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Large Displacement Issue

Question asked by Aaron Gradeen on Jan 23, 2014
Latest reply on Jan 23, 2014 by Aaron Gradeen

I'm analyzing the bending stress on a 40 mm pin in a pin/clevis assembly. The load on the pin is applied through a spherical plain bearing. I have inserted an image of the assembly below (bearing is not shown, those are just spacers on the pin which locate the bearing. I have also inserted an image of the assembly cut in half for symmetry in the simulation study. Here you can see the inner race of the spherical plain bearing is modelled. I am applying a force on the flat which I have created. Typically I use flats on cylindrical parts that are not rotationally constrained since this seems to stabilize them from spinning infinitely in the model. I have "no penetration" contacts setup between the bearing and the pin as well as between the clevis bore and the pin. A global friction value of 0.33 is applied. Symmetry is applied to the three cut faces on the clevis, pin and bearing. The face of the clevis which is parallel to the plane of symmetry is set as fixed.

Pin Clevis Assembly.JPGPin Clevis Simulation.JPG

Even with the soft spring effect enabled I am getting large displacements.  I believe the bearing is spinning and expanding a large amount under the infinite centripetal force. I don't want to constrain this bearing more than I need to since overconstraining a model adds unrealistic stresses. The maximum bending stress in the pin is very important in this case since it is used in a fatigue calculation. I am using a standard high quality mesh (oddly enough it ran fine with draft quality mesh...perhaps something to do with fewer degrees of freedom?)  Any input would be greatly appreciated