2 Replies Latest reply on Oct 5, 2011 3:29 PM by Roland Schwarz

    These Axial Forces Unrealistic???

    Dave Huth

      I am a new simulation user and am having a hard time believing the results of the "list bolt forces" in my study.  The frame seen below is subjected to a 73kg force roughly halfway up and a smaller force of 6kg on the base.  This is half of the frame so I applied a symmetry constraint to the open ends as shown.  All the tubes are welded together and I assumed them to be bonded.  The two small machined pieces on the bottom left are used to pin the assembly to the floor so I have fixed the holes of the outer piece to simulate this.  The other machined piece is held onto the tube frame by (4) M8 Bolts torques to 21.2 Nm.  Friction between the frame and the "adapter" is 0.45.  Due to the loading, I was initially concerned about the shear stress on the bolts.  After the study was run, it appears that the axial loading on the bolts is more of a concern...This seems very strange to me considering the loading situation.  Am I missisg something in my study or am I having an engineering brain lapse?...I don't forsee much axial stress on these bolts.  Please help.

       

       

       

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        • Re: These Axial Forces Unrealistic???
          Ryan Werner

          Hi Dave,

           

          I know what you are talking about.  I have never been able to fully believe what I am seeing when it comes to the forces Simulation reports on bolts that I have added to a study.  In my experience, usually not much more than the recommended preload causes the bolt to fail according to Simulation's Bolt Check.  I am still using Simulation 2010 so am not sure if this has been improved upon in either 2011 or 2012.  At this point I really only use bolts in my analysis to simulation the contact or grounding situation I am looking for and rely on good old hand calculations to determine bolt strength.  Maybe someone else will be able to offer up more information on this. 

           

          Ryan W.

          • Re: These Axial Forces Unrealistic???
            Roland Schwarz

            You can get these results from SW Motion.  Probably better results, actually.  Model bolts as really stiff springs (with a touch of dampening) and get resultant deflections.