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Mrt

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  1. Ekaterina liked a post in a topic by Mrt in Topology optimization results interpretation   
    The penalization technique used is the “power law representation of elasticity properties,” which can be expressed for any solid 3D or 2D element as follows:
    K(r) = K*ρ^p 
    where K and K represent the penalized and the real stiffness matrix of an element, respectively, ρ is the density and p the penalization factor which is always greater than 1.
    In OptiStruct, the DISCRETE parameter corresponds to (p - 1). DISCRETE can be defined on the DOPTPRM bulk data entry. P usually takes a value between 2.0 and 4.0. For example, compared to the non-penalized formulation (which is equivalent to p=1) at ρ=0.3, p=2 reduces the stiffness of the element from 0.3 to 0.09 times the stiffness of the fully dense element. The default DISCRETE is 1.0 for shell dominant structures, and 2.0 for solids dominant structures (the dominance is defined by the proportion of number of elements)
  2. tinh liked a post in a topic by Mrt in Topology optimization results interpretation   
    The penalization technique used is the “power law representation of elasticity properties,” which can be expressed for any solid 3D or 2D element as follows:
    K(r) = K*ρ^p 
    where K and K represent the penalized and the real stiffness matrix of an element, respectively, ρ is the density and p the penalization factor which is always greater than 1.
    In OptiStruct, the DISCRETE parameter corresponds to (p - 1). DISCRETE can be defined on the DOPTPRM bulk data entry. P usually takes a value between 2.0 and 4.0. For example, compared to the non-penalized formulation (which is equivalent to p=1) at ρ=0.3, p=2 reduces the stiffness of the element from 0.3 to 0.09 times the stiffness of the fully dense element. The default DISCRETE is 1.0 for shell dominant structures, and 2.0 for solids dominant structures (the dominance is defined by the proportion of number of elements)
  3. Mrt liked a post in a topic by Hyperman in Energy Error Limit Reached   
    Hi @PhilippFr
     
    this error is common with inappropriate mass scaling, that is when you impose a time step which is too high. Check the mass error due to mass scaling in the engine .out file: in your model the mass scaling increases the system's mass by more than 100 times! It is suggested to keep the overall mass increase below 2% and even then it has to be checked if the mass is added to parts that are moving, which would increase the kinetic energy and therefore decrease the simulation accuracy. A short video on energy and timestep error
    https://altair-2.wistia.com/medias/osd349gz4k
     
    Energy error.pdf
     
    Alternatively, you could try with advanced mass scaling (AMS) which does not add mass.
     
    You can find more information from Introduction to Explicit Analysis using RADIOSS – A Study Guide in Time Step Control chapter. Also recommended is 2017 Radioss user guide starting from page 30.
     
    However, the model you presented is not suited for explicit simulation as the minimum natural timestep due to CFL condition is 1e-11, which is practically unsolvable with the current computational capabilities. Rethink your modeling approach (beam instead of solid) or solve the problem with implicit. 
  4. Mrt liked a post in a topic by Jan Grasmannsdorf in How to export a CAD Geometry from Optimization Results?   
    To recover your data in a CAD-readable Format (STL), you can use the HyperView Tools – Export – Iso Surface Option.
    Other ways to recover STEP oder Polynurbs Geometry (smoother results) are:
    -        Use HyperMesh -> Pulldown Menu Optimization -> Ossmooth -> Geometry Format STEP to export a CAD File of the optimized result
    -        Use Polynurbs in solidThinking EVOLVE or INSPIRE. See here for more details:
    http://solidthinking.com/training/2016/inspire/content/polynurbs/polynurbs_tools.htm
     
    Kind Regards
     Jan
  5. tinh liked a post in a topic by Mrt in Is there any example about extracting and repairing midsurf for a complex plastic geometry?   
    hello, @Roy Duan!
    what tool did you use?
    have you ever used this feature for midmesh?
    Direct Midmesh Quick Start Guide - v1.pdf
  6. Mrt liked a post in a topic by nvn in Cabin Thermal Simulation   
    Hi,
     
    i have to simulate the airdistrubiton on the windshield, so i modulated a cabin with a airflow. So i have 2 volume, how can i define the intersection(surface) between airflow-volume and cabin-volume ? I have set on the  Type: wall and  wall function : None , is that correct ?
     


  7. Mrt liked a post in a topic by Premanand Suryavanshi in Meshing only the void volume of an existing mesh   
    Hi Dakshitha
     
    You can separate the fibers from liquid/rubber using Boolean operation and then retrieve only liquid/rubber material and mesh it separately.
    Please follow below post for reference
     
    Thank you
  8. Mrt liked a post in a topic by Nachiket Kadu in varying SPCF for Nonlinear quasi-static analysis.   
    I think it maybe a bug....plotted using "build Plots", it give correct plots.
     
    Regards 
    Nachiket

  9. Mrt liked a post in a topic by ydigit in HyperMesh 2D Mesh Import Error in AcuSolve   
    Please import the mesh_intersections.nas in HyperMesh. This will give you an idea of where the problem region is this. As the name tells, there are intersecting elements in this region. 
     
  10. Mrt liked a post in a topic by Farzin in Contact Penetration   
    Hi @Prakash Pagadala
    Thanks a lot for your efforts.
    Unfortunately, I have no acces to Abaqus Modell. I just received the Mesh and built the model all by myself in Hyperworks. I read a Research, that used the same Model in Abaqus. I used their boundry conditions for my Modell (same Material_same Forces ...). I have no clue about Abaqus convergence Algorithm.
     I will update you, if i find something new.
  11. Mrt liked a post in a topic by ppraf in Points in a different coordinates system   
    Hello -
     
    You should be able to do this by using the "Parametric Points" tool.
    In 2017.2,  it is available in the side toolbar as shown in the attached image
     
    Regards
    Praful
     
     
     

  12. Mrt liked a post in a topic by tinh in how to export H3D to UNV file in Hyper Works using script   
    I think people don't have time to help you from A to Z
    So it's better if you do some initial codes, and ask for help in details eg: how to read file/ write file by tcl...
  13. Mrt liked a post in a topic by Hyperman in ERROR ID : 257   
    Hi Antonio,
     
    there are so many modeling errors I suggest you check the Radioss free ebook. Also please go through the attached tutorial on how to create a 3 point bend test.
    For model debugging use Tools>Model Checker>RadiossBlock and review the .out files for errors and warnings.
     
    I have modified the model so it can run:
    -contact was not defined properly
    -shell elements that come into contact had wrong normals orientation 2D>composites>element normals>reverse
    -the plies were not referencing elements
    -the laminates were missing
    -delete the ^tempCompSurfSegment component
    -delete the type 2 tied interface as equivalencing nodes (shift+F3) works better to connect face sheets to honeycomb
    -delete the RBE3 component and use RBE2 to create rigid on stamp component
    -create boundary condition on the independent node of RBE2 to block all DOF except Y translation
    -edit the TH group, as it is referencing non-existing component ID 7
    -the mass scaling is imposing one magnitude lower timestep (7e-7) than natural (6e-6). Instead, mass scaling should be used to impose a higher timestep.
    -time scaling is recommended as 420 seconds is inefficient for explicit. Reduce the simulation duration until you get a quasi-static  solution (total kinetic energy to the total internal energy is small enough - normally less than 5%).
     
    RD-T_ 3595 Three Point Bending with HyperMesh.pdf
    3pb_radioss_modified_0001.rad
    3pb_radioss_modified_0000.rad
    3pb_radioss_modified.hm
  14. antonio.dortona95 liked a post in a topic by Mrt in Failed mesh   
    your mesh is good, guy!
    don't worry=)
    just unchek "min size"


  15. Hyperman liked a post in a topic by Mrt in 3d meshing support needed   
    at first-Do you use HyperMesh? or LSprepost?
    your surface:

    just mesh it!=) like this, Anna!





    p.s. i don't know why, but in this area your mesh shoulbe like in my pic below... otherwise HM won't make solid mesh right.
    if your solver will be dyna you should know about timestep.=)

     
  16. Mrt liked a post in a topic by Pranav Hari in error id 760   
    Hi
     
    The corrected file is shared here.
     
     
    BENDING_0000.rad
    BENDING_0001.rad
  17. Mrt liked a post in a topic by Pranav Hari in error id 760   
    Hi yugang
    You can click delete button from the tool bar,  select elements by config.
    Then select the shell elements and click, delete
     
     

     
     

     
     

  18. Mrt liked a post in a topic by tinh in How to morph an arc with keeping the tangency and symmetry constraints?   
    Hi,
    First, you draw the final profile ACD,
    From menu Morph>Free hand:
    1) Morph B to D

     
    ==> 

     
    2) Enter panel F7>remap
    remap below misaligned nodes:

     
     
    3) Enter panel smooth to adjust mesh lines

     
     
    ==> Is this OK for you?

  19. Mrt liked a post in a topic by MattM in How to creat 2D element from nodes   
    I agree, I would calculate with shell elements.
     
    However, I have tested this myself. I created a simple model of a cantilever beam and compared different solid meshes with the max output von Mises stress result.
     
    Via hand calculations (baseline): Stress = 600 MPa
    1x HEX8 element through thickness: Stress = 565 MPa
    2x HEX8 element through thickness: Stress = 604 MPa
    1x TET4 element through thickness: Stress = 154 MPa
    2x TET4 element through thickness: Stress = 387 MPa
    1x TET10 element through thickness: Stress = 623 MPa
     
    The results are a bit iffy because the max stress is located near the constraints (I should've done this using a 3-point bending model...) You can clearly see here that TET4 elements are bad at calculating stresses through the thickness due to bending. However the TET10 element (with midside nodes) is a lot better.
     
    Still, for best results calculating stresses through the thickness I would be using HEX elements (where possible) for thick components and QUAD elements for thin shell components.
  20. magicbarald liked a post in a topic by Mrt in "Element Densities" definition   
    With the density method, the material density of each element is directly used as the design variable and varies continuously between 0 and 1; these represent the state of void and solid, respectively. Intermediate values of density represent fictitious material. The stiffness of the material is assumed to be linearly dependent on the density. This material formulation is consistent with our understanding of common materials. For example, steel, which is denser than aluminium, is stronger than aluminium. Following this logic, the representation of fictitious material at intermediate densities does reflect engineering intuitions.
    In general, the optimal solution of problems involves large gray areas of intermediate densities in the structural domain. Such solutions are not meaningful when we are looking for the topology of a given material, and not meaningful when considering the use of different materials within the design space. Therefore, techniques need to be introduced to penalize intermediate densities and to force the final design to be represented by densities of 0 or 1 for each element. The penalization technique used is the “power law representation of elasticity properties,” which can be expressed for any solid 3D or 2D element as follows:
    K(r) =K* ρ^p
    where K and K represent the penalized and the real stiffness matrix of an element, respectively, ρ is the density and p the penalization factor which is always greater than 1.
    In OptiStruct, the DISCRETE parameter corresponds to (p - 1). DISCRETE can be defined on the DOPTPRM bulk data entry. P usually takes a value between 2.0 and 4.0. For example, compared to the non-penalized formulation (which is equivalent to p=1) at ρ=0.3, p=2 reduces the stiffness of the element from 0.3 to 0.09 times the stiffness of the fully dense element. The default DISCRETE is 1.0 for shell dominant structures, and 2.0 for solids dominant structures (the dominance is defined by the proportion of number of elements). An additional parameter, DISCRT1D, can also be defined on the
    50
  21. Mrt liked a post in a topic by tinh in Checking penetrations between parts   
    Could you try running it in hypermesh (not hypermesh desktop)
  22. Mrt liked a post in a topic by tinh in Checking penetrations between parts   
    OK. so i will make a script with a loop that project node to the closest elem
  23. Mrt liked a post in a topic by tinh in Checking penetrations between parts   
    Could you explain by images? 
    I think every fuction in ansa can be made in hm
  24. Mrt liked a post in a topic by Livil Lyle in TCL Scripting   
    Below resources will help you get started with tcl/tk programming. 
    https://www.tutorialspoint.com/tcl-tk/ 
    https://www.packtpub.com/networking-and-servers/tcltk-85-programming-cookbook
    https://www.tcl.tk/man/tcl8.5/tutorial/tcltutorial.html
  25. Mrt liked a post in a topic by Livil Lyle in TCL Scripting   
    Hello Punith, 
     
    You can try the below,

    *createmark surf 1 "displayed"
    catch {*solids_create_from_surfaces 1 4 -1 2} status;
    if {$status == 1} {
        puts "Solid Created Successfully";
    } else {
        puts "Solid Creation Failed";
    }
     
    to create using loops, please give more information. 
     
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