2 Replies Latest reply on Jul 28, 2017 5:29 PM by Naga Ranjith Kumar Addagalla

    Bolt thread fatigue

    Bence Rivasz

      Hey,

      Im a little bit confused and i cant find answer: How is it possible to set up an accurate fatigue simulation for a threaded bolt connection?

       

      Problem: The bolt has a standard Torque, but with this load the firs roots of the thread go far over the yield strenght what is alredy unaccaptable for fatigue.

      After the constant preaload should come the axial dynamic load  (arrow, see picture)

      Is there a special evaluation for these Problems?

       

      Unbenannt.jpg

      Thanks

        • Re: Bolt thread fatigue
          Ryan Dark

          Hi Bence,

          You are right, if the stress exceeds yield your fatigue analysis won't be worth anything (at least not in those regions of the model).  Have you achieved mesh independence on your model here (smaller element size yielding the same stress results)?  Have you determined whether the high stress you are seeing is a singularity?

          • Re: Bolt thread fatigue
            Naga Ranjith Kumar Addagalla

            Generally, all the bolt holes and bolt threads have to be symmetry when you have torqued.  But the image file shows that the concentrated stress is only at single thread and at the end of the bolt.  Please do check that once.  Because, as Ryan Dark said that there are singularity points.

             

            I hope your yield stress might reduce and will get success in your answer.

             

            Thanks

            Naga Ranjithkumar A