How to get solution solved faster in 2D Explicit Dynamics

FernandoTorresFernandoTorres Madrid, SpainMember

Hi, currently I'm solving a 2d explicit dynamics problem with approx. 9k nodes and 9k elements with 1.6058e-8m mesh size on a server (32Gb Ram and 2 cores). Estimated Solution time is 1236 hrs (ofcrs not feasible).

Any way to solve it faster and get accurate results. Thanks.

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  • FernandoTorresFernandoTorres Madrid, SpainMember

    I'll try to go "transient"...

    But what if I increase cores, and with a "reasonable enough mesh", will this solve the problem little faster?

    i.e. does solution time of a 2d explicit analysis depends on ram, cores or both (I'm asking for hardware here not cfl equation parameters)

    Thanks a lot.

  • @FernandoTorres

    For any solver, if you go from 2 cores to 16 cores, you will reduce the solution time by less than a factor of 8.

    If you double the computer clock speed from 2 GHz to 4 GHz, you will reduced the solution time by a factor of 2.

    Implicit solvers need more RAM, but if the problem size fit in the existing RAM, increasing the amount of RAM will have no effect.

    The maximum time step size is set by the minimum element length for Explicit, while for Implicit solvers, it is set by the highest natural frequency of interest in the structure. The ratio of the maximum time step of Implicit/Explicit for your nano-scale elements might be a factor on the order of 1000.

  • FernandoTorresFernandoTorres Madrid, SpainMember

    Thanks Sir @peteroznewman , shifted the model from explicit to transient but the tool is getting into the workpiece without cutting anything i.e. tool just moves inside workpiece without cutting the material. Tried to setup the contacts manually but it didn't work. What could be the issue?

    Thanks.

  • FernandoTorresFernandoTorres Madrid, SpainMember

    Great Article Sir @peteroznewman , but I have issues in material removal (chip formation). When I run the same experiment in explicit dynamics, cutting is shown with proper chip formation, BUT ONCE I shift the model to TRANSIENT structural, there is no cutting like shown below (tool moves freely into the material without cutting). I know this is a childish question but it is what it is.

    thanks for your help.


  • FernandoTorresFernandoTorres Madrid, SpainMember

    Thanks Sir @peteroznewman , I'll check that out in more detail. "Parallel processing is only available for 3d models" says the AUTODYN Solver for my 2d explicit dynamics problem. I know you have stated about the hardware on top of this page but I wonder if that is still valid for AUTODYN 2D Explicit Analysis.

    Thanks.

  • FernandoTorresFernandoTorres Madrid, SpainMember

    @peteroznewman what if I shift this material cutting simulation to LS DYNA from AUTODYN.

    1. For 2d explicit analysis, would LS DYNA use multiple cores? (solution time compared with autodyn?)

    2. Would results be same or different than using AUTODYN?

    Thanks.

  • I don't know about parallel processing in LS-DYNA, I don't have a license.

    The results would be very similar.

  • FernandoTorresFernandoTorres Madrid, SpainMember

    Thanks Sir @peteroznewman , I set the end time to 0.01, but the solver finished the solution for time 2.4E-4. i.e in video animation of result, the animation (and solution) stops after 2.4E-4s. Thanks.

  • @FernandoTorres Are you talking about the LS-DYNA solver or the AUTODYN solver?

    An error occurred during the solution that caused it to stop before the end time. These solvers track various energy levels and if a specific type of energy has a threshold to maintain the quality of the solution, the solver will stop when that threshold is crossed.

  • FernandoTorresFernandoTorres Madrid, SpainMember

    Sir @peteroznewman, using AUTODYN

    Solver hasn't shown me any error or warning upon completion. It was quite long simulation, I used to pause, then save and then resume from cycle. But it did not show me any warnings or errors in messages.

  • @FernandoTorres

    The solver may not show you an error, you might have to go into the folder structure and look for errors in one of the files. I don't know which file or folder that is, but I have seen replies in other discussions in the Explicit Dynamics forum that say which file and folder to check.

  • mjimji Forum Coordinator

    If you wish to use parallel with Ansys Explicit, you may extrude your 2D model one element side in the third direction to make it 3D, then you can use Parallel.

  • @mji Please describe the boundary conditions that must be applied to the nodes on the offset plane.

  • FernandoTorresFernandoTorres Madrid, SpainMember
    edited November 10

    Hi @peteroznewman , I was thinking to shift that 2d material cutting simulation to 3d in explicit dynamics. Please elaborate ALL the changes I should make as you have stated " describe the boundary conditions that must be applied to the nodes on the offset plane", do you mean those surface displacement constraints or something else? Please let me know any other important points (conditions) too (if we have)

    Thanks as always!

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