Good morning,
I am using a general static analysis to model a pneumatic steel structural section. I haven’t defined a boundary condition but have put a tie constraint around the edges of the member to simulate welding (not sure if this is the best way to do it). A uniform pressure is applied to the inner surfaces of the section. The Mises stresses, as you can see in the attached photo are the highest near the edges but not everywhere throughout the beam. I am wondering what the reason(s) might be for this unequal stress distribution.
Thank you for your assistance,
Best regards.
Not sure what you mean by unequal. Looking at it, I would say coarse, uneven mesh to begin with. Try to generate a structured, more refined mesh.
If you mean that it doesn't look like a classic bending stress distribution, it can be because if you clamp all edges, the part can't shrink/expand (Poissons ratio) and you introduce additional stresses. Solution is to use more realistic BCs
You are not clear with BC., if you have just fixed two ends of the model and applied pressure to the whole model, then you will get more expansion in the central part of the model (like a balloon) therefore you will get more stresses close to the ends. i.e. this is the due to the BC. For example if you remove the BC in a way that there is no radial restriction to expansion then you will get uniform stress distribution. number of elements and their shape, distribution, and order are not that influential.
Also keep in mind that contour plots are extrapolated from values at integration points. So if the mesh is not homogeneous, the contour plot may strongly exaggerate what is actually going on at different points in the simulation.
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