5 Replies Latest reply on Mar 17, 2011 9:36 AM by Bill McEachern

    Simulation, Beams, Joints and neautral axis... its all gone wrong!

    Michael Sheen

      Hi All,

       

      I have been struggling for some time with a frame in simulation.  The frame is all made from weldments with some bends.  The main problem i have is that the joints do not show up because the neutral axis is not valid.  Its seems to be when you put a bend in that Solidworks gets confused and needs a sit down...  I have attached my file as I am totally fed up!!!

       

      I find that some frames work and some don't... there is no trend apart from the number of bends.  I thought by increaseing the angle it would help too, which worked then it didn't.  This bug restricts my simulation design table massively so it actually hinders my work.  I am starting to question Simulation on Solidworks!

       

      Any help, much appreciated.

       

      Mike 

        • Re: Simulation, Beams, Joints and neautral axis... its all gone wrong!
          Bill McEachern

          I do not have time to look at your model. However, you need to remember what abeam element analysis is - the structure represented as line with a real constant set that defines the properties of the beam. So, cut outs, mitered corners, coped corners, holes and all that stuff just causes the program to get confused about what the beam looks like. Just makethe structural member model dead ass simple - a bunch of corss sections that interesect at certain locations - don't trim or make relief cuts if one member goes through another - this all detail not in a beam model. In other words, build an analysis model first and then do the details.

            • Re: Simulation, Beams, Joints and neautral axis... its all gone wrong!
              Michael Sheen

              Hi Bill,

               

              I know what you mean.  I am cautious of making the model too simple, so it works on simulation, which then gives inaccurate results.  YOu have given some good tips here, so i'll try removing the trims etc. Cheers 

                • Re: Simulation, Beams, Joints and neautral axis... its all gone wrong!
                  Bill McEachern

                  I am not advocating overly simplified. Just makle the solid model match what can be "analyzed" in a beam model. In the old days (as with many other codes currently) you would have to build the line geometry, mesh the lines with beams, merge the nodes,  apply the section properties to the beams, add materials, add loads & BC's and run. Just think that way when you are building a beam model and you cna get it to work more or less in Solidworks. Typically, I am not super thrilled with the quality of the beam model you get with all the automation - beams are not straight (get kinks near joint - seems to be a mesh density dependent pehnomena), joint connections mis-behave. etc. But on the whole, as long as you are prudent you can get a model that works but I do require large margins. Oh, and watch out for torsional effects - you need to add the right parameters to make that work correctly.

              • Re: Simulation, Beams, Joints and neautral axis... its all gone wrong!
                Loic Ancian

                hello

                You get this problem because of the curved beam.

                I don't know the exact english word for this but if you uncheck this option then you don't get the red cross any more:

                Capture.JPG

                 

                But in fact you now have three beams and the middle one (curved) for some reason cannot be modeled as a beam. It should in 2011 if I remeber well but anyway...

                 

                So a workaround would be to modify your orginal sketch and replace the curve by a straight line. It worked for me and results should not be too far. Here is the mesh obtained :

                Capture2.JPG

                 

                Bye