3 Replies Latest reply on Nov 17, 2017 9:30 AM by Iain McEwen

    Same setup, different results Static vs Nonlinear Study

    Jordan Truitt

      What does it indicate when the results of a static and nonlinear study are different when everything else is identical? I was expecting the results to be the same or similar.

        • Re: Same setup, different results Static vs Nonlinear Study
          Iain McEwen

          Hi Jordan,

           

          If everything is identical, it would suggest that the problem is nonlinear. Every static simulation could be run as nonlinear, so this should always provide the more accurate results. If you could share the simulation it would be interesting to take a look at?

            • Re: Same setup, different results Static vs Nonlinear Study
              Jordan Truitt

              I wanted to say that the nonlinear result is the correct one but couldn't support it with my limited understanding.

               

              Here's a pic of my setup. The top part interference fits with the bottom press fit part. I'm using shrink fit contact sets. I'm applying a -40C temperature load to the top part and trying to find how much force it would take to pull the part off. I'm fixturing the bottom surface of the top part in only the Z-axis and fixturing the top hole from rotation. My goal is to find how much force it takes to slide the part off but that's proving difficult. I feel pretty confident in the contact force calculated on the interference fit features, multiplying that by friction seems like a reasonable value. But if the nonlinear study is correct then these stresses are around yielding and I have to learn how to perform this with a different material model.

               

              Any insight into performing this would be helpful, I've been struggling to get consistent and repeatable results.

               

              Thank you.

               

              setup1.png

                • Re: Same setup, different results Static vs Nonlinear Study
                  Iain McEwen

                  I assume that your material model is linear, so this likely won't come into it. With the thermal expansion and changes in geometry due to loads that would occur in the model, nonlinear can account for this whereas the static model cannot. This means that it can not only account for this in the stress effects but also the direction of applying the force. This is likely the greatest cause of the mismatch. What sort of displacements is it currently looking at?