How to perform craig-bampton method
Altair EmployeeI have been working on Craig-Bampton method for normal mode analysis in which I aim to get a faster computational time result for 16 modes. Until now I unable to do so. I tried to use all the information obtained from the internet, but I failed miserably since I have no idea how to do it. I'm working with superelement . Just a simple structure. One superelement and one residual. With this, I attached my explanation of the structure I'm working with.
<?xml version="1.0" encoding="UTF-8"?>
Answers
-
I am sending a sample model with the steps for creating the CMS deck for that model.
0 -
For the grid data section in superelement, did I need to include the sub B grid also?
0 -
I am sending a simple file; cantilever_cms.fem. It writes out the pch file attached (it shows the MAAX) which we include in the final residual run – reduced_cms.fem.
0 -
I keep on getting this error
. I used EIGRL and CMSMETH for load collector and Normal modes for load step
Im not sure what type of load step use in the centilever example. Is it normal modes? for both EIGRL and CMSMETH load collector?
0 -
Then I only used EIGRL load collector for normal modes load step, but I dont know what type of load step for CMSMETH load collector
This is the error appear:
Control cards 'METHOD=n' are not allowed when CMSMETH card is present.
0 -
Could you share us file in which you are working?
0 -
i've sent the file to your dropbox
0 -
Hi Ahmad,
Can you share the .out file here in forum?
0 -
Ahmad,
Can you remove the normal modes subcase and run the analysis?
Have only a generic subcase with CMS active.
0 -
@Prakash Pagadalaplease check your dropbox. I have sucessfully generate the .pch file. But there is no mass matrix (MAAX) in it. Only stiffness matrix (KAAX). Plus at the .out file, there is warning and problem on the CMSMETH. Can you please check the .fem file if there is anything wrong I made.
0 -
Ahmad,
I am sorry, I don't have access to dropbox here.
Can you share the .out file?
0 -
FYI,
check in your out file whether mass matrix is written or not in .pch file.
<?xml version="1.0" encoding="UTF-8"?>
0 -
@Prakash Pagadala This are the files. I have checked the .out file. There is no mass matrix written. Only stiffness.Can you please check the .fem file if there is anything wrong I made.
One more, I supposed to get this 2 output from the optistruct but I only get the DMIG (.pch) only. Not the H3D file.:
1.The successful run will have DMIG matrix (Super Element).
2.The successful run will also have H3D file (binary Super Element)
0 -
Ahmad,
provide number of modes or upper frequency in CMSMETH card and try again.
0
