Jump to content
Sign in to follow this  
sbasude

OptiStruct/Hypermesh -- Strange Movement/Unwanted Direction

Recommended Posts

Hello all,

 

I am trying to load a femur model according to a local coordinate system. When loading in the non-desired direction for testing (Z-dir) the model node moves predictably. But when I try to load in the desired direction against the springs (X-dir), the model does some crazy twisting and weird movement. Would love some help resolving this issue. I have a suspicion it may have to do with the springs... making them very compliant still didn't solve my issue though.

 

.fem files attached

6_25_Altair_Question.zip

Share this post


Link to post
Share on other sites

Hi. It is a correct movement, i think.

Pbush1d cannot support rotation (constrain dofs 456 are meaningless).

So when you compress it noncoaxially, it will rotate. It's tough to make the load coaxially.

20190626_084303.thumb.jpg.d6e3cf4923512fa5a9f07c1b1749b0a4.jpg

 

To hold dofs 456, don't bind springs to 1 node, or use cbush (has 6 Ks)

sbasude likes this

Share this post


Link to post
Share on other sites

Hello Tinh,

 

Thanks so much, this makes sense. I tried created CBUSH elements and using the PBUSH card. To test, I set all K values to 1000 on the PBUSH card. This is the error I am getting:

 

  *** ERROR #  99 ***
  CBUSH element 270584 references incompatible PBUSH.
  K2/M2/B2, K3/M3/B3, K5/M5/B5, and K6/M6/B6 on PBUSH must be zero for
  CBUSH with no G0, CID, and blank X1, X2, and X3.
 

I do not see fields for G0, CID, and Xx on the card though.

Share this post


Link to post
Share on other sites

Tinh,

Thanks to your help I've progressed quite a bit. After setting the CID in the CBUSH card for all springs I think I have something close to what I need and should be able to figure it out with some tweaking. Thanks for your help.

Femur_Model_6_26.hm

tinh likes this

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
You are posting as a guest. If you have an account, please sign in.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...