General Mechanical

General Mechanical

Calculate shell with arc length method

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    • j.drozdowski
      Subscriber

      Hello.
      I'm trying to calculate compressed shell with the arclength method (it is course example so I know the proper answer).
      No matter what ARCLEN parameters or how many substeps or I'm setting up, the analysis is failing just after bifurcation point. I cannot proceed to the post failure state (which should be doable with arc length method).

      What is THETA ? How to deal with the situation when it is to large ? Solver is stopping after 10 bisection cuased by "Theat is to large"

    • John Doyle
      Ansys Employee

       The only documented reference to "theta", regarding the ArcLength method, is in equation 14-192 of MAPDL Theory Manual.

      I am not sure if this is the same 'theta' that the solver output is referring to, but it seems reasonable to assume this.   The new time increment reported after the bisections is 0.018, which does appear to be pretty small already, but can you try an increment one or two orders smaller (as a test)?  Also, try tightening the range of time step size. 

      As you have already reported, Arc Length method can be very sensitive.

      • j.drozdowski
        Subscriber

        Thank you John for the reply. Is there a way to allow for more bisections in the Arc Length method ? Or to change the theta limit ?

        By trials and errors I found one magical number of substeps for which my analysis is working. But id doesn't work for any higher or lower number. Which should not be the case i guess.

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