7 Replies Latest reply on Jul 12, 2014 2:19 PM by Jared Conway

    Cantilever Beam at Different Temperatures Study

    David M

      Hello All,

       

      I'm working on assessing bending deflections of a simply supported cantilever beam at different temperatures.

       

      My problem is having SolidWorks take my inputted geometry as the geometry of the piece at any temperature. In other words, having my inputted geometry dimensions be the dimensions after the thermal expansion.

       

      For example, having a beam 1in. wide x 5in. tall x 50in. long at 400 degrees F and those be the dimensions after the thermal expansion has taken place.

       

      I want to do this so that I may see only the deflections due to load at the different temperatures. How can I do this?

       

      Thank you in advance!

       

      -David

        • Re: Cantilever Beam at Different Temperatures Study
          Shaun Densberger

          I'm working on assessing bending deflections of a simply supported cantilever beam at different temperatures.

           

          For clarity sake, what do you mean by, "simply supported cantilever beam?" I ask because a simply support beam is a beam with a pin joint on one end and a roller on the other, whereas a cantilever beam just has a fixed end on one side. Do you have some sort of combination of the two?

           

          My problem is having SolidWorks take my inputted geometry as the geometry of the piece at any temperature. In other words, having my inputted geometry dimensions be the dimensions after the thermal expansion.

           

          This isn't really an issue with SW. The issue I see here is that you know the geometric shape after thermal expansion, but not the total strain state after thermal expansion. The total strain of the system is the combination of both mechanical and thermal strains, but only mechanical strains give rise to stress. If the system is allowed to undergo free thermal expansion, there the total strain will just be the thermal strain (i.e. there is zero mechanical strain and therefore zero stress). However, if the system is constrained such that it cannot undergo free thermal expansion, then there will be some mechanical strain in the system, thereby giving rise to stress.

           

          I want to do this so that I may see only the deflections due to load at the different temperatures. How can I do this?

           

          To answer this will require more information about the problem. If there are different mechanical strains at different temperatures, then this needs to be accounted for prior to loading the beam. This is because these mechanical strains could modify the stiffness matrix of the system, which impacts the level of deflection that you'll see. The realistic solution might be to determine the geometry shape of the beam prior to thermal expansion so that you can first simulate the thermal expansion (and as such, the thermal and mechanical strains the arise) and then simulate the loading.

           

          Also keep in mind that metals at elevated temperatures will experience creep, which may or may not be important depending on a number of different factors.

            • Re: Cantilever Beam at Different Temperatures Study
              David M

              My mistake, this is just a cantilever beam.

               

              Thank you for the advise, I will calculate the size before thermal expansion and apply that to the simulation.
              Although I am lost with how to run the simulation thereafter. If I find the geometry before the thermal expansion and then have the part expand to my set dimensions, how should I constrain the piece to where there will be no strain due to the constraint?

               

              This is how I currently have the simulation set.

               

              beam.png

               

              beam 2.png

               

              1x5x50in.

              100lb loading

              AISI 316 SS
              800F Temperature Load

               

              Lastly, if I do constrain the part to where the thermal expansion does not cause strain, how can I measure the deflection due to load. SolidWorks at this point gives me the total deflection, including that of the the thermal expansion.

               

              beam 3.png

               

              Thank you

            • Re: Cantilever Beam at Different Temperatures Study
              Jared Conway

              so you've modeled the final state

              and you want to find out what geometry you need to start with and what temperature change is required to get to that starting position?

               

              seems like a simple problem, you have the final state

              put the temperature load as a negative

              then your result will be the starting state

              export the model (if you have sim pro)

              check your process by applying the same temp load but in the positive direction

              you should have your "end state"

               

              but generally people would model the start state and then apply the temperature condition and see what the end state is

              • Re: Cantilever Beam at Different Temperatures Study
                Jerry Steiger

                David,

                 

                Is your cantilever mounted to a similar material so that you can ignore any stresses due to the differential expansion at the base? If so, it seems like you could just define a material whose values match those of your material at the temperature of interest.

                 

                Easier yet, if you are primarily interested in the deflection and the deflections are not large, you can just scale the values based on the Young's Modulus at temperature versus room temperature.

                 

                Jerry S.

                • Re: Cantilever Beam at Different Temperatures Study
                  Nicholas Luyster

                  Hi David,

                   

                  Jared is right on this one. It's important to keep in mind that by setting the initial temperature within the study properties, you are effectivly changing the geometry of the model. 

                   

                  Take a look at the example part which I've attached. The only difference between the two studies is the initial temperature.  The final temperature is the same between the two simulations. However, the displacement results are completely differrent between the two studies. 

                   

                  This can make thermal simulations tricky. 

                   

                  All the best,

                   

                  Nick Luyster

                  Gosimulation.com

                  Online SolidWorks Simulation Training

                  • Re: Cantilever Beam at Different Temperatures Study
                    David M

                    Thank you everyone for your replys. It has taught me a lot and lead me towards my solution.

                     

                    The key that I was missing was the referance temperature at zero strain. By setting that, and the thermal load, to the same temperature (Might be redundant, haven't checked). I could evaluate the material at whatever temperature, without it undergoing thermal expansion. Another thing to keep in mind if anyone has a similar question, is to make the elastic modulus a temperature dependent variable.

                     

                    By having such a simple load and beam, I have verified this with hand calculations and the simulation provides the correct result.

                     

                    Again, thank you all very must for your help and great advise!