

October 12, 2024 at 6:49 am3343534645Subscriber
I've been trying to implement eigenvalue buckling simulation for solid elements using MATLAB to perform linear buckling analysis. When calculating the geometric stiffness matrix for eigenvalue buckling, I referred to ANSYS documentation Help 361: https://www.mm.bme.hu/~gyebro/files/ans_help_v182/ans_thry/thy_geo3.html. However, after trying it out, I found that the geometric stiffness matrix calculated using the formula differs from the one output by ANSYS APDL, which makes me doubt the result. Does anyone know how to solve this? I’d appreciate any help or advice from experienced folks.

October 14, 2024 at 2:45 am3343534645Subscriber
I derived Cook's theory and also rewrote Borst's theory. When they introduced the calculation formula for the geometric stiffness matrix of solid elements, the geometric stiffness matrix they computed had nonzero elements. Why is the geometric stiffness matrix output by ANSYS APDL entirely composed of nonzero elements? Was the calculation incorrect?

October 14, 2024 at 6:15 amhenrich1klassenSubscriber
In ANSYS APDL, the geometric stiffness matrix for solid elements is often fully populated with nonzero elements due to the nature of how the stiffness matrix accounts for deformation in various directions, including coupling effects between different nodes and degrees of freedom. This doesn’t indicate an incorrect calculation. Instead, it’s likely related to the complexity of the solid element formulation, where even small geometric changes can introduce stiffness contributions in all directions. Cook’s and Borst’s theories might present a simplified view, but finite element software like ANSYS tends to handle more complex interactions. worms zone io mod apk


October 14, 2024 at 10:59 am3343534645Subscriber
Thank you for your reply. Could you recommend any literature? I would also like to personally implement linear buckling analysis in MATLAB and benchmark it against ANSYS, which would be a very rewarding task! Thank you so much!

October 15, 2024 at 8:53 am3343534645Subscriber
Why haven't any ANSYS staff responded to me? Recently, I also tried Němec's theory (http://creativecommons.org/licenses/by/4.0/). However, the geometric stiffness matrix calculated from the theoretical formulas still doesn't match the one in ANSYS APDL. What could be the reason for this? I sincerely hope that someone knowledgeable can resolve this longstanding confusion for me.

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