9 Replies Latest reply on Oct 28, 2009 9:29 PM by Justin Sue

    Simple Torsion Stress in Tubes Part 2 - Spline shafts

    Matthew Johnson
    Matthew Johnson Oct 15, 2008 7:22 PM
      Again, I'm a newbie to FEA and Cosmos. Please be patient.

      Moving on with my actual design project separate from my previous thread, I am trying to determine the minimal wall thickness I can obtain in a spline shaft while applying a predefined torque and reasonable FOS. I would assume the first failure mode to be when the part moves out of the true elastic limit. Now when modeling for shear, what would be the best material property to set as the target? I was looking at the tensile yield strength for AISI 1018, hot rolled, 19-32 mm round, but I'm not sure that's a direct correlation to shear.

      In modeling the part, I have performed hand calculations as seen in the attached pics. I tried two different end conditions using the design torque and then the failure torque as seen with sample test pieces. With the first end condition, the ends are engaged up to a depth of 0.900" from the end faces. So I created 0.001" extrusions on the spline teeth to simulate an area of contact between the spline and yoke. With that I had to divide the torque total among the 20 teeth. This type of loading/restraint seemed to create the greatest stresses. The second end condition I used was to apply a torque to one end face and the restraint to the other end's face. This seemed to generate results more in line with the hand calculations. Now, I just want to replicate my real world results as reasonably as possible. Any suggestions on applying the load and restraints and then correlating the results back to an actual failure (yield) number that I can design with?

      Sample 1 is solid. Sample 2 has a 0.5" inner diameter and was tested in the same manner as mentioned above.

      Thanks.
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        • Simple Torsion Stress in Tubes Part 2 - Spline shafts
          Bill McEachern
          Bill McEachern Oct 15, 2008 8:13 PM (in response to Matthew Johnson)
          Hi Matt,

          Haven't got much time ....If I was doing this problem the approach would be, at least to start,....
          -Get the problem down to somehting reasonable - I would use symmetry and explore one or two spline contacts.
          -You need to realize that you have to model the contact and this is best done with a reasonable approximation of hte spline teeth.
          - you need to ralize that your formula on shear stress to von mises is only valid in a state of pure shear.
          - rule of thumb on contact is infinite life at 3 time Sig yield - for Hertzian contact type stresses - this does not apply to bending induced stresses in the spline root.
          - given the above it may not be critical to accurately resolve contact stresses if failure of spline if from bending at root.
          put a simple model together with both the male and female - restrain one end of hte male (or female) and apply the torque to the other end and transmit the torque across the contact.

          that is a start for you thinking - I have to run.
          • Simple Torsion Stress in Tubes Part 2 - Spline shafts
            Andrew Hallas
            Andrew Hallas Oct 16, 2008 4:54 AM (in response to Matthew Johnson)
            Matt,

            Your hand calculations do not take into account any effects of stress concentration caused by the spline teeth. Your FEA model should show the max stress occurring at the root of the spline teeth. The Australian shaft design code uses a stress concentration factor for splined shafts of 1.8.

            For loading the model either load the end of the shaft with your torque and restrain the other end or model the hub as well and apply the torque to the end of the splined shaft and restrain the end of the hub. You will need to setup the contact conditions between the hub and shaft teeth so that the load is transferred between the faces of the teeth.

            I did a very similar exercise for splined shafts for my undergraduate thesis and had good correlation between my hand calcs and FEA models. I did the FEA using Ansys Workbench but setting the FEA model up should be the same.
              • Simple Torsion Stress in Tubes Part 2 - Spline shafts
                Matthew Johnson
                Matthew Johnson Oct 28, 2008 11:31 AM (in response to Andrew Hallas)
                Thanks for your responses guys. I've integrated end couplers to the design to simulate contact loads.

                Andrew, I'm reading over relevant articles on shaft design currently. I'd be interested to see what your thesis has to offer on the subject. Do you still have an electronic copy that you could attach or possibly e-mail me?
                • Re: Simple Torsion Stress in Tubes Part 2 - Spline shafts
                  John Jablonski
                  John Jablonski Oct 28, 2009 6:06 PM (in response to Andrew Hallas)

                  Hi. I know I'm resurrecting an old thread, but I am trying to mate two splined shaftes together and am so far unable to do it.

                   

                  I have two shafts (obviously). The internal spline I created using GearTeq. The mating part was supplied by a customer, and while I don't know how it was created, it does appear to be an accuracte spline (converting the edges into a new sketch at least gives me a spline segment).

                   

                  Ultimately I want to put these into cosmos and do some stress analysis.

                   

                  What is the correct/best way to mate these? I have been trying to do some kind of face-to-face mate. I have not tried creating reference points and mating using those.  If that way would work, would it be acceptable for cosmos?

                   

                  thanks,

                  john

                   

                   

                  p.s. i'm running SW2009-4.1 & cosmoworks 2007 btw (on different computers)

                    • Re: Simple Torsion Stress in Tubes Part 2 - Spline shafts
                      Anthony Botting
                      Anthony Botting Oct 28, 2009 6:19 PM (in response to John Jablonski)
                      Hi John: I've done gears a few times and found that you really don't have to mate the parts in the traditional sense. Just use collision detection in SolidWorks and locate the shafts together until they hit on some surface that makes sense to you by observing the collision highlights on-screen. Then, use the node-to-surface option to define a contact set, one pair at a time. You have to take baby-steps with this, to get it to work. Use draft quality elements initially so you're not waiting hours for the contact iterations to go through. Get one set of surfaces working, then stop and add another set. Hope that helps.
                  • Simple Torsion Stress in Tubes Part 2 - Spline shafts
                    Andrew Hallas
                    Andrew Hallas Oct 30, 2008 4:45 AM (in response to Matthew Johnson)
                    Matt,

                    I can email you the chapters from my Thesis if you provide your email address. My thesis looked at the power transmission through splined and keyed drives and was actually a work related project.
                    • Simple Torsion Stress in Tubes Part 2 - Spline shafts
                      Pedro Nunes
                      Pedro Nunes Oct 30, 2008 9:56 PM (in response to Matthew Johnson)
                      Hi, Matt can i have a look into it too please?

                      My email is pedro.sousa.nunes@gmail.com

                      Thanks.