17 Replies Latest reply on Apr 12, 2013 8:04 PM by Jared Conway

    Analysis of a spherical bearing

    Jahee Campbell
    Jahee Campbell Mar 16, 2012 9:26 AM

      I'm trying to model a spherical bearing for a project I'm doing at university, I've drawn the model and it behaves as it should when I manually manipulate the model, rotating freely in the housing, however when I try and run any analysis on it in simulation to ensure it behaves as it should when it's used in the assembly it is to be inserted in, the bearing becomes rigid and I get some very strange and inaccurate results..

       

      Does anyone have any experience with designing these, I'm sure it's a simple problem but it's had me baffled for a couple of weeks now.

       

      I can provide pictures and models along with any other information anyone needs if requested.

       

      Thanks in advance

      Edit: There are no interferences, i've set the global contact to 'no penetration' and defined the surfaces that shouldn't be penetrated using the component contact definitions under connections drop down

      First picture uploaded is the bearing assembly

      Second picture is the analysis, with a simple bolt inserted to act as a lever.

        • Re: Analysis of a spherical bearing
          John Burrill
          John Burrill Mar 16, 2012 9:18 AM (in response to Jahee Campbell)

          Jahee, can you post a screen capture of the bearing and answer the question: what type of simulation are you doing?  (motion, theremal, structural)

          • Re: Analysis of a spherical bearing
            Bill McEachern
            Bill McEachern Mar 16, 2012 11:00 AM (in response to Jahee Campbell)

            I took a look at the pictures. The load case does not make sense from casual inspection. What are you trying to do? How are you trying to load the bearing? The shaft has a load but no restraint. the restraint on the bearing face is non-sensical. Isn't the shaft connected to something else?

              • Re: Analysis of a spherical bearing
                Jahee Campbell
                Jahee Campbell Mar 18, 2012 4:10 PM (in response to Bill McEachern)

                Bill, admittedly my knowledge of solidworks is self taught so i may be approaching this the wrong way, but what i'm trying to do with this study is just to ensure the model acts as it should during analysis, my expected outcome is that the bearing and pin would simply rotate until they reached the housing, and stop at that point with some stresses concentrating at the point at which the two surfaces interact.

                 

                The bearing is to be a part of another assembly, so i want to see that it moves freely and represents the real component correctly in this isolated simulation before creating the next assembly. That's the only aim of this test.

                 

                The reasoning behind the restraint on the bearing face is that without it, the bearing dislocated from the housing,

                 

                It might be of use for you to know how the components are mated? I created a reference point at the 'centre of face' of the bearing and the inner housing and mated them coincidently..

                 

                 

                John, i am unable to put this to the test until tomorrow but i'll let you know how i get on with that.

                  • Re: Analysis of a spherical bearing
                    Bill McEachern
                    Bill McEachern Mar 19, 2012 2:59 PM (in response to Jahee Campbell)

                    You don't need simulation for what you want to know - just drag it around in SWX with collission detection on. Remember sigmaF=0 (must) in a static analysis. You can simulate the contact described but why would you? Wouldn't your design insure that never happens? You need toi set up contact pair on the surface and restrain the shaft with some small spring whose magnitude is imaterial in the big scheme of things to ensure the contact is caputred - shoudl work any way.....

                • Re: Analysis of a spherical bearing
                  Unspecified Unspecified
                  Unspecified Unspecified Apr 12, 2013 5:26 AM (in response to Jahee Campbell)

                  Hello

                   

                  I think I have the same problem as the one you mentioned here. I've spent the last few weeks dealing with this but it just won't work, whatever I try. I have tried using the bearing connector but the results aren't right, the deformations are opposite of expected. If you somehow managed to solve it, please let me know (my problem is the main problem of my thesis). I tried connecting the inner face of the outter ring with a point in the middle of the section of the shaft using trusses but I just couldn't connect the joints to the outter ring. Now I'm trying with a concave circular ring and it still doesn't work.

                    • Re: Analysis of a spherical bearing
                      Jared Conway
                      Jared Conway Apr 12, 2013 8:04 PM (in response to Unspecified Unspecified)

                      "results aren't right"

                      "deformations are opposite of expected"

                       

                      you'll have to elaborate on what that means, and show some pictures and post your setups. last I looked at your problems, the issue was that you didn't have a static problem which was resulting in large displacement warnings or similar or the need for soft springs which invalidate the results. when the appropriate restrains were added, things moved as expected. until you find a static problem and add the appropriate restraints you will continue to have issues.