Hello,

I have to simulate buckling in case of a hydraulic piston rod. One end of the rod is fixed whereas the other end of the rod i.e the piston head is guided inside the cylinder tube. The force is applied axially on the piston.I tried using the cylindrical faces fixture under advanced fixtures but i am unable to understand what the values of x,y,z in that mean physically. My object can move only in the axial direction and changing the value of 'z' in the cylindrical face fixture gives very different results. What does the value of 'z' exactly signify here? I have tried various other types of fixtures on the piston head but none of the results are convincing. Also with a decrease in load my displacements increase which makes no sense at all. Can anyone please suggest what changes i can make to obtain a better result? Please find attached a screenshot of my simulation.

First things first. What do you want to do with these results? Are you trying to determine the load at which buckling will occur? If so, then keep in mind that the values calculated from a "Buckling Analysis" are non-conservative; i.e. the buckling value calculated by the software will be higher than the real buckling value (by an unknown amount). More realistic values can be obtained with a nonlinear analysis.

Now, regarding your questions on constraints, it'd help if you could post the model itself. The mode(s) of buckling within a structure are directly related to how the structure is constrainted, so it's critical that you accurately represent the constraints in simulation. Does a "fixed" constraint on one end of the rod accurately represent the real system? Trying out different constraints can be a good way to understand what each does, but it's better if you do it on a very basic model that you'll understand all of the outcomes.

Typically, the x,y, and z values corresponded to enforced displacements with respect to the world coordinate system. For SolidWorks, if the box is left blank, then that degree of freedom is free (i.e. it's allowed to move) and any numeric value is the enforced displacement.