Dear all,
When turning on NLGEOM option of Abaqus, I obtained unequal magnitudes of top and bottom strain components from the same shell element S4R. This element is part of a thin plate modeled with S4R Abaqus elements subjected to out-of-plane displacement and clamped from its corners. Is such result relevant, any explanation or reference? otherwise should another strain quantity apart from the log(V) strain be used (for instance Green's strain)? Note that even by using elements satisfying Kirchoff assumption the result is still the same.
Many thanks for your help!
Hi
If you are working with high strain-displacement problems you should turn the NLGEOM on and take its result accurately but if the strain is not matter of importance for you, so you should turn it off and use its outputs.
Dear Erfan, strain is of importance so that NLGEOM should be turned on. thanks for your reply.
It looks like you are modelling a flat plate - presumably with a normal pressure loading? With NLGEOM=OFF then no membrane behaviour will occur but with NLGEOM=ON then this will occur. If membrane behaviour occurs then you will have in-plane forces and these will lead to the observation you are making. Think of how an axial force in a beam changes the stress/strain distribution from that for pure bending. The different plate formulations (Kirchhoff versus Reissner-Mindlin) will not change the statement made above. Kirchhoff is only appropriate for relatively thin plates and it is the span/thickness ratio that governs whether or not Kirchhoff is valid. You can check this by running models with both element types and look at the different results.
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