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Simon Križnik

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Everything posted by Simon Križnik

  1. Hi, Unfortunately, there are no mid-size cars bellow 100k nodes. But you can remesh the models with coarse mesh to stay bellow the limit. Attached is the reduced Chrysler Neon model (from Altair university model repository, originally from NCAC/GWU databse) If you appreciate the content shared, please hit the like button Neon_reduce.hm
  2. @Abeba Tsegay attached is the Chevrolet C2500 Pickup, Reduced model (10,500 elements), which I converted from LS-Dyna to Radioss using Hypercrash. NOTICE: While using these FE Models, please use the following Courtesy Notice: "This model has been developed by The National Crash Analysis Center (NCAC) of The George Washington University under a contract with the FHWA and NHTSA of the US DOT" Please note there are no general claims to the validity and accuracy of the model by the NCAC or the US DOT. These models are developed for research purposes as documented in the associated reports for each model. C2500.hm
  3. Hi Nachiket Kadu, there is one more option available in Radioss user profile: Utility>Radioss Tools>RBODY manager where all rigid elements are listed with their related master nodes.
  4. You're welcome. From Radioss help on /ACCEL: Share the model if the issue persists.
  5. Hi Andy, The issue might be preserved nodes. analysis>preserved nodes to clear them. Other similar queries:
  6. Hi, If only one integration point through thickness is used, a membrane only behavior will be obtained. In case of an elastic behavior, one gets the exact solution from three integration points – that is to say that the bending moments are exactly integrated through the thickness of the shell. In case of a plastic behavior, the bending moments are not integrated exactly. Using more integration points, the solution becomes more accurate; so it is recommended to use five integration points. It also controls hourglassing. Hourglass modes are element distortions that have zero strain energy. Hourglassing may easily lead to excessive distortions To control hourglass assign Ishell-24 and N-5 for shell elements. And for solids use Isolid-14. For explicit structural analysis Ishell=24 formulation (QEPH shells) is recommended, due to balanced accuracy vs. speed. QEPH shells are more accurate for elastic or elasto-plastic loads, whatever the loading type - quasi-static or dynamic. Fully integrated 12 QBAT shells eliminate hourglassing, but are slower to compute. Try with different settings to study the hourglassing effect by postprocessing the hourglass energy in HG.
  7. Hi Laure, assuming you are referring to contact pressure output: it is not supported in linear static analysis. Please search the forum for queries first, if they are already treated as in this case:
  8. Hi LOKESH KATARI, flexible bodies are created with modal analysis of each component, so it will output natural frequencies (in .h3D and .out files). If your query is about performing modal analysis on flexible body assembly, you may find useful:
  9. Use the filter in the menu bar and choose from many types. Then shift+click the curve and define filtering parameters. NHTSA Butterworth was used in the below example, where the only parameter is the cut-off frequency to tune the response. These are similar queries:
  10. You may find useful this playlist about hexahedral meshing:
  11. Hi Farzin, I am not familiar with contact stabilization methods in Abaqus, but maybe you will find param>expertnl>CNTSTB option useful. CNTSTB was treated in the following topics: https://forum.altair.com/topic/18328-contact-analysis-in-optistruct/ https://forum.altair.com/topic/23731-large-displacement-problem/
  12. Hi virtro, Perhaps you can put the 2d>mesh edit>imprint to good use. Please refer to HM help (F1) and some tips and tricks . A similar problem was already treated:
  13. BHi saiful85, Using the result mapper in Hypercrash (2017.2.4.) with the shared files gave similar results. Everything looks fine in HCrash until export: -deformed shape is not exported -results are split into 4221 Tables (this is the probable reason for failure) But I did manage to get the model working using Hypermesh with the procedure (starting from 100mps_10cycle_15hz_simpl_0000.rad): -delete the Include files -delete the Tables (all 4242 entries) -import the solver deck ballshot_13082018_0011.sta file with FE overwrite ticked mapper_0000.rad mapper_0001.rad mapper.hm
  14. OK, I will update you through e-mail
  15. @marta in the STEPII files you shared, there is reference to .sty files (/INISTA control card). Instead, I have turned off this card and imported .sta file (with FE overwrite) from STEPI and the simulation runs fine. step2.hm step2_0000.rad step2_0001.rad STEPI_0001.sta
  16. I just found that negative jacobian can't be bypassed. So the only option is to reconstruct the mesh (starting from 2D). It is difficult to give useful tips without direct access to the model. If you are unable to share the model due to proprietary reasons, maybe you can share only the part or change the proportions (using Hypermorph) or construct sample geometry with features similar to the problem.
  17. @marta can you share the troublesome model? The NEGATIVE VOLUME error happens when solid elements are very deformed and their characteristic length goes to 0. For large strain formulation the time step of an element goes to 0 when the element is compressed. 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. This means that the solid elements using Ismstr =2 will use large strain formulation while their time step remains greater than tmin, and will then switch to small strain formulation. **ERROR : NEGATIVE STIFFNESS NODE is probably due to initial penetrations so you should clear those.
  18. That part is challenging, because it is difficult to get good quality mesh and ensure mesh continuity near acute angles. It is essential to start with good quality 2D mesh: -create 2D elements with QI optimize on Automesh panel -check and edit the mesh using quality index -repair the mesh using elem cleanup or smooth panel Even then some elements near sharp corners might be of bad quality. Use the triangular element at the tip, and if still unable to get good quality there are three options: -refine the mesh in the area -move the nodes outside geometry boundaries to satisfy quality criteria, but losing geometric accuracy -accept the bad quality mesh, if major stress/strain is not expected in that area. To bypass Optistruct element check: Analysis>Control Cards>PARAM>CHECKEL>NO
  19. Hi Momo, to access filters in Hyperview/Hypergraph: File>Load>Preference File>Vehicle Safety Tools Filter category will then become available in the menu bar.
  20. Hi Sawant Singh, this is strange- can you share the model files?
  21. No problem Solid map applied on complex shapes can have issues with node associations between source and destination geom (like the 2nd picture with skewed mesh). Defining along geom might help. Another option is to duplicate and project elements (tool>project>to surface) from source geom to dest geom and pick those elements as elems to drag and elems to match, respectively. To model the difference in geometry through thickness I would trim the solid with sweep lines in the thickness direction using 2 lines forming the "L" shape (at the tip of the arrow in the 1st picture). Basically, we want inner edges to be imprinted on outer surfaces to facilitate mesh transition. The solid should then be split using the trim with plane/surf panel into 3 longitudinal parts. Then I would 2D mesh the side and bottom faces, which would be used in solid map panel to extrude all in one go (and delete the unwanted elements) or it can be done in three sequential steps through the thickness.
  22. 1. The idea is to use the 2D mesh to impose a mesh pattern on hexa mesh. If you want a specific mesh pattern in the through-thickness direction you can also 2D mesh the sides and use nodes or elements as guides (elems to drag/match, along geom). Note that imposing mesh patterns in 2 directions requires well thought out meshing plan as it needs to be 2 directionally mappable. Maybe you will find videos on solid map helpful . 2. surf geom in the case of provided screenshot can be set to none, because it is already defined by elems to drag. Select the surface opposite to the 2D mesh as dest geom. Please hit the like button on useful tips
  23. Sure, first create 2D elements with 2D Automesh panel (F12) on the top surfaces of solids. Then use these 2D elements to create the 3D hexa mesh in two different ways: -if the component has constant thickness you can use 3D>elem offset>solid layers panel -for better mesh control in the thickness direction use the 3D>solid map>general panel and select 2D elements to drag After Hexa mesh is created delete the 2D elements. Is there a reason to split the solid in such a pattern? Otherwise, only washers should be split around holes.
  24. Hi Aslan, it looks like solid map went wrong. The outline and temporary nodes are automatically created around distorted elements. You should delete the mesh and rebuild. If the component does not have complex thickness variation it can easily be meshed: first in 2D and then extruded to 3D hexa mesh. Also, considering only the displayed geometry splitting the part seems excessive, which also causes bad meshing around holes.
  25. Hi Marta, I suggest using .sta files instead of .sty files, which is a legacy format. The procedure to carry over stress and strain state of elements is to create STATE engine cards in the 1. step: /STATE/BRICK/STRAIN/FULL /STATE/BRICK/STRES/FULL if there are shells also create additional cards (search Radioss help with keyword: STATE) /STATE/DT (define start time and frequency to write state files and declare components to be included) Run the simulation which creates model_name.sta file, which is then imported into the original model. It will overwrite the original mesh with deformed and there should also be Tables entry in the model browser (stress & strain information for each element that can be edited). Attached are the modified files and also some tips about STATE files. inista.rar StateFile_1200.docx
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