10 Replies Latest reply on Jun 8, 2014 11:57 PM by Jared Conway

    simulation of a T-shirt

    Sam Bernard

      Hi,

       

      I work on a project whitch aim is to create tents for Africa but I am confronted to a problem. I would like to modelise and simulate a hessian with the behavior of a cloth on Solidworks but i don't know if it is possible.

      The simulatioon include gravity and wind load.

       

      Please, could you help me ?

       

      Your faithfully.

        • Re: simulation of a T-shirt
          Shaun Densberger

          Depends on what you're after results wise. Modeling the frame of a tent is possible, but if (for whatever reason) you need to accurately model a fabric, then I don't think SW will be able to do that. If you can give more information on what you want to do (i.e. determine if the frame is strong enough to withstand wind loads and gravity), then I think we can help.

           

          If you absolutely, positively need to model the fabric (i.e. it's a core structural component), then you'll want to take a look at LS-DYNA (ABAQUS might have a fabric material model as well; I'm not too sure though).

          • Re: simulation of a T-shirt
            Jared Conway

            what do you want to learn about the tent?

            • Re: simulation of a T-shirt
              Sam Bernard

                   This is my model. I would like to simulate it with wind load. But when i apply my wind on the half dôme, the fabric doesn't deform like i want. The deform for a wind of 50 km/h is 5.5 cm. I find it strange. I don't know if it's my fabric modeling or my simulation that is insoveld.

               

              Could you help me for making a greater simulation ?

               

              Thank you.dome.png

                • Re: simulation of a T-shirt
                  Shaun Densberger

                  How are you modeling the fabric?

                    • Re: simulation of a T-shirt
                      Jared Conway

                      like shaun says, what material are you using for the fabric and how are you handling that it really only works in tension?

                       

                      what do you want to learn about the fabric?

                       

                      how will you load it to match a 50km/h wind?

                       

                      when you say it deforms 5.5cm, what are you measuring?

                       

                      to me, it seems like the frame is probably the important part to analyze

                      you come up with a load from the fabric surface area and wind velocity and pressure

                      load the appropriate members based on the wind direction

                      run the analysis

                      accept the results under the condition that the load is directly applied to the beams rather than in between them through the fabric and accept relative improvements as a good place to start your design

                        • Re: simulation of a T-shirt
                          Sam Bernard

                                I have created my fabric with a surface of revolution to design the roof of the dome.

                           

                          I specified a thin shell of 0.2mm and used nylon 6/10 for the material.

                           

                          The wind load is calculated with a formule, I found 11 591 N for 50 km/h. I would like to apply the variable distribution in order to divide the wind load,

                           

                          But, I need a continuous surface to apply it correctly. So, it is necessary to model the fabric shape.

                           

                          I want to measure the structure displacement.

                           

                          I think it's not the best solution but I don't know how to make the fabric.

                           

                          Please, could you help me again ?

                           

                           

                          Thank you for your answer.


                           

                                       

                          .

                            • Re: simulation of a T-shirt
                              Jerry Steiger

                              Sam,

                               

                              I don't know where the wind load number came from, but it doesn't make any sense to me. It certainly doesn't make any sense to try and analyze the deflection of a tent shaped like yours with a single force. The "real" wind load will apply positive pressure on the front side, negative pressure on the top and sides, and probably a wildly varying positive and negative pressure on different areas of the back side, due to the separation and turbulence. The pressure will vary in a continuous manner across the surface until you reach the back where it might become much less continuous.

                               

                              The above assumes that the fabric is stretched tight enough to not deflect too much away from the structural ribs. If it is relatively loose, then you will have a much more difficult problem to solve, as the wind moves the fabric.

                               

                              As a first pass at an analysis, you probably need to use CFD to establish the pressure distribution across your tent. You could then do a structural analysis to see how the fabric and ribs deform. This change in shape would then change the pressure distribution, so it would be best if you did a coupled aerodynamic-structural analysis, where it iterates to the final solution.

                               

                              Modeling the actual behavior of the fabric will probably be very tricky as well.

                               

                              Your tent looks like a hemisphere. You might be able to find the pressure distribution across a hemisphere, but the results may not apply too well, depending on the Reynolds number of the flow and model that was measured versus your tent.

                               

                              Jerry S.

                                • Re: simulation of a T-shirt
                                  Jerry Steiger

                                  Sam,

                                   

                                  Another complication that I forgot about. What is the distribution of the wind velocity? If your tent is sitting on the horizontal ground at the top of a cliff, there will be a very small boundary layer above the ground. If your tent is sitting in the middle of a vast plain, the ground boundary layer is going to be much thicker. That will mean that the bottom of the tent will see lower wind velocities. That may or may not be significant. That level of detail is probably the least of your worries. This is a very difficult problem to solve.

                                   

                                  Jerry S.

                                • Re: simulation of a T-shirt
                                  Jared Conway

                                  see jerry's response, i don't thinking your goals through fully

                                  or how you will apply the force based on wind