53 KB

imaginary
imaginary1156×612 9.39 KB

Apparently, limitations of CalculiX prevent you from getting the results in this case. I’m not sure if it can be even called a bug but maybe yes - after all, there is a LOAD CASE parameter for BCs. Perhaps it just doesn’t work well in combination with other features.

12

Thanks for your double check, so if i got correctly using Calculix I can’t assign non-zero BCs ( in FREQUENCY DOMAIN ANALYSIS) considering IMAG part but just the real one, Am I correct?

Thnaks Giuseppe

13

It’s not mentioned in the documentation so would require additional testing with as simple models as possible. It may just not work in certain configurations. There were serious issues with SSD analyses in previous versions of CalculiX. They got fixed but there may still be other problems that we don’t know about.

14

Thanks for the support I will investigate it.

15

Maybe you should consider using the large mass (seismic mass) method instead, using *Cload as in the manual examples.