×
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

Releasing a forced displacement

Releasing a forced displacement

Releasing a forced displacement

(OP)
In NE Nastran the SPCD command will enforce a displacement on a node. In a non-linear run placing the SPCD command in a SUBCASE and then removing it in the next SUBCASE results in the enforced displacement being ramped down leaving me where I started. My goal is to remove the enforced displacement simply be removed and the structure then find it's free state. There is contact in this model.

Does anyone have an idea as to how to remove the SPCD displacement without having it ramp back to zero?

RE: Releasing a forced displacement

Maybe the NOLIN forcing functions could do the trick instead of SPCD????

RE: Releasing a forced displacement

(OP)
I'm doing non-linear static so NOLIN is out of the picture. Somebody suggested using a gap to allow load in one direction and relieve the load when the SPCD moves back to zero. That seems to be doing the trick. Thanks for the suggestion.

RE: Releasing a forced displacement

Loads will ramp back to zero.  SPCD is treated like a LOAD.  Use the SPC entry which is selected from the case control using SPC.  If you specify a different SPC from one subcase to the next, it will immediately change to that new SPC.  Is that what you want to do?  If so you have to add this by hand in the editor because FEMAP does not support it.

RE: Releasing a forced displacement

(OP)
Thanks. SPC did the trick.

RE: Releasing a forced displacement

I think you can do this within FEMAP using the text dialogs in Executive Control etc.

Basically, anything you can do in the text editor can be done in FEMAP buy sometimes it's a bit more complicated. On the other hand, if you use Analysis Set's you only have to do it once. There are Pros and Cons to both methods.

Regards

Thomas

RE: Releasing a forced displacement

(OP)
I just edited my .nas file with UltraEdit and put in the additional boundary conditions. If I had started out on this path I would have just created several different constraint sets. I am not sure what you are refering to in Executive Control. I haven't used that yet.

RE: Releasing a forced displacement

Can any body advise on the best practice for calculating point mobility using Nastran.

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