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pohan

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  1. pohan liked a post in a topic by Mr.Alb in Missing Element to import hypercrash   
    Hi Korosh,
    I checked your model. It seems that you have made some mistakes with elements. I fixed your model, but you can fix it yourself by updating elemet types (2D>elemt types>elems>All>update), then export your rad and import it again in hypercrash.
     
    I tried, it works. Let me know!
    new_0000.rad new_0001.rad
  2. Simon Križnik liked a post in a topic by pohan in Tmax for Puck failure model   
    Hi.
    Then I think we should run the model without failure mode first to dectect the moment when the failure is expected!
     
  3. pohan liked a post in a topic by Simon Križnik in Add mass for rigid body   
    You're welcome.
     
    Yes, you should fully define the gravity loading. Make sure to select all the nodes in your model (master as well as slave nodes of a rigid body). Here is the procedure:
     
  4. pohan liked a post in a topic by Simon Križnik in Add mass for rigid body   
    Hi,
     
    You can directly add mass to the rigid body. Select rigid body with Rbody Manager or Card Edit in the graphics area and input added mass in MASS field.

  5. pohan liked a post in a topic by Simon Križnik in Tmax for Puck failure model   
    Hi,
     
    the time step should not vary significantly during the run and could be a sign of some modeling error.  Use timestep control CST mass scaling or AdvancedMassScaling to impose a constant time step. Or use the smallest timestep from the moment when the failure is expected.
  6. pohan liked a post in a topic by Pranav Hari in Node number for independent node of RBE2   
    Hi Nachiket Kadu
     
    I think by this way also we can find it out. Try this too
    Click Card edit > Select rigids > edit
     

     
     
     
     
     
     
  7. pohan liked a post in a topic by Simon Križnik in Trouble creating Rigid Body Radioss   
    I prefer Utility>Radioss Tools>RBODY manager where all rigid elements are listed with their related master nodes. There are other ways to get master node ID:
     
  8. pohan liked a post in a topic by Simon Križnik in Trouble creating Rigid Body Radioss   
    Hi
     
    initial velocity and gravity should include all slave nodes of a rigid body as well as its master node. Other boundary conditions require only the master node. 
  9. pohan liked a post in a topic by Simon Križnik in Negative % ERROR IN RADIOSS   
    Hi,
     
    Use the recommended contact parameters for interface Type 7:
    Istf=4
    Igap=2
    Fscale_Gap=0.8
    INACTI=6
    Gap_min=1
    Fric = 0.1
    Iform=2
     
    Another reason for timestep drop and energy error is because Interface type 7 does not deal with edge to edge impact. When the mesh is fine enough, edge to edge penetration is often followed by a node to shell contact. The main problem with edge to edge impact is the locking situations. If there is a change of load after edge penetration, locking is unavoidable since a node to surface contact is detected. This usually leads to high penetration; therefore, the analysis comes to a standstill as time step is reduced. If locking occurs, the use of interface type 11 in this area is necessary to solve the problem.
     

    Share the model file if the issue persists.
  10. pohan liked a post in a topic by Simon Križnik in Negative % ERROR IN RADIOSS   
    Hi,
     
    Large contact energies relative to total energy can cause large negative Energy Errors because contact energy is not part of the Energy Error equation. If the simulation has friction and a lot of sliding contact, then the large contact energy and resulting energy error can be considered acceptable.

    example-edit_0000.rad
  11. pohan liked a post in a topic by Simon Križnik in Is it possible to activate boundary condition at certain time?   
    Hi,
     
    it is possible to activate (BCS) or release (BCSR) boundary conditions by using BCS/TRA and BCS/ROT engine cards. 
     
    Refer to the following examples:
    RD-E: 4200 Rubber Ring: Crush and Slide
    RD-E: 5501 Fan Blade Rotation Initialization
    Kinematic Conditions.pdf
  12. pohan liked a post in a topic by Rahul Ponginan in Elements assign specific colors   
    best to import into HyperMesh, select the elements and organize into separate components, 

     

    You could create sets in HyperView for selected elements and change the colour of the sets if necessary to do it in hyperView itself. 

  13. pohan liked a post in a topic by Simon Križnik in QUASI STATIC RADIOSS   
    Hi,
     
    glad to help.
     
    In the explicit quasistatic analysis it is recommended:
    The loading should be gradually ramped up from zero over a reasonable period (at least 0.3 s). Instantaneous loading (non-zero loading at time zero) causes propagation of a stress wave through the model similar to impact load. The kinetic energy should be bellow 5% internal strain energy throughout the simulation to ensure a quasistatic process without inertial effects. Vibrations should be damped using for instance /DAMP Rayleigh damping.  
    The implicit quasistatic analysis with instantaneous loading has convergence difficulties as the equilibrium solution at initial load is far from the initial position. As a workaround try:
    create two engine files with the first engine ending after the preload is applied using the ramping function and the second simulation starts in the equilibrium condition perform pretension analysis and export deformed shape and stress fields using STATE file. Then initialize the stresses and deformed position in the original solver deck. However, this approach is not tested as I am away from my Hyperworkstation. Implicit and explicit solutions can be compared only if the explicit solution satisfies above recommendations regarding slower loading and damping- both will increase explicit solution CPU  time. The implicit solution could be further optimized for better convergence. Note also that Radioss implicit is only meant to complement explicit (capability to switch during simulation)- otherwise use NLSTAT non-linear quasi-static analysis in Optistruct.
  14. pohan liked a post in a topic by ravinder muppidi in TCL/TK script : get entity type Slave/Master   
    Hi hugo
     
    Please can u share us the tcl script.
     
    It will be useful for many users....
    Thank you in advance!
  15. pohan liked a post in a topic by Simon Križnik in Energy error differences   
    Hi,
     
    this is because of the different contact interface definition:
    tetra model had Iform=2 brick model had Ifric=2
  16. pohan liked a post in a topic by Amith Ganta in Videos related to Impact analysis Set up for RADIOSS   
    Please send me the model files which were used in this video
     
     
  17. pohan liked a post in a topic by Pranav Hari in Radioss Error 784: Error in Table definition   
    Hi Madhura
     
    1. Right click on the model browser and click create a curve.
     

     
    2.  click "new" and create a new curve. Change the option to /Table/1
     
    .
     
    3. Close all other windows and select the curve you just created from the model browser. change the options as in the image below. click on data:Ifunc and enter the values in the popup dialogue box
         
     

     
    4. There will be 3 fields to define. Ifunc, Strain rate (Ai) and Temp (Bi).
    HM lists this as Ifunc, V(0), V(1).
     
    5. Now you can assign this curve from the material data: Table_ID
     

     
     
    Hope it is clear...
     
  18. pohan liked a post in a topic by tinh in How to create and mesh an ellipse   
    Cut ellipsoid by a plane, you'll get ellip
    Or scale a circle along 1 direction.
  19. pohan liked a post in a topic by Simon Križnik in How to assign orientation for solid elements   
    Glad to help.
     
    You can verify the element orientation by performing analysis on a simplified model (single element) with highly anisotropic material parameters.
  20. pohan liked a post in a topic by Simon Križnik in How to assign orientation for solid elements   
    Hi,
     
    these threads might help:
  21. pohan liked a post in a topic by Simon Križnik in Error % keeps increasing   
    Hi, 
     
    there are intersections in the "self dummy" contact- all intersections and penetrations should be removed before running the model.
    Check and remove manually or automatically any initial intersections and penetration in your model by using Tool>> Penetration or in Hypercrash by Quality>>Check all solver interfaces. Please go through HM-3320: Penetration tutorial in Help Menu which shows fixing penetrations.

    New Feature in HW 2017 - Collision Detection Tool - Altair University
    Try to run the attached solver deck. There are some other modeling issues remaining.
    seatbelt_0000.rad
  22. pohan liked a post in a topic by Pranav Hari in Material law69   
    Hi pohan
     
    fct_IDblk is an option that provides additional control for the incompressibility.
    Please refer this forum post which discusses about MAT law 69.
     
     
     
     
    Thanks
     
     
     
  23. pohan liked a post in a topic by Simon Križnik in Non-linear material model   
    This error is regarding the material function. This law models an isotropic elastoplastic material using user-defined functions for the work-hardening portion of the stress-strain curve (for example, plastic strain vs. stress) for different strain rates. The first point of yield stress functions (plastic strain vs stress) should have a plastic strain value of zero.
     
    There are other material laws (for example law 38) that allow stress-strain to be prescribed over the whole strain range. What kind of material is it? Judging from the stress-strain presented it is not metal so material law 36  might not be the best fit.
  24. pohan liked a post in a topic by Simon Križnik in Non-linear material model   
    Hi,
     
    1. please refer to Reference Guide>Starter Input>Materials in Radioss help. Search with keyword "tabulated" for material models allowing stress-strain input. Choose the material model that will allow you to specify materials properties relevant to your simulation (strain rate, viscoelasticity, hyperelasticity,...)
    2. stress-strain values are referenced in material models by curves (XYPlots>Curve Editor)
     
  25. Simon Križnik liked a post in a topic by pohan in Contact   
    Hi @Ivan 
    My problems is when I set Igap = 1 2 or 3 I got initial penetration so I set it to 0 
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