So far, based on the above discussion it was decided to solve the plain cylinder (without holes) and shown that the modal analysis was in agreement with Donnell’s equation.
Subsequently, two S4 meshes with different refinements were used in the nonlinear analyses, where the cylinder is subjected to a displacement controlled axial compression of 100 mm (roughly 1% of its length). You can find the input files below.
https://limewire.com/d/8atp3#sOQ7dvjt8y
Interestingly, the relatively coarse mesh (lc=128) converged up to 56% of the total displacement, while the finer mesh (lc=64) only converged up to 26% of the total displacement.
What is the reason for the early termination (divergent behavior)? In the thread External solver comparison for nonlinear analysis of shell element much higher deformations are obtained by @xyont.
- Is it our use of SHELL element as opposed to SOLID elements there, that impede convergence?
- Does including plasticity as a material nonlinearity result in a favorable condition for convergence?