Difference in Shell and Solid Von Mises Stress

[lucas5M83V]

Dear all,

I am trying out the difference in analysis results between a shell and solid idealization. The von mises stress for the shell model indicated a higher von mises stress as compared to the solid model; I would have thought both would be showing close results. May I know what is the reason for the difference in value, and which should be followed?

Appreciate your response. I have attached both the shell and solid files. I am using Inventor Nastran 2021.

[John_Holtz]

Hi @lucas5M83V 

Have you tried refining the mesh? The mesh sizes in the models you provided were quite different. Getting an accurate result right at a constraint can be difficult (due to the mathematics of the analysis), but a finer mesh will help.

When I used a mesh refinement of 0.5 mm around the constraints, I get von Mises stress of 115 in the shell and 126 in the solid. That is about as good as it will get considering the 3D nature of the results right at the constraint. (Obviously the shell elements do not have much of a 3D result - at least not like the solid with multiple elements through the thickness.)

John