3 Replies Latest reply on Jun 29, 2009 10:03 PM by Bill McEachern

    Odd Torsion Analysis Results

      I calculated the max shear stress in a rod and then checked it with a simulation. It was a straight .125" diameter rod subjected to 35 in-lb of pure torque. The torsion equation I used was:

      Max Shear Stress = 16 * Applied Torque / (pi * rod diameter^3)

      The value I got from the torsion calculation was 91 KSI but the analysis indicated a max stress of 158 KSI. The analysis was just a simple rod fixed on one end and with the torque applied close to the opposite end. The 158 KSI value was from the outer surface in the middle away from either end. Click here for a PDF showing the basic setup.

      Somehow I must have set up the analysis wrong. Any ideas on how to do it correctly? The next step is to add a flat to the shaft and I want to make sure the analysis is set up correctly before including features that cannot be checked with simple calculations.

      Jeff Wickham