Using Geometric Nonlinearity with the Elasticity Solver

[LC_BM]

Hi,

To try to make my doubt as clearer as possible, I did a test case with a rectangular prism of similar dimensions and mechanical properties to what I want to model. For comparison, I used the solver for linear elasticity (LE), and the solver for nonlinear elasticity (Elasticity Solver), both without considering geometrical nonlinearity (WOGNL) and considering it (GNL). The BCs used were a couple of fixed nodes on one of its walls (∆x=0, ∆z=0). The “loading” was an applied displacement (∆y) in the y-direction (the longitudinal axis of the rectangle) on each of its lateral walls. All of it using the GUI interface.

As far as I understand, in the case of WOGNL, one should obtain the same results (maximum von Mises Stress) as with LE, since the results of WOGNL are linearized, while on the case of GNL, one should obtain a nonlinear curve. However, I'm obtaining the opposite, a nonlinear curve (towards the end) with WOGNL and a linear one with GNL (I checked the slope, not just how the graph looks like).

What I’m doing: I am checking the box of “Elastic Solver Linear” when I want to model WOGNL and leaving it unchecked when I want GNL to be taken into account as described in the xml file of “nonlinearelasticity.xml”. I did it both for plane stress and plane strain.

The question is then:
• Would it be possible that the software is taking it the other way around, this checkbox checking? Or
• Is the linearization not being done correctly (WOGNL) and the nonlinear case (GNL) is not being considered at all? which would be weird, since if this was the case, then the values would be exactly the same as in the linear case (LE), but they differ a bit in the decimals.

An additional question would be:
• The LE case gives the same result whether I have Plane stress selected or not, why would this be?

I am including the following attached:
• The sif files (of the Plane Stress cases since they are the same as for Plane Strain except for the additional line)
• The mesh file (.unv). (since I made groups in Salome in order to apply the BCs)
• The images (plane stress and plane strain cases) with the corresponding table and graph of the results (Maximum Von Mises Stress).

Thank you very much in advance.