Nonlinear Column Buckling

[spacecase]

Greetings all,

I need to tighten up my buckling analysis and would like to head into the nonlinear realm. I am basically dealing with an eccentrically loaded column. The compressive loads applied to the column are not enough to yield the material, so I should be in the elastic range. Running NASTRAN linear buckling with fixed free conditions yields a Pcr of 54lbs. Using the Secant formula to take into account eccentricity, I have a value of 12lbs.

How would you all go about running this in a nonlinear analysis? I know there is a nonlinear eigenvalue buckling solution that can be done. I’ve also heard that you can run a nonlinear static run and see where it diverges.

I tried the nonlinear static run up to 60lbs and did not see a divergence. I incremented for every 0.5lbs in that run.

I am a newbie analyst and really love the knowledge sharing that goes on here! Thank you all.

 

[craigj]

If youre really brave you can try a nonlinear static simulation using the arc-length method as the iteration scheme. This will allow you to accurately identify the stiffness = 0 point of the curve (i.e. buckling point).

This method is not for the faint of heart and is normally reserved for modeling snap through buckling behavior.

CJ