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Simon Križnik

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Everything posted by Simon Križnik

  1. Hi, if the geometry changes significantly it is possible the crash dynamic also varies from the original in: mass, affecting the kinetic energy stiffness, because of different load paths/crushing behavior It is difficult to estimate how much submodel affects the global model. This is why the reanalysis of the optimized global model is recommended. RD-E: 5400 Cut Methodology Conclusion (from Radioss help):
  2. Looks like the CWELD element is not attached directly to adjacent elements but through the tie contact. In Radioss user profile there is the option to include tied contact. Unfortunately, such functionality is not supported in Optistruct user profile.
  3. Hi, try this procedure: -isolate CWELD elements of interest with the mask panel (F5) -in the Find panel (shift+ F5) find elements attached to the CWELD elements. The attached elements will be unmasked. -check if the unmasked elements contain 3d elements (use the mask browser to show/hide entities by element types).
  4. Hi, The long calculation issue is not due to the unloading curve; the time step will drop due to the element compressive deformation. This happens when elements are very deformed and their characteristic length goes to 0. In the case of large strain formulation, the time step of an element goes to 0 when the element is compressed. In a mathematical way, the element can not reverse its orientation since its stiffness increases to an infinite value; but due to numerical accuracy, the element may go to reverse its orientation. In order to solve the problem of both the drop in cycle time step and subsequent termination of the run due to a negative volume, you might first check that the material used is well-suited to the physics which is represented. Then switch the elements to a small strain formulation. This is done as follows: In the RADIOSS Starter input file (Runname_0000.rad), use Ismstr =2 in the solid property or in the option /DEF_SOLID; in RADIOSS Engine file (Runname_0001.rad) use the option /DT/BRICK/CST which will set the time step value symbol_tritmin at which the solid elements will switch to small strain. This means that the solid elements using Ismstr =2 will use large strain formulation while their time step remains greater than symbol_tritmin, and will then switch to small strain formulation. Their volume will then remain constant and the element can even reverse its orientation. The drop of their time step normally stops except for some materials, especially viscous materials. Check the attached video for more information (relevant from 6:00) V_h_Solid Elements in RADIOSS - Altair University
  5. Hi, Hyperview can be used to post-processing animations files. Hyperview can be used to plot time history files. Energy balance curves are output by default, only need to define TFILE output frequency. Check the following video (relevant from 1:38:30): 2016 Directed Learning Webinar Series - Crash Analysis with RADIOSS - Altair University TP005_editT01 TP005_edit_0001.rad TP005_edit_0000.rad
  6. Hi, Radioss solver is capable of highly nonlinear transient dynamic and quasi-static analyses. To answer your general question would require an extensive reply. Therefore I suggest you first check the free Radioss ebook and some videos: Introduction to Radioss Radioss for Non-linear Crash using Altair HW SE Impact Attenuator Crash Analysis for SUPRA SAEINDIA 2017 - 3D Meshing & Analysis using HW SE 14.0 Impact AOC Webinar: Introduction to Radioss for Explicit Nonlinear Impact AOC Webinar: Nonlinear Analysis using Radioss by HW SE 14.0 Hypermesh Crash Simulation HyperWorks 2019 - Radioss - Steel Ball and Plate Impact Simulation BAJA SAEINDIA Online Training-Dynamic Crash Analysis using Altair RADIOSS AOC India 2019 RADIOSS Crash simulation 2016 Directed Learning Webinar Series – Crash Analysis with RADIOSS https://altairuniversity.com/learning-library/2016-directed-learning-webinar-series-crash-analysis-with-radioss/ SUPRA SAEINDIA 2015 - Webinar Series - Day - 5 SAEINDIA BAJA 2016 Online Training Session Day 3 https://www.youtube.com/watch?v=Aa1NBx6Kqh8 AOC2015: Linear / Non-Linear Contest Models Solution recorded webinar https://youtu.be/eFh5xngYuLs?t=1823 Dynamic Crash Analysis of Roll cage Radioss for Dynamic Analysis Dynamic Crash Analysis using Radioss
  7. Hi, to check element quality use: check elements (F10) to check each quality criteria one at a time 2D>qualityindex can concurrently display multiple quality criteria (chosen in QI settings) Quality Index - Altair University
  8. Hi, please refer to HM-3410: Create Area Connectors. HM-3410_ Create Area Connectors.pdf frame_assembly_1.hm
  9. Hi, Tperiod is period to be damped (less than or equal to the highest period of the system). Please refer to RD-E: 1600 Dummy Positioning about how to use various damping options. /ADYREL Dynamic relaxation with auto-defined adaptive damping is supported since 2019.1 version.
  10. Hi, to model revolute joint use: Kjoint (property type 33) between deformable (flexible) bodies Kjoint2 (property type 45) between rigid bodies
  11. Glad to help. Error ID 44 is a general error and can be due to many modeling issues. Share the model for debugging if possible. With total tensile failure defined, the element will be deleted when the specified strain is reached. To output damage evolution use /ANIM/SHELL/DAMA which generates animation files containing a damage value for each layer of a shell element. The damage value is the maximum of damage over time of all failure criteria associated with the material. You may also find this presentation useful (especially p18-19): https://altairuniversity.com/wp-content/uploads/2012/11/Presentazione_Dolci2.pdf
  12. Glad to help. 1. The load collector 'displacement_spc' constrains the moving plate in all degrees of freedom except z translation. Without this constraint the plate could rotate and/or displace in unwanted directions. 2. The master segments are both plates. Usually, the stiffer component is chosen as the master. In case both components use the same material, the coarser mesh is chosen as the master. 3. I haven't used this function yet. 4. Yes, Type 7, 11, 19 need to have initial clearance (non-zero gap, Physical gap).
  13. Hi, non-linear penalty-based contact interfaces require a non-zero initial gap. Type 24 linear contact interface can be used with a zero gap. Type 19 is computationally inefficient and since there is no edge to edge issue in your model a type 7 will be more efficient. A rigid body was put on plates so they will not affect the timestep. The model and boundary conditions are symmetric so a quarter symmetry could be used for efficiency (this will also properly constrain the cylinder in the symmetry planes- currently it is held in place only by friction). plate_cylinder_edit_0000.rad
  14. The model you shared had several issues: no card image and material parameters were assigned to the "rubber" material rigid elements should be placed in a separate component the pressure load collector did not have pressure versus time function referenced (The cause of error id 120) only one linear (first order) tetrahedral element through thickness is not recommended (too stiff in bending). In order to calculate the bending stresses accurately in thin-walled structures, a minimum of 3 solid elements through the thickness should be used. You can take advantage of geometry and boundary condition symmetry by modeling only a quarter of the model. Use Quality> ModelChecker in HyperCrash or Tools>model checker>radiossblock in Hypermesh https://insider.altairhyperworks.com/wp-content/uploads/2017/09/T-T-1248-HyperMesh-Model-Checker.pdf In order to get different buckling modes and Buckling load factor a geometric imperfection should be introduced. Either use a /RANDOM nodal noise or the procedure described in thread:
  15. You need to define simulation controls. Use Tools>engine file assistant to set up the simulation controls. Define animation output frequency ANIM/DT to get the animation output.
  16. Supported Ls-Dyna result types: HyperView LS-DYNA Results Reader.pdf
  17. In the run folder open: 3PBBend.h3d file with Hyperview to review animation output 3PBBendT01 file with Hypergraph to review time history output
  18. Hi, results can be investigated in Hyperview, not in Radioss solver window.
  19. Hi, to asses if the component will break you need to define failure parameters on law 25 or add failure model. The yield stress parameters only relate to the start of plasticity, not rupture. See the attached document and links for more details: Elastic-plastic Orthotropic Composite Shells.pdf https://insider.altairhyperworks.com/accuracy-matters/ https://insider.altairhyperworks.com/composites-rupture/ With Composite stress, you look for stress in each ply (ANIM_SHELL_TENS_RESTYPE). The other stress is homogenized one over the entire laminate (ANIM_ELTYPE_RESTYPE). In composites, it's important to understand stress in each ply. With /ANIM/SHELL/TENS/STRESS/ALL and /ANIM/SHELL/TENS/STRAIN/ALL keywords we can output the stress and strain for all plies in the composite material. In case failure cards for the composite are provided (like /FAIL/LAD_DAMA, which describes the Ladeveze failure model for delamination (interlaminar fracture) you can input /ANIM/SHELL/IPLY/MAXDA, /ANIM/SHELL/IPLY/DAM keywords in the engine file for extracting damage parameters.
  20. Actually, Radioss also supports Yeoh material (law 94). Check the attached tutorial RD-E: 5600 Hyperelastic Material with Curve Input. RD-E_ 5600 Hyperelastic Material with Curve Input.pdf Postbuckling behavior is difficult to converge for implicit solvers like Optistruct. There are two tutorials and one example on NL buckling: RD-T: 3030 Buckling of a Tube Using Half Tube Mesh (Hypercrash) RD-T: 3530 Buckling of a Tube Using Half Tube Mesh (Hypermesh) RD-E: 0300 S-Beam Crash RD-T_ 3030 Buckling of a Tube Using Half Tube Mesh.pdf RD-T_ 3530 Buckling of a Tube Using Half Tube Mesh.pdf RD-E_ 0300 S-Beam Crash.pdf
  21. Hi, check if you can run Transient heat transfer analysis for composites with this model: CARBON LAMINATES- Thermal.hm
  22. Hi, my suggestion is to use Radioss solver due to nonlinear geometry (buckling) and material (hyperelasticity) and possibly contact. Radioss also supports implicit method which can be used for preloading and quasistatic analysis.
  23. Hi, you need to import either the solver deck (*.fem file) or model file (*.hm). Note the former contains only FE entities while the latter also includes geometry with the possible mesh-geometry association.
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