20 Replies Latest reply on Oct 23, 2013 3:02 PM by Jared Conway

    Unexpected bolt forces (preloads) in Simulation

    Loren Sackett

      When I use the bolted connectors feature and use a bolt/nut vs bolt/threaded hole, and I apply the same preload, I get different preload values when I run the FEA.

       

      More details:

       

      To recreate this problem, I made two plates each with two holes.  One one hole, I used a bolt connector with a nut on the other end of the bolt (type: Standard or Counterbore with Nut).  On the other hole, I told SolidWorks to use a threaded hole instead of a nut (type: Standard or Counterbore Screw).  On both of the bolt connectors I applied the following preload:

       

      Torque: T=1000in*lbs

      K factor: K=0.2

      Nominal bolt diameter: d=0.5in

       

      Using the standard bolt torque equation F=T/(K*d) I get a bolt preload of 1000in*lbs/(0.2*0.5in) = 10,000 in*lbs.

       

      When I run the FEA with no external loads, the only loads on the bolts are the preloads due to torquing the bolts.  When I list the "Pin/Bolt/Bearing Force" SolidWorks tells me that the bolt/nut combo has an axial force of 10,000 lbs (exactly what we expect), but the bolt/threaded hole combo shows an axial force of only 8,333 lbs - which is not what I expect.  A little experimentation showed that a bolt/threaded hole combo always yielded 83.3% of the expected value.

       

      Is this an error in SolidWorks Simulation or am I missing something?

       

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