Extraction of Stiffness matrix(s) in Abaqus for Nonlinear FE case

[adas_11]

Hi,

I am studying the behaviour of a soft robotic manipulator with elastomer material like rubber which has nonlinear material behaviour.
For solving a nonlinear FE case with 'Nlgeom' ON, the Stiffness matrix and external load vector are updated at each iteration by the relation. [K(x)]x = F_ext(x). how do I extract the Stiffness Matrix at each time step?

Regards,

Apurba

 

[Erik Panos Kostson]

You should post this in the abaqus forum - you will get much more help there.

(PS: I know that you can extract the FE matrices, but not sure if it is possible during the NR iterations when these are updated for every iteration - sure someone will know in the abaqus forum)

 

[FEA way]

You can extract matrices using *Matrix generate keyword but it’s a linear perturbation step. The documentation states that initial stress and load stiffness effects caused by preloads and initial conditions are included for NLgeom analysis.

For more information see the documentation („Generating matrices” chapter) or this article:

https://xizou.github.io/2016/04/07/how-to-export-stiffness-matrix-from-abaqus/