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Everything posted by Hyperman

  1. Hi, Large contact energies relative to total energy can cause large negative Energy Errors because contact energy is not part of the Energy Error equation. If the simulation has friction and a lot of sliding contact, then the large contact energy and resulting energy error can be considered acceptable. example-edit_0000.rad
  2. Hi, Use the recommended contact parameters for interface Type 7: Istf=4 Igap=2 Fscale_Gap=0.8 INACTI=6 Gap_min=1 Fric = 0.1 Iform=2 Another reason for timestep drop and energy error is because Interface type 7 does not deal with edge to edge impact. When the mesh is fine enough, edge to edge penetration is often followed by a node to shell contact. The main problem with edge to edge impact is the locking situations. If there is a change of load after edge penetration, locking is unavoidable since a node to surface contact is detected. This usually leads to high penetration; therefore, the analysis comes to a standstill as time step is reduced. If locking occurs, the use of interface type 11 in this area is necessary to solve the problem. Share the model file if the issue persists.
  3. Hi, negative energy error represents energy dissipated from the system and this can be from many sources like plastic deformation, hourglass energy, contact with friction, damping,... Review the energy balance to identify the source of this error. Since the energy error is high in combination with timestep drop (remaining time increasing) my guess is hourglass issue. Use Isolid/Ishell=12 or 24 and try running the simulation. Check the out file for warnings and errors. In this case the error 1109 is because no variable is defined for output request. The default output requests are defined by entering DEF in the Data: Var table.
  4. Hi, it is possible to activate (BCS) or release (BCSR) boundary conditions by using BCS/TRA and BCS/ROT engine cards. Refer to the following examples: RD-E: 4200 Rubber Ring: Crush and Slide RD-E: 5501 Fan Blade Rotation Initialization Kinematic Conditions.pdf
  5. Hi, only global variables like energy balance, timestep, mass, etc. are output by default to the time history file. Specific quantities of interest have to be requested by output blocks. Refer to step 8: Create Time History Output the attached tutorial on how to define force output request of a rigid body. RD-T_ 3500 Tensile Test Setup.pdf Alternatively, the force output request can also be defined in a cross-section. Referer to step 17: Create a Cross Section and then set up a TH/SECTIO output request. RD-T__3540_Front_Impact_Bumper_Model.pdf Plot the appropriate X and Y components in Hypergraph. The cross-plot function may also be useful: https://insider.altairhyperworks.com/wp-content/uploads/2018/02/T-T-1292-HyperGraph-Cross-Plot.pdf
  6. Hi, use loads on geometry. HM-4040__Work_with_Loads_on_Geometry.pdf
  7. Hi, assuming the Radioss solver is used you can try Sub-modeling (cut approach). https://altairuniversity.com/learning-library/radioss-sub-modeling-cut-approach/
  8. Hi, with the setting Z0=blank, the plies will be arranged symmetrically, i.e. half the laminate thickness on both sides of the surface geometry (see image attached). Or have I misunderstood what you are trying to do? composite_laminate_edit.hm
  9. Hi, on the PCOMPP card set Z0 OPTIONS to REAL and leave Z0 blank (no value). Share the model if the issue persists.
  10. Hi, the TOP_BCS load collector constrains all DOF, which is incompatible kinematic condition with the imposed displacement in the Y translational direction on the same node of a rigid body. Therefore Y translational DOF has to be free in the TOP_BCS load collector. seck_debug_edit_0000.rad Check unit consistency: the unit system declared in the BEGIN CARD is kg, m, s however the material parameters used are consistent with tonne, mm, s.
  11. Hi, If the deformations go past the values defined in the table, the curve is extrapolated linearly (the slope is taken from the last two data points defined). I think Optistruct does not support rupture (failure), but Radioss does.
  12. Hi, yes is the answer to both questions. /TH/INTER outputs the sum of contact force in contact interface in the time histroy output /ANIM/VECT/CONT and /ANIM/VECT/PCONT outputs the contact forces and/or pessures at nodes in the animation output
  13. Hi, Ctrl+F search for any keyword (input in the upper right corner). Use PREPRT>YES to output .CPR file.
  14. Hi, friction in kinematic joints is available in Radioss: /PROP/TYPE45 (KJOINT2). Frictional force versus displacement function is input instead of static and dynamic friction coefficients. Motionsolve does support CMS flexbody and friction in kinematic joints. _PROP_TYPE45 (KJOINT2).pdf MV-2000_ Introduction to Flexible Bodies.pdf
  15. Hi, the shared HM model has some issues: -the Passive contact had an empty slave group -the Disc constraint did not block Y DOF resulting in rigid body motion. Solid elements have only translational DOF so no need to block rotational DOF -check unit consistency: begin card declares unit system kg, m, s- this means units for stress and modulus should be Pa. The disc with 50 m diameter weighing 14g does not make physical sense. -the thermal linear expansion coefficient used 0.01 is too high. The usual range for α is from 10E−7 K−1 for hard solids to 10E−3 K−1 for organic liquids. Schnappen_edit1_0000.rad
  16. Hi, axisymmetric analysis is supported in Radioss. Refer to the attached example. Hopkinson Bar.pdf
  17. Hi, /STATE/SHELL/ORTHL is a State Engine Keyword which saves the orthotropy direction for shell elements. A block /INISHE/ORTH_LOC or /INISH3/ORTH_LOC or /INISHE/ORTH_LOC or /INISH3/ORTH_LOC is written into each state file, for each part declared into /STATE/DT.
  18. Glad to help. Refer to the last page in the attached tutorial for available material models. Radioss also supports user programmed material laws. https://www.altairuniversity.com/wp-content/uploads/2012/08/radioss_user_code_interface_jun_2012.pdf RADIOSS 14.0 Tutorials.pdf
  19. Hi, in the model you shared there are no thermal expansion coefficients defined. Activate /THERM_STRESS/MAT (under HEAT_Input) to add thermal expansion property for Radioss material with curves relating thermal linear expansion coefficient as a function of temperature. I have edited the model by inputing some random CTE on one of the components, just to get some results. The model you shared has no initialized stress state. Otherwise, there should also be Tables entry in the model browser. Please do not post the same questions in multiple threads so as not to clutter the forum. _THERM_STRESS_MAT.pdf Schnappen_edit_0000.rad
  20. Hi, there are some modeling errors: check elements(F10)>1D>duplicates: there are some duplicate beam elements tools>find connectivity: the Undercarriage beams are not connected with the rest of the model. Equivalence the nodes in edges panel (shift+F3). You should reconsider the boundary conditions. There are point supports which cause stress singularities (as the mesh is refined, the stress and strain energy will tend to infinity) and even worse- displacement singularity (displacements will also increase with refinement). Constrain a cluster of nodes to avoid this issue. Consider how the hopper wagon is constrained in real life- the model is only constrained with 4x point support on one end and rely on XZ plane symmetry to constrain the other end. As a result, the wagon is lifting vertically in the symmetry plane. Gravity and lateral loads should probably be applied to the whole model, not just SPH. The lateral load was ramped up during settling under gravity stage when kinetic relaxations was still active. It should be ramped up only after this stage instead. I have no explanation about the "Brownian motion", but when I ran settling under gravity it was well behaved. The contact forces are actually distributed, but you are only seeing the peaks as the legend contours according to the max value. Contour panel>legend>edit legend...>type:dynamic scale or input small number in the max field. The coarse mesh is stiffer so it is normal to see more deformation with finer mesh. My guess (without h3d it's hard to tell) for the roof is the frame beams are deforming (coming together in the Y direction) imparting compressive forces to the roof which is buckling elastically. This may be because the undercarriage beams were not connected. Use the deformed shape scale factor to magnify deformations. Consider if the beam layout should also be optimized. The interface is controlling the timestep in the 2nd run, which may be due to too high AMS imposed timestep. Output the number of AMS iterations per cycle via /DT/AMS/Iflag=2 which may help monitoring convergence quality at no extra CPU cost. Maximum allowed iterations before the divergence stops is 1000. 75 to 100 iteration per cycle is a sign of a poor convergence, 50 still may provide some speedup and 30 iterations or less is considered a good convergence.
  21. Hi, the first run ended with the -0.7% energy error and the second run starts from 0% energy error. The energy error is reset to zero on restart so there is actually no energy increase. To restart from the previous energy balance a *.ctl file should be created with /STOP defined (similar to the checkpoint CHKPT command in Radioss Solver Run Manager). The /AMS in the starter is used to declare components on which AMS is applied and is defined only once. /KEREL is applied in the engine file.
  22. Hi, my bad, sorry for the confusion- the lateral acceleration was 5 m/s2 indeed. Consider splitting the simulation into two parts (otherwise kinetic relaxation will be applied throughout): 1st engine file: settling under gravity with /KEREL for about 0.5s 2nd engine file: lateral loading till peak response + 0.1 or 0.2s margin Looking forward to hearing about the results.
  23. Hi, searching for Bailey-Norton law in Hyperworks documentation did not produce results so it may not be supported.
  24. Hi, hopefully, someone from Altair support will look into the issue. the unit system is N, m, s and the plate dimensions are 0.05x0.26. In the description above you mentioned the shell thickness is T=0.4 (meters?) but in the model the shell thickness is 0.0004 (0.4mm) resulting in the warning message reported in the out file: While I'm not sure if this might be causing unexpected oscillations, it should at least be checked. Unfortunately, I have no experience with comparable models to give useful tips.
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