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Hyperman

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Everything posted by Hyperman

  1. Hi @Merula I think the topology results are as expected. With inertia relief the object is "floating" and the stiffest design is the one where most material is near load application points, i.e. regions experiencing the most deformation. The force magnitude has no effect on topology optimization minimum compliance results, but ratio between different loads does. Try using DOPTPRM>DISCRETE to get better converged 0/1 design.
  2. Hi, This can be done by first assigning the nodes to a cylindrical coordinate system and then constraining radial and trasnlational directions with SPC and enforcing displacement in the tangential direction with SPCD. 1. From the Analysis page, enter the systems panel. 2. Select the assign radio button. 3. Make sure the entity selection switch in front of set: is set to nodes. 4. Click the yellow button nodes to open the extended entity selection window and select all. 5. Click the yellow button system to activate it and select the red colored system from the graphic window. 6. Click set displacement. The message on the footer bar “The analysis system has been assigned” appears. 7. Click return.
  3. Hi, 2 surfaces failed to mesh in your model. Unmeshed surfaces can be found in the automesh panel (F12)>unmeshed. The mesh failed probably due to bad geometry. One option is to perform automatic geometry cleanup Geom>autocleanup, but this option can suppress necessary feature edges. Some edges have to be manually edited with Geom>edge edit>toggle or (un)suppress (also in quick geometry edit panel F11). wing_top_edit.hm
  4. Hi, when the shell element size is small compared to thickness it loses validity. Solid elements are more appropriate for this object and you can perform shape optimization instead. Quote https://www.linkedin.com/pulse/shells-vs-solids-finite-element-analysis-quick-review-kuusisto-p-e- Constraining the hole where loads are applied effectively eliminates this load. I suggest you perform inertia relief analysis (PARAM>INREL>-2) instead. Reanalyse_Interpretation_edit.hm
  5. In the model you shared, only constraints are defined but no loads. Provide more details about the model (what is the simulation objective, loads,...). You should also check unit consistency, as material 2 has unphysically high Young's modulus and no Poisson's ratio. Please refer to Radioss>User Guide>Implicit Structural Finite Element Analysis for details about Implicit Analysis. Quasi-static Analysis Notes.pdf Implicit Structural Finite Element Analysis.pdf Check examples: RD-E: 1602 Dummy Positioning IMPLICIT Solver RD-E: 4200 Rubber Ring: Crush and Slide
  6. Hi, this is strange. Try view>panels A similar query was already posted and got resolved by updating.
  7. Hi, the reason for very low stress and strain values is because the element size is too big to capture local stress distribution. In the model you shared the shell elements of tank walls are 235mm, while 5-10mm element size is recommended in a typical crashworthiness analysis. Because the whole tank is too big to be solved with such a fine mesh, I recommend you to somehow isolate the area of high stress and solve it using smaller mesh size (found through mesh convergence study). https://enterfea.com/correct-mesh-size-quick-guide/ If you plan to do a convergence check, consider performing at least one refinement of the model after the first run. If neighboring elements display large differences in stress, the gradient was probably not captured in these areas, therefore some mesh refinement is recommended. In general, increasing the number of nodes improves the accuracy of the results. But at the same time, it increases the solution time and cost. Usual practice is to increase the number of elements and nodes in the areas of high stress (rather than reducing the global element size and remeshing the entire model) and continue until the difference between the two consecutive results is less than 5 to 10%.   I recommend you to go through free ebook Practical Aspects of Finite Element Simulation (A Study Guide) which covers 9.12 Mesh Density And Solution Convergence.
  8. Hi, 1. Constraints and loads applied on single nodes will cause stress singularity. For more details refer to: https://www.comsol.com/blogs/singularities-in-finite-element-models-dealing-with-red-spots/ 2. and 3. are due to bad mesh. You should remesh the model using the these tools: Geom>autocleanup to clean up the geometry 2D>automesh>QI optimize (F12) to mesh using quality criteria 2D>elem cleanup 2D>qualityindex tool>check elems>2D (F10) to check elements There are more then 4 million elements in the model you shared. Reduce the element count (increase element size), unless you have access to supercomputer to solve this model in a reasonable time. There are some great learning materials from Altair university- Practical Aspects of Finite Element Simulation is a good starting point. https://altairuniversity.com/free-ebooks-2/ Check the following Youtube channels: Altair University Altair India Student Contest ELEATION By Apoorv Bapat https://altairuniversity.com/wp-content/uploads/2012/04/HM_Geometry_extract.pdf https://altairuniversity.com/wp-content/uploads/2014/02/HM_Automeshingintro.pdf https://connect.altair.com/CP/SA/training/self_paced/aero_v13/PDF/chapter4_demonstration.pdf The Like button is an easy way to show appreciation for a post
  9. Sure, you can share it here. 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. Here are two videos about quasistatic analysis:
  10. Hi, the starter out file (run_name0000.out) should be checked when errors and warnings are reported. Tensile failure strain in the material direction 1 (EPST1) at which stress starts to reduce should be less then Maximum tensile strain in material direction 1 (EPSM1) at which the stress at the element is set to zero. Tsai-Wu Formulation (Iform =0).pdf
  11. Hi, these are the errors: No material was defined for components ID 24, 25 and 26. There is no variable defined for output request. The default output requests are defined by entering DEF in the Data: Var table.
  12. Hi, You can simulate a quasi-static loading more computationally efficient by time scaling, which means applying the load more quickly in order to reduce the simulation time. However, the kinetic energy should be low (5-10%) compared to the internal energy for most of the simulation, to minimize the inertial effects. You can check the energy fraction in Hypergraph by plotting both energies and using Vehicle safety tools (File-Load-Preference File) to divide curves (Math-Two Curves-Divide w/Zero). You can plot kinetic, internal, contact, hourglass and total energy in Hypergraph. Those variables are output by default and can be loaded in HG (file: runname_T01)>Global Variables>Y requests>MAG to plot.
  13. Here is a video about working with session files: Session File and Report Templates in HyperView Tips and Tricks
  14. For explicit analysis time step is the time required for a shock wave to propagate across the smallest distance of the element. Time step of a model is directly proportional to the length of an element and is inversely proportional to the speed of sound. So, if the material is stiffer (higher modulus of elasticity), the speed of sound increases resulting in a lower solution time step, as both material modulus and density control the speed of sound. Using the same mesh from implicit will usually result in long solving time in explicit due to small element length. III_Considerations about Time-Step - Altair University You can simulate a quasi-static loading more computationally efficient by time scaling, which means applying the load more quickly in order to reduce the simulation time. Usually the load is ramped up in 0.3 seconds. However, the kinetic energy should be low (5-10%) compared to the internal energy for most of the simulation, to minimize the inertial effects. You can check the energy fraction in Hypergraph by plotting both energies and using Vehicle safety tools (File-Load-Preference File) to divide curves (Math-Two Curves-Divide w/Zero). You can plot kinetic, internal, contact, hourglass and total energy in Hypergraph. Those variables are output by default and can be loaded in HG (file: runname_T01)>Global Variables>Y requests>MAG to plot. This topic might help: https://forum.altair.com/topic/30209-is-it-normal-that-radioss-solver-showing-huge-amount-of-time-remaining-to-solve-a-problem/ From Radioss help: Recommended Checklist.pdf
  15. Hi, you can update element types in two ways: 1D>config edit 1D>elem types
  16. Hi, these are items you need to define: material parameters tetramesh requires PSOLID property assign material and property to components loads loadstep I suggest you go through free Altair e-books, start with Practical Aspects of Finite Element Simulation. 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 EngineBlock12_edit.hm
  17. Hi, right-click the Assembly Hierarchy>Show, then ctrl+middle mouse button to fit the model to screen. Share the model if the issue persists-file size is a good indicator if elements/geometry are in the model.
  18. Hi, in the model you shared, the FAIL/XFEM/JOHNS was not referring to material card. The quarter symmetry boundary conditions were incorrectly assigned (see attached RD-T: 3500 Tensile Test Setup). You should also consider mass and/or time scaling, as the natural timestep and the imposed velocity used would take a lot of time to solve. RD-T_ 3500 Tensile Test Setup.pdf
  19. Hi, glad to help. Unfortunately, I do not have much experience with HyperStudy to be able to answer your questions. Hopefully, someone more familiar with this software can provide answers.
  20. Hi, looks like symbols for connectors- yellow are unrealized and red are failed. Open the Connectors browser by clicking View > Browsers > HyperMesh > Connector from the menu bar. Right-click the connector in the connector entity browser and select delete>connectors. Refer to tutorial HM-3400: Creating Connectors for more details.
  21. I think the mesh is there- it just looks like it's lost because the surface geometry is obscuring the mesh. Hide the surface or display wireframe geometry to verify.
  22. Hi, the problem is indeed with the mesh- there are some elements with small characteristic length penalizing the natural timestep and the AMS timestep imposed is too high for this mesh. Remeshing is recommended while paying attention to the smallest length. Use check elements panel (F10)>time to check timestep of elements. Use 2d>elem cleanup and/or qualityindex panel or remesh with automesh>QI optimize with minimum element size criteria.
  23. In the shared screenshots PLSOLID is defined, which is only compatible with MATHE material card. The property should be PSOLID instead. Perhaps there are also 2D elements in the component assigned with solid property. Use View>Browser>Hypermesh>Mask to show/hide 2D or 3D elements.
  24. glad to help When h/L is large, shear deformation is at its maximum importance and the user should use solid elements. When h/L is small, transverse shear deformation is not important and thin shell elements are the most effective choice. Thick shells are used when thickness to length ratio is between solid and thin shell recommended range.
  25. Hi, the model you shared actually has asymmetric loading: one load is missing in the second row. To get results similar to the b) image, the mesh should be refined and minimum member size reduced. Mesh refinement should also improve connectivity.
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