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sbasude

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About sbasude

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  1. Hi Rahul, I see the "STRN" option in MATF, but the bulk data description does not explain how to add strain criteria. What would be your suggestion to implement this?
  2. Hello, I am trying to assign a failure criteria based on strain. For example, I want to be able to remove or replace the material properties of elements that reach 0.9% strain, or do the same thing when the principal strain of an element exceeds 10000 microstrain (these figures are from literature). The MATF card only takes stresses. How can I implement these strain-based criteria? Thanks.
  3. .fem file Femur_Model_7_1.fem
  4. I am having trouble figuring out why there are strange reaction forces in my model. The rightmost node allows for rotation (vector out/in screen) and the bottom left node pushes up at a set displacement. The rightmost node should not have so much force in the x-direction. Any help in figuring out why this is happening is much appreciated. Femur_Model_7_1.hm
  5. For anyone else referencing this thread, the following picture shows how to edit the loadstep to output an .op2 file. Still need to figure out the FBD process for my springs.
  6. I am trying to construct a FBD, but I am unable to export the .op2 file needed to do so.
  7. Where is the information on how to export the .op2 file?
  8. Hello, I have a group of springs from which I want to extract the total force in a simulation. Is there a quick and easy way to do this? I'd really appreciate your help
  9. Does anyone know how to make the stress change with each displacement step in an optistruct simulation? Currently when I have it show me the stress heat map, it doesn't change at each displacement step.
  10. If 4, 5, 6 don't matter, how come changing stiffness of K6 made a big difference? I changed K6 to Rigid and the model went flying in a wrong direction. However making K6 0 actually made the model a lot better. This doesn't really make sense to be, since I thought that making the stiffness higher would constrain the motion more. Addl Edit: My main issue is that I am having trouble visualizing the degrees of freedom for the springs and how the stiffness will change their motion. Changing stiffnesses according to the CID that I've assigned to them is not making them change movement in a predictable way...
  11. I am trying to squeeze a femur model with two sets of stiff springs top and bottom, and allow it to rotate with the other (spring BCs come from a research paper). Instead, the model bends where the mesh meets the springs that should remain mostly straight. However, I have tried adjusting all DOF stiffnesses in the PBUSH card without luck. All springs have been assigned to the local coordinate system (shown in right on photos) using CBUSH card. It seems to me I need to stiffen K2 or K6 (y-tension, z-moment), but neither of these solves the issue. Attached graphs show "TY" stresses. Femur_Model_6_26.fem
  12. 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
  13. I tried setting K2, K3, K5, and K6 to 0, but this just creates the same motion I had in the 1D case.
  14. 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.
  15. Hello all, I am attempting to use some RBE3 elements to apply loads and I am receiving this error: A fatal error has been detected during input processing: *** ERROR # 774 *** When a grid's component has no stiffness, then that component cannot be an independent d.o.f. in an RBE3. RBE3 id = 270584 grid id = 326669 weighted components = 123 max d.o.f with stiff = 1 Would greatly appreciate some advice regarding this. Thanks
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