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ajd-brown last won the day on March 11 2016

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  1. Hi Prakash, This seems to have solved my problem thank you very much for your help! Regards, Anthony
  2. It is likely that you have not assigned a material to your model. 1. Create a Material 2. Create a property 3. Set the properties material as the one you created in step 1. 4. Right click on the property, click assign and select the elements you wish to have that property. If that doesn't help then more information about the problem is needed before anybody can help you. You can post your .hm file and .out file to help give a better understanding of the problem.
  3. I've created a new model, and even with only 100N load on a full size bicycle wheel there are large displacements. I really don't understand what is going wrong! The results from the pretension are exactly what I would expect, but as soon as a force is added, everything goes crazy! The displacement should be minimal since the tension in the spokes is so much greater than the applied force. I have used PBEAM elements for the spokes and rim with cross sections assigned from HYPERBEAM, should I have used a different element type? I used the equivilence tool to join the spokes to the rim and RBE3's constrainted in 12345 (free in 6) to attach the spokes to the hub. I must stress that the pretension works perfectly but everything falls apart when a force is added. . Regards, Anthony hub_V14.hm
  4. Hi Prakash, I have checked the loads and I have placed 3 loads on three nodes of roughly 2000N combined , the pretension in the spokes is around 1200N on one side and 860N in the other. I would have expected that the wheel could sustain these loads without much trouble, my instinct could be wrong however! Thanks, Anthony
  5. Hi Guys, I am having a problem with unrealistic displacements. The first image below shows the wheel modelled with pretension in the spokes (different tensions on each side) This is what I expect to see.... The spokes are under tension and the rim mainly under compression with areas of peak stress around the parts where the spokes attatch. However when an additional force is added to the rim, I get the response in image 2. The forces added at the bottom, they are around 0.75kN in x,y,z. The problem is that the spokes which should increase in tension just stretch without increasing in stress?? (the stress is the same as the first image) . The main error here is the displacement of the spokes even though they are fully constrained. Iteration Subcase Variable Grid/Elem ID Value --------------------------------------------------------- 0 1 MaxDisp 209 -391.773 0 1 MaxStress 1474088 8083.37 Does anybody know how i can stop this displacement from occurring? I'm pretty sure its not a constraint issue this time! Thanks, Anthony Initial_Hub_V6
  6. I have a question about how to correctly apply a load to an RBE2 which connects to the nodes on the inside of a hole. If this RBE2 is representing a bar in the hole, then the force should only be applied to the nodes which are under compression by the bar (in front of it marked green in the image) From what I have seen, it applies the force to all nodes selected since they are all selected. (doing as its being told to). Is there a way to only have force applied to `arms' of the RBE which are in compression (being compressed by the bar) and anything in tension has no force applied? I suspect there must be a better way to do this, but I can't see/find anything. Please see the image for reference. Thanks in advance for any help! Regards, Anthony
  7. Dean have you managed to fixed your issue yet?
  8. Hi Prakash I have just received the same error from one of my simulations, Should I start a a new thread or post my file in here? Regards, Anthony --EDIT-- I have fixed the problem, I had two adjacent faces with two different RBE2's on, and the shared edge between them was throwing up an issue!
  9. Hi Rahul, I am performing a similar analysis to the above, is this method an efficient one or are there faster/better methods? Regards, Anthony
  10. Hi, Please post the output file here so we can see the errors, go to view>output file If you have closed the solver already, just locate the .OUT file in the save location
  11. Hi Rahul, I believe my model should be OK for topology with a single VM stress, I do not need to place different stress constraints in different parts of the model. I am not familiar with the DSIZE card or its location in the software , how can I implement this in a topology optimization? I think I have already used the "STRESS optional continuation line on the DTPL" as shown in the image below but this failed to constrain the optimization or am I mistaken? Regards, Anthony ---------- Prakash, Thank you for your advice!
  12. Hi Rahul, Ok thank you for the info, can size optimization be used simultaneously or after with a stress constraint? What is the best alternative if not? Regards, Anthony
  13. Hi Prakash, The results are similar to what I would expect from the loads however the stress constraint in the topology design variable is being violated / completely ignored! I gave a value of 125 in the DESVAR parameters, but the solver screen shows a stress of ~350, even after 50 iterations! Why is my 125 not being taken into account / What can I do to perform a stress constrained topology optimization? Regards, Anthony
  14. Hi Prakash, Just to ensure I understand the problem: You say there are 5000 free nodes, presumably, these are the nodes where my Design and NonDesign spaces meet but are not joined together properly? So my using the equivalence tool it found ~2400 Nodes which were close to but not equal. So by making these nodes equivalent, they are then connected to the rest of the model rather than floating in space (which is why they got infinite displacement?) and the displacement should return to normal? You say there were 5000+ free, the equiv tool found ~2400, is this ~2400 pairs of similar nodes (=~5000) or am I still missing something? As you can see from the attached image, its iterating! Thank you so much for your help!
  15. I have set up a case which completes in optistruct however produces unrealistic displacements in the order of e+12. I believe the part is fully constrained with two 6DOF constraints at the top and bottom, with only 2 forces added for braking torque and braking force + Weight. Could anybody advise what I should try next? Thanks, Anthony Iteration Subcase Variable Grid/Elem ID Value --------------------------------------------------------------------------------------------------------- 0 1 MaxDisp 27810 -0.203066E+12 0 1 MaxStress 354993 34.7560 0 0 Objective_MinimizeMASS 0 0.541146E-03 0 0 MaximumConstraintViol% 0 0.00000 Upright.hm
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