4 Replies Latest reply on Oct 1, 2009 9:45 AM by 1-7ECR3R

    Shell meshing taking hours

    Justin Sue

      Hi all,

       

      Im currently working on doing analysis of the superstructure of a train carriage so its quite a large assembly of  shells representing all the members of the underframe, side wall framing and roof framing. In total there are about 800 surfaces and when I go to mesh it, it zipps through all the surfaces quite quickly until the last surface in the se and then it takes about 10 hours to finish meshing completely. If I remove that last surface it then pauses on the next surface in the list that is not last. Is there anything that I am doing wrong or is it the software it sellf?

       

      The mesh is all shell elements on draft quality mesh with about 50000 nodes.

       

      Any help is much appreciated.

       

      Regards

      Justin

        • Re: Shell meshing taking hours
          Ian Hogg

          Hi Justin,

           

          The most likely cause of this is the algorithm that aligns all non composite shell normals:

           

        • Automatic shell surface re-alignment for non-composite shells. When selected, the software automatically realigns the shell surfaces (non-composites) so that all bottom/top faces have uniform orientation. If this option is not selected, you may need to flip the misaligned shell surfaces manually. Select the desired faces, right-click the Mesh icon in the Simulation study tree and select Flip Shell Elements.

        •  

          You can disable this option under Simulation options - Default Options - Meshing. Depending on what results you are looking at and the loading determines the importance of this. But as it says, you can go and manually adjust the mesh on faces to align normals too.

           

          Let me know if that helps you out.

           

          Cheers,

           

          Ian

            • Re: Shell meshing taking hours
              Justin Sue

              hi,

               

              yes that works by unchecking it. also reaglined the top and bottom surfaces better than when it was checked.

               

              Now on to the next problem which is when I mesh it one of the pieces dissapears, see the attached pictures. At the moment I have cut the body and the underframe and I'm just concentrating on getting the roof going with out any problems.

                • Re: Shell meshing taking hours
                  Ian Hogg

                  From my experience, the most common situation where parts disappear when you mesh the model is when the study gets out of synch with the model geometry.

                   

                  Try using the update components option (right click on the root branch of the study to get this selection) and then re-mesh the model.

                   

                  If that does not work, create a new study, and then drag and drop your settings from the existing study. Sometimes I find this a more reliable way of starting fresh, yet still take advantage of all the properties and setup from an existing study.

                   

                  Cheers,

                   

                  Ian

              • Re: Shell meshing taking hours
                From your images, it seems that this problem could be easily solved using beam mesh, that would result in a simpler and ligher mesh, not to mention the significant improvement in calculation time and results accuracy. Have you considered that option?