General Mechanical

General Mechanical

How do calculate time step size in ANSYS transient structural?

    • VijayKGadwala
      Subscriber

      Hello 


      I have a doubt concerning time step calculation in transient structural? How can we findout the exact time step for the simulation?


      Thanks & Regards


      Vijay

    • peteroznewman
      Subscriber

      The exact time step is reported in the solve.out file.


      You can see the contents of the solve.out file while the solver is running.


      In Mechanical under the Solution Information folder, set the type to Solution Output and the information will be in the Worksheet window.

    • VijayKGadwala
      Subscriber

      Hallo,


      How can we choose the exact time steps before to start the simulation. What will be criterion for selecting the time step for transient simulation?


      Thanks


      Vijay

    • VijayKGadwala
      Subscriber

      Dear community members,


      I would really appreciate your advice and experience concerning the following question:



      • What are best practice guidelines to choose an appropriate time step size in transient simulations (apart from always performing the transient simulation)


      Thanks a lot in advance!


      Best regards,
      Vijay

    • VijayKGadwala
      Subscriber

      Dear Community members,


      How can I calculate the number of time steps and time step size for Transient Simulation?!


      Thanks


      Vijay

    • peteroznewman
      Subscriber

      Before doing a Transient simulation, you should always do a Modal analysis. This will tell you the frequencies of the first 6 modes by default. You can request more modes if you choose.  Suppose mode 6 was 30 Hz.


      The guidance for Transient simulations is to have 20 time steps within the highest frequency of interest. So if you want to include 30 Hz, then the solution frequency should be 20x30 = 600 Hz and that means a time step of 1/600 seconds.  That should be the initial time step and the maximum time step. The minimum time step can be 10 times smaller.


       

    • VijayKGadwala
      Subscriber

      I need to apply force with intervals of 0,10,20,30,40,50 and 60 mN. So how should I take time step 

    • peteroznewman
      Subscriber

      It sounds like you want to apply 6 different forces and see 6 separate results (excluding 0 force) and that is a simple Static Structural model with 6 steps and you type in 10, 20, etc. into the six rows made on the Force load after changing the number of steps to 6 under Analysis Settings.


      In a Static Structural model, time is just a placeholder, so you could have an end time of 6 seconds and each row can be 1 second apart. There are no dynamic effects.

    • VijayKGadwala
      Subscriber

      Hi,


      I would to know the Analysis settings since I was using transient structural. I have doubts in taking number of steps, current step number, step end time. Moreover if we consider Auto time steeping off then how can we placehold time step. Incase if we consider auto time stepping on i was getting (Initial time step,  Minimum time step and maximum time step). So how should I take the time step please let me know below i am giving my simulation data


      Total time: 0,000025471


      I would like to consider 20 steps so Step size is 0,0000127, I was applying force of 10 to 60mN which I have to make it in 20 steps in tabular data.


      Thanks


      Vijay

    • peteroznewman
      Subscriber

      In Workbench, on the Transient Structural analysis block, right mouse click on row 1 Transient Structural and in the popup, select Replace With then pick Static Structural.


      If you want a smooth curve of the response vs the load, you can have 100 points on the curve by simply having a 1 step analysis with an end time of 1 second and turn on Auto Time Stepping and set the Initial and Minimum Substeps to 100 and Maximum Substeps to 200.  Set the load to 60 mN and solve.

    • VijayKGadwala
      Subscriber

         


      Thank you for your response. I have partially understood your answer. I have to do the transient analsysis , my main query is how to make analysis setting with respect to 20 steps (how should i consider initial time step, Minimum time step and maximum time step). I have total time: 0.00025471 and I chose total time into 20 steps so each step size is 0.0000127. Could you let me know how do I arrange this data into analysis setting. 

    • peteroznewman
      Subscriber

      The Minimum Time step must be < or = the Initial Time Step.

    • VijayKGadwala
      Subscriber

      Hi,


      where can I get Ansys Mechanical theory guide? Could you provide me the source 


      Thanks & Regards


      Vijay

    • Sandeep Medikonda
      Ansys Employee
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