OptiStruct/Hypermesh -- Strange Movement/Unwanted Direction
Altair EmployeeHello 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
Answers
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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.
<?xml version="1.0" encoding="UTF-8"?>
To hold dofs 456, don't bind springs to 1 node, or use cbush (has 6 Ks)
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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.
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I tried setting K2, K3, K5, and K6 to 0, but this just creates the same motion I had in the 1D case.
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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.
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