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    • Rahul Ponginan

      Please click here for a short but important announcement   03/26/17

      Dear Users Our Commercial and Academic users around the world can use these same forums here as before i.e. the Altair Support Forum , Commercial users from India with solver queries can go to the Solver Forum for India Commercial Users , Academic Users from India and AOC India Participants are requested to go to the Forum for India Academic Users and AOC India Participants , We will be tending to all queries in all the forums promptly as before, thank you for your understanding. 

Ivan

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  1. Hi, I am running Radioss topology optimization to minimize compliance with constrained volume fraction. The plate has all translations constrained on the left and right edges and mass is added. The expectation was that reinforcing ribs would connect supports across left-right direction, which was confirmed with Optistruct. However Radioss optimization produced counterintuitive result with reinforcements running along supports. From the .eslout file it became evident the objective function was minimize maximum compliance; in Optistruct run the objective was minimize compliance. How to set up Radioss optimization to get results similar to Optistruct? The solver decks are attached bellow if anyone would like to look into. test_optistruct.fem test_radopt.eslout test_radopt.radopt test_radopt_0000.rad test_radopt_0001.rad
  2. Tyre Assembly Analysis

    Pneumatic structures can be modeled in Optistruct by applying outward facing pressure load.
  3. fabric hinge

    Thanks Prakash, your question actually resolved my issue. Membrane behaviour can be modeled by referencing an additional isotropic material of negligible stiffness with USER option on MID2 and MID3. optistruct_fabric2.hm
  4. fabric hinge

    Hi, I am trying to model fabric material in Optistruct with NLGEOM solver. The material model should be orthotropic, membrane behaviour (no bending and transverse shear) and have different modulus of elasticity for tension and compression. There are some issues: 1. Is there another way to define different modulus of elasticity in tension/compression for shell elements? 2. Membrane type behaviour is modeled with MID2 and MID3 set to blank as was suggested in this topic. Alternatively it could be set up with NIP=1 in PSHELLX extension. However, after analysis is completed the result display only the initial configuration. The file is attached for debugging purposes. optistruct_fabric.hm
  5. Hi George, thanks for response. Turns out it is quite simple to determine mass at specified pressure. In quasistatic simulation the mass/time function should slowly increase and the mass at the required pressure can be found in Hypergraph.
  6. Hi, The airbag injectors are defined by a function of mass/time so it takes some trial and error to converge on the pressure required. Is there a more direct way to determine the pressure at the end of inflation?
  7. Orthotropic orientation

    Hi, I have a similar query regarding orientation of orthotropic property /PROP/TYPE9 (SH_ORTH). There is an option to orient the property by reference vector. That is fine for flat surfaces, but how it works for more complex curved surfaces like spheres?
  8. Ply orientation, RADIOSS Block format 110

    Vx, Vy and Vz are x,y and z components (global coordinate system) of a vector V which defines material orientation. Those are filled in automatically when you reference by nodes. Woven composite is modeled by inputting the same Young's modulus E11=E22 into material law definition.
  9. Time step smaller than DT/INT/DEL

    Hi, you should define type 11 line interface in addition to type 7 (or just type 19 which is a combination of type 7 and 11) in order to avoid nodes passing through master surfaces. Radioss user guide describes:
  10. tied interface and AMS

    Comparing energy error time history with animation it became apparent there was a modeling issue: shell elements were penetrating into solid edges.
  11. tied interface and AMS

    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.
  12. tied interface and AMS

    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).
  13. tied interface and AMS

    Thanks for being helpful as usual, George. The interface could also be made stiffer by increasing stiffness scale factor Stfac.
  14. tied interface and AMS

    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):
  15. tied interface and AMS

    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
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