3 Replies Latest reply on Feb 2, 2009 7:48 PM by Rich Bayless

    Compressible Material Analysis

      My company is getting into some areas of extrusion that might be able to use fluid flow analysis. Before I start looking at doing any cost justification, I kind of have to get an idea of what material/fluids that SW has in their database, and what limitations there might be. For instance, if we compound a special rubber product that also contains a set amount of calcium carbonate, is this something I could either find a similar material of or readily create without having to have a lab get involved indetermining physical properties? I'm looking to do extrusion shape analysis and the rubber makes it somewhat involved with the compressibility and different temperatures. Any help/comments would be appreciated.
        • Compressible Material Analysis
          Rich Bayless
          Hello Rich,

          The material database includes a polyethylene and a polystyrene material, as well as one slurry material. The two polymers use a typical power law viscosity model, while the slurry uses a power law viscosity with a yield stress. these two models may or may not work for your particular rubber, rubber properties can be quite different from polymer properties. In other words, if your rubber does not fit a viscosity model that Floworks includes, you may not be able to get good results.

          Find out from your material supplier what is a proper viscosity model for your material. You'll have to ask for the right person at Solidworks to get more specific answers as to the capability of Floworks for other viscosity models.

          I used to work for a plastics (not rubber) extrusion company. There is such a huge variation of viscosity between the different extrudable materials, that you must get specific measurements for your particular material. Usually you can get lab measured material properties from the material supplier.

          Good luck!

          Rich.
            • Compressible Material Analysis
              Thanks for the info. Most the stuff I've been looking at with flow simulation usually involves custom blended materials, and if I had to get too far into lab studies to fully define the polymer properties it would make it difficult to cost justify for an extrusion designs I had to do. If there was a way to custom define your own polymer by generically combining the properties of several pre-defined materials (a bit "seat of pants", but that's where experience helps), then I might be able to pull it off.
              You mentioned a plastics extrusion company you worked for, did you do extrusion die design? If so, I'm curious to know if you found CFD to help you out much.
                • Compressible Material Analysis
                  Rich Bayless
                  Hi Rich,

                  sorry, I was out of town for a bit.

                  I did many extrustion die designs way back when I worked at the extrusion machinery company. Being creeping flow, Reynolds number around 1.0e-5, using basic pressure drop equations for a pipe or for a slot worked very well. The basics worked very well, IF you had accurate viscosity data. We measured our own viscosity curves using an extruder and a rod die.

                  Can't say that I've ever used Flow Simulation for die design, so I can't help you with your cost justification.

                  Rich.