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Ivan last won the day on March 3

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  1. Ivan

    Angular momentum of solid part

    You're welcome. Hand calculation can be useful for result verification.
  2. Ivan

    Applying forces in an angle/ specific direction

    Hi, check this thread:
  3. Ivan

    Negative Inertia on Node ID

    Hi, check this thread and attached document from Radioss FAQ Kinematic Conditions.pdf
  4. Ivan

    Angular momentum of solid part

    Hopefully, someone from Altair support team can look into this and clarify. There is also an option to output angular momentum of /THPART/GRBRIC, but unfortunately I don't know how. Since the angular momentum output works for shell components and because angular momentum is simply a product of moment of inertia and angular speed I propose the following workaround: 1. create a skin of shell elements on the solid component with tools>faces panel. Assign negligible thickness on dummy shells as not to influence the momentum or stiffness of the solid part. Define output block request on dummy shell component and run the simulation. 2. Open starter .out file (runname_000.out) and find PART MASS & INERTIA summary. Calculate the ratio between solid and shell component's moment of inertia in all three directions (Ixx, Iyy, Izz) 3. Open Hypergraph and plot angular momentum of dummy shell component. Go to Define curves and apply the calculated scale factor (solid divided by shell moment of inertia) in appropriate directions. rotate1_0000.rad
  5. Ivan

    Angular momentum of solid part

    Hi, This is strange- I'm able to get the rotational momentum output in the simple model attached. rotate_0000.rad
  6. Ivan


    As mentioned before, highly nonlinear models can be solved only with the explicit method. The Radioss model was updated to include material nonlinearity. This model buckled approximately at 40% loading near the top and again at 70% near the base (see attached animation and graph). An implicit method would fail to converge at those points. Attached is the revised Radioss model and explicit dynamic Optistruct model (it runs Radioss in the background). amasker_expdyn.hm amasker_radioss_0000.rad amasker_expdyn.fem
  7. Ivan

    Topology Optimization

    Hi, this geometry found by topology optimization is the most efficient load path for given loads and BCs. If for some reason you want to have optimized design connected over the whole shell area then put some adjacent layers of solid elements into non-design space. Or change loads and BCs to get the shape you want- some intuition is required.
  8. Ivan


    Attached are Radioss model file and result. The load is linearly ramped up over 0.3 seconds. amasker_radioss1.hm amasker_radioss1.h3d Surprisingly the pillar did not buckle, but the stresses are huge (almost 4GPa) so it would fail across the top and at the base. The image shows elements exceeding 1000MPa in red.
  9. Ivan


    @Amasker Either convert (tools>convert>optistruct>to Radioss) and solve in Radioss or use Nonlinear direct transient analysis in Optistruct. Check these tutorials and examples: OS-T: 1310 Direct Transient Dynamic Analysis of a Bracket OS-E: 0200 Beam Bending OS-E: 0205 Car Bumper Impact OptiStruct Nonlinear Learning Center Also check the attached chapter from free eBook: Introduction to Nonlinear Finite Element Analysis using OptiStruct Nonlinear Direct Transient Analysis.pdf The latest model you shared still fails to converge beyond 35%. One of the reasons is because high concentrated loads are applied on only two nodes. This is unrealistic (applying 1 tonne of force on a single node, similar to introducing the load through a needle leading to high-stress concentrations) and also causes numerical difficulties. A more sensible approach would be to apply the same force as pressure load or distribute it over more nodes. However, the computation will still probably diverge in case of buckling instability.
  10. Hi Laurence, the Config Edit panel is used to make changes to the configuration of existing elements. Actually, the elements should be CBEAM after config edit>bar2. You can verify with Card edit. A good practice is to the use Organize panel to move those elements into another component with PBEAM property assigned, or at least rename the ^edges component because using edge panel again will overwrite the existing elements. The orientation of CBEAM elements should be updated with 1D>bars>update. Use the 1D detailed element representation to visually check beam orientation. That should Hyperwork Attached is a simple cantilever model, where CBEAMS were created following the above procedure. CBEAM.hm
  11. Ivan


    @Amasker Your model failed to converge beyond 41% of total load- possibly due to buckling. Models with geometrical (large displacements, rotations, buckling), material (plasticity and rupture) and contact (sliding, friction, open/close) nonlinearity are more efficiently solved with explicit method. If nonlinearities are severe (crash and drop tests) then explicit is the ONLY option (also including inertial effects).
  12. The slave nodes height with respect to the master segments should be as small as possible. Indeed, the geometrical concordance is necessary for Interface Type 2 to work normally, and will help to get a lower added mass. Please go through the FAQ in Help Menu on Kinematic Conditions where this is well explained. Using fully integrated elements in combination with spotflag=0 is OK, but rotational DOFs are not transmitted. Check the attached documents for details. Tied Contact (_INTER_TYPE2).pdf Spotweld (Bolt or Adhesive Connect).pdf
  13. bar2 will translate to CBEAM
  14. @Nitin Jain type 2 tied contact interfaces with spotflag=1 will add mass. From Radioss help:
  15. Hi, can you share the solution? The model did converge reasonably fast using small displacement, however a warning about exceeding the limit of small deformation theory was reported due to large strains and rotations. It seems this model could be solved more efficiently using explicit (Radioss).