4 Replies Latest reply on Aug 6, 2010 5:40 PM by Mark McGee

    Framed Structure Analysis in Assembly (with pictures)

    Mark McGee

      I am doing a structural analysis on a welded frame which supports a 3500 pound x-ray enclosure. I first ran the simulation as a weldment part with the loads applied to the supporting beams. Now I have run it as an assembly to compare the results. The assembly has two parts: the frame weldment which is treated as beams and the box which has a weight of 3500 pounds. I have restrained the frame at four joints on the bottom beams. I have applied a bonded contact set between the supporting beams and the box. This does not allow the beams to flex, so it is not a representative model. From my reading, it appears I need a 'no penetration' contact set to allow the beams to flex. But this type of contact set does not seem to work with beams. When I select a beam face it tells me "Invalid entity on beam body was selected". So am I limited to 'bonded' contact set type?

       

      The Assembly:

      Frame and Enclosure.jpg

      Joints, Restraints, and Contact Sets:

      Contact Sets, Joints, and Fixtures.jpg

      Axial Stress Results:

      Axial Stress.jpg

      Displacement Results:

      Displacement.jpg

        • Re: Framed Structure Analysis in Assembly (with pictures)
          Ryan Werner

          Hi Mark,

           

          Since you have a relatively small and simple weldment here I would try running it as a solid body.  This will save you the trouble of trying to get the correct contact sets working between the solid bodies and the beams and you will for sure be able to use the no penetration contact.  This will require more resources though and the use of a no penetration contact set will dramatically increase the solving time.  Since you have a large body (x-ray enclosure) in your model you will have to create a mesh with a very coarse global size so that you do not create a lot of pointless and resource draining nodes and elements.  This will probably cause the other bodies to fail but you can use mesh controls to create finer meshes on these parts.

           

          Just wondering, when you ran it as a weldment did you use the remote load/mass or just equivalent forces?  This may give you another method to compare results to.

           

          Ryan W.

          • Re: Framed Structure Analysis in Assembly (with pictures)
            Jim Andrews

            Mark, does the box just sit on the frame in the real world?  Is it bolted at a few points?  Welded in?  I ask because if it is actually welded in, it will probably stiffen the structure dramatically.

             

            Also, may I ask why you aren't exploiting symmetry?  It appears the model has a high degree of symmetry -- you could probably get away with modeling 1/4 section.  This would be particularly valuable if you are going to proceed with a model using solid elements.

             

            Regards,

             

            jim

              • Re: Framed Structure Analysis in Assembly (with pictures)
                Mark McGee

                The lead box just sits on the frame and can be lifted off with a crane. So I divided the weight in half and applied it to the two supporting beams. I also applied gravity because the frame weighs some 650 pounds. Notice the bottom crossmembers are split at the longitudinal members. These are forklift tubes. The designer put in 16 gussets to beef it up at the junctions. Those are the points of highest stress. This analysis was run as beams with no gussets.

                Here's the stress plot.

                Stress plot.jpg