10 Replies Latest reply on Nov 28, 2016 11:30 PM by Hana Hayati

    Error: Model may not have adequate fixtures

    Mo Fazel

      I performed an Static FEA analysis on an ellipsi between two parallel plates. The ellopsi and plates were assembled and matted by Tangent and Width constraints. 

      A pressure applied to the upper plate and the lower plate is fixed. The contact surfaces between the plates and ellipsi have roller/slider joints. After Running, I got this error:

       

      "The Iterative Solver stopped.

      The solver has numerical difficulties.

      Model may not have adequate fixtures

      No results saved."

       

      I think the problem would be with contact surfaces because when running the ellipsi, it worked. I have tried different ways but it didn't work.  

       

      Any help would be appreciated.

       

      Mo

        • Re: Error: Model may not have adequate fixtures
          Jared Conway

          if you have sim pro and above, this would probably be better done with 2d study

           

          also i think you've got contact and fixtures mixed up, you'll need no penetration contact between the ellipse and the plates (right now you have bonded)

           

          but once you do that, your problem will be unstable. you can get some stability by making it a quarter symmetric model.

           

          i would actually start a little simpler and just run this as a part analysis to start

          • Re: Error: Model may not have adequate fixtures
            Jerry Steiger

            Mo,

             

            I would just like to reinforce what Jared said. A 2D quarter symmetry model will run much quicker and won't have any stability problems. But in real life, you are going to have stability problems.

             

            Jerry S.

              • Re: Error: Model may not have adequate fixtures
                Mo Fazel

                Jared and Jerry;


                Thanks for your comments;

                 

                I am working on a project from the industry and the actual model is a 3D simulation.

                I am not allowed to attach it here; the company asked me to be discrete regarding this project.

                Firstly, I started with a 2D simulation and run the simulation but I have to run the 3D simulation; the actual problem is “Asymmetry.” It is required to place the model between two parallel plates and squeeze it under certain pressure. The ideal is to have roller between the semi-circles and flat plates.


                I would be grateful if you could provide me some comments how to deal with this problem.

                 

                Mo

                  • Re: Error: Model may not have adequate fixtures
                    Jared Conway

                    can you post a picture that shows the whole model so that we know why it has to be done with 3d

                     

                    why does it have to be compressed between the 2 plates?

                     

                    what prevents it from slipping in the physical test? can you describe what it is and how it is done?

                     

                    i don't understand your comment about roller between semi circles. it might be helpful to diagram out what you're trying to describe.

                      • Re: Error: Model may not have adequate fixtures
                        Mo Fazel

                        This is a problem from a company which I am working; I am not allowed to distribute the whole model; the company plans to file a patent on that. The objective is to optimize the strength and mass of a small structure that needs to retain certain shape characteristics.

                        This is in the problem definition.

                        - the structure should resist cracking when squeezed between 2 flat plates.

                        It's an optimization problem which involes mass/volume and load constraints;  

                         

                        The top and the bottom of the structure (which are in contact with two flat plates) are semi circles similar to what I have in the attachement above; It's requrired that the the top and bottom surface can slip on the flat surfaces; 

                        The ellopsi and plates were assembled and matted by Tangent and Width constraints (= they can't move relative together;).

                         

                        Thanks for your time and consideration;