Hello,
I am modeling an impact as a part of my project and due to the large deformations in this phenomenon, I turned the NLGEOM (GEOMETRIC NON-LINEARITY) on, but in a paper, I came across this point:
"Effects of large scale displacements were not included in the study. Soil plasticity at impact was much more significant, and a solution with time-stepping, plasticity, and geometric
non-linearity was not feasible."
Is the mentioned point correct?
I would be so thankful for your help.
Pan Fang Thanks for your response. I thought maybe, using plasticity and geometric non-linearity together would result in incorrect answers. I want to know that can I use these two together, in general?
Yes , It is possible to add the plasticity characteristics into material properties, non-linearity can be switched on. If the impact analysis is done and non-linearity occurs during the process it will accounted.
In principle, using both geometric and material non-linearity should improve correlation with model tests for impact problems. However it will increase the solution time and can sometimes prevent convergence of the iterations. One way to assess the need is to run a linear model and check whether the deflections produce significant P delta effects and/or yielding of soil or metal.
Ideally you should consider both geometric and material non-linear behaviours, when you have large scale deformations. As this may lead to convergence problems, you should try to run both components separately and assess how well the experimental results are captured.
Dear Farzaneh,
the need to use NLGEOM is also related to the type of material model,
for instance, non-linearity should be taken into account in crystal plasticity simulations.
There is no general drawback when using NLGEOM, apart from the increased computational time.
"...solution with time-stepping, plasticity, and geometric non-linearity was not feasible..."
Not clear what they mean by "not feasible". It is certainly possible, as I do it daily.
Best Regards,
Nicolò
possible to add the plasticity characteristics into material properties strain-stress to expérimental .
If you are using plasticity with material non-linearity activated, the geometric non-linearity also shall get considered automatically. In pure elastic simulations involving no plasticity, in general as a rule of thumb, if the displacement exceeds 1/3rd the dimension (In a cantilever, if the selection is more than 1/3rd of the height of cross-section), you need to invoke the geometric non-lineairty and rerun.
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