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Showing content with the highest reputation since 08/21/17 in all areas

  1. 3 points

    Update Hypermesh Extensions

    Hello everybody I made a new function for Hypermesh to export entity by right-click on model browser MenuExportDeck.zip Open Hypermesh, from menu File>Run>Tcl/Tk Script , browse to Installer.tcl in folder MenuExportDeck to install it in hmcustom.tcl Related post: I made a new function for Hypermesh to copy mesh among sessions hmcp.zip <updated for HM2017> + <update installer.tcl to install in any folder> Please announce me if any error. - "Extract here" package hmcp.zip, copy the folder "hmcp" to anywhere you want to store. - Open hypermesh and run Installer.tcl file by enter menu File>Run >Tcl/Tk Script - start Hypermesh, it should shows an icon and provide some information like below: - You can copy elements selected in any current panel: - Once again, this topic is to introduce extensions for Hypermesh. I let updated version of hmdnd (drag and drop function) here tkdnd2.6.zip <updated installer.tcl so you can install it to any folder, just open hypermesh and File>Run>Tcl/tk script to run installer.tcl> related post: - And a package to help making your own toolbars: tbopts.zip <update installer.tcl so you can install it to any folder> related post
  2. 3 points
    Hi Amar, The nodal time step equation is : sqrt (2m/k), where m is nodal mass and k is equivalent nodal stiffness. A scale factor will be also used to calculate the time step. Please go through https://altairuniversity.com/learning-library/considerations-about-time-step/ which is a webinar showing time step calculation in RADIOSS. RADIOSS will calculate nodal and elemental time steps of the model and will choose the highest of these to run. From Check Elems (F10) panel it is possible to determine the approximate minimum time step for explicit solvers based on element dimensions.
  3. 2 points
    In fact, it's not so simple to compare. In case of shell element, you have stress on upper/lower layers. But in case of solid element, the stress in general is not computed at surface. In my previous tests, I have to apply a very thin skin on solid element to capture the membrane stress which can be compared to shell stress.
  4. 2 points
    George P Johnson

    Joining 2D mesh to 3D mesh

    Hi, I'm attaching a webinar here on RBE's in RADIOSS where the use of rbe's are explained with examples. The load transfer in rbe's are shown in this video. PS: The video is in .swf format, which plays in GOM player. Radioss_RBEs_MPCs_engl_May13.swf
  5. 2 points
    Hello Badheka, Lets start with the effect of the segment radius. For the segment radius, I would suggest that you use the radius that you need to simulate - don't make the wire infinitely thin thinking the answer is more correct for some reason. If the ratio of the radius to length become to extreme, then it is time to use a cylinder (triangles) instead of segments. What I mean by "extreme" is that the MoM segments uses a thin wire model and the approximation becomes better the longer the segment is relative to its radius (or rather, the smaller the radius for a given segment length). You can get good results even with relatively fat segments (5 to 1 ratio). FEKO will give a warning and eventually an error if the segments are too think compared to the segment length. Your main question was about the effect of creating too long or too short segments. Obviously if you make the segments too short, the segment length to radius ratio will start violating the thin wire approximation and your results will become less accurate (see the comments in the previous paragraph). Also, increasing the number of segments by making them shorter increases the size of the model since more unknowns need to be taken into account. The CEM model is solved by breaking the model into small pieces, associating basis functions on the elements and then solving the unknown coefficients associated with the basis functions. If you mesh too coarsely (coarser than lambda/10), the results would become less accurate and at some point it would simply be incorrect. FEKO will give a warning and later an error when elements are meshed too coarsely. If you mesh finer and finer, the answer generally becomes more and more accurate (converge to the exact answer). There is a point where meshing finer could start diverging again. The exact behaviour depends on the solution method (MoM, FEM, etc.) and the basis functions that are being used. The comments above are very general and apply to various methods and elements (segments, triangles, tetrahedra, etc.). How do you know how fine to mesh a model? The best is to have a good starting point and the general rules are provided in the FEKO manual. It is good practice to do a mesh convergence test - the basic idea is to refine the mesh until the results converge (stop changing). Another approach is to calculate error estimates on the elements and instead of refining the entire mesh, only refine the mesh in the areas where the errors are estimated to be the largest and again continue this process until the results converge. Using the suggestions for meshing (standard and fine) should give accurate results in most cases. The coarse mesh setting is expected to give less accurate results, but faster simulations due to the model begin smaller. The optimal point depends on your model and the accuracy that you need from the simulation.
  6. 2 points

    LUA Scripting with FEKO

    Great! I'm glad it helps. It's definitely worth it to go through the Examples Guide example, though. It takes you through the basic concepts and shows you how to navigate the API documentation.
  7. 2 points

    LUA Scripting with FEKO

    Hello @mustaphos, @JIF beat me to it...! Of course, this is the "more correct" way to learn how to do scripting and automation. The shortcut way to get started with scripting (in CADFEKO) is to use "Macro recording". You'll see in the status bar (in the bottom of the application) a button with a puzzle piece and a red circle. If you press this, then CADFEKO will record every action you take that changes the model. In other words, if you start recording and create / modify / delete a variable, then a script will be recorded that shows you how to do precisely that one bit of scripting. It's cheating but I won't tell anyone.
  8. 2 points
    George P Johnson

    Plot displacement vs force

    Hi Ajay, Please go through these documents where you will get some relevant information. http://insider.altairhyperworks.com/scripts-of-the-month-jan-2016/ http://insider.altairhyperworks.com/transfer-path-analysis/
  9. 2 points
    Attached PPT contains the tests to be done to verify the Creo configuration in SimLab. SimLab_Creo_Configuration_Test.pptx
  10. 2 points

    Skateboard Tutorial

    There you go: https://altairuniversity.com/skateboard/ I made a video series about it:
  11. 2 points
    Hi, Currently there is no options to export only element id in .txt file from element group. But we can export the element id's along with the corresponding node id's in .csv format from selected entity. Please follow below steps to get it. 1. Go to File > Export > Other > CSV 2. Give file name 3. Pick only element toggle in dialog 4. Select entity like elements / faces 5. Click Ok. Hope this will help you.
  12. 2 points

    Hexa Meshing

    Your mesh looks good. But it's possible to do that better. In fact, in FEA world, we have to know where we have to ... stop to get something acceptable :-)
  13. 2 points
    Hi Mohamed, Thanks for the model. There are a few things that could explain why you're not seeing the characteristic modes in the attached model: The model doesn't contain any geometry. There is only an infinite ground plane and a cable instance, both of which are approximations that can be used instead of complex geometry. For characteristic modes, a model that will be solved using the Method of Moments (MoM) is needed. In other words, there typically needs to be CAD that can be meshed into triangles and wire segments. The ports for the model are both Finite Element Method (FEM) line ports. FEM is a separate solver from MoM and doesn't support characteristic mode analyses. Neither port is excited or connected to anything. I recreated what I think the model is trying to do (see stright wire modified.cfx) using MoM. Note that you need to add the requests that you are interested in; at the moment only the characteristic mode eigenvalue data is being calculated. Are you trying to reproduce results from an article/measurements/calculations? Do you have any reference data? Without further information, this is as far as I can go. I would urge you to go through the Examples Guide and some overview documents on the feko.info website: http://feko.info/product-detail/productivity_features/characteristic-mode-analysis/characteristic-mode-analysis_6_3 http://feko.info/applications/white-papers/intelligent-design/CMA
  14. 2 points

    Memory allocation

    I think when you "allocate" 1500MB memory, Optistruct solvers understands that's the MAX limit of memory. So if your model is not so big the real used memory will be smaller that allocated value.
  15. 2 points
    Hi, The (t) and (s) are tensor and scalar representation of the results. You can try with /ANIM/BRICK/TENS/STRESS/ALL for getting stress (t) in solid elements. Von Mises criteria is a failure criteria uses distortion energy theory, which is widely used by designers to check whether their design will withstand a given load condition. So, I feel you can go ahead Von Mises criteria for your model.
  16. 2 points
    Hi BM Kung You can increase the number of characteristic modes to be calculated where you set up the problem in CADFEKO: I reran your model with 12 modes requested and then the first 6 modes were completely tracked across the frequency range from 2 to 5 GHz. (You could perhaps get the results you require by requesting fewer than that, i.e. selecting between 6 and 12 modes.)
  17. 2 points

    CONTACT- Node to surface

    Hi Prakash, I am using HM v14.0. Error solved by using both master and slave entity as sets instead of SSID- set and MSID- contact surface
  18. 2 points
    Rahul R


    PFA document for Global Automotive Safety Regulations .(ECE R14 Seat belt anchorage regulation) Global_Automotive_Safety_Regulations_in_Nutshell.pdf
  19. 2 points
    George P Johnson

    Setting Up Initial Contact

    Hi Brandon, For type 7 interface you can try with Fpenmax=0.75 and Inacti=5 and any node that is penetrated more then 75% of the gap is removed from the contact and nodes penetrated < 75% gap have their gap reduced due to Inacti=5. Or reduce your Gapmin to a very small amount if you are using constant gap or for variable gap set Igap=2 and Fscalegap=0.999. If issue persist please share the model file.
  20. 2 points
    Hi Nabil, I am having a look at this. Could you please also share the reference that you mentioned? One comment already is that there is no need to simulate the foam substrate (or at least not initially) - the permittivity is so close to vacuum that it will only have a nominal effect on the modes.
  21. 2 points
    George P Johnson

    Airbag Modelling

    Hi Evgeniy, Apologies for the delay. Please find the video attached which shows Airbag Simulation. Also go through http://altairatc.com/europe/Presentations_2009/Session_02/ALTAIR_Airbag_Folding_ehtc_003b.pdf , which is a document on Airbag Folding with RADIOSS Pre- Simulation which may be helpful for you. Also, please go through HyperCrash > HyperCrash User's Guide > Safety>Airbag Folder in Help Menu which gives the basic and important guidelines for Airbag Modelling in HyperCrash. Airbag_simulation_setup_.mp4
  22. 2 points
    The equation of motion for a static analysis is as below: [K] {X} = {F} ------------------------------------------ (1) [K] --> Global Stiffness Matrix {X} --> Unknown Displacement {F} ---> External Force Applied. For the body to be in static equilibrium, the net force acting at every node must be zero. Therefore, the basic statement of static equilibrium is that the internal forces, I, and the external forces, F, must balance each other: [K] {X} is nothing but internal force 'I' Equation (1) now becomes, ==> I = F or I - F = 0 -----------------------------------(2) In Dynamic Analysis, the imbalance between the external and internal forces results in an acceleration: F - I = M a. F --> External Forces I ---> Internal Force M*a --> Inertial Forces (mass times acceleration) In linear static analysis the stiffness matrix is constant and shall not change/update throughout the analysis. There are many check need to be performed once you have linear static results for well conditioned problems. The equation (1) is decomposed one time to find the unknown displacement. [K] {X} ={F} After decomposition, a singularity may lead to an incorrect solution. In static analysis to obtain {X} (displacements). Using these displacements, One can calculate a “residual” loading vector as follows: [K] {X} -{F} =δ F This residual vector should theoretically be null (equation 2) but may not be null due to numeric roundoff. In Nonlinear static analysis, The stiffness matrix changes in each and every iteration since the stiffness matrix is dependent on the external load. The external load in Nonlinear static analysis is applied in increments and time here has no physical meaning. Time is just a convenient way to apply full load in nonlinear static analysis. In Optistruct the incremental load is controlled by 'NINC' field in the NLPARM card for NLSTAT load steps, this is a fixed load increment method. If you add the PARAM,EXPERTNL,YES to the deck, the time increment method becomes automatic in which case, the increment (load) is increased or cut back based on the convergence rate. NLGEOM loadstep has automatic time step by default. In NLGEOM loadstep the RAMP load curve can be defined using TABLED1 card and then refer this in NLOAD1 card. In nonlinear static analysis, OptiStruct uses the Newton-Raphson method to obtain solutions for nonlinear problems to maintain the residuals close to zero (equation 2) In a nonlinear analysis the solution usually cannot be calculated by solving a single system of equations, as would be done in a linear problem. Instead, the solution is found by applying the specified loads gradually and incrementally working toward the final solution. Therefore, OptiStruct breaks the simulation into a number of load increments (NINC) and finds the approximate equilibrium configuration at the end of each load increment. It is important that you clearly understand the difference between an analysis step (NLSTAT / NLGEOM), a load increment (NINC of NLPARM card), and an iteration (MAXITER of NLPARM card) The load history for a simulation consists of one or more steps. Within a step you will have many no of increments (NINC), within increment there can be many no. of iteration (MAXITER). OptiStruct checks the equilibrium equation ( equation 2) for each and every iteration. If the solution from an iteration is not converged, OptiStruct performs another iteration to try to bring the internal and external forces into balance. An increment is part of a step. An iteration is an attempt at finding an equilibrium solution in an increment when solving with an implicit method. If the model is not in equilibrium at the end of the iteration, OptiStruct tries another iteration. With every iteration the solution OptiStruct obtains should be closer to equilibrium; sometimes OptiStruct may need many iterations to obtain an equilibrium solution. When an equilibrium solution has been obtained, the increment is complete.
  23. 2 points

    AcuSolve Motionsolve cosimulation

    Dear All, Both AcuSolve (CFD) and MotionSolve (MBD) Hyperworks Solvers can be coupled, cosimulation is possible. Certain Applications being real time Aerodynamics simulations, Wind turbines, Fuel tank sloshing, Pressure check valve etc. Click here to view the webinar on AcuSolve (CFD) & Motionsolve (MBD) coupling Attached is a tutorial on the same coupling - Pressure check valve. Regards, Kamlesh CFD_MBD.zip
  24. 2 points
    George P Johnson

    Tensile Test MAT25

    Hi, By creating time history output for elements it is possible to output stress and strain for the elements. Go to Analysis>Output Block> elements, select elements. Card edit the created output block and change the keyword accordingly. Use DEF keywprd to output the default outputs. Please go through the Help Menu on Output Blocks which describes about the various outputs available in Time History. Also please go through ths webiniat at https://www.youtube.com/watch?v=Ef7Spn-j7fA&list=PL1u26y75SCrA_BOCLaSewVCNY7xRvCTnA&index=6 which describes about creating output blocks. Using cross plot option you can crate load-displacement curves...etc. The steps for cross plotting is shown in an example file below. Please go through the documents attached. Cross plot values along a specified node path.pdf Cross_Plot.pdf
  25. 2 points
    Rahul Ponginan

    element selection

    To select elements within a circle, Shift + Single click and release of the mouse displays the entity selection pop-up menu: From the entity selectionpop-up menu, choose one of the first six quick window selection modes: •Inside of circle selects the entities that are inside of a circle window.