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Everything posted by Hyperman

  1. Ctrl+F search for any keyword (input in the upper right corner).
  2. 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
  3. 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.
  4. Hi, in Hyperview load the animation file (run_nameA001 in the run folder).
  5. Ctrl+F search for any keyword (input in the upper right corner).
  6. Hi, TIE contact can be automatically created using tools>contact browser>AutoContact https://altairhyperworks.com/pdfs/tips/1095.pdf Even though the GUI has changed the functionality is similar.
  7. 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.
  8. 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.
  9. Hi, the stress-strain slope should be positive (the data points must be in ascending order). Convert the engineering stress-strain to true stress-strain. The first point of yield stress functions (plastic strain vs stress) should have a plastic strain value of zero. The curve should be nearly flat (slightly increasing) after the ultimate strength. To model failure use εt,εm, and εf parameters or dedicated failure models. Materials.pdf
  10. I can help you learn, but do not expect me to do your work. First try yourself and ask for help only if you fail.
  11. Attached is the model file and result for a simply supported plate on all four sides. multiBC2.hm multiBC2.h3d multiBC2.op2 multiBC2.out multiBC2.pch multiBC2.fem
  12. The solver deck you shared is a Nastran bdf file and that error was reported by a Nastran solver. Nastran issues should be posted on Nastran forums (this is Altair forum). Optistruct can import bdf files and I was I able to run your model without issues- see attachments. multiBC.out multiBC.pch multiBC.h3d multiBC.fem multiBC.hm multiBC.op2
  13. Hi @Sony Dhotre create a separate load collector for each set of boundary conditions. For example, create a load collector with all DegreesOfFreeedom fixed and a second load collector fixing only translational DOFs. Create only one load collector if you need to constrain only one set of DOFs.
  14. 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
  15. 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.
  16. PBEAML allows selecting from a library of standard cross-section shapes such as BAR, BOX, BOX1, CHAN, CHAN1, CHAN2, CROSS, H, HAT, HEXA, I, I1, L, ROD, T, T1, T2, TUBE, or Z. PBEAML.pdf
  17. Hi, there are several issues in your model: the payload is modeled with shell elements, but solid element would be more appropriate. The upper surface shell would sag under gravity and its weight would be transferred only by side shell surfaces. Solid elements would equally distribute the weight over the floor. the "lc6" load collector referenced in linear static load step is empty, which is invalid (the solver will error out). Reference a gravity load collector "0.1_z negi" instead. the master component is usually stiffer or in case of equal stiffness the one with the coarser mesh. In your case, the cargo has the same stiffness and mesh size as a steel cargo box, but I would still choose the cargo as a slave. Sliding contact might not work using linear static analysis. In linear static analysis, the contact status does not change, does not slide and the contact stiffness is constant. Freeze Contact enforces zero relative motion on the contact surface, the contact gap opening remains fixed at the original value and the sliding distance is forced to be zero. Additionally, rotations at the slave node are matched to the rotations of the master patch. The FREEZE condition applies to all respective contact elements, regardless of whether they are open or closed. Freeze Contact can be activated using TYPE=FREEZE on the CONTACT, MU1=FREEZE on the PCONT entry or by using the Penalty-based Tied Contact. Penalty-based tied contact is activated by using the TIE entry for the contact interface (with CONTPRM,TIE,PENALTY, the default).
  18. It is possible the restart file is corrupt- try deleting (or just moving to another folder) the last restart file and restarting from the second to last. Restart file without a model file is useless. Unfortunately, I can not provide further help with the given information. Check FAQ on restart: Restart.pdf
  19. Hi, the von Mises stress will be output by default when using PBARL or PBEAML with standard cross section. beam.fem
  20. @tranty these parameters require strain value input: EPS_p_max is Failure plastic strain EPS_m is Maximum tensile failure strain at which the stress in element is set to zero.
  21. Hi, choose the Optistruct user profile. Here is a video on how to import geometry: I recommend you go through FREE eBooks: Practical Aspects of Finite Element Analysis Introduction to Practical Aspects of Composites with Altair OptiStruct Check the following webinar: Alo search for other videos related to composites: https://www.google.com/search?q=composite+optistruct&sxsrf=ACYBGNSfNx5x1oRFY-AfexZKWyQXsUDT-w:1574068736682&source=lnms&tbm=vid&sa=X&ved=0ahUKEwj3n5v_tvPlAhWvlosKHTfYBU8Q_AUIEygC&biw=1858&bih=977
  22. Hi, the file you shared is empty. Either the restart file is not compatible with the version you are using or there is some problem with the restart file. Can you share the model? This error was already posted:
  23. Hi, To fix free edges of the holes use Geom>surfaces>Spline/filler or quick geometry edit (F11)>filler surf 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 such as min size 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 retrovisor_esfuerzos_NO_edit.hm
  24. Hi, such abrupt termination is unusual. The run is usually prematurely terminated either with an error message or by user intervention. I was able to run the model to the 7th frame, after which I manually stopped the simulation (see attached out file). In your run the Radioss calculation process was probably terminated. You can try restarting: There is no engine file because the engine file was merged with starter on export. Since you have checked "Merge starter and engine file" option, the engine control cards defined will be in the starter file (_0000.rad) itself and that's why the engine file was not created separately. Open the _0000.rad file in Textpad or Notepad and ensure that engine control cards are present. 11_11_2edit_0001.out
  25. You're welcome. Actually, tie contact can not be automatically converted with tools>convert>Optistruct>to Radioss while connectors elements like CWELD can be converted. Type 2 tied contact is tie contact equivalent in Radioss and can be easily recreated. I am not sure how to export version 2017 compatible model but here is the solver deck: TopologyReconstruction-edit.fem
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