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Simon Križnik

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Everything posted by Simon Križnik

  1. Hi, make sure there are no initial penetrations and intersections. There are 2 possible reasons for penetrations during the run: -the edges are not detected because Interface type 7 does not deal with edge to edge impact. Define an additional symmetric type 7 interface or type 11 or 19 interfaces. -there is a large difference in stiffness between contacting components Share the model, if the issue persists.
  2. Hi Chris, thanks for your interest. The objective is to design a compliant mechanism by performing integrated structural and system level optimization (similar to OS-E: 4015 Optimization of MBD System Level Response). Flexible links are modeled with CMS flexbodies and hinges (small length flexural pivot) with NLFE. HM is preferred because it is easier to modify flexbody mesh and use Hypermorph to generate shape design variables, as opposed to Motionview where parameterization is done with hardpoint coordinates and there is no way to modify the mesh once it is imported.
  3. Thanks for your response. Hopefully, NLFE will be supported in a future version of HM. As a workaround, is it possible to append Motionsolve xml commands with BULK or CASE_UNSUPPORTED_CARDS?
  4. Hi, can Non Linear Finite Elements (based on Absolute Nodal Coordinate Formulation or ANCF) be created with Hypermesh preprocessor?
  5. Hi, actually only one SPRING2N element is created; the other two elements on either end of spring are plot elements (1D elements with 2 nodes used for display purposes only). Use proper post script to realize connectors upon creation. Otherwise use the realize subpanel.
  6. Without the model file, my best guess is the contact at the edges are not detected. If that is the case, define an additional type 11 or 19 contact. You may find helpful Free eBook: Introduction to Explicit Analysis with Altair RADIOSS. I have recently revised the third edition which should be available in the near future.
  7. You need to define local skew and Def_orth=1 only for those plies that have an invalid orientation assigned by /STACK (in your case Vx=1, Vy=0, Vz=0 means only plies whose normal points in global x-direction has to be corrected). All elements with PCOMPP prop_ID type must belong to a ply (/PLY) inside a stack (/STACK). CarbonBox_edit_0000.rad
  8. The first anisotropic direction of material could be defined with angle ϕ and global vector (Vx ,Vy ,Vz ). It is also possible to use angle ϕ and skew. In this case, x-axis of skew replaced the global vector V. The orthotropy direction is set with Vx, Vy and Vz parameters in /STACK card (laminate). To override laminate direction set up ply with local skew and Def_orth=1. CarbonBox_edit_0000.rad
  9. Can you share the model?
  10. Hi, when assigning material orientation, make sure the direction is not perpendicular to shell elements. You have probably assigned material orientation in the height direction for the whole component, which is invalid for the elements on top (check material orientation of element 1600). The best practice is to assign material orientation for each surface one by one.
  11. Welcome, refer to step 8: https://connect.altair.com/CP/SA/training/self_paced/aero_v13/PDF/chapter10_demonstration.pdf
  12. Upon looking into the model again I found the reason why the buckling initiates at the base of upper crashbox. Looking at the cross-section (deformation scaled 5x) it is revealed the clamping region at the base of upper crashbox slightly rotates inwards, which initiates the buckling. The reason for this behavior is the primary load paths are not aligned (crashbox diameters are different) which induces bending moment.
  13. Hi, the geometry has to be properly partitioned before using automatic hexa mesher (one volume, multisolids). In case of complex shapes, it is challenging to properly partition the solid in order to be mappable in one or more directions- it is even more challenging to strategically plan how these mappable solids come together to produce a structured mesh. Unfortnately, there is no easy fix for hexa meshing as it is the most difficult type of meshing. Refer to the following for details: https://www.altairuniversity.com/wp-content/uploads/2012/04/HM_SolidMesh_Extract.pdf https://altairuniversity.com/wp-content/uploads/2012/03/Bracket_Geometry.pdf https://blog.altair.com/art-of-map-meshing/
  14. Hi, this is a strange issue. However, the issue is resolved in recent versions as /ADMAS no longer requires visualization node and the COG is computed correctly. Therefore I recommend updating the version you are using.
  15. Hi, there are modeling errors: -3 beam elements have collinear nodes (invalid orientation node). Use the 1D>beam>update panel to resolve this issue. -remove intersections and penetrations with tools>penetration check -the timestep imposed is a bit too high TP004_2_edit_0000.rad The deformation starts at the base of the upper crashbox due to random mesh flow lines that behave as a geometric imperfection. 2-D quad mesh should be systematic (ruled or mapped), avoid 2-D auto mesh: Flow lines should be maintained with minimum number of trias and diamond or rotating quads should be avoided. Use of the auto mesher on surfaces sometimes results in a zig-zag or random mesh which might lead to unexpected problems later. Better Mesh Flow: For crash or non-linear analysis, systematic mesh flow lines where all the elements satisfy the required quality parameters is very important. Using a mix-mode element type instead of pure quad element type helps to achieve better flow lines and convergence of solution. Refer to the page https://www.altairuniversity.com/wp-content/uploads/2014/02/2Dmeshing.pdf
  16. Glad to help. You need to split the geometry into design & non-design components using geometry>solid edit>trim with nodes, lines or plane/surf. Solid_Edit_Panel.pdf
  17. Hi, it is common practice to create a rigid (RBE2) spider and apply the load to the independent node. In general, it is best not to apply loads and displacements directly to design spaces, as this often leads to incorrect results. Instead, you should split the part into design and non-design spaces, and apply loads and displacements to the non-design spaces.
  18. This error is due to non-convergence (check the out file for details). Increase the number of cutbacks allowed (NCUTS) in the load collector with NLADAPT card image and refer this load collector under NLADAPT subcase definition (loadstep). However, there is a limit when implicit methods become computationally inefficient (buckling, wrinkling, unconstrained rigid body motion, large deformation, rupture, contact with friction,...). These cases can be solved by the explicit method. 30Diametro-edit2.hm
  19. Hi, looks like something is preventing the writing of the *.avi file: -if writing for the first time, make sure you have permission to write to the specified folder -if rewriting the existing (previously created) file, make sure it is not opened in other applications
  20. Hi, I would also like to know if this functionality (marker orientation tracking between two moving bodies) is available yet?
  21. Glad to help. I suggest you go through free Altair e-books and start with Practical Aspects of Finite Element Simulation. You can also learn from learning and Certification program: https://certification.altairuniversity.com/ > (Learn Modeling and Visualisation) Check the following youtube channels: AltairUniversity Altair India Student Contest ELEATION By Apoorv Bapat If you are new to FEA I recommend Finite Element Analysis For Design Engineers by Paul M. Kurowski: https://www.sae.org/images/books/toc_pdfs/R449.pdf
  22. Hi, 1. Use large displacement non-linear static (LGDISP NLSTAT) or transient analysis. Only explicit analysis (Radioss) can converge in case of wrinkling. 2. To get membrane behavior set MID2 and MID3 as BLANK. Membrane has no bending stiffness which can cause convergence difficulties. As a workaround, assign another material of negligible stiffness under MID2 & MID3. 3. Linear static cannot be used because of geometric non-linearity inherent to inflatable structures. 4. It is necessary to assign thickness in any type of analysis. 5. Material MATHE cannot be referenced by properties other than PSOLID/PLSOLID. Therefore it can not be used with shell elements. 6. For computational efficiency this model could employ quarter symmetry as load, BC and geometry are all symmetric. 30Diametro-edit.hm
  23. Hi, use 1D> HyperBeam> solid section to define custom beam section with lines, surfaces, elements or section cuts. Refer to step 5 of HM-4020: Assign Properties Using HyperBeam HM-4020__Assign_Properties_Using_HyperBeam.pdf
  24. Hi, Emax and EPS_max are not mandatory, if the loading curve is defined. From Radioss help:
  25. Hi, SOLVTYP defines the solver type to be used for static and dynamic analysis. Load collector>SOLVTYP card image --> Load Step>SOLVTYPE (subcase option). SOLVTYP.pdf Solvers.pdf
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