1 Reply Latest reply on May 27, 2010 10:27 AM by Anthony Botting

    Mixed Mesh vs Solid Mesh

    Alec Chalmers

      I just ran two frequency studies on the same assembly with no restraints (to get the rigid body modes) with the only difference being that one used the default mixed shell and solid mesh and the second had all solid mesh (manually selected). The results for the mixed mesh model indicated a non-rigid mode as mode 4 with a frequency of 70Hz. The results for the solid mesh model indicate a non-rigid mode as mode 7 with a frequency of 521Hz.Has anyone else noticed this difference and which is considered to be accurate?

        • Re: Mixed Mesh vs Solid Mesh
          Anthony Botting

          If the mode 7 of the solid mesh model is the same basic shape as the mode 4 for the mixed mesh, (i.e., you believe they are representing the same mode), it is likely that something is causing the higher frequency model to be much stiffer. I have seen cases where mixed mesh models are difficult to "fasten" together at contact, seams, and joints and the structure is basically much more "loose" than an all-solid model where all the nodes are connected properly across part and component bodies. It normally requires the user to very carefully inspect all contacts and areas that need to be connected are verified as such. I had this problem the other day and we resolved it by applying loads to various areas in the model to try and "...pull it apart at the seams...", so to speak (using static analysis). We found numerous areas where the mesh nodes were not matched in position (and thus not connected) and we were able to sew them up (via mesh controls and careful contact set definitions). Hope this helps. Tony