3 Replies Latest reply on Jun 25, 2013 3:31 AM by Shaun Erasmus

    Smooth Varying Shell Definition for Static Simulation

    Shaun Erasmus

      Hi,

       

      I am looking into simulating the top load on a plastic bottle. I believe the bottle is first injection molded to get the lid thread accurate and then blown to get the basic shape of the bottle. This means that the body has an outher shell that is non-uniform as the thickess varies around the bottle's cross-section. Is there any way to model this using multiple shells that will have a smooth transition between the thicknesses?

       

      Thank you in advance.

        • Re: Smooth Varying Shell Definition for Static Simulation
          Tom dunn

          Hi Shaun. I have a section in my on training book "advanced part modeling? it shows creating a model for a plastic bottle. I don't know if I can scan the whole section for you and send it or not. (it is 32 pg's) In the book is shows using a sweep feature to create the basic shape, then it shows to use the shell command but it has using a multiple thickness one for the top threaded section and then another for the body. What version of solid works are you using? I am 2012. I might be able to send you the finished file also. I'll see if I still have the training file. Tom

           

          I just created a bottle with my own dimensions. In the book it says to create the profile sketch's first (my sketch's 4 &5).

            • Re: Smooth Varying Shell Definition for Static Simulation
              Jared Conway

              thomas, i think he's talking about simulation shells (vs solid elements)

               

              thomas, there isn't a way to create a shell that is a blend between 2 other shells. you could use split lines to define thicknesses that change. but for your first pass, why not go with the worst case scenario and then second pass best case scenario? then you can get fancy with additional shells in between.

               

              good question though! does anyone know if other softwares deal with this differently?

               

              another option would be a hybrid mesh where the transition area is a solid that you can control the thickness.

            • Re: Smooth Varying Shell Definition for Static Simulation
              Shaun Erasmus

              Thanks Thomas and Jared. Yes I am looking at the shell elements (should have been more specific), but the approach of the sweep may be useful to use the hybrid mesh approach?

               

              Unfortunately I cannot do a worst and best case scenario as I am looking at the effect of the thinner wall causing the bottle to buckle by assigning a thinner shell in various locations and monitoring the effects.

               

              I generated a simple surface model and split them into quadrants using the default planes. I ran a simulation of a topload with all of the faces the same thickness. I duplicated that study and then selected two faces and made them thinner than the rest of the body. As expected, the stresses in the thinner facer is definitely greater and more distributed (rather than concentrated), but what was really interesting was that there were no stress concentrations between the faces of varying thickness. I imagined there would be a lot of shear along the split lines, but there seems to be none.

               

              I have included a screenshot to supplement the above-mentioned. The shot on the left is the one with uniform thickness, the centre shot shows the manner in which the bottle has been split into quadrants and the shot on the right shows the stress when two faces have been assigned a thinner shell thickness than the rest of the body.

               

              Shell Thickness Comparison.png