i do some test of deep slender beam (steel), the webs is thin and subjected to shear due to patch loads. using elastic material, large deformation and contact analysis is solvable for both full model and half symmetry, deformation result modes shown as expected and captured well to experimental.
however, it’s divergences when using nonlinear material applied. i seen from the stress elastic distribution has yield about 5 to 15 times higher, massively in large area of webs.
Do you mean that there’s no convergence in these cases with large plastic strains? Maybe adjusting the plasticity model could help. Or refining the mesh in critical regions. I would also try with different types of elements - the choice of element type can be particularly important in analyses involving plasticity in CalculiX.
I think that it’s a good idea and I would try this.
If the original author used Riks solver and this problem involves large instabilities then it’s very likely that ccx’s traditional NR algorithm can’t handle them. The lack of an arc length solver is one of the most significant disadvantages of CalculiX.
How do this post end up?.
I can’t achieve consistent results on my plastic analysis with Calculix. Only for very simple uniaxial tensile / compressive stress patterns.
As soon as the problem involve more complex stress distributions with shear or noticeable bending the results do not agree with other references.
By other hand, I suspect that ccx cannot manage sign reversal on the strains during the loading path on plastic models. I have found that PEEQ doesn’t stop when the model is unloaded. ¿Do you know if plasticity in ccx is limited to monotonic load patterns?
I really apreciate and consider your opinion and would like to ear about any update you can provide about your findings ( and the element that better perform to you if possible)
Sorry if this are too much question. Any answer you could provide is appreciated.
i’m not further investigate the problem, it did not finished yet. been trying to compares with different opensource solver with arch length algorithm capabilities.
it seems not only related to material plasticity, but equilibrium path at large deformation (shear buckling). theoretically the element stiffness is very low or nearly zero at areas with yielded materials. Newton Raphson algorithm sometimes is hard to find the path were Arch length is not.
Good to cited and respect the author name and reference paper. It’s rare in use. Someone may think is something like new were actually an old and already discussed by another.
indeed, nonlinear buckling it’s old topics in Abaqus, printed book from publisher available but fairly new and rare in CalculiX. I began to start the discussion also in old Yahoo group specifically about saving deformed mesh for imperfection in CGX and answered by the authors.
maybe someone thinking, nonlinear buckling in CalculiX is exactly the same with Abaqus by simple copy the keywords, so the manual, book or paper can directly be used and cited. It’s probably wrong since many significant different steps of imperfection apply in CalculiX, solver algorithm and setting also.
p.s don’t forget creating new duplicated threads as much as possible, external forum also just keep going since there’s no lawsuit in general, only unethics in educational or research institution i’m shaped.
basically, all steel design code has covered this problem type and given estimation value of ultimate capacity. Many empirical correction factors based on test calibration adopted, but in fact still have large discrepancy for many cases.
previously i doubt it can be solved in CalculiX since many references i read using Riks algorithm to solve in Abaqus. Later, the condition changed after known Newton-Raphson is capable also. This opening the possibilities to conduct another similar problem in complex nonlinear buckling with CalculiX, thanks much.
just keep going since there’s no lawsuit in general, only unethics in educational or research institution i’m shaped.