9 Replies Latest reply on Nov 10, 2011 1:18 PM by Keith Ewing

    Load Capacity of a Cart

    Keith Ewing

      Can someone please help me with determining the load capacity of a cart assembly?

      I am new to simulation and do not have enough time to tackle it on.

        • Re: Load Capacity of a Cart
          Sander Buys

          Here is how I would do it:

          Get rid of the bolts and the wheels. Mesh the profiles using beam-elements. At fixed geometry fixtures to the 4 bottom joints (these represent the points where your cart is connected to the wheels). Create a bonded contact between the plate and the beams supporting it. Apply an arbitrary load to the top-plate (force or pressure, depending on what you want). Run the analysis.

           

          From these results you should be able to determine the maximum Load (depending of course on your criteria: FOS allowable displacement and so on).

           

          To got somewhat more realistic results you can use an advanced fixture to manually create some sort of roller/slider fixture to the bottom joints. But you will have to stabilize your model with softsprings my guess if you do so...

            • Re: Load Capacity of a Cart
              Keith Ewing

              Thanks for the tips! I'll be working on it.

              • Re: Load Capacity of a Cart
                Sander Buys

                couldn't help it, i created the study for you. Altough I noticed one thing : the "the roller fixture" I tried to create using an advanced reference geometry seems to result in just a normal fixture without any degrees of freedom.But my guess is that it won't affect your results that much, it will just result in a slightly higher value for the stress. But better this than the other way around. Consider it as an extra Factor of Safety.

                 

                Does anybody know if it is even possible to create something like a roller fixture to a joint of a beam ? Just curious about that...

                Before I forget : I created the study using Solidworks 2011, don't have any previous versions installed anymore.

                I must also note that 2012 is way better in making contacts between beam and other elements because it imprints the actual shape of the beam to the face.

                 

                You could further refine the study by meshing the plate as a shell, to get more accurate results for that...

                 

                screenshot-cart.jpg

                  • Re: Load Capacity of a Cart
                    Keith Ewing

                    Thanks for all the help. This cart is going to be used to transfer sheet metal blanks, so most of the surface area of the plywood will be utilized evenly, if that matters.

                    • Re: Load Capacity of a Cart
                      Sander Buys

                      I just thought of a workaround to create the roller/slider fixture:

                      you could design 4 small little flat plates at the bottom of you cart (at the location of your wheels). You can add bonded contacts to those bodies in your study and the beams they are attached to. Than you can use just standard roller/slider fixture to the faces of those 4 bodies. you will also have to use softsprings in your studieproperties to stabilize the model...

                       

                      Nevertheless I'm still curious if it is possible to create such a restraint to the joint of the beam itself...

                        • Re: Load Capacity of a Cart
                          Keith Ewing

                          My SW 2010 keeps crashing on me. Haven't quite been able to complete analysis. Last error I got was "unstable" "restraints may not be adequate". I'll keep working a little while longer. Too bad I cannot open your "newer version" file. Thanks for playing around with this, I am learning from your comments.

                            • Re: Load Capacity of a Cart
                              Sander Buys

                              Whenever you get the unstable message, it's a good practice to run your study with the softsprings turned on. This will artificially stabilize your model. Your model will still be underconstrained, but you will be able to get results which will allow you to determine which contact is missing (as one of the components will probably just fly away). My guess is that a bonded contact between beam and plate is missing...