6 Replies Latest reply on Nov 4, 2014 10:20 AM by Jared Conway

    Drop test including modeled preloaded joint

    Nick Hahn

      I would like to perform a drop test simulation on an assembly that contains a preloaded joint.  The preloaded joint is not a fastener that I can treat as a beam - it is two large threaded parts (imagine pipes with shoulders that bottom out on each other and are then torqued further) and I am interested in if the joint separates during the drop (I don't care about the thread stress, they can be considered bonded there).  I have successfully modeled the preload portion using the "shrink fit" boundary condition in a static study.

       

      This can't be done in a standard drop test study, can it? Can a static analysis (i.e. with the "shrink fit" BC) be used as an input to a nonlinear dynamic one?

       

      Assuming the above is not possible, is there a sequence of load/displacement/force curves and/or restart cases that might make this work?

       

      I have done many simulations before but I'm new to SW Simulation, so I'm trying to figure if this is possible. We've always had to ignore the preload before but that is quite conservative.

       

      A similar case I'd also like to examine has a press fit item that I would like to include in a dropped assembly. 

        • Re: Drop test including modeled preloaded joint
          Shaun Densberger

          Can you post an image of the system? I'd like to get a better idea of the system before making an alternative suggestion. That being said, I wouldn't do this with non-linear dynamics (even if it was technically possible) for a number of reasons.

            • Re: Drop test including modeled preloaded joint
              Nick Hahn

              See below (from different CAD package, but this is the gist of it). This is a simplified version of the threaded interface. I am interested in making sure the upper seam in the second picture doesn't separate under drop. For preload I would model it as slightly interfering, with interference amount based on stress-strain relationship of the thin section that's in tension.

              clip_for_forum.jpg

            • Re: Drop test including modeled preloaded joint
              Jared Conway

              swx simulation is what you see is what you get

              so unless you can develop the preload with a temperature or bolt connector or equal and opposite forces or a spring in the study that you want, you can't do it.

              i think nonlinear dynamic is the only option but like shaun said, will be challenging because you will also have to sequence the application of the preload..etc.

              i'd stick with your conservative method for now or if this is something you do often, look at abaqus or work with your reseller to work through your first attempt at this.