2 Replies Latest reply on Jul 2, 2012 8:15 AM by Pascal Bigot

    mohr coulomb criteria?

    Pascal Bigot

      Good morning

       

      I need for an analysis to use the Mohr Coulomb criteria.

      I tried to use it on a simple case: a torque applied to a rod

      essai mohr-coulomb1.JPG

      I mesh and run a static analysis. And then I visualyse the criteria value of the center area

      (The material use to calculate the criteria has the following properties: ultimate tensile strenght: 20MPa , ultimate compressive strenght:690MPa)

       

      Firsly  I visualise the Von Mises security criteria distribution:

      essai mohr-coulomb2.JPG

      The result is coherent as it show an high coefficient in the center of the rod which decrease when we go to the periphery of the rod.

       

      Secondly , I visualise the Mohr coulomb criteria distribution:

      essai mohr-coulomb3.JPG

      I can't explain the result! according to me this doesn't have any sense?!

      Is there a bug in solidworks?

       

      Can somebody help me?

        • Re: mohr coulomb criteria?
          Dave Laban

          Which version of SW are you using?  We found a critical issue with the mesher in SW11 SP5 (see https://forum.solidworks.com/message/250006 ) that threw out unusable results, it may be you are seeing a result of the same problem in a different way?

          • Re: mohr coulomb criteria?
            Pascal Bigot

            Dave thank you very much for your answer.

             

            I have got SW12 x64 SP4.0.

             

            I have a look at the post you indecated to me.

             

            however I don't think this is the same problem. I have made several trials with different models and different meshes and for each ones the results is not what we could expect.

            futhermore the other graph (VonMises strain, displacement, P1,P2,P3 , etc) seems to be correct. Then it should indicate that this is not a mesh problem

             

            I thinks the formula of Mohr Coulomb criteria, is not well calculated.

            essai mohr-coulomb4.JPG

            I have extract in excel the P1 en P3 values for the nodes located at one end of the rode (the shape is a disk). Following the solidworks equation, I have calculated the Mohr coulomb criteria. As i have the coordonnates of the nodes, I have also calculated the distance of each node from the center of the rod (ie. the radius).

            I draw the Mohr Coulomb criteria against the radius:

            essai mohr-coulomb5.JPG

            like expected, the M-C criteria is proportional to the radius. SW don't show the same result!

             

            This indicate that SW calculated well P1 and P3 but that the calcul of Mohr-Coulomb criteria is wrong?