11 Replies Latest reply on Jan 12, 2014 5:04 PM by Jared Conway

    Question in drop test

    Aaral Gupta

      Hello,

       

      I'm making a drop test of a plate supported by legs, the first time the plate is not loaded with anything, but the second test with loads on the plate.

      both tests shows the same result!, is that correct ?

        • Re: Question in drop test
          Jared Conway

          what do you mean by loads are on it? can you post a screenshot of the 2 setups? (the drop test setup dialog)

            • Re: Question in drop test
              Aaral Gupta

              Sorry if i wasn't clear in explaining it.

               

              The model is a simpliefed version of a flying robot base, I'm trying to study two cases:

              1- the robot is not carying any items (no blocks)

              2- with the some items (blocks = 150 g each)

               

              Rotors will cary this structure, I'm tyring to know what will happen to the structure when it falls from a distance of 10 m.

              The setup is attached (same for both cases).

              my concern is, in both cases the displacement results are the same.

                • Re: Question in drop test
                  Jared Conway

                  i would double check that the weights of those blocks is correct. what is the weight of the blocks relative to the weight of the block?

                   

                  it does seem strange that the max is the same, can you create new plots for both studies to see if they change at all?

                   

                  the patterns do change slightly and the blocks follow the pattern. in addition to the new plots you might want to also reduce the scale to get a better idea of what is happening around the blocks. maybe the change is there but it is really small.

                    • Re: Question in drop test
                      Aaral Gupta

                      The weight of  the circular block is 1000g, small block each 300g.

                      I made a new study where  the small block weight is 5000g, the result is almost the same as the previous study. it doesn't look like

                      solidworks is considering the what above the circular block.

                        • Re: Question in drop test
                          Jared Conway

                          doesn't make sense

                          please make a sample that shows the same behavior and post here so that we can try it out

                            • Re: Question in drop test
                              Aaral Gupta

                              ok, the file I'm using is attached

                                • Re: Question in drop test
                                  Jared Conway

                                  just to make sure we're on the same page, what are you expecting to see as differences between the 2 simulations?

                                    • Re: Question in drop test
                                      Aaral Gupta

                                      Larger deformation in the second study

                                        • Re: Question in drop test
                                          Jared Conway

                                          would you expect that if they hit the ground at the exact same velocity?

                                           

                                          what would you expect if you stiffened up the legs or made them softer?

                                           

                                          what would you expect if you changed the dimensions, location and weight of the blocks?

                                           

                                          i'm seeing the same thing on your model, i haven't tried a new study or a test model but would recommend you do this before we go too much further. the reason I ask these questions is because i have a theory but need to get some more information about what your expectations are and whether this problem is isolated or not.

                                            • Re: Question in drop test
                                              Aaral Gupta

                                              This model  is a simplefied version of the actual structure and items, my purpose is to know at what will happen to the base (circular) when it fall from 10 m height carrying 2 kg of components.

                                               

                                               

                                              I was planning to make two studies, first of the base carrying all the components (around 2 kg).

                                              the second study is same, but with cutting material from the base to make lighter.

                                              I'm adding shock aborbers on the legs in both cases.

                                               

                                              that was the original plan, but when I tried it with this model (attached previously) from heights from 10m to 50m and with/without weights on the base I got worried that something is wrong when the results are almost the same.

                                               

                                              would you expect that if they hit the ground at the exact same velocity?

                                               

                                              without the shock absorbers, I'm expecting the base to break.

                                               

                                              what would you expect if you stiffened up the legs or made them softer?

                                              will break the base, legs will break

                                               

                                               

                                              what would you expect if you changed the dimensions, location and weight of the blocks?

                                              not much change.

                                               

                                               

                                              sorry of the long reply, I though this way it will be more clear.

                                               

                                              Thanks.

                                                • Re: Question in drop test
                                                  Jared Conway

                                                  to isolate a software issue i would recommend setting up at least one more test that is similar to see if it behaves the same, this will confirm it is a software issue vs a problem with your setup.

                                                   

                                                  from there i would test some of the variations to see if it trends the way you expect. if not, again pointing towards a software issue.

                                                   

                                                  unfortunately just don't have the time to go through these permutations and combinations. are you on the latest 2014 sp1.0 and also using a commercial license? you could also work with your reseller on this.

                                                   

                                                  one thing i'd suggest is running the simulation with the same velocity at impact or reviewing the velocities/accelerations to see if they are the same or different. my only theory is that there is something going on with the "conversion" to a dynamic simulation that is making things act the asme. but at the same time, i have a sneaking suspicion that it is something with this model or study specifically which is why i'm saying try at least one other model.