×
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!

*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

Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

(OP)
Dear all.

I am running a pre-stressed modal analysis. A stator for a rotating machine consist of several modules tied together with a tie-rod, which also works as a guide.

When assembling, the stator will only be clamped in one end, tied together, and then clamped in the other end. When running the analysis, i would thus like to use a fixed support first for the structural analysis, and then before the modal analysis, add a fixed support to the opposing end.

Is it possible to add the additional fixed support after the structural analysis for use in the modal analysis?

Thanks in advance, and best regards,
Mikael Mosbech Eronen

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

Yes it should be.

If you are using WB then you need though to add command snippet for the restrain that will be done with the D apdl command.

Med venlige hilsen

EPK

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

According to the Workbench documentation it can’t be done but, as it often happens, GUI limitations may be omitted by editing the code manually. Before you try with you complicated model I suggest simple test on a beam for example.

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

(OP)
Thanks Erik.

I was hoping there would be a more WB friendly way of doing it, but i guess i will look into how to use the APDL command within WB.

Best regards,
Mikael

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

No worries. For the command snippet first create a nodal named selection (called say FIXNODES) of the nodes and then use the D command, say:

CMSEL,S,FIXNODES ! This selects the nodes
D,ALL,UX,0 ! Fix X for sel. nodes
D,ALL,UY,0
D,ALL,UZ,0

ALLSEL,ALL ! Selects all nodes again

From an Fea point of view it is fine, since the static analysis generates the geometric stiffness matrix which is added to the standard global matrix and then the BC are just changed (so dof will be condensed out form the global matrix). Try it out on a simple model.

@ FEA way - please if you are not really sure about this do not provide help (unless you have a long exp. in Ansys which I cannot see in this forum) - because if advice is not correct things can go wrong!

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

@Erik Panos Kostson I just said that in Workbench it can’t be done without code modifications and to try with simple example first. Nothing incorrect or uncertain here since you basically confirmed that some code lines must be added and provided them to the OP.

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

Sure, but in general I would advice to be careful with advice (including myself, when I am not sure I will write it out and advice to seek further advice say from a person that knows the subject), and a lot of referencing, especially when not sure.

RE: Pre-stressed modal analysis: Adding additional supports in between structural and modal solves

Yoy’re right. That’s why I always try to give advices only to the safe extent not to confuse the reader. And in case of FEA software I always recommend reading the appropriate documentation chapters since they are usually very comprehensive and helpful. At least in case of Abaqus. This software made me develop the habit of using and advising the use of documentation. Ansys seems to have nice manuals too so I refer to them sometimes.

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! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close