Stability/Energy Question from ABAQUS output

[jrw501]

For a structure that I believe to have passed its stability point (based on load-deflection behavior that has passed a point with zero tangential stiffness/went through a maximum) can anyone confirm that at that I should be able to verify the stability point has been reached using energy output from ABAQUS like the following:

Total Potential (TP) = Internal (IE) + External Energy (EE)

The latter two terms I can get from ABAQUS, then by finding the slope of sequential terms using the difference in displacement in the denominator (so I have something like (TP2-TP1)/(u2-u1)) I get the first variation in the total potential function.

The first point where this value becomes zero becomes negative should imply neutral/unstable equilibrium?

Thanks!

 

[rb1957]

maybe i'm wrong, but i'd've thought that internal energy (strain energy) = external energy (work done by loads) for a stable model.