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Hyperman

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  1. Hyperman 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!
     
  2. francesca liked a post in a topic by Hyperman in Optistruct_Free Size Optimization_Warnings   
    Sorry, I overlooked the shared pdf had multiple pages. 

    The signed von mises stress basically displays the tensile (+) and compressive (-) von mises stress.

    There are two issues:
    -If I understood the mechanism correctly there should be loads acting on the other end of the pin (as you sketched in the latest post, also see image below). Extract these counterbalancing forces and moments from MBD.
    -applying loads on the same nodes as constraints is not recommended. In cases like this, inertia relief (Analysis>control cards>PARAM>INREL>-2) should be used to constrain the model.  

    You should not give up so easily- I think you are actually doing great. You can find support on this forum, but you will also have to study on your own. I suggest you go through free Altair e-books, start with  Practical Aspects of Finite Element Simulation and for optimization refer to: Practical Aspects of Structural Optimization with Altair OptiStruct
     
    You can learn from learning and Certification program. Please follow below link.
    https://certification.altairuniversity.com/  > (Learn Modeling and Visualisation)
     
    Check the following youtube channels:
    AltairUniversity
    Altair India Student Contest
    ELEATION By Apoorv Bapat
  3. Hyperman liked a post in a topic by francesca in Optistruct_Free Size Optimization_Warnings   
    I load (on dropbox, here I can't because of the size) the h3d with the result of the static analysis so you can see what I've tried to explain above:   
     
    https://www.dropbox.com/s/4whuo2cvxtgdlr3/carro-rev-rinforzi-mesh-statica-1LoadStep.h3d?dl=0
     
    the pdf contains a possible solution..? I've thought about putting another constraint in component t28..
     
     
    component_t28.pdf
  4. pohan liked a post in a topic by Hyperman 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:
     
  5. pohan liked a post in a topic by Hyperman 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.

  6. Sony Dhotre liked a post in a topic by Hyperman in Rubber shell in Radioss   
    Glad to help. You can show appreciation by liking the content.
     
    Yes, the issue is with the G13 , G23 parameters. Are you sure you are not confusing the material property matrix parameters (Gij) with the shear modulus? If material data is specified with the Engineering Constants E1, E2, E3, NU12, NU13, NU23, G12, G23, and G13, then use the MAT9OR data.
     
    Analysis>control cards>PARAM>CHECKMAT>NO, but it is possible CHECKMAT is not supported in HM 9.0. It will not solve your problem as mentioned before.
  7. konrad_cure liked a post in a topic by Hyperman in High Energy Error   
    Hi,
     
    "ZERO OR NEGATIVE VOLUME" warning happens when solid elements are very deformed and their characteristic length goes to 0. For large strain formulation, the time step of an element is reduced when the element is compressed. Solid elements assigned with a relatively compliant material can be deformed so severely that its nodes go through the opposite side and even cause a negative volume. 
     
    In RADIOSS Starter input file (Runname_0000.rad), use Ismstr =2 in the solid property and in RADIOSS Engine file (Runname_0001.rad) use the option/DT/BRICK/CST which will set the time step value tmin at which the solid elements will switch to small strain. /DT/BRICK/CST option is used to control the time step of the analysis. The time step becomes constant after reaching Tmin specified by the user.

    This honeycomb component can not absorb all of the initial kinetic energy. You should define failure criteria to avoid zero or negative volume and obtain more realistic results. 
     
    The master-slave definitions were swapped in the type 7 contact- the master should be stiffer, coarser meshed component. Contact parameters were modified to the recommended. There were initial penetrations so the impactor plate was moved.
    SteelDummy_edit.hm
  8. konrad_cure liked a post in a topic by Hyperman in High Energy Error   
    I have reviewed your model again because the deformation just did not look right. You forgot to define the material orientation of the honeycomb property (by default if no orientation is provided it takes element orientation). Also, as per the tutorial, the wrong shear yield stress function was assigned. The honeycomb component can now absorb all of the initial kinetic energy.
    SteelDummy_edit2.hm
  9. Hyperman liked a post in a topic by konrad_cure in High Energy Error   
    Thank you so much for your help. Maybe I just didn't see it in the tutorial. As I'm fairly new in using the software I probably just didn't catch that.
  10. pohan liked a post in a topic by Hyperman 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.
  11. bijubalancollins liked a post in a topic by Hyperman in Radiation heat transfer modelling in Optistruct   
    No problem, you can do the same manually.  /THERMAL  just makes it easier to adjust the model with a single parameter:
    The physical time will be reduced by time-factor. All thermal properties will be automatically scaled, no need to change the Radioss Starter inputs. Time values in Radioss Engine input file must be modified.
  12. bijubalancollins liked a post in a topic by Hyperman in Radiation heat transfer modelling in Optistruct   
    Ctrl+F search for any keyword (input in the upper right corner).
     
  13. Hyperman liked a post in a topic by bijubalancollins in Radiation heat transfer modelling in Optistruct   
    Thank you very much Hyperman! Let me try those and would seek help if I face any further challenges. Really appreciate your help.
  14. bijubalancollins liked a post in a topic by Hyperman in Radiation heat transfer modelling in Optistruct   
    Yes, both are supported in thermal analysis. Please refer to RD-E: 5300 Thermal Analysis where nodal mass scaling is used. 
    moving_source_0000.rad moving_source_0001.rad
     
    /THERMAL Factor to speed-up the thermal analysis may be used for time scaling.
  15. bijubalancollins liked a post in a topic by Hyperman in Radiation heat transfer modelling in Optistruct   
    Hi,
     
    for models without discretization errors (mesh refined until convergence) utilizing structural materials (relatively high stiffness, low density) the 300 seconds simulation would probably not be solvable in a reasonable time without supercomputers.
     
    Explicit simulations can be solved faster using:
    -DT/NODA/CST or Advanced Mass Scaling
    -Time scaling applies the load more quickly than in the quasi-static experiment in order to reduce the simulation time. To minimize the inertial effects the kinetic energy should be low (5-10%) compared to the internal energy for most of the simulation. 
    However, there are practical limits on how much faster the solution can be obtained without invalidating the results. 
  16. francesca liked a post in a topic by Hyperman in Optistruct_Free Size Optimization_Warnings   
    Glad to help. 
     
    There are free nodes in your model. Either apply autocorrect in model checker or remove by Analysis>preserve node>clear all preserved.
     
    The 1662 warning is due to PARAM>AUTOSPC>YES (by default) Automatically constrains degrees-of-freedom with no stiffness- in your case it applied to free nodes:
    GRID 1417172 DOF 6
    GRID 1549910 DOF 4
     
    Use Tools>Model Checker>Optistruct to find & correct modeling errors and warnings.
    https://insider.altairhyperworks.com/wp-content/uploads/2017/09/T-T-1248-HyperMesh-Model-Checker.pdf
     
  17. francesca liked a post in a topic by Hyperman in Optistruct_Free Size Optimization_Warnings   
    Hi,
     
    The model can be downloaded by copy-pasting the link in the browser's address bar. It is easier to debug a smaller, coarsely meshed model. 
     
    Element Quality Check reports a warning that 56 elements exceeded the recommended range. Use the following tools to obtain a better quality mesh: 
    Geom>autocleanup to clean up the geometry 
    2D>automesh (F12)>QI optimize>edit criteria to define element quality criteria 2D>elem cleanup can be used to clean up a group of elements  2D>qualityindex where element quality can be checked visually and edited using cleanup tools one at a time. The failing elements can be saved to later be retrieved in elem cleanup or automesh again  tool>check elems>2D (F10) to check elements  The warning 5628 is due to large compliance. The "t8" tub is so thin and unsupported it sags excessively (710mm). The analysis results are invalid because large displacements and rotations violate the linear static assumptions. 
     
    The "vincoli" constrains the Z translational degree of freedom at the bottom, but the "carichi2" has a force acting in the same DOF so it does not have an effect. 

  18. Hyperman liked a post in a topic by Robert Lawson in Changing Constraints Every Iteration During Size Optimization   
    Crashphys - 
    You can't accomplish exactly that, but here's a work-around.  Create a DRESP1 with your stress response.  Then create a DRESP2 with DEQATN.  Pass the stress response and the property thickness (assuming this is a DESVAR) to the DEQATN.  I'm not sure if you intend a linear relationship or something else.  But your DRESP2/DEQATN could be written such that your stress responses is adjusted for thickness (or some function of thickness).  Then constrain that stress with DCONSTR.  
    - Robert
  19. Crashphys liked a post in a topic by Hyperman in Unchanged results from Composite Free Size Optimization   
    Hi,
     
    the optimization problem is not well-posed: the weight is constrained to be the same as the initial weight. Laminate thickness can not increase in free-size optimization. Therefore the optimization result is the same as the initial configuration. Try lower mass constraint than the initial mass or use volume/mass fraction constraint. 
     
    The 3.6 mm thickness is actually the result of the 1st iteration that starts with 0.6 material fraction by default with mass constraint . 


    CompositeOptimization2-edit.hm
    CompositeOptimization2-edit.fem
  20. Crashphys liked a post in a topic by Hyperman in Automatically connect any loose nodes on beam elements to shell elements   
    Hi,
     
    tie contact can be used in Linear Static Analysis (STATICS) and Small Displacement Nonlinear Analysis (NLSTAT). Penalty-based and MPC-based TIE contacts are available and can be selected using CONTPRM, TIE.
     
    TopologyReconstruction-edit.hm
     
    Connectors can be used alternatively. Refer to tutorial HM-3400: Create Connectors.
  21. ElineH liked a post in a topic by Hyperman in stress constraint in design variable vs. as constraint topology optimization   
    Glad to help.
     
    The topology stress constraint acts as a  global stress control. It will filter out only the artificial local stresses caused by point loading or boundary conditions so artificial stresses will not be removed. Refer to Topology Optimization of a Hook with Stress Constraints. Those stress concentrations can be removed in the subsequent design fine-tuning stage such as size, shape and free shape optimization with DRESP1 stress constraint.
     
    The artificial stress concentrations are stress singularities due to a point load or constraint, sharp re-entrant corners, corners of bodies in contact,... For more information refer to:
    http://www.acin.net/2015/06/02/stress-singularities-stress-concentrations-and-mesh-convergence/
    https://www.comsol.com/blogs/singularities-in-finite-element-models-dealing-with-red-spots/
    https://www.digitalengineering247.com/article/dealing-stress-concentrations-singularities
     
  22. ElineH liked a post in a topic by Hyperman in stress constraint in design variable vs. as constraint topology optimization   
    Hi,
     
    Stress constraint is not recommended in the design concept stage: topology, topography and free-size optimization.
    
    The stress constraint definition in a topology optimization is a global constraint and does not target local stress concentrations.  These areas can be addressed subsequently through size, shape, and free shape optimization or a combination thereof.  Artificial stress concentrations are filtered out during topology optimization with stress constraints.  These include regions around rigid connections, concentrations due to hard geometric features such as corners, etc.
     
    Stress constraints for a partial domain of the structure are not allowed because they often create an ill-posed optimization problem since the elimination of the partial domain would remove all stress constraints.  Consequently, global stress constraint applies to the entire model when active, including both design and non-design regions. Stress constraints may not work well in a model where there is a large differential in response values between design and non-design spaces. In these cases, it is recommended to modify the problem formulation to say, compliance based for example. It is not recommended to use the global stress constraint along with a mass/volume constraint. The constrained mass/volume may not allow the stress constraint to be satisfied.
     
    DRESP1-card stress constraint is used in subsequent design fine-tuning stage such as size, shape and free shape optimization. 
  23. ewsaputro liked a post in a topic by Hyperman in Roll over analysis simple bus   
    Hi,
     
    here is the Procedure to apply Initial_velocity around an axis

    9- Procedure to apply Initial_velocity around an axis - Altair University
     
    Also, make sure to constrain de independent node of a rigid body in all other degrees of freedom. 
    Share the model if the issue persists.
  24. ewsaputro liked a post in a topic by Hyperman in Roll over analysis simple bus   
    Hi,
    -you have created rigid with the master node on a structural element- this is not allowed. Make sure you use the "calculate node" or pick a free node (not connected to other elements) as independent node when creating rigid elements. Set Icog=3 or 4 so the master node will not be moved to CG
    -check unit consistency: the material properties are in tonne, mm, s so the gravity should be 9810. Also, define appropriate units in the begin card
    -gravity was acting in the wrong direction, so a negative scale factor was applied to reverse the direction
    -the boundary condition on the tilted platform constrained 1236 DOF. It should constrain 12345 instead
    -the contact sets between wheels and tilting platform were swapped
    -advanced mass scaling AMS is used instead of DT/NODA/CST mass scaling
    -the run time was extended to allow the bus to hit the ground
    -the floor is not large enough: rigid wall can be used as ground instead
    simple_bus_7_edited.hm
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