Random Response Analysis Grid/Nodal Force Response/Output

Imrich

Hello,

I would like to know how to set up PSD nodal force output from RANDOM Response analysis because I have problems with this.

I find out it should be possible trough  XYPEAK / XYPLOT / XYPUNCH I/O Options and Subcase Information Entry.

However, when I use CASE_UNSUPPORTED_CARDS with option e.g. 'XYPLOT,FORCE,PSDF / 184934(T2)' where 184934 is ID of grid point in the model, I get following error in

.out file: 

 

 *** See next message about line 13 from file:
     D:/subory/PHP/Priprava_Modelu_Sendvica/Modalna_analyza/pokus6/Random/test/model_12_5_20__10_26.fem
  'XYPLOT,FORCE,PSDF / 184934(T2)'
  
 *** ERROR # 1651 *** in the input data:
 Syntax error in XYPLOT/XYPRINT/... card - last item read: 'T2'.

 

 

 

I have also tried use command as follows: 'XYPLOT,FORCE,PSDF / 184934(2)' which leaded to error:

 

 

 

*** ERROR # 6034 ***
 Nonexistent element 184934 referenced by XYPUNCH/XYPLOT/XYPEAK request.

************************************************************************

 A fatal error has been detected during input processing:

  *** ERROR # 6034 ***
  Nonexistent element 184934 referenced by XYPUNCH/XYPLOT/XYPEAK request.

 

 

 

which is weird because I would like to see grid/nodal output (no element output).

I have also tried use of  Tools->Process manager->Freq Resp Process->Random PSD frequency response.

Here I don't need to enter the command directly, but trough GUI of process manager which reduces possible mistakes of mine.

In the manager I used besides other sections also section 'Define Responses'->'Select Nodal PSD Response' where what I need should be possible in my opinion.

I used 'Add DOFs' where I choose 'Response Type: FORCE' and I have selected mentioned node then I choose Y direction and set 'Assign Format' to XYPLOT

However, eventualy I get same kind of CARD (CASE_UNSUPPORTED) with absolutely same command in it and I get also same error.

I have attached model .fem file if it helps.

So, I would apreciate if someone can help me.

 

 

Thank you.

Unable to find an attachment - read this blog

Imrich

Hello, 
-I have solved this problem.
-I have used cbush elements with very high stiffness in places where I wanted to measure forces, instead requesting nodal force output.
-CBUSH element support PSD and RMS output trough ELFORCE output request.

Alejandro da Silva

Hi Imrich, I've just stumbled across your post. Just one thing, if you want to recover stress/forces by using dummy elements, thake care of not using high stiffness properties so that could affect your initial model.

Leonardo Rosa_20310

Please, have a look at OptiStruct's Documentation.

 

Version 2020 (https://2020.help.altair.com/2020.1/hwsolvers/os/topics/solvers/os/results_output_by_optistruct_r.htm) does not support Grid Point Forces for Random Response.

However, Version 2020 supports Grid Point Forces for Frequency Response Analyses. Therefore, you can calculate the Random Response by hand.

alex sunny

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Michael Herve

Hello,

 

as I just got a user facing the same error message, here are few tips to get rid of this error message:

 

1) make sure that you set a valid code between parenthesis after your entity (nodes for force, displacements, velocities and elements for strain or stress)

To consult the supported codes, check in OptiStruct help for DRESP1 item codes

for disp/vel/acc: https://2021.help.altair.com/2021/hwsolvers/os/topics/solvers/os/dresp1_psd_rms_displace_vel_accel_bulk_r.htm

for stress/strain:

https://2021.help.altair.com/2021/hwsolvers/os/topics/solvers/os/dresp1_psd_rms_stress_strain_bulk_r.htm

 

2) XYPLT, XYPEAK and XYPUNCH are set up in HyperWorks through unsupported card. Make sure you leave no blank cell below your XYPLOT instruction in the unsupported cards, otherwise this will likely lead to an error message

 

Best Regards,

Michael