General Mechanical

General Mechanical

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Creep Simuation

    • Chandra Sekhar Narra
      Subscriber

      Hi group members,

      I have made a model in Ansys  and I would like to do creep for that model. I made it for 1000hours, but am getting very less total defomation. I did not understand, what would be the reason for this. Can someone help me?

      Here am attaching the pictures regarding the problem.

      Boundary conditions:

      • F1 = 0.92N
      • F2 = 0.94N
      • F3 = 2.68N
      • Fixed support at one end
      • Temperature given as a tabular data

      Kind regards

      Chandra

      Total deformation

    • Chandra Sekaran
      Ansys Employee

      Hi, Are you applying the load 'stepped' or 'ramped'. One way would be to do 2 load steps. You can do the first load step (may be end time of 0.01 or some small time value) with creep effects turned off and you apply your base loads. Then in the second load step (end time of 1000*3600 seconds) you turn creep effects ON and let creep run. I am wondering if you ramping the loads over 1000 hours. Another quick check would be to use a spreadsheet like Excel and estimate the strain using the Norton constants you have input in case you have the constants typed in incorrectly.

      • Chandra Sekhar Narra
        Subscriber

        Hi Chandra Sekaran,

        Thank you very much for your response.

        I made two load steps as per your suggestion. But now am getting the error and the solution is not solved.

        Here am attaching the error.

        Can you please help me with this regard?

        Thanks in advance!

        Kind regards

        Chandra

    • John Doyle
      Ansys Employee

      As you know, the Norton Creep expression is a function of Equivalent Stress and Temperature.

      Your C1 constant (= 1e-63) is a multiplier on stress^C2.  

      How large is your equivalent stress?  Is Rate turned on from the beginning of time or are you establishing the initial stress state first with RATE off (at LS1 for very small initial endtime) and then turning Rate ON (at LS2)?

      Also, you might have done this already, but if not, sometimes it is helpful (for troubleshooting) to take your creep expression into an excel spreadsheet and calculate expected creep strain from these coefficients, for an assumed stress state and temperature.  

       

      • Chandra Sekhar Narra
        Subscriber

        Hi,

        Thank you very much for your response.

        I calculated in excel, the creep strain is too high. If I compare it with the Ansys creep strain, both having very large difference.

        Could you please help me?

        Kind regards

        Chandra

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