5 Replies Latest reply on Mar 18, 2015 1:12 AM by Jared Conway

    How do I do this Statics simualtion in Simulation xpress

    Sammy Redshaw

      I have a bar  which 4mm thick plain carbon steel and 24mm wide with 2 dowel pin holes 200mm apart  on the end of  one dowel pin is a vertical mass of 50kg.

      When I simulate the bar  with one hole fixed and the other loaded the dowel pin holes distort.

       

      fea link.PNG

       

      My experience tells me the the stress should be toward the centre of the bar rather than around the hole as the dowel pins will act as a solid part.

       

      taking the holes out  I get this

       

       

      fealink 2.PNG

       

      The stress is not symmetrical as one end is fixed and on end is loaded

       

      I guess because the problem is symmetrical  I should cut the bar in half

       

      fea link 3.PNG

       

       

      Is this the best way to approach the simulation in SimulationXpress?

       

      A  colleague has the premium license with the full blown Simulation suite how would I approach the simulation in regards to fixtures.

      just fix it in on direction?

       

      Thanks

       

       

      Sammy

        • Re: How do I do this Statics simualtion in Simulation xpress
          Jared Conway

          the half model is better for the reason you mentioned about fixing one end and loading on the other

           

          as for the holes distorting, it comes down to what faces you applied the force on. but that is expected. even if you had the dowel in there, it would only pull on one side and distort the size of the hole but it would restrain it. another option would be to model the dowel as a solid in your model for simulation xpress and apply it to the shaft of the dowel. but now it will be like a solid dowel welded to your tab.

           

          in sim prem you have a lot of options, bearing load, you could model the pin and apply contact. but in the end, a simple force should be plenty to get you what you want. but the rest are great exercises for you to understand the assumptions of just applying a force to the hole or half the hole.

            • Re: How do I do this Statics simualtion in Simulation xpress
              Sammy Redshaw

              Thanks for the reply

               

              I have spent too many years modelling and drafting in inventor ( I will never take an inventor job again!!!)  so I am trying to figure out how to do engineering again.

               

              I guess the limitations of xpress fixtures show when you want to do a more complex load case.

               

              The main issue is that the Factor safety goes from about 4  in the first two examples to about 20 in the half model load case.

              From seeing  other people set the FEA simulations badly I just  wanted to check what is right approach.

               

              I want to model a pin in the premium version to simulate contact  but the 2012 simulation training manual confuses me a little bit. Do you have a simple example of  a pinned assembly that I work through?

              I would also like to simulate the whole assembly in the premium version but, I not sure what it the be strategy for Setting a production assembly for FEA analysis. Do I simplify the model by taking out the fasteners and split the faces that are loaded unloaded. or is there a better approach?

                • Re: How do I do this Statics simualtion in Simulation xpress
                  Jared Conway

                  a loaded question

                   

                  fos > I would be checking that you're not just looking at the max, areas of singularities may show a localized max that isn't real

                   

                  right approach > the half model is definitely the way to go with a split to only load the bottom of the hole

                   

                  simple example of a pinned assembly > do you mean a pin pulling a hole or do you mean a pin connector?

                   

                  best approach for analysis > I always recommend simplifying the model first and using idealizations like pin connectors. bolt connectors use split lines but pin connectors do not.

                   

                  i'd highly recommend going through the tutorials and all of the training lessons before attacking a problem and if you have some professional development funds, it pays to have someone walk you through your first analysis

                    • Re: How do I do this Statics simualtion in Simulation xpress
                      Sammy Redshaw

                      Jared

                      This is the load case in more detail

                      load case.PNG

                      Distance between clock wise moment M and load is 193mm

                       

                      load is 50kg * 9.81m/s = 490.5N

                       

                      Clockwise Moment  M = 490*5 *193mm =94730 N/mm

                       

                      anti clockwise moment there is = to the clockwise moment

                       

                      F1 is equal to the anti clockwise moment  /distance between the clock wise moment M and f1 which is 70mm

                       

                      therefore  F1 = 94730N/mm /70mm =1353N

                       

                      this F1 with the beam vertical in really should be F1 *cos* angle but I want worse case.

                       

                      The question is in this case would I be better of analysing/investigating the whole assembly with bolted connections or just the beam under tension?

                      kind regards  Sammy