8 Replies Latest reply on May 7, 2013 3:47 PM by Jared Conway

    Help for beginner

    Ari Arponen

      Ok, here's the deal. I need to make calculation for very simple part.

      beam1.png

       

      I need to make calculations for that lower beam part (circled in red). It is fixed to floor and to that stretcher platform with 8M countersunk screws.

      beam2.png

      I have made the floor holes fixed and try to apply a force to upper holes. So that G forces goes lenghtwise and the faces that take the force are those screw holes. I have applied material as cast alloy steel, but for some reason even with smallest force applied the results appear very bad. Like this:

       

      beam3.png

      Im trying to this just for the part, not assembly. Any ideas what I'am doing wrong? The main goal here is to simulate 20G crash on this part, so I need to see where I put reinfocements etc... I tried to check the tutorials came with Solidworks, but looks like im going to need more help than those.

        • Re: Help for beginner
          Patrick O'Hern

          SolidWorks automatically scales up the deformations in Simulation so that it is easier to see it what directions it is deforming.  It looks like you have only added restraints/forces to the holes in one end of the beam.  This is most likely the cause of the twist that is being added.  You need to look at not only the shape, but also the values that are being output.

           

          SW Simulation is very easy to set up and run, but it can be somewhat of an art to correctly determine the results that are output.  I would suggest taking a class on Simulation if it is something you will be using very often.

          • Re: Help for beginner
            Mike Pogue

            Ari,

             

            The maximum deformation I see is 3 nanometers.

            • Re: Help for beginner
              Jared Conway

              Ari, it would be good to describe how you would test this in the physical world. Then we could help you translate that to a simulation.

               

              Right now you've told the software that it is bolted to something rigid on 2 holes and you have a big force on the other 2. The otherside isn't restrained at all.

               

              You should also be careful about using a static analysis for a dynamic simulation. If you really want a shock/crash test, it is best done with dynamic analysis. You will need Simulation Premium for that.

                • Re: Help for beginner
                  Ari Arponen

                  Thnaks for the answer guys. I have put the same information shown in second image to all six holes in the beam. And what am I looking for is the simulation of crash test. Its done by pulling the assembly at 20G force forward.

                  And the weights are:

                  beams ~18kg

                  platform 53kg

                  stretcher 35kg

                  patient 75kg

                  total 181 kg.

                  So it would be pulled with 3620kg mass forwards.

                   

                  Shoud I do a assembly test with this and put the forces to all holes? Or try to do what I've done above? If I have understood this simulation thing correctly, when I fix the holes to floor (the green ones) Solidworks will keep them fixed? No matter the force?

                   

                  Here's similar beams in real life test:

                  That stand top of beams simulates the platform.

                   

                  We have Solidworks premium license, so I think it does not support the premiun simulation license.

                    • Re: Help for beginner
                      Jared Conway

                      Hi ari, your picture didn't make it.

                       

                      Have you considered the effect of the ground on your beam, or how the pulling load is distributed along the beam and the holes because of the structure above it?

                        • Re: Help for beginner
                          Ari Arponen

                          whops, heres the image. We just need to trust that our fixation on floor holds. Usually the weakes structure are the beams. It might be bit difficult to create situtation like this in SW, atleast by me. Still a rookie here, but I want to learn.

                           

                          So basicly rear part force is going upwards and the front part downwards, as you make the pull from packages centre of gravity.

                          testsituation.png

                           

                          One important thing here is that we are usually very close to vehicles maximum weight and we need to make these support beams as light as possible. And it would be great to have some calculations before tests, because every test day costs thousands of euros.

                            • Re: Help for beginner
                              Patrick O'Hern

                              Rather than applying a force to the upper holes, you might try adding a Remote Load/Mass.  Set it to the mass of your assembly and locate the COG correctly, then add a Gravity load of 20g's in the direction of the force.  If you do this, you would probably need to show both lower beams in order to get the load constrained correctly.

                              • Re: Help for beginner
                                Jared Conway

                                Patrick's idea is a really good one here. But I don't know why you wouldn't analyze the whole structure. The assumption you're making is that the part above the bottom plates are infinitely rigid. Also, with who accurate it sounds like you're wanting the results to be, I'd be concerned with using a static test for a dynamic need.