Element Matrix Output in Elastic NLGEOM Analysis

[W00dman]

Hello,

After doing an elastic, static NLGEOM analysis on my model, I recuperate the elementary matrices, nodal displacements and efforts.
After assembling the elements, and doing K*U - F I don't get zero. Whereas if the analysis is linear the sum is equal to zero.

I have a feeling it's because the reference configuration is updated at every increment.

Thank you for your answers,
Great site!
Nicholas

 

[W00dman]

Answering my own question...
In a non linear analyses in Abaqus, the Newton solver used updates the reference configuration at every iteration.
The equation that is solved is no longer K*U-F
but K*U - F = Ktan*(deltaU)

with Ktan the tangent stiffness matrix and deltaU the last variation on the displacement.

Cheers,