×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Nastran Punch Files for Stiffness Matrix

Nastran Punch Files for Stiffness Matrix

Nastran Punch Files for Stiffness Matrix

(OP)
Hi,

I am would like to know how can I get the stiffness matrix at some specific nodes of a Nastran Finite Element Model?

I believe that I should prepare a punch file with contents similar to the following lines:

DMIG    KAAX           0       6       2   0                 363
DMIG*   KAAX                     815               1
*                815              1 2.094630203D+05
DMIG*   KAAX                     815               2
*                815               1 5.452199544D+01
*                815               2 7.202035606D+04
DMIG*   KAAX                     815               3
*                815               1-1.187792338D+04
*                815               2-8.340854301D+01
*                815               3 7.054812146D+03
DMIG*   KAAX                     815               4
*                815               1 5.956672400D+03
*                815               2 1.614047795D+06
*                815               3-9.830448080D+03
*                815               4 8.008238936D+07
DMIG*   KAAX                     815               5
*                815               1-3.302141465D+06
*                815               2 4.679375985D+03
*                815               3-6.878970667D+05
*                815               4 6.516078489D+05
*                815               5 2.395260092D+08
DMIG*   KAAX                     815               6
*                815               1 2.197964123D+03
*                815               2 9.450145395D+05
*                815               3-5.384814661D+03
*                815               4 4.320186476D+07
*                815               5 4.148338821D+05
*                815               6 2.530261259D+08



Thanks,
A.A.Y.

RE: Nastran Punch Files for Stiffness Matrix


Hello feajob,

            what you should do is run a file where the GRIDs for which you require the stiffness values are defined via the ASET card:

ASET1     123456   GRID1   GRID2    ...   GRIDn

and add in the parameter section of the same file the line

PARAM,EXTOUT,DMIGPCH

It should give what you are asking for.

Regards,

Spirit

 

'Ability is 10% inspiration and 90% perspiration.'

RE: Nastran Punch Files for Stiffness Matrix

(OP)
Hi Spirit,

Thank you for your response. I put the following lines in a model.

aset1,123,3245
PARAM,EXTOUT,DMIGPCH

And, I got a punch file as follows:

DMIG    KAAX           0       6       2       0                  155520
DMIG*   KAAX                        3245               1
*                   3245               1 1.169233642D+02
DMIG*   KAAX                        3245               2
*                   3245               1-5.191796938D+00
*                   3245               2 1.489866977D+02
DMIG*   KAAX                        3245               3
*                   3245               1 4.308966685D+01
*                   3245               2 6.827149784D+00
*                   3245               3 2.929045851D+02
DMIG    PAX            0       9       2       0                       4
DMIG*   PAX                            1               0
*                   3245               1 8.973292961D-01
*                   3245               2-2.682531133D-02
*                   3245               3-2.384527642D-01
DMIG*   PAX                            2               0
*                   3245               1 8.254319696D-01
*                   3245               2-2.436249156D-02
*                   3245               3-2.537991949D-01
DMIG*   PAX                            3               0
*                   3245               1 8.194554349D-01
*                   3245               2-2.450994401D-02
*                   3245               3-2.631562907D-01
DMIG*   PAX                            4               0
*                   3245               1 4.426057545D-01
*                   3245               2-3.810084949D-02
*                   3245               3-2.589523757D-01
DMIG    VAX            0       9       2       0                       1
DMIG*   VAX                            1               0
*                   3245               1 1.000000000D+00
*                   3245               2 1.000000000D+00
*                   3245               3 1.000000000D+00

Actually, I was looking only for KAAX. Please let me know if you know anything about PAX and VAX. I guess that PAX is related to load matrix, but I don't know any thing about VAX.

Thanks,
A.A.Y.

RE: Nastran Punch Files for Stiffness Matrix

Hello feajob,

             the PAX matrix indeed refers to the reduced matrix of loads. I don't know the exact meaning of the VAX part, I read somewhere that it should be related to the rigid mody motion of your model (not sure though).
I usually erase it happily from my reduced structures files anyway.

Regards,

Spirit

 

'Ability is 10% inspiration and 90% perspiration.'

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources