# Convergence issues with plastic deformation **URL:** \ **Category:** General Questions\ **Tags:** results\ **Created:** [March 2, 2026, 11:54am UTC](https://prepomax.discourse.group/t/convergence-issues-with-plastic-deformation/3305 "2026-03-02T11:54:49Z")\ **Posts on this page:** 1\ **Showing post:** 11
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [March 2, 2026, 7:57pm UTC](https://prepomax.discourse.group/t/convergence-issues-with-plastic-deformation/3305/11 "2026-03-02T19:57:46Z")
Extrusion to 3D (or actually revolution in this case) often helps with convergence and other issues because of how CalculiX’s 2D elements are internally expanded to solids with some nonlinear subprocedures potentially interfering with nonlinearities in the model: [Rigid-body constraint convergance problems - #25 by dhondt - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).](https://calculix.discourse.group/t/rigid-body-constraint-convergance-problems/369/25) This is especially the case with shells, but it may occur with other 1D and 2D elements as well. Another known problem is that rigid body constraints don’t work with such elements in explicit dynamics. Here’s a list of all the major known CalculiX’s limitations: [Known CalculiX limitations](https://prepomax.discourse.group/t/known-calculix-limitations/3050) However, this case doesn’t seem so bad. If you make the suggested changes, add nonlinearities carefully and adjust some inputs, it should converge eventually. If it doesn’t, the 3D solid wedge approach (2° and one layer of elements if we want to replicate what CalculiX does internally here) with cyclic symmetry or even just BCs in cylindrical CSYS can always be applied. --- _[View the full topic](https://prepomax.discourse.group/t/convergence-issues-with-plastic-deformation/3305)._