dear Masoud 

i use this scripts for my example:

>>> import odbAccess

>>> a1=odbAccess.openOdb('testbuckling.odb')

Warning: The database has been opened with readOnly flag on. It will remain readOnly.

>>> a1.steps['Step-1'].frames[1].mode

1

>>> a1.steps['Step-1'].frames[1].description

'Mode 1: EigenValue = 9038.8'

Hallo Mr. Masoud Ahmadi,

before submetting Eigenvalue analysis you should do the following:

1- right click on model Name (default usually named as Model-1)

2-Edit Keywords

3- after the line of 

* Output field

write the following line:

* NODE FILE

U

this two lines will extract for you the eigenvalue and place them in a file with the name of job you submitted in this form

jobname.fil

hope this help

Warm Regards,

Tamer Qaimari

Dear Tamer Qaimari

Thanks for answering

how can open "*.fil" file?

abaqus Visualization just open "*.ODB" filles!

thanks

Hallo

accessing the  .fil file can be done  using the user subroutine URDFIL. there are other softwares without programming can be used. Check abaqus documentation for URDFIL or google to download a software to view the data.

Tipp: dont Forget to introduce imperfection in you input file. regarding my experince loads to buckle a structure using FEM tend to be very high compared to analytical (Euler) results!

Warm Regards,

Tamer Qaimari

Dear Tamer, thanks for your answer.

But I'm searching for a shorter way for this.

Hello,

You can use the following Python code to Access the EigenValues.

from odbAccess import *

odb = openOdb(path = '\...\jobName.odb')

STEP = odb.steps.values()[0]

for i_frame in STEP.frames:

             ModeEigenValue[i_frame] = STEP.frames[i_frame].description

####

### Note the output will be string, more code need to turn to number.

from odbAccess import *

odb = openOdb(path = ODBpath)

STEP = odb.steps.values()[0]

ModeEigenValue=[]

stei=0

for i_frame in STEP.frames:

print i_frame.description

if stei==1:

f1=i_frame.description

MinEigen=float(f1[28:48])

stei=stei+1

MinEigen

Mr.Zhenglai Shen & Mr.Hamid Moa

Thanks for your answering.

dear Masoud 

i use this scripts for my example:

>>> import odbAccess

>>> a1=odbAccess.openOdb('testbuckling.odb')

Warning: The database has been opened with readOnly flag on. It will remain readOnly.

>>> a1.steps['Step-1'].frames[1].mode

1

>>> a1.steps['Step-1'].frames[1].description

'Mode 1: EigenValue = 9038.8'

Mr.Eidani

Thanks for your answering