3 Replies Latest reply on Nov 19, 2013 11:22 PM by Jared Conway

    Verifying Tensile Test on Sheet Steel

    Ben Morrissey

      Hey guys,

       

      Okay so next week I'll be preforming a tensile test on SS304 sheet metal dogbone specimen and currently I'm doing a FEA to determine what results are likely to be seen. I'm only analysing the elastic region.  Now I've done some hand calculations aswell, with the hope that I run FEA at various levels, record the stress strain and displacement and then compare to hand calculations.

       

      Now straight off the mark they are not similar, theres about 0.05 mm difference between them! Any idea why? I've used same Young's Modulus for both. Is it that Solidworks is taking into account variables which arent assumed in basic hand calcs?

       

      This is when i add fixture and loads to the pieace on top and bottom. Now realistically I should be using split contacts and gripping it on the sides. However when I do this I get crazy high stress values at loads where it shouldnt be beyond yield but it is.Any ideas on this too?

       

      I attached some pics if anyone can help I'd be really greatful.

        • Re: Verifying Tensile Test on Sheet Steel
          Jared Conway

          take a step back and walk us through your calculation, the assumptions it makes and then the setup. feel free to post your model and the calcs using the advanced editor.

           

          the reason i suggest this is i looked at your screenshots, some have 3000N, some have 6000N and i can't tell what you're loading or restraining in your model because they are all deformed models.

           

          my suggestion for this is to fix (on a splitline) on one end, this will assume a super bond to the machine there.

          and then on the other end displace the end the distance that it will displace in the test

            • Re: Verifying Tensile Test on Sheet Steel
              Ben Morrissey

              Heya,

               

              I attached images showing the fixtures and loads more clearly.

               

              Well using a force of 6000N and using the same value for youngs modulus as solidworks used I worked out that there should be a displacement of about .28 mm but fea in solidworks is giving me .19mm. Now is it as close as I'll get due to assumptions made in hand calculations that arent realistic or is there a better way to fix and load the speciemn to more closely approximate testing in machine.

               

               

              Screenshot (9).pngScreenshot (10).png

                • Re: Verifying Tensile Test on Sheet Steel
                  Jared Conway

                  what assumptions do your hand calcs make?

                   

                  what do your physical testing results say? (this is the end all be all answer)

                   

                  what are the assumptions your simulation makes?

                   

                  a few things i see:

                  1. you're pulling and restraining only the very ends of the material, is that really how it is held in the machine?

                  2. simulation is taking into account the change in area, are your calculations taking that into account?