5 Replies Latest reply on Mar 31, 2011 10:53 AM by Paul Kellner

    Adding thermal effects to bolted static study

    Garrett Casey
    Garrett Casey Mar 23, 2011 3:12 PM

      I have a static study that is shown in the image below.  It comprises of a resonator (top piece) and a housing (bottom piece).  The resonator is bolted to housing.  To simulate this in solidworks I have applied a "Bolt Connection".  Now if I take out the thermal effects, this simulation runs fine and gives me fairly accurate results.  However, once I apply thermal effects and an initial temperature (85 Celcius) to both the housing and resonator, the simulation blows up.  Can anyone direct me down the right path, I have looked into the other threads about thermal effects but they seem to be for non-linear analysis and I don't have that package.  Thanks for any help you can provide.

       

      Thermal_Study.jpg

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        • Re: Adding thermal effects to bolted static study
          Paul Kellner
          Paul Kellner Mar 30, 2011 9:29 AM (in response to Garrett Casey)

          Did you setup a reference temperature in the run properties dialog?

           

          Did you include thermal effects?

           

          Did you try all the solver options?

            • Re: Adding thermal effects to bolted static study
              Garrett Casey
              Garrett Casey Mar 30, 2011 9:32 AM (in response to Paul Kellner)

              might be the reference temperature that I didn't do right.  My understanding was to apply the reference at which there is zero "extra" strain due to thermal?  I applied the reference temperature of room temp ~25C.  This could be my problem.

               

              I set an temperature on all the parts.

               

              I tried all solver options.

                • Re: Adding thermal effects to bolted static study
                  Paul Kellner
                  Paul Kellner Mar 30, 2011 9:38 AM (in response to Garrett Casey)

                  If you are looking at the effect of a change in temperature on your part you have to set a reference temperature and include the new temperature as a boundary condition. If a bolt is involved you have to change the nodal temperature on all the nodes in the bolt. This adds a term to the strain calculation for each element based on deltaT*alpha where alphe is the LCTE. This can also mess with the stiffness matrix.

                    • Re: Adding thermal effects to bolted static study
                      Garrett Casey
                      Garrett Casey Mar 30, 2011 10:57 AM (in response to Paul Kellner)

                      I am using the "bolted connector" option in solidworks.  I'm not sure what goes on behind the scenes but I don't think that there is a mesh associated with it because there isn't an actual object there, just a boundary condition.

                        • Re: Adding thermal effects to bolted static study
                          Paul Kellner
                          Paul Kellner Mar 31, 2011 10:53 AM (in response to Garrett Casey)

                          Once upon a time I asked the SRAC folks about this. Specifically I asked whether it was an RBC and IIRC they said, no, they did it another way. If the docs don't say it can take a thermal load, I wouldn't count on it doing so unless testing showed otherwise.

                           

                          In other codes an RBC (Rigid Body Connector) is a way to map displacements from one node to  another in way that the connection acts like an infinitely rigid bar. In Cosmos/M I might use a Truss or Beam element and a group of cpdofs to model a bolt. I don't know if the Help documents the bolted connection very well other than telling you how to use it.

                           

                          The old fashioned way of putting preload on a bolt is to set it's reference temp to zero and apply an appropriate nodal temperature load such that it causes the bolt to "shrink" enough to get the necessary preload. This has it's drawbacks.