nonlinear buckling with restart

[meolo2002]

hi to everybody... i've some problem with a simple test of a cantilevered beam subject to a compression...
the body is made by a solid cylinder.
i've preformed nonlinear static analysis at first
then restarted from loadstep 5
i get the following error
*** USER FATAL MESSAGE 4512 (CASE02)
SUBCASE 2 REFERENCES UNDEFINED NLPARM CARD WITH ID =2.
*** SYSTEM FATAL MESSAGE 3007 (CASE)
ILLEGAL INPUT TO SUBROUTINE CASE02
here attached both bdf (buckle is the nonlinear, buckle2 is the restarted)

 

[hezhj2000]

Why do you want to use restart for nonlinear buckling? You can run nonlinear buckling in a single job. Even with restart, your second job doesn't define any buckling subcase.

You can go to page 201 in the Nastran v2001 release guide for an example of nonlinear buckling analysis in a single job. Search nlsolidb in your Nastran installation folder, and you will find the example file.

 

[meolo2002]

Thank you very much for your reply...
I've learned a lot!!
I've still some problems... i've performed another simply test with a cantilevered plate (solid)
used PARAM,BUCKLE,2 ( i've found an integrated option in subcase parameter)
made a comparision between nlsolidb and mine and main differeces are in METHOD and EIGRL (by the way i would learn more about methods)

now i've a strange memory fatal error...

*** SYSTEM FATAL MESSAGE 6704 (DFMFRD)
LOGIC ERROR 2 IN NUMERIC PHASE OF SPARSE DECOMPOSITION.
USER ACTION: INCREASE MEMORY BY 30627744 WORDS.
0FATAL ERROR

but which memory has to be increased? ram? -_____________- could you help me?

 

[hezhj2000]

I found a website that helps you to convert words to Mb:

http://deviceanalytics.com/memcalc.php.

I tried that, and it showed 30627744 WORDS = 116.84 Mb. Of course this is the incremental memory, not the total memory you should use.

 

[meolo2002]

ok i've overcome that issue with command mem=0.25Gb, so about 250 mb in this case.
Now another prolbem cames out:

*** SYSTEM FATAL MESSAGE 7340 (LNNHERR)
PROCESS ERROR REPORTED BY SUBROUTINE LNNP2CD (IER= -725)
USER INFORMATION: NUMBER OF COMPUTED EIGENVALUES EXCEED ALLOCATED STORAGE.
*** SYSTEM FATAL MESSAGE 7340 (LNNHERR)
WARNING REPORTED BY SUBROUTINE LNNDRVD (IER= 725)
USER INFORMATION: NUMBER OF COMPUTED EIGENVALUES EXCEED ALLOCATED STORAGE.
How much is allocated storage for this job? How i can change it?
Possible tath such simply test needs so much memory?

 

[hezhj2000]

I have never got such error message before. And I am not sure if it is related to memory or hard disk space. I think you can put more memory like 'mem=3gb smem=2gb'. Also, you can check the EIGRL entry. For buckling analysis, you don't need to calculate a lot of eigenvalues as usually we only care about the lowest one.

 

[meolo2002]

still having problems...
i think material properties are ok but i've found this error:
*** SYSTEM FATAL MESSAGE 3034 (LNNHERR)
INTERNAL FAILURE IN THE LANCZOS PROCEDURE:
M-ORTHOGONAL QR PROCEDURE FAILED TO CONVERGE. PROBABLE CAUSE:
MASS MATRIX IS INDEFINITE (MODES) OR STIFFNESS MATRIX IS INDEFINITE (BUCKLING).
USER ACTION: CONTACT MSC CLIENT SUPPORT.

*** fatal error no. -728 *** subroutine lnnp2cd
unrecoverable termination from lanczos iteration
internal error code: -6
where's the error in this model ?
thank you for the help