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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. 


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  1. Multi point Constraint

    Thank you for the tip, however I am unable to properly apply this workaround. The reason is this model probably needs node to node constraints like MPC. Could you please look into the confidential files I have shared through DropBox?
  2. Multi point Constraint

    Hi, I would also like to know how to create MPC in Radioss user profile to model cyclic symmetry. An example using this type of kinematic constraint would be appreciated.
  3. Hi George, I have tried with Isolid=17, which eliminates horglassing, but the run stil terminates with negative volume. There is also the problem with contact type 3 stiffness between soft (rubber) and hard (wood) parts. Attached are excerpts form Radioss User Guide 2017 which discusses such situations. To get the stiffnes ratio of hard over soft material the Young's or bulk modulus is required, but I only have ogden material parameters. I have also unsuccessfully tried type 5 interface with arbitrary contact stiffness scale factor of 170. planestrain_hinge_convolute.hm
  4. Thanks George, it does work with SKEW/MOV2. I have some more queries: 1. Which control cards should be requested to output contact forces/pressures and strains for quad elements in 2D plane strain analysis? 2. The run terminates with: There is also a lot of hourglassing. The property for hyperelastic material are exactly the same as in Example 42 - Rubber Ring: Crush and Slide. Can you suggest some solution? 3. What are recommended shell property settings for nearly incompressible hyperelastic materials in 3D analysis?
  5. Hi, I have already checked that thread about frame/skew, but I am still confused. You can check the sample I am trying to solve. I have set up imposed displacement, but it is not responding as required. If you delete the imposed diplacement you will get desired behaviour which is provided by spring (darker blue). I would like to get the same response with imposed displacement to have control over relative distance throughout simulation (prescibed by curve function). planestrain_hinge.hm
  6. I am trying to set up imposed displacement between two nodes with moving skew or frame (not sure which should be used). Coordinate system of imposed displacement should be aligned between those two nodes and updated throught simulation. The function curve is defined so the distance between nodes should be gradually reduced. The required behaviour is similar to pretensioned spring but with prescribed displacements throughout simulation.
  7. quasi static test

    Hi Roy, quasi-static simulation could be done using Rayleigh damping, kinetic or dynamic relaxation (see Example 16). This way the dynamic effects (inertia forces, vibrations) are neutrailzed so the simulation run time could be reduced. To control the number of steps I suggest using imposed displacements (instead of velocity) and matching the Time History or animation output intervals with test data points.
  8. Radioss optimization to minimize compliance

    Hi, thanks for update. I would also like to know how to setup radopt syntax so optimization parameters (DOPTPRM) and shres ouput requests are passed down with /BULK to OptiStruct deck during design optimization. The following had no influence on the run: /BULK/IO/1 OUTPUT,SHRES,ALL /BULK/DATA/2 DOPTPRM,DESMAX,200,DISCRETE,4.0
  9. Radioss optimization to minimize compliance

    Hi, a gentle reminder: is there anything I can help you with to resolve this query?
  10. 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
  11. Tyre Assembly Analysis

    Pneumatic structures can be modeled in Optistruct by applying outward facing pressure load.
  12. 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
  13. 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
  14. 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.
  15. 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?