Hello,
I have used the 8 noded 3d solid element to analyze the structure displacements and stresses. My task is to built a FEM program using MATLAB which will give the structure displacements and stresses. I got the results for the displacements exactly as same as COMSOL simulation. But for the stresses (Normal stresses and Shear stresses) my results are not the same. My question, when the displacement result is exactly same is it obvious that stresses result should be the same for COMSOL and MATLAB simulation?
Thanks in advance.
Stresses and strains depend on the derivative of the displacement and hence may not be continuous across linear elements. Finite element softwares employ a numerical technique known as stress smoothing to make it look continuous. You may be missing that in your MATLAB code. You will notice that the nodes which are not shared by elements will give you the correct values of stresses and strain.
We have made in the past a comparison between Matlab, Comsol and Ansys for the computation of strain and stress of a cantilever beam and the stress results were all different within 5-8 %. The results in the FEM code depend on the meshing quality and the type of elements selected for the purpose. Also derivation as stated previously may have an affect since computed with some error from software to another.
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