4 Replies Latest reply on Jan 8, 2014 11:24 AM by Jared Conway

    FFEPlus vs Direct sparse

    Devi Prasad Samal

      Hello guys i am doing a analysis with same setting but with different solver. but problem is i m getting high stress in direct sparse while FFEplus gives lower stress.

       

      In direct sparse i am getting stress approx 1200MPa

       

      while in FFEPlus it gives stress near to 800MPa.

       

      Just curious which ine to consider in case of nonlinear no-penetration contact.

       

      Why it is happening? See attached pic for reference stress plot result.

        • Re: FFEPlus vs Direct sparse
          Lukasz Siwiec

          Hi,

          When you are using the Direct Sparse solver, it calculates the solution using a direct method, creating and inverting matricies to obtain values. However, when you are using the FFEPlus solver you are obtaining the solution through iteration. This means that any slight numerical instability in your model will cause the Direct Sparse solver to fail while an FFEPlus solver may be able to iterate past the point of instability to obtain results. You should double check the accuracy of the results obtained by the FFEPlus solver if you see you have numerical instabilities in when you use the Direct Sparse solver.

          You should also check the boundary conditions in your model.

          • Re: FFEPlus vs Direct sparse
            Jared Conway

            that is too big of a difference to be just from changing the solver

             

            like lukasz says, i would be looking at the setup of your model

             

            are you using soft springs or anything like that?