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Everything posted by Hyperman

  1. Comparing energy error time history with animation it became apparent there was a modeling issue: shell elements were penetrating into solid edges.
  2. Hello, I have sent the requested files to dropbox. Some parts were modeled with under-integrated elements but hourglass energy is constant throughout. I also ran the fully integrated model and the same issue occurs.
  3. Increasing the min_gap worked, but during computation the energy error suddenly drops to -99.9% and unrealistic stresses propagate through the structure, when compared to the run with traditional mass scaling (at 1/10 the timestep of AMS).
  4. Thanks for being helpful as usual, George. The interface could also be made stiffer by increasing stiffness scale factor Stfac.
  5. Hi George, Thanks for the tip. The manual also suggests this contact deactivation can be avoided by using Spotflag=25 or 26 (TYPE2 penalty formulation). Both methods avoid WARNING ID : 852 ** WARNING SLAVE NODE OF AN INTERFACE TYPE2 & AMS; however some slave nodes of type 7 are still de-activated during simulation, eventhough they are not referenced in type 2. So this de-activation is probably caused by type 7 interface definition (ouput file):
  6. Actually, the deactivation of nodes was due to another interface (type 7) and it was solved by setting the Irem_gap to 1. I would still like to know the reason of WARNING ID : 852
  7. Hi, I am trying to run a model with tied interface (Type 2) and AMS. The interface is defined with contact surface as master and nodes on the slave side. During starter the following warning appears: WARNING ID : 852 ** WARNING SLAVE NODE OF AN INTERFACE TYPE2 & AMS and during computation: WARNING INTERFACE 2 NODE xxx DE-ACTIVATED FROM INTERFACE Can this deactivation of slave nodes be avoided when using AMS and type 2 interface? The same model was run successfully using DT/NODA/CST.
  8. Just wanted to update: the problem was I did not give reduction factor (R_E) which is 1 by default on material law 19 (fabric), so elastic modulus is the same in compression and tension. Bellow is the simulation with R_E at 0.001 giving good results.
  9. Thanks for the quick reply, Prakash.
  10. Hi, I am trying to convert Radioss file containing monitored volume (perfect gas) to Optistruct. In the convert browser the monitored volume is marked green i.e. "all active attributes for a given entity are mapped". After conversion there is control volume listed as type airbag, but with no parameters other than entity selection. When running analysis in Optistruct (static and explicit dynamic) it seems like monitored volume has no effect on the results. Am I missing something?
  11. Thanks again, Prakash. Actually, I was referring to minimum thickness (THICK), not member size (MEMBSIZ), but the syntax is the same. I am still having difficulty setting up radopt so looking forward to GUI.
  12. Hi matteoconese, you can check transparency in Surface Transparency Panel (shortcut ctrl+t).
  13. Hi Alexander, after checking the box, click return and then click update in the responses panel. What is the point of using weighted compliance with only one loadstep?
  14. Hi Prakash, thanks for the info. How is the minimum thickness defined in radopt syntax? I was unable to run with the following:
  15. Hi George, my issue with stress response is the run terminates at the end of first outer loop with ERROR # 382 (as described in my opening post) so I get no results. Apparently there is no such problem on your end since you managed to get some results at all. I have no idea what could be the cause, if you did not modify the files.
  16. Hi George, I tried as instructed but the issue remains- it looks like solver runs just as well with either *.rad or *.radopt file extensions. The issue seems to be with stress response in particular, because other responses worked fine.
  17. Hi all, I am trying to perform optimization in Radioss through -radopt command. The trouble is that computation terminates at the end of first outer loop when stress response is used: I have attached files, if anyone would like to check it out. test1_0000.rad test1_0001.rad test1.rad
  18. Thanks for the tip, George. It is worth mentioning that the spring element must connect slave nodes of different rigid bodies.
  19. Hi, can someone upload a file where KJOINT is used (for example with revolute joint)? I tried to follow the steps by LoHo, but I struggle to understand step 3. Relate SPRING2N to FE-Mesh or rigids
  20. Is it possible to model the fabric hinge in Radioss with cable (tension only) instead of shell elements? In Optistruct this can be achieved with CGAP element, however I could not convert or use it with Radioss solver.
  21. Hi Prakash, thanks for assistance- I will check it out.
  22. Hi, I truly appreciate your help in resolving the issue.
  23. Hi, the element formulations are: ISHELL: 4 Ismstr: 4 I sent the file- thanks for assistance.
  24. Hi Prakash, second order elements almost simulated the collapse I was looking for sort of In the attached animation it can be seen that second order shell elements were converted to nodes and detached from wood panels. What did I miss?
  25. Thanks for the tip, however the results are the same with LAW58. The model is attached if anyone would like to check in case I made some mistake. Alternative material/property combination is Kevlar2 & Hinge2. In this research paper (page 34) it is suggested to use Mooney-Rivlin material in Optistruct (probably MATX42) as substitution for fabric material. detail3.hm
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