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Simon Križnik

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Everything posted by Simon Križnik

  1. Welcome, node-to-node connectivity is preferred (edges panel (F3)>equivalence). Tie or freeze contact can be used to connect nonmatching mesh. Use auto-contact in the tools>contact browser to automatically create contacts. i beam DND_2_edit.hm One element through the thickness is not recommended for bending problems. Remeshing the flanges with many elements through-thickness might lead to bad element quality (aspect ratio) or an excessive number of elements (bad computational efficiency). Given the web and flanges are relatively thin they could be meshed with shell elements instead, which should also enable node-to-node connectivity. https://knowledge.autodesk.com/support/inventor-nastran/troubleshooting/caas/sfdcarticles/sfdcarticles/Thin-parts-can-have-inaccurate-results-when-using-solid-elements.html
  2. There is a tool for material system review: Tools>orientation review>material system Orientation Review - Altair University
  3. Stresses are calculated in the material coordinate system. The material coordinate system may be defined as the basic coordinate system (CORDM=0), a user defined system (CORDM = Integer > 0), or the element coordinate system (CORDM=-1). Edit the PSOLID property and change the CORDM to USER and select the coordinate system which will be the material orientation. Alternatively, material orientation can be assigned to elements directly with analysis>systems>material orientation. In the model you shared the CHEXA elements are oriented with THETA option. The element angle option for Hexa solid (Theta) is very useful if the material system is changing from element to element. Make sure to define only one of these options to avoid confusion. Perform a simple 1 element tensile test to verify material orientation. The like button is a nice way of showing appreciation for the help
  4. Hi, as far as I know, there is no simple way to get the percentage of added mass per each part (part mass output using /TH/PART does not include the mass added, due to mass scaling). Using the animation output option /ANIM/NODA/DMASS or /H3D/NODA/DMASS, the relative mass increase per node can be visualized in a post-processor as a contour plot.
  5. For shell elements, the contact and tie search considers the shell thicknesses. This implies that the defined search distance is expected to be the true distance between the shell surfaces facing each other. For example, in the case of shells without offset, if the geometric distance between the two shell surfaces facing each other is 5.0, and the shell thicknesses are 2.0 each, then the actual distance between the shell surfaces facing each other is 3.0. If the Search distance field is now set to 3.0, then the contact is generated as expected (in this scenario, if SRCHDIS is set lower than 3.0, then there is no contact generated). For more details, please refer to the attached document. To constrain the plate from sliding: -use symmetry (refer to 10.3) -constrain some nodes in the Z DOF Contact.pdf
  6. The initial velocity should be a negative number along the global Z direction. There is a crashbox tutorial in the Radioss ebook, and here are a few videos:
  7. Glad to help. RBE2 transmits the displacements and RBE3 transmits the loads (MPC Forces). Dependent and independent nodes are reversed in RBE2 and RBE3, therefore it is invalid to constrain the RBE3 master node, which is dependant on the deformation of the independent nodes. For more details refer to: http://www.endurasim.com.au/wp-content/uploads/2015/02/EnDuraSim-Rigid-Elements.pdf https://www.predictiveengineering.com/sites/default/files/predictive_engineering_white_paper_on_small_connection_elements-mpc_and_cbush_rev-1.pdf
  8. Hi, RBE3 is used for load transfer and the load (but not constraints) can be applied on the dependent node. In your case, the dependent node of the bottom RBE3 is constrained and this is causing the error. As a workaround: -stiff: change the bottom RBE3 to RBE2 (config edit) -compliant: create cbush and connect one end with RBE3 and constrain the other end For more info refer to:
  9. Glad to help. Try to model aluminum foam with /MAT/LAW33 (FOAM_PLAS) and any of the compatible solid properties. This material model was used in a similar application: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.940.3859&rep=rep1&type=pdf
  10. Hi, The laminates were connected to the core with freeze contact. Since both components have matching nodes on the surface the connection can be established with node-to-node connectivity (equivalence in edges panel- F3). The supports were penetrating the plate and are tied to it with freeze contact (equivalent to gluing the supports to the plate). This is the possible reason for discrepancy compared to test- sliding contact should better approximate the test boundary conditions. Some friction should be able to prevent the plate sliding in Z direction. Quarter or half symmetry can be used for better computational efficiency and also constrain the plate from sliding. 3PB_NLS_edit2.fem 3PB_NLS_edit2.hm Refer to example OS-E: 0180 3-Point Bending using RBODY 3Point_Bending_RBODY.fem OS-E_ 0180 3-Point Bending using RBODY.pdf
  11. Hi, go to check elements panel (F10)>1D and specify "length" as 0 or some very small number and "save failed". Open delete panel (F2), click "elems" to access extended entity selection, then "retrieve" and finally "delete entity".
  12. Either pick elements or components- the latter is less time consuming if proper tolerance is used. If no nodes were highlighted with preview equiv it means no nodes were found within the tolerance specified. Increase tolerance until expected nodes are highlighted. The ^edges component will remain in the model unless you delete it. Share the model, if the issue persists.
  13. Try adopting the approach from Radioss example RD-E: 2300 Brake BRAKE2_0001.rad BRAKE2_0002.rad BRAKE2_0000.rad
  14. Hi, The ACCEL, ACCEL1, and ACCEL2 entries are used to define the application of static acceleration loads at grid points in the model.
  15. Hi, The errors are due to: -the shell property has no thickness defined (T field) -the moment load has no grid/gridset definition If you are new to finite element analysis I recommend you go through: Free eBook: Practical Aspects of Finite Element Analysis
  16. Hi, as far as I know, there is no way to get contact time history output in a local coordinate system. As a workaround, you can request contact force output /ANIM/VECT/CONT. In postprocessing with Hyperview, create a local coordinate system and use this system under Resolved in User system. Finally, use the query to extract the force components as resolved in the local coordinate system. Here is the procedure:
  17. The Like button is an easy way to show appreciation for the help. The common approach is to ensure node-to-node connectivity with equivalence in the edges panels (shift+F3): I would not recommend connecting with RBE2 elements, because these connections are infinitely stiff. The thick shell approach might work, however they are more useful for thick shell structures with massive junctions. It may give better stress distribution and capture deformation modes more accurately but it will significantly increase the computational cost.
  18. Hi, actually there are no contact interfaces in your model (otherwise it would be listed in the browser). Consequently the "check all solver contact interface" can not be done unless you first define contacts. Here is a procedure to create type 7 contact: If you are new to Radioss I recommend Free eBook: Introduction to Explicit Analysis with Altair RADIOSS. I have recently revised the third edition which should be available in the near future.
  19. Hi, the following topics may resolve you query:
  20. Thanks for your suggestions. However, changing the units to milliseconds does not solve the issue. The displacements even after 1 microsecond are not zero and running longer duration reveals the same instability:
  21. Hi, simulating a curved hyperelastic NLFE cantilever beam returned unexpected results: the beam is unstable instead of holding the initial arc shape in the absence of gravity load. The issue does not happen with a linear material. What is the cause and how can it be resolved? NLFE_curved_hyperelastic.mdl
  22. Hi, if you have correctly set up the lattice optimization, the design variables (and design variables property relationship) should be generated automatically after the first phase. Just import the modelname_lattice.fem file at the start of the second phase. I recently made a video on lattice optimization, which you may find useful: Also refer to tutorial OS-T: 3300 Lattice Optimization Process
  23. Hi, use HvTrans tool to convert animation files A00 to h3d file. HWD-0050_ Translating Results - HvTrans.pdf
  24. Hi, use Tools>model checker>optistruct to check and correct modeling errors. https://insider.altairhyperworks.com/wp-content/uploads/2017/09/T-T-1248-HyperMesh-Model-Checker.pdf
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